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#27 2019-10-09 19:44:32

kbd512
Moderator
Registered: 2015-01-02
Posts: 2,962

Re: Nuclear power is safe

louis wrote:

The fact you might require 100 KP Units to power propellant production on Mars is a game changer I think. Once you start to think seriously about the logistical problems involved you have to ask why bother with all those logistical difficulties when you can simply roll out some flexible PV in a few minutes.

Once you start to think seriously about real engineering, you'll see that we don't have any megawatt-class solar generating stations where the people designing them just said, "Well, we'll just throw our solar panels out there in the dirt and hope because it's so cheap and easy to do."

So, why didn't they just do that when it was clearly so easy and cheap to do?

Maybe those same engineers know that you can't cover something up with dust and mud and everything else that the wind blows around and then expect your panels to produce much power when sunlight can't actually reach the panels?

Your plan is to throw multiple football fields worth of thin film panels out there on the ground...  But you don't see any problems at all with that approach.

Somehow...

1. photovoltaics sitting on the ground won't accumulate dust and quit working
2. despite the fact that the array is at least the size of dozen or more football fields, none of the dust will land back on the rest of the panels when we try to clean them
3. plastic coatings on the photovoltaics won't craze from being constantly sandblasted or cleaned with compressed CO2
4. photovoltaics that cover at least a dozen football fields won't weigh significantly more than a comparative handful of fission reactors
5. miles of heavy wiring won't be required to connect everything to simply not produce more heat from wiring resistance than electron flow
6. inverter electronics won't freeze at night when they're not being used, nor require much power for heating to keep them warm
7. batteries won't require any power to keep them from freezing at night, nor weigh nearly as much as they do in aircraft-rated / space-rated configurations, nor have much chance of suffering an electrical short when tens of thousands of little batteries are used
8. no manual labor will be required to assemble / connect / test everything, or happen at a rate at least an order of magnitude faster than the solar generating stations built here on Earth, where there are no functional limits to the amount of manpower or weight of equipment that can be thrown at the "time is money" problem
9. everything connected will operate optimally with as much or more than an order of magnitude input power differential that the powered equipment normally receives to produce as much propellant as possible whenever power is actually available
10. the propellant plant will started up and shut down every day, with no material fatigue issues from thermal swings of hundreds of degrees for both the Sabatier reactor and the compression / liquefaction portion of the plant

Never mind that we don't do any of that here on Earth.  It must all be for completely arbitrary reasons or related to money.  It can't possibly have anything to do with the fundamental impracticality of trying to run a power grid like that.  So, yeah, if we can just suspend basic physics and nearly every aspect of electrical engineering that gives our electric utilities fits when operating power grids that only see a small fraction of the output and load fluctuation that this micro grid will see during the course of daily operations, then this sounds like a fantastic idea.  On a more personal note, I'd love to see the exasperated look on an electrical engineer's face after pitching this idea to him or her.

And oh by the way, nuclear fission doesn't have any competition from solar or wind whenever the Sun stops shining or the wind quits blowing.  That only happens every single day here on Earth, specifically because of the rotation of this planet... which is nearly identical to the rotation of this other planet we want to colonize... hmm...  Nope, no problems whatsoever with this solar power idea.

I seem to have misplaced the magic wand we'd need to make this idea work.

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#28 2019-10-09 20:15:20

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 16,181

Re: Nuclear power is safe

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#30 2019-10-10 06:05:05

tahanson43206
Member
Registered: 2018-04-27
Posts: 1,072

Re: Nuclear power is safe

For SpaceNut re #29

The story about the teenager designing reactors is encouraging.  This is the kind of innovative thinking that our civilization needs if we are going to progress beyond the limitations of chemical energy.

I would like to see other nations replicating the NASA work on small safe reactors.  Based upon the reply received from NASA Glenn, I am doubtful that the United States will take the lead in providing mass produced nuclear power plants on the scale that is needed for expansion away from Earth.

The caveat is that the US appears more than capable of producing and deploying safe nuclear reactors for military use.  My interest is in civilian applications, and we humans simply have to master atomic energy if we are going to progress.

In a way that I find surprising, perhaps the American insistence on providing every citizen with the firepower to kill and maim hundreds of people will pave the way for civilian ownership of atomic energy plants.   I live in a State where the gun rights folks control the legislature, and a recent attempt by the Governor to try to introduce sensible gun regulation was declined.  Perhaps there exists a future in which citizens can be trusted with the means to kill everyone at the drop of a snide remark, and where they refrain from doing so.

(th)

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#31 2019-10-10 10:34:54

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 3,653
Website

Re: Nuclear power is safe

Tahanson43206:

Not all guns and gun ownership are bad,  despite the political propaganda otherwise.  I live on a rural farm,  where there are lethally-venomous rattlesnakes,  and predators that kill livestock.  What neighbors I have in recent years are close enough that using a rifle can be dangerous,  so I no longer use one for such defense.  So instead I use a shotgun.  And a semi-automatic shotgun at that. 

A 12 gauge,  with buckshot,  and the plug out,  so as to have as many rounds as possible available.  I need the stopping power first,  and the faster firing rate second.  For me,  5 or 10 rounds is enough to do what I have to do.  I do not need a giant magazine.  More about that below.

All that being said,  I do NOT need a machine gun!  No one does,  although getting to shoot one would be fun.  The ban on civilian machine guns dates to 1934 and had very wide support to be implemented.  The death toll in the streets from mafia gang violence was very high,  due to the combination of high firing rate,  high stopping power,  and huge magazine sizes,  specifically as embodied in the Thompson submachine gun with the big round magazine.  All three characteristics taken together constitute a public danger,  that only two together do not.  And THAT triple combination is the key!

I have no problem with that machine gun ban,  and actually recommend examining today's popular weapons in terms of the simultaneous presence of those three critical characteristics together.  Not separately!  We the people might,  or might not,  want to ban some of the things now out there,  I dunno.  That debate has yet to take place,  in terms of the real threat:  those three characteristics taken together,  not separately.

But remember,  any such ban must have wide public support!  And don't forget,  there are a lot of people in the middle of the country,  particularly those of us living in rural settings,  who actually need the guns to live and thrive safely.  Like me.  That is quite unlike big city folks,  especially on the east and west coasts. 

The gun control issue is only one facet of solving the overall gun violence problem,  which in turn is far bigger than the rash of mass shooters we have been having,  while the other facets are being totally ignored.  So,  we who need the guns are understandably very skeptical of the mostly-politically-motivated gun control movements,  as they currently exist. 

Now to nuclear power.  Louis definitively revealed his emotion-driven opposition to nuclear power with this quote from post 25 above: 

“I honestly can't see fission as part of the future energy mix. Fission =  radiation  =  big risks =  preventative measures = high cost.

Fusion maybe at some future date but fission never.  Fission is going to disappear from the energy agenda I predict. It can't compete with wind and solar in the absence of government grants.”


Those statements are as wildly non-factual as they are wildly emotional.  Fusion does not yet exist except as a bomb.  Even so,  it too has lots of radiation!  We’ve seen it since popping the very first one in 1952.  Risks requiring preventative measures is the one and only kernel of truth in his entire statement!  Mitigating risks with preventative measures is just what we do,  and quite routinely.  Example:  going to unleaded gasoline to lower lead-poisoning brain damage in babies living within a mile or two of highways. 

I gave an outline in post 24 above,  of the many technological ways to make nuclear power quite safe,  and thus make nuclear accidents really rare indeed.  A quote from my post 24 above,  which set off Louis’s emotional outburst:

“As for safer nuclear,  I've already described what happens when you enforce prioritizing safety over dollars,  as in the US Navy nuclear program,  for pressurized water reactor technology.  RobertDyck has described the far-safer CanDU approach,  which only needs updating with the more modern emergency cooling technologies,  something easily done.  And Kbd512 and Oldfart1939 have been describing the far-safer thorium technology,  being developed big-time in India.”

The big issues with nuclear are less about safety,  and more about non-profitability.  Which is driven by inappropriate regulations and scare propaganda,  in an environment where disasters have happened due to human stupidity that should never have happened in the first place.  The regulations we have focus on too many costly irrelevant things that we don’t need,  and not as much as is needed on enforcing the priority of safety over cost. 

Fix THAT,  and GET RID OF THE SCARE PROPAGANDA,  and nuclear can be profitable again.

As Spacenut and I have pointed out,  NASA is dragging its feet on getting Kilopower ready in a timely fashion.  You ran smack into that when you contacted NASA Glenn.   What is needed is for some private concern to “steal” that technology and get on with its timely development and demonstration. 

Given the government monopoly on things atomic in this country,  that will have to be an outfit that the government already knows and feels confident to license to do nuclear stuff.  I dunno who those entities are anymore,  I did not keep up with that.  Zubrin might know some names.  He worked in nuclear stuff. 

As for the Kilopower debates that have gotten wrapped around axles here on these forums,  be aware of what Kilopower really is and how it actually works.  The reactor is engineered to be utterly safe,  and is no radiation threat until it has been turned on.  All it really does is get glowing hot.  And emit nuclear radiation,  that you must shield in some way.

There are heat pipes that take that heat from that core to the appropriate location of a closed-loop heat engine.  I’m not sure which kind of heat engine,  but that doesn’t matter to this discussion.  The heat engine output is shaft power,  converted from the input heat,  by thermodynamics.  Its efficiency varies with the skill of the designers,  but falls between an upper bound of Carnot efficiency and a lower bound of zero efficiency. 

Carnot efficiency is estimated from source and sink temperatures for the heat in the process:  Carnot efficiency = 1 – Tsink/Tsource,  where temperatures must be on an absolute scale.  For the heat engine in the Kilopower design,  Tsource is not the core temperature,  but the temperature at the end of the heat pipe sticking into the heat engine.  My ignorant guess for that is 2000 F = 2460 R.  Tsink is not the effective sky temperature,  but the temperature of the radiating surface.  My ignorant guess for that is 1200 F = 1660 R. 

The resulting Carnot efficiency estimate is then 1 – 1660/2460 = ~0.33.  The actual number is less than that upper bound at 0.25.  Which means 75% of the heat is waste heat to be rejected.  There is thus inherently a lot more waste heat to get rid of than there is shaft power output.  You ignore that at your peril.

The shaft power output from the heat engine drives something rather similar to your car’s alternator:  in fact,  an electric generator.  That conversion is rather efficient,  usually above 80%,  and sometimes above 90%.  Varies with how off-design the generator is being operated.

There is a closed-loop cooling “circuit” between the heat engine and its “sink” for the waste heat:  an infrared radiator surface.  This is unlike the “radiator” in your car,  which works by convection to the atmosphere,  not by radiating-away infrared energy.  This is a surface that you point at the sky.  The waste heat brought by the coolant loop makes this surface hot,  and it radiates this power to the sky by the classic radiant heat exchange law: 

Q/A = e sig (T^4 – Tsurr^4),  where Q is the power,  A is the area of the surface doing the radiating,  e is the thermal emissivity of that surface,  “sig” is Boltzmann’s constant,  T is the surface temperature,  and Tsurr is the effective temperature of the sky that this device is radiating to.  The quantity of heat to be rejected,  and the heat/area from the equation,  size the radiating surface.  Which is very nontrivial. 

Not being a convective device,  like your car “radiator” is,  this Kilopower radiator does not work inside any enclosure of any kind!  It MUST see the sky to work!   It works in vacuum,  or in thin atmospheres better,  but it will still work on Earth,  as long as it can see the sky.  It was intended for use on the moon,  in space,  and on Mars.  On Earth in daylight,  the effective temperature of the sky is about 300 K.  Out in space looking away from the sun,  it is 4 K.  That makes quite a difference in your Q/A ratio,  which sizes the radiating surface.

Kilopower output is supposed to be up to 10 KW electric,  with 30 KW of waste heat to be rejected.  Their sum (per conservation of energy) is the 40 KW thermal produced by the hot reactor core.  Overall,  the thermal efficiency is 10 KW electric / 40 KW thermal = 0.25,  or 25%.  Not bad for a small,  compact,  relatively-portable device.  Your car’s thermal efficiency is at most about 15% on the highway, and something like 0-5% in city traffic.  Giant power plants in the 1000+ MW electric range have higher thermal efficiencies.  These vary with the age and obsolescence of the design,  but something near 40% is common.

GW

Last edited by GW Johnson (2019-10-10 10:45:56)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#32 2019-10-10 14:51:21

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 84

Re: Nuclear power is safe

An interesting paper on the relative steel and concrete inputs for different power plant types and designs.  The values concern the amount needed in tonnes, to produce a MWe of power, taking into account capacity factors.  To cut a long story short; wind power plants have appallingly low power density.

http://fhr.nuc.berkeley.edu/wp-content/ … _input.pdf

Focusing on steel mass (tonne)/MWe:

Wind = 450-470 tonnes;
Coal = 90 tonnes;
Nuclear PWR (1970s vintage): 40 tonnes;
Nuclear ESBWR: 30 tonnes;
Nuclear (AHTR): 10-20 tonnes;
Gas turbine (natural gas): 3.3 tonnes.

It will surprise no one reading these figures to know that gas turbines powered by natural gas, have dominated new power plant technology in Europe and the US, for over two decades.  The reasons are simple: so long as natural gas remains relatively cheap, the much greater power density of gas turbines makes them the least capital intensive generating system.  If we could find natural gas and oxidizer on Mars and access it without too much drilling and pipework, then a gas turbine would probably be the most economical power source for a Martian base.  Unfortunately, it is unlikely that we will find such convenient resources on Mars.

The steel mass required for 1MWe of wind, does not include any arrangements made for storage.  An energy storage system is essentially a whole other power plant, that eats intermittent electricity as fuel and spits out dispatchable electricity as an output.  If the embodied steel requirement is taken to be the same as a coal power plant and a 30% energy loss in storage is assumed; the real embodied steel requirement for wind power is about 800 tonnes of steel per average MWe.  This is 20 times greater than the steel requirement of a 1970s PWR; some forty times greater than a Generation 4 HTR.

We are in a desperate race to replace fossil fuels, in the limited time that we have before the EROI of remaining resources is too low to be profitable and before the environmental effects of their release products begins exerting a serious toll on human civilisation.  Wind power has fallen in price due to scale economies, and before the cost of storage is taken into account, it may even be competitive with nuclear and fossil fuels in some locations.  Although embodied energy and materials requirements are much greater for wind turbines, they are simpler devices, that can be built quickly.  After storage is accounted for, wind is very expensive, both financially and in terms of resources.

We clearly need to focus development on options that have some hope of replacing fossil fuel power at an achievable resource cost.  If fuel and pollution were not a problem, it is unlikely that we would choose to produce electricity using anything other than gas turbines.  Given the restraints that we do have, high temperature nuclear reactors are the next best thing.  The barriers to realising these reactors are legal and institutional.  They have to do with regulatory requirements that increase build time and costs and the simple fact that there are no established economies of scale or established supply lines for the required components.

Last edited by Calliban (2019-10-10 15:12:00)


Interested in space science, engineering and technology.

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#33 2019-10-10 15:49:27

louis
Member
From: UK
Registered: 2008-03-24
Posts: 4,924

Re: Nuclear power is safe

These aren't very helpful comparisons. I'd like to know if coal includes all the steel and concrete that goes into ports, railway lines and mines.

Nuclear is very labour intensive. Does it include the steel in all the cars of all the people who work in the plant every day? I doubt it - but they are part of the production process.

Why isn't solar included in the list? Does it come in under gas turbines? Probably.

Then there is the issue of lifetimes.  I have been of the view that there is no reason that the towers for wind turbines won't last for 70 years or more. Obviously I can't prove that but we have WW2 sea platforms in the Thames estuary that are structurally sound and North Sea oil drill platforms from the 1970s that show no sign of collapsing.

And how much steel and concrete does a nuclear power station consume year by year? My guess is more than a few tons for various purposes.


Calliban wrote:

An interesting paper on the relative steel and concrete inputs for different power plant types and designs.  The values concern the amount needed in tonnes, to produce a MWe of power, taking into account capacity factors.  To cut a long story short; wind power plants have appallingly low power density.

http://fhr.nuc.berkeley.edu/wp-content/ … _input.pdf

Focusing on steel mass (tonne)/MWe:

Wind = 450-470 tonnes;
Coal = 90 tonnes;
Nuclear PWR (1970s vintage): 40 tonnes;
Nuclear ESBWR: 30 tonnes;
Nuclear (AHTR): 10-20 tonnes;
Gas turbine (natural gas): 3.3 tonnes.

It will surprise no one reading these figures to know that gas turbines powered by natural gas, have dominated new power plant technology in Europe and the US, for over two decades.  The reasons are simple: so long as natural gas remains relatively cheap, the much greater power density of gas turbines makes them the least capital intensive generating system.  If we could find natural gas and oxidizer on Mars and access it without too much drilling and pipework, then a gas turbine would probably be the most economical power source for a Martian base.  Unfortunately, it is unlikely that we will find such convenient resources on Mars.

The steel mass required for 1MWe of wind, does not include any arrangements made for storage.  An energy storage system is essentially a whole other power plant, that eats intermittent electricity as fuel and spits out dispatchable electricity as an output.  If the embodied steel requirement is taken to be the same as a coal power plant and a 30% energy loss in storage is assumed; the real embodied steel requirement for wind power is about 800 tonnes of steel per average MWe.  This is 20 times greater than the steel requirement of a 1970s PWR; some forty times greater than a Generation 4 HTR.

We are in a desperate race to replace fossil fuels, in the limited time that we have before the EROI of remaining resources is too low to be profitable and before the environmental effects of their release products begins exerting a serious toll on human civilisation.  Wind power has fallen in price due to scale economies, and before the cost of storage is taken into account, it may even be competitive with nuclear and fossil fuels in some locations.  Although embodied energy and materials requirements are much greater for wind turbines, they are simpler devices, that can be built quickly.  After storage is accounted for, wind is very expensive, both financially and in terms of resources.

We clearly need to focus development on options that have some hope of replacing fossil fuel power at an achievable resource cost.  If fuel and pollution were not a problem, it is unlikely that we would choose to produce electricity using anything other than gas turbines.  Given the restraints that we do have, high temperature nuclear reactors are the next best thing.  The barriers to realising these reactors are legal and institutional.  They have to do with regulatory requirements that increase build time and costs and the simple fact that there are no established economies of scale or established supply lines for the required components.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#34 2019-10-10 17:19:22

louis
Member
From: UK
Registered: 2008-03-24
Posts: 4,924

Re: Nuclear power is safe

kbd512 wrote:
louis wrote:

The fact you might require 100 KP Units to power propellant production on Mars is a game changer I think. Once you start to think seriously about the logistical problems involved you have to ask why bother with all those logistical difficulties when you can simply roll out some flexible PV in a few minutes.

Once you start to think seriously about real engineering, you'll see that we don't have any megawatt-class solar generating stations where the people designing them just said, "Well, we'll just throw our solar panels out there in the dirt and hope because it's so cheap and easy to do."

So, why didn't they just do that when it was clearly so easy and cheap to do?

Maybe those same engineers know that you can't cover something up with dust and mud and everything else that the wind blows around and then expect your panels to produce much power when sunlight can't actually reach the panels?

Your plan is to throw multiple football fields worth of thin film panels out there on the ground...  But you don't see any problems at all with that approach.

I think, kbd, that like many people, you read straight across from Earth to Mars - which is always a mistake. 

1.  The weather (apart from the temperature range and major dust storms) is essentially benign on Mars, unlike Earth.  On Mars there is no need for very strong structures to protect the integrity of PV panels.

2.  In the absence of dust storms the amount of dust being blown about varies greatly from one location on Mars to another. There are low dust areas and the NASA criteria for landing sites favours those because of landing and launch requirements. So it's logical we will be looking to low dust areas for the Mission location.

3.  Decisions about how to construct solar farms on Earth are based mostly on economics. It makes sense on Earth to protect PV panels from extreme weather events, to ensure they have a long life, that they have reasonably high efficiencies and that their construction costs are minimised. On Mars those considerations either don't apply or are less relevant. And a Mars Mission has its own constraints or objectives e.g. trying to limit the mass of the energy solution, ensuring that the energy system can be deployed easily with minimal EVAs etc.

4. Insolation on Mars is much more diffuse than on Earth owing to dust and its wobbly spin. Angling panels is less important on Mars than on Earth.

5.  For Mission One on Mars, cost is hardly a consideration. Getting it right is all that matters. Even if it costs 100 times the cost of PV on Earth, if it works, the price will be right. Even if it costs $1 billion per annum to produce that 1 Mwe it really doesn't matter, if it works.

Somehow...

1. photovoltaics sitting on the ground won't accumulate dust and quit working
2. despite the fact that the array is at least the size of dozen or more football fields, none of the dust will land back on the rest of the panels when we try to clean them
3. plastic coatings on the photovoltaics won't craze from being constantly sandblasted or cleaned with compressed CO2
4. photovoltaics that cover at least a dozen football fields won't weigh significantly more than a comparative handful of fission reactors
5. miles of heavy wiring won't be required to connect everything to simply not produce more heat from wiring resistance than electron flow
6. inverter electronics won't freeze at night when they're not being used, nor require much power for heating to keep them warm
7. batteries won't require any power to keep them from freezing at night, nor weigh nearly as much as they do in aircraft-rated / space-rated configurations, nor have much chance of suffering an electrical short when tens of thousands of little batteries are used
8. no manual labor will be required to assemble / connect / test everything, or happen at a rate at least an order of magnitude faster than the solar generating stations built here on Earth, where there are no functional limits to the amount of manpower or weight of equipment that can be thrown at the "time is money" problem
9. everything connected will operate optimally with as much or more than an order of magnitude input power differential that the powered equipment normally receives to produce as much propellant as possible whenever power is actually available
10. the propellant plant will started up and shut down every day, with no material fatigue issues from thermal swings of hundreds of degrees for both the Sabatier reactor and the compression / liquefaction portion of the plant

1.  Clearly that doesn't happen on Flat Holm Island where Rapid Roll has been used. Why would it happen at ALL locations on Mars. Is that your claim? That PV will stop working on Mars if you lay it flat on the ground? Any evidence, citations etc.

2.  You're assuming dust would be blown off rather than sucked up.  There are two options.

3.  This can be tested. If testing confirms you have a 10% degradation over two years, then increase your PV array by 10%. But I don't accept that will be the case.

4.  The Kilopower units mass 1.5 tons at least each at 10Kwe.  Nothing else is on offer in time for a Mars Mission by 2024 and even then it's extremely doubtful that KP units will be ready. If  they are you are looking at probably around 200 tons for a mission if propellant production requires 1Mwe. If you can get a PV system that masses at 1 Kg per sq. metre for about 1 Kwhe per sol then
you can beat nuclear by a large margin, even when you add in meth-ox generators, increased meth-ox production and additional chemical batteries.

5.  Not entirely following that with all the negatives...but if I read you right, the positive about a PV system is that a lot of the cabling can be integrated into the PV panelling. But I am not necessarily saying PV wins out on cabling...just that KP units may require a lot of cabling as well.  I have never seen a proper study about this. Most people, even academics, seem to ignore it. I seem to be one of the few people who keeps referencing it. If you had 100 KP units all located 1 Km from a base and each had a cable connection to the base then that would be 100 Kms of cabling! If it weighed 1 kg per metre it would be 100 tons.  I am not saying it will be like that - just giving that as an indication of the importance of cabling.

6.  I would expect the major electrical equipment to be housed in dedicated aerogel habs so don't see that as a problem. Whether PV units  themselves require some heating, I am not sure. Quite possibly, in which case that does have to be accounted for.

7.  Again I always work on the basis that batteries will be housed in habs - they heat up when charged don't they? So I expect there will be waste heat around that helps keep them at the desired temperature.

8. The idea that the Rapid Roll type of system couldn't be robotised seems absurd to me. We have robot warehouse pickers, robot parking of our cars, robot this and that...laying flexible solar on the Mars surface should be a doddle. With any system things can go wrong but the robotic laying of the PV will be tested thousands of times.

9.  I accept the propellant production facility may need to be larger with a solar power energy system. But this will be marginal I think.

10.  No I don't accept that the propellant production facility will have to shut  down every sol.  With at least 5000 Kwhes of battery power available from the Starships, before any dedicated battery system is included, I am sure the facility can be kept working day and night, just at a slower rate of production than during daylight hours.

Never mind that we don't do any of that here on Earth.  It must all be for completely arbitrary reasons or related to money.  It can't possibly have anything to do with the fundamental impracticality of trying to run a power grid like that.  So, yeah, if we can just suspend basic physics and nearly every aspect of electrical engineering that gives our electric utilities fits when operating power grids that only see a small fraction of the output and load fluctuation that this micro grid will see during the course of daily operations, then this sounds like a fantastic idea.  On a more personal note, I'd love to see the exasperated look on an electrical engineer's face after pitching this idea to him or her.

There you go with the "read across" fallacy.  Mars is not Earth and Mars Mission One is not subject to the usual commercial rules that apply on Earth.

Nowhere have I suggested we defy the laws of physics. I suggest we work with the laws of physics. That's why I think it's better with the solar solution to take a larger propellant facility, rather than more battery storage. Mass is a crucial factor when you have to take it all the way to Mars through two gravity wells.

Any electrical engineer worth their salt is going to leap at the chance to get in the history books as the guy who designed the first electrical generation system on Mars.

And oh by the way, nuclear fission doesn't have any competition from solar or wind whenever the Sun stops shining or the wind quits blowing.  That only happens every single day here on Earth, specifically because of the rotation of this planet... which is nearly identical to the rotation of this other planet we want to colonize... hmm...  Nope, no problems whatsoever with this solar power idea.

I seem to have misplaced the magic wand we'd need to make this idea work.

Really? Is that the best you can do? 

Bridging a "gap" of maybe 10 Mwhes on Mars (if we are talking about the sort of system I propose) during maybe 80% of the sol when insolation is below the desired minimum, is not beyond our capabilities.  At 300 whs per kg that would be just over 33 tons of mass in terms of batteries. Remember nearly half of it would be required anyway for fin actuation in any case, so it is really making use of a resource that will already be there.

No magic wands required, just Musk-style focus, determination and innovation.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#35 2019-10-11 06:13:12

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 84

Re: Nuclear power is safe

louis wrote:

5.  For Mission One on Mars, cost is hardly a consideration. Getting it right is all that matters. Even if it costs 100 times the cost of PV on Earth, if it works, the price will be right. Even if it costs $1 billion per annum to produce that 1 Mwe it really doesn't matter, if it works.

Are you sure about that?  Cost is really what all this is about.  There is no doubt that a Mars mission can be mounted using either Kilopower reactors or lightweight solar arrays.  But cost per mission will be different.  This is an important metric and so are the risk and capability limitations imposed on the mission.  We could nullify the risk and capability limitations by devoting even more mass to even larger solar arrays and more mass to various means of energy storage.  But cost would increase even more.

Do you seriously believe that cost does not matter?  That would make it different from practically every space mission that we have carried out to date.  If something costs a billion dollars more than it should do, then 'as long as it works' won't be a good enough justification for not using something that also works at a fraction of the price.  The more it costs, the more likely the mission will be scrubbed and the fewer missions you will ultimately afford.  Value for money always matters.


Interested in space science, engineering and technology.

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#36 2019-10-11 13:21:15

kbd512
Moderator
Registered: 2015-01-02
Posts: 2,962

Re: Nuclear power is safe

louis wrote:

The fact you might require 100 KP Units to power propellant production on Mars is a game changer I think. Once you start to think seriously about the logistical problems involved you have to ask why bother with all those logistical difficulties when you can simply roll out some flexible PV in a few minutes.

The fact that you think thousands of rolls of solar panels will be deployed faster than 100 reactors can be placed on the surface of the ground, just like any solar panel, even if we just drop it in the dirt, despite the fact that we never do that with solar power plants for reasons you have yet to explain, is the first denial of basic physics.

louis wrote:

I think, kbd, that like many people, you read straight across from Earth to Mars - which is always a mistake.

Yet Louis comes here stating that we can just roll out solar panels on the ground on one of the most dusty planets in the solar system because someone rolled out a tiny solar panel on the ground for a day on some grass covered island here on Earth that doesn't have much in the way of dust blowing across it and twice as much insolation to work with.  That has to be one of the most deliberately obtuse things I've responded to.

louis wrote:

1.  The weather (apart from the temperature range and major dust storms) is essentially benign on Mars, unlike Earth.  On Mars there is no need for very strong structures to protect the integrity of PV panels.

Apparently, a planet with blowing abrasive dust and an atmosphere that's just shy of a vacuum, with temperatures colder than the coldest Antarctic winter, is a "benign environment".

Benign to what?

Certainly not the dead solar powered robots NASA has sent there.

Electronics and batteries die in cold environments.

Solar panels fail to produce power when they're coated with dust.

Second denial of basic physics.

louis wrote:

2.  In the absence of dust storms the amount of dust being blown about varies greatly from one location on Mars to another. There are low dust areas and the NASA criteria for landing sites favours those because of landing and launch requirements. So it's logical we will be looking to low dust areas for the Mission location.

Unfortunately, the entire surface of the planet can be shrouded in a dust storm.  We've observed this multiple times.  The solar powered rover observed it until it died from lack of power.  The nuclear powered rover never lost a single Watt of power because of that.

louis wrote:

3.  Decisions about how to construct solar farms on Earth are based mostly on economics. It makes sense on Earth to protect PV panels from extreme weather events, to ensure they have a long life, that they have reasonably high efficiencies and that their construction costs are minimised. On Mars those considerations either don't apply or are less relevant. And a Mars Mission has its own constraints or objectives e.g. trying to limit the mass of the energy solution, ensuring that the energy system can be deployed easily with minimal EVAs etc.

Yet it doesn't make sense to protect PV panels when people would quickly die if they didn't produce power?

Did you ask the people going there if dying from running out of power was relevant to them?

Solar and batteries doesn't limit the mass of the solution.  It drastically increases it.  You've provided zero math showing that it won't.  My mass estimates are based off the data and actual equipment provided by the only people who have ever sent anything to Mars on a routine basis- NASA and JPL.  SpaceX hasn't sent one single thing to Mars... ever.  NASA and JPL were sending robots to Mars before Elon Musk was born.  If they don't know, then guess who else doesn't know?

louis wrote:

4. Insolation on Mars is much more diffuse than on Earth owing to dust and its wobbly spin. Angling panels is less important on Mars than on Earth.

That's rather odd, seeing as how that statement runs directly counter to what the people who send things to Mars have to say about that.

Do you have access to data to support your assertion that they don't?

louis wrote:

5.  For Mission One on Mars, cost is hardly a consideration. Getting it right is all that matters. Even if it costs 100 times the cost of PV on Earth, if it works, the price will be right. Even if it costs $1 billion per annum to produce that 1 Mwe it really doesn't matter, if it works.

You've said repeatedly that you think nuclear power is too expensive.

Now you're saying cost isn't an issue since it applies to photovoltaics.

Which is it?

Pick one.

If cost isn't an issue for PV, then cost isn't an issue for nuclear, either.  I'm not abiding any circular logic here.

We've spent countless billions on PV development and the damn things still don't produce power in the dark and we still don't have anything remotely resembling a practical solution to energy storage.

louis wrote:

1.  Clearly that doesn't happen on Flat Holm Island where Rapid Roll has been used. Why would it happen at ALL locations on Mars. Is that your claim? That PV will stop working on Mars if you lay it flat on the ground? Any evidence, citations etc.

Maybe because Mars is a giant dust bowl, quite unlike Flat Holm Island, and we have pictures of "it" ("it" being defined as "the dust storms") happening at "ALL" ("all" being defined as every point in space located on the surface of the planet) locations on Mars?

Mars is not like Earth.  You can't "read straight across from Earth to Mars".  Remember when you wrote that?  I do.

Does it get cold enough to freeze gasoline on Flat Holm Island?

Can you still breathe the air on Flat Holm Island if the power goes out?

Can you take a stroll outside in your birthday suit on Flat Holm island?

Does Flat Holm Island routinely experience dust storms that last for weeks or months at a time?

No?  Well, then you obviously can't "read straight across from Earth to Mars".

louis wrote:

2.  You're assuming dust would be blown off rather than sucked up.  There are two options.

Sucked up by what means?  Certainly not generating a vacuum on a planet with an atmosphere that's just short of a vacuum.

louis wrote:

3.  This can be tested. If testing confirms you have a 10% degradation over two years, then increase your PV array by 10%. But I don't accept that will be the case.

It doesn't matter what you accept because it's already been tested.  It gets re-tested every time we land something there with another set of solar panels on it.  When we try the same experiment again and again, expecting a different result, we've functionally achieved the dictionary definition of insanity.

louis wrote:

4.  The Kilopower units mass 1.5 tons at least each at 10Kwe.  Nothing else is on offer in time for a Mars Mission by 2024 and even then it's extremely doubtful that KP units will be ready. If  they are you are looking at probably around 200 tons for a mission if propellant production requires 1Mwe. If you can get a PV system that masses at 1 Kg per sq. metre for about 1 Kwhe per sol then
you can beat nuclear by a large margin, even when you add in meth-ox generators, increased meth-ox production and additional chemical batteries.

Nothing will be ready to go by 2024, most certainly not this giant new rocket that SpaceX is building, never mind everything else required for Musk's ideation to become reality, so this is a non-argument.  That unimportant life support equipment to go there and back with reasonable assurance that it runs acceptably well for two years hasn't been run for two years yet.  We should probably do that first, operating under the wild and crazy assumption that we're unlikely to find many suitable volunteers (people who aren't simply bat guano crazy and willing to try anything, no matter how ill-advised) for the second mission if the first mission ends with a failure of the life support equipment.

Sure, using solar panels that don't exist, batteries that don't exist, and meth-ox generators that don't exist, you can beat nuclear power by whatever make-believe margin you've made up in your head.  Since it's all make-believe, nothing but faith matters.  We can just pull whatever numbers we need to make ourselves feel good out of our rear ends.

louis wrote:

5.  Not entirely following that with all the negatives...but if I read you right, the positive about a PV system is that a lot of the cabling can be integrated into the PV panelling. But I am not necessarily saying PV wins out on cabling...just that KP units may require a lot of cabling as well.  I have never seen a proper study about this. Most people, even academics, seem to ignore it. I seem to be one of the few people who keeps referencing it. If you had 100 KP units all located 1 Km from a base and each had a cable connection to the base then that would be 100 Kms of cabling! If it weighed 1 kg per metre it would be 100 tons.  I am not saying it will be like that - just giving that as an indication of the importance of cabling.

Whenever you read something that disagrees with what you want to believe about how well something will work, you contort it to agree with your belief system.  I couldn't help but notice that whenever real career engineers tell you there's a problem with your proposal, it gets transformed into a glowing endorsement.  Your proposal more closely resembles a religious article of faith than sound engineering practice.

With a multi-MW PV array, most of the cabling would need to be assembled / fabricated from components on the ground because there's no way to know ahead of time whether or not the terrain would permit the exact array configuration you'd like to have.  You're going to make thousands of electrical connections.  That said, an end-to-end configuration to minimize the array area and construction time also happens to be one of the worst physical array configurations to reduce wiring mass and gauges.  A central inverter with the panels all connected to it would minimize the length of the wiring runs and different gauges of wiring required, along with resistance losses.

If there's no need to run a power cable from each panel in a PV array, then there's no need to run a power cable from each reactor, either.  Do some simple math and stop making silly and lazy false assertions about issues that would apply with equal or greater force to a solar power system if there was any validity to such assertions, thereby explaining to yourself why our "academics" don't need to conduct "studies" of wiring configurations to reduce the length and mass of wiring runs.  There are tools available to do this for you online, so that you merely have to punch in the length of the wire, the voltage and amperage that wire will having running through it, and the tool will give you the minimum gauge and mass of the wire, along with resistance values.

louis wrote:

6.  I would expect the major electrical equipment to be housed in dedicated aerogel habs so don't see that as a problem. Whether PV units  themselves require some heating, I am not sure. Quite possibly, in which case that does have to be accounted for.

Why would you ever put something that must dissipate tens of kilowatts of heat through re-radiation, as a megawatt class power inverter would, at least when its in operation, into a well-insulated enclosure?

It's certainly possible to keep the electronics acceptably warm at night, but if that ever fails, even once, then you can probably junk those fancy control electronics.  Extreme heat and extreme cold, when combined with wild temperature swings, is the kiss of death for solid state electronics.

You obviously think about this stuff every day, so why not devote a little slice of your time to learn about how it works?

What could that possibly hurt?

louis wrote:

7.  Again I always work on the basis that batteries will be housed in habs - they heat up when charged don't they? So I expect there will be waste heat around that helps keep them at the desired temperature.

I always work on the basis that you never put things that are prone to exploding or catching fire from an electrical short into the same pressurized environment that your astronauts live in, unless you have another pressurized place for them to go within mere seconds that the fire can't spread to.  You won't find any space agency or private contractor that ever does this because it's such a terrible idea.  Pure O2 environments were another terrible idea that nobody does anymore, either.  All primary batteries stay outside of pressurized spaces whenever they're in operation.

louis wrote:

8. The idea that the Rapid Roll type of system couldn't be robotised seems absurd to me. We have robot warehouse pickers, robot parking of our cars, robot this and that...laying flexible solar on the Mars surface should be a doddle. With any system things can go wrong but the robotic laying of the PV will be tested thousands of times.

If rolling out a solar panel can be automated, then deployment of a fission reactor can also be automated.  Just remember that if the robot doesn't work, that means a human has to do it.  A pair of human with a hand crane can move a fission reactor or roll of solar panels.  If 100 objects are too difficult to move with those tools, then moving 1,000+ objects won't make the task any easier.

louis wrote:

9.  I accept the propellant production facility may need to be larger with a solar power energy system. But this will be marginal I think.

The components that actually produce the propellant is not where the major weight increase is coming from.  It's the power conditioning equipment that starts getting really heavy as you scale it up to handle power fluctuations measured in megawatts.  If you had an inkling of what you're asking for, you'd know this.  When the array produces 1MW of power, the power components have to handle that 1MW.  Sure, it's heavy equipment, but it's a known mass that's the same no matter what the input source happens to be; solar / wind / nuclear / hydro / doesn't matter in the slightest.  When the oversized array produces 5MW of power, the equipment must handle 5 times as much input power.  All that power has to go somewhere and the reason it has to go somewhere other than ground is because you don't get to pick and choose which days you make propellant on, assuming the goal is to bring everyone home alive after 2 years.  With a nuclear power system, that power input to the propellant plant will be the same boring value, sun up / sun down / anywhere in between / dust storm / no dust storm.

louis wrote:

10.  No I don't accept that the propellant production facility will have to shut  down every sol.  With at least 5000 Kwhes of battery power available from the Starships, before any dedicated battery system is included, I am sure the facility can be kept working day and night, just at a slower rate of production than during daylight hours.

Your battery mass will be at least 79t using existing space-rated battery technology (quite unlike the battery pack that Tesla puts in cars that can simply be abandoned as junk if it ever catches fire), assuming you're willing to trash it all after about 1,000 charge / discharge cycles (roughly two years of operation).  If you want it to last about 10 years, then roughly speaking you're looking at tripling that tonnage figure.  However, this is using accepted wear leveling practices for Lithium-ion batteries, rather than make-believe batteries that don't exist or batteries with cycle lives that don't exist.

louis wrote:

There you go with the "read across" fallacy.  Mars is not Earth and Mars Mission One is not subject to the usual commercial rules that apply on Earth.

Any operational result subject to the laws of physics and engineering must be some variant of your "read across" fallacy.

You're ideation about how this stuff works is exactly like these people who think they can shoehorn a V8 car engine, that weighs twice as much as the air cooled aircraft engine that it purports to replace, into an existing airframe by simply "declaring" an operational weight increase for the aircraft.

Did the engine mount attachment points on the airframe suddenly become capable of supporting twice as much weight just because you bolted double the engine weight up to it?

When the airframe's CG was drastically shifted by doubling the engine weight on the nose or tail of the airframe, is it still within the design CG limits for that airframe?

Will landing and aero loads on the airframe become less with twice as much engine weight?

Will a prop designed to transmit significantly more power become significantly lighter?

Was the airframe designed to handle a power increase that's likely produce level flight speeds in excess of its previous Vne?

No?

Well...  Then, in the real world, which happens to be the only world we actually live in (clearly quite different from the world in our heads), that won't work!

Why is stuff like that not painfully obvious?

Why is it not obvious that quadrupling the power input that a piece of equipment has to handle not a simple design requirement, and certainly not one that's likely to come without a significant weight increase or some other significant trade-off?

Why is it not obvious that steady and predictable power input makes it so much easier to design a reliable propellant plant?

louis wrote:

Nowhere have I suggested we defy the laws of physics. I suggest we work with the laws of physics. That's why I think it's better with the solar solution to take a larger propellant facility, rather than more battery storage. Mass is a crucial factor when you have to take it all the way to Mars through two gravity wells.

Perhaps you actually believe what you're saying, but that still doesn't change how what you're asking for will actually work in the objective world.  Your proposal is in direct opposition to very well established physics and electrical engineering principles that were empirically arrived at, meaning through gathering of evidence, not gathering of assertions.  All the engineers here with first-hand knowledge and experience seem to directly oppose your assertions.  Is it possible that they're all trying to tell you something that you don't want to hear?

louis wrote:

Any electrical engineer worth their salt is going to leap at the chance to get in the history books as the guy who designed the first electrical generation system on Mars.

All of the electrical engineers I know would refuse to design anything that they know won't work.

louis wrote:

Really? Is that the best you can do?

Small portable fission reactors are the best that we can do, given the "not-so-benign" Martian surface environment and the requirement to produce 1,100t of propellant in less than two years time using power we can guarantee rather than power we could potentially get.  I'd love to have magic solar panels and batteries, too, but we seem to be all out of those.

louis wrote:

Bridging a "gap" of maybe 10 Mwhes on Mars (if we are talking about the sort of system I propose) during maybe 80% of the sol when insolation is below the desired minimum, is not beyond our capabilities.  At 300 whs per kg that would be just over 33 tons of mass in terms of batteries. Remember nearly half of it would be required anyway for fin actuation in any case, so it is really making use of a resource that will already be there.

So what if we have 300Wh/kg batteries?

A 20% energy density improvement over the batteries we're currently using means exactly what in the grand scheme of things?

You realize that when we start talking about the energy density of batteries that we're talking about the mass of the battery itself, irrespective of any packaging or other kind of required ancillary hardware or wiring to use the individual cells, right?

The greatest mass associated with battery systems used for space flight applications is not batteries.  It's packaging.  The batteries are heavy on their own for the energy they store, but the packaging is typically at least twice the mass of the batteries.

louis wrote:

No magic wands required, just Musk-style focus, determination and innovation.

In lieu of magic wands, I'd settle for you reading a book about electrical power generation and distribution.

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#37 2019-10-11 19:06:26

louis
Member
From: UK
Registered: 2008-03-24
Posts: 4,924

Re: Nuclear power is safe

kbd512 wrote:

The fact that you think thousands of rolls of solar panels will be deployed faster than 100 reactors can be placed on the surface of the ground, just like any solar panel, even if we just drop it in the dirt, despite the fact that we never do that with solar power plants for reasons you have yet to explain, is the first denial of basic physics.

The reason we don't do it on Earth is that it could be blown away, or washed away. Another reason is that a solar farm is an economic enterprise and it makes sense to create a long-life facility, maybe 20 years or more, which then justifies the infrastructure required to protect the panels. Likewise it makes sense to aim for high efficiency, to produce high output per panel. The PV system for Mars is not an economic investment. It is simply the energy solution for Mission One. The main requirements for an energy system are reliability and failsafeness, low mass and ease of installation.

I see no reason why flexible PV on Mars can't be laid out almost as quickly as Rapid Roll on Earth.

Yet Louis comes here stating that we can just roll out solar panels on the ground on one of the most dusty planets in the solar system because someone rolled out a tiny solar panel on the ground for a day on some grass covered island here on Earth that doesn't have much in the way of dust blowing across it and twice as much insolation to work with.  That has to be one of the most deliberately obtuse things I've responded to.

We know a lot about dust levels on Mars at various locations.  Dust levels do vary a lot on Mars. One of the criteria for landing sites is low dust levels. I have always advocated robotic cleaning of the PV facility.

Apparently, a planet with blowing abrasive dust and an atmosphere that's just shy of a vacuum, with temperatures colder than the coldest Antarctic winter, is a "benign environment".

Benign to what?

Certainly not the dead solar powered robots NASA has sent there.

Electronics and batteries die in cold environments.

Solar panels fail to produce power when they're coated with dust.

Second denial of basic physics.

Benign to PV panels, which is why they have worked so well on Mars. We know electronics and batteries have survived out on the surface of Mars for 14 years.  Mission One is for two years and most batteries and electronic equipment will be accommodated in aerogel habs.

Unfortunately, the entire surface of the planet can be shrouded in a dust storm.  We've observed this multiple times.  The solar powered rover observed it until it died from lack of power.  The nuclear powered rover never lost a single Watt of power because of that.

This is accepted and accounted for in my proposals. But a dust storm does not reduced insolation to zero as nukophiles like to suggest. The solar powered robot survived six dust storms. We'll see how the nuclear power robot does.


Yet it doesn't make sense to protect PV panels when people would quickly die if they didn't produce power?

Did you ask the people going there if dying from running out of power was relevant to them?

Solar and batteries doesn't limit the mass of the solution.  It drastically increases it.  You've provided zero math showing that it won't.  My mass estimates are based off the data and actual equipment provided by the only people who have ever sent anything to Mars on a routine basis- NASA and JPL.  SpaceX hasn't sent one single thing to Mars... ever.  NASA and JPL were sending robots to Mars before Elon Musk was born.  If they don't know, then guess who else doesn't know?

It doesn't make sense to protect the PV facility from hail, rain, hurricanes and tornadoes if those things don't exist on Mars. 

So what's your tonnage for a nuclear solution based on a deliverable system, say Kilopower, rather than some fantasy reactor?

That's rather odd, seeing as how that statement runs directly counter to what the people who send things to Mars have to say about that.

Do you have access to data to support your assertion that they don't?

I didn't say angling won't increase the amount of insolation captured - I said it was less important than on Earth. You yourself said Mars is a very dusty planet. Dust diffuses sunlight. Or do you dispute that? If it's more diffuse, attempts to capture direct beam insolation will be less productive than on Earth.

You've said repeatedly that you think nuclear power is too expensive.

Now you're saying cost isn't an issue since it applies to photovoltaics.

Which is it?

Pick one.

If cost isn't an issue for PV, then cost isn't an issue for nuclear, either.  I'm not abiding any circular logic here.

We've spent countless billions on PV development and the damn things still don't produce power in the dark and we still don't have anything remotely resembling a practical solution to energy storage.

Yet again you're reading across from Earth to Mars. Nuclear power is too expensive compared with rival energy systems on Earth.
That is irrelevant as to whether it is the right energy choice for Mars. So yes, I saying cost is essentially (within reason) not a factor for the Mars Mission.

There has been some research into capturing infrared radiation on the underside of solar panels at night, so it's not impossible you could capture energy at night, but probably not worth doing.

Maybe because Mars is a giant dust bowl, quite unlike Flat Holm Island, and we have pictures of "it" ("it" being defined as "the dust storms") happening at "ALL" ("all" being defined as every point in space located on the surface of the planet) locations on Mars?

Mars is not like Earth.  You can't "read straight across from Earth to Mars".  Remember when you wrote that?  I do.

Does it get cold enough to freeze gasoline on Flat Holm Island?

Can you still breathe the air on Flat Holm Island if the power goes out?

Can you take a stroll outside in your birthday suit on Flat Holm island?

Does Flat Holm Island routinely experience dust storms that last for weeks or months at a time?

No?  Well, then you obviously can't "read straight across from Earth to Mars".

But we can test how a flexible PV system would operate on Mars in those areas which are less dusty than some others.

Sucked up by what means?  Certainly not generating a vacuum on a planet with an atmosphere that's just short of a vacuum.

Is suction really not feasible?  Well if not, then I guess blowing it will have to be. I guess you would work in the direction of prevailing winds, to reduce redistribution.  A robot travelling along a 50,000 metres array with 2 metre strips, could probably complete the job in one sol - about 25 Kms at 3 kms an hour. 

It doesn't matter what you accept because it's already been tested.  It gets re-tested every time we land something there with another set of solar panels on it.  When we try the same experiment again and again, expecting a different result, we've functionally achieved the dictionary definition of insanity.


Systems degrade at different rates but Mission One will be for two years. There is no requirement to establish a long-life array.

Nothing will be ready to go by 2024, most certainly not this giant new rocket that SpaceX is building, never mind everything else required for Musk's ideation to become reality, so this is a non-argument.  That unimportant life support equipment to go there and back with reasonable assurance that it runs acceptably well for two years hasn't been run for two years yet.  We should probably do that first, operating under the wild and crazy assumption that we're unlikely to find many suitable volunteers (people who aren't simply bat guano crazy and willing to try anything, no matter how ill-advised) for the second mission if the first mission ends with a failure of the life support equipment.

Sure, using solar panels that don't exist, batteries that don't exist, and meth-ox generators that don't exist, you can beat nuclear power by whatever make-believe margin you've made up in your head.  Since it's all make-believe, nothing but faith matters.  We can just pull whatever numbers we need to make ourselves feel good out of our rear ends.

What are you on about? Space X have already announced they will be using Tesla batteries on the Starships. Those batteries exist.

Methane generators exist and meth-ox generators have been tested.

Flexible PV exists, PV panels that have been used on Mars exist.

Whenever you read something that disagrees with what you want to believe about how well something will work, you contort it to agree with your belief system.  I couldn't help but notice that whenever real career engineers tell you there's a problem with your proposal, it gets transformed into a glowing endorsement.  Your proposal more closely resembles a religious article of faith than sound engineering practice.

With a multi-MW PV array, most of the cabling would need to be assembled / fabricated from components on the ground because there's no way to know ahead of time whether or not the terrain would permit the exact array configuration you'd like to have.  You're going to make thousands of electrical connections.  That said, an end-to-end configuration to minimize the array area and construction time also happens to be one of the worst physical array configurations to reduce wiring mass and gauges.  A central inverter with the panels all connected to it would minimize the length of the wiring runs and different gauges of wiring required, along with resistance losses.

If there's no need to run a power cable from each panel in a PV array, then there's no need to run a power cable from each reactor, either.  Do some simple math and stop making silly and lazy false assertions about issues that would apply with equal or greater force to a solar power system if there was any validity to such assertions, thereby explaining to yourself why our "academics" don't need to conduct "studies" of wiring configurations to reduce the length and mass of wiring runs.  There are tools available to do this for you online, so that you merely have to punch in the length of the wire, the voltage and amperage that wire will having running through it, and the tool will give you the minimum gauge and mass of the wire, along with resistance values.

You don't seem to understand just how detailed surveying on landing sites areas on Mars can be. Space X with help from NASA will  be able to measure the terrain with great exactitude, every bump and crack. I think you are finding objections for the sake of it now.

A 50,000 sq. metre array (223 x 223 metres) might cover an area of 223 x 350 metres. I have read proposals to site Kilopower reactors well away from the hab - but I don't know how far that would be. Which option might use most cabling is open to debate.

Why would you ever put something that must dissipate tens of kilowatts of heat through re-radiation, as a megawatt class power inverter would, at least when its in operation, into a well-insulated enclosure?

Well two reasons I can see: 1. To avoid any problems with dust contamination and 2. you might as well make use of the waste heat for other heating e.g. the rover hab, a science and tech hab.

It's certainly possible to keep the electronics acceptably warm at night, but if that ever fails, even once, then you can probably junk those fancy control electronics.  Extreme heat and extreme cold, when combined with wild temperature swings, is the kiss of death for solid state electronics.

You obviously think about this stuff every day, so why not devote a little slice of your time to learn about how it works?

What could that possibly hurt?

There hardly any point is there? Trying to second guess experts!  I would trust NASA and Space X to know how to keep electronics alive on Mars.

I always work on the basis that you never put things that are prone to exploding or catching fire from an electrical short into the same pressurized environment that your astronauts live in, unless you have another pressurized place for them to go within mere seconds that the fire can't spread to.  You won't find any space agency or private contractor that ever does this because it's such a terrible idea.  Pure O2 environments were another terrible idea that nobody does anymore, either.  All primary batteries stay outside of pressurized spaces whenever they're in operation.

I never suggested putting the batteries in the accommodation hab.  Large battery stations would have their own dedicated hab would be my suggestion. This might be a discrete part of a science and tech hab.

If rolling out a solar panel can be automated, then deployment of a fission reactor can also be automated.  Just remember that if the robot doesn't work, that means a human has to do it.  A pair of human with a hand crane can move a fission reactor or roll of solar panels.  If 100 objects are too difficult to move with those tools, then moving 1,000+ objects won't make the task any easier.

In theory, yes. But it depends what you are proposing. Are you creating berms of digging ditches for your reactor(s). I'm struggling to visualise what you are proposing. Is the Kilopower reactor going to have any packaging? How will it be handled with or without packaging. Are you proposing humans working in EVA suits? I think a roll of flexible PV could be automatically rolled off the Starship by chute onto an inflatable bed to bounce off on to the surface. Nothing like that could be attempted with a KP unit.

The components that actually produce the propellant is not where the major weight increase is coming from.  It's the power conditioning equipment that starts getting really heavy as you scale it up to handle power fluctuations measured in megawatts.  If you had an inkling of what you're asking for, you'd know this.  When the array produces 1MW of power, the power components have to handle that 1MW.  Sure, it's heavy equipment, but it's a known mass that's the same no matter what the input source happens to be; solar / wind / nuclear / hydro / doesn't matter in the slightest.  When the oversized array produces 5MW of power, the equipment must handle 5 times as much input power.  All that power has to go somewhere and the reason it has to go somewhere other than ground is because you don't get to pick and choose which days you make propellant on, assuming the goal is to bring everyone home alive after 2 years.  With a nuclear power system, that power input to the propellant plant will be the same boring value, sun up / sun down / anywhere in between / dust storm / no dust storm.

My proposal is for something like 70% of PV power to be stored in batteries. I think you might need to allow for up to 3 Mwes. That would be the limit.

Your battery mass will be at least 79t using existing space-rated battery technology (quite unlike the battery pack that Tesla puts in cars that can simply be abandoned as junk if it ever catches fire), assuming you're willing to trash it all after about 1,000 charge / discharge cycles (roughly two years of operation).  If you want it to last about 10 years, then roughly speaking you're looking at tripling that tonnage figure.  However, this is using accepted wear leveling practices for Lithium-ion batteries, rather than make-believe batteries that don't exist or batteries with cycle lives that don't exist.

Where do you get the 79 t figure from?

Everything I've read about space rated batteries is that they are giving you state of the art performance - the highest charge per kg.

Any operational result subject to the laws of physics and engineering must be some variant of your "read across" fallacy.

You're ideation about how this stuff works is exactly like these people who think they can shoehorn a V8 car engine, that weighs twice as much as the air cooled aircraft engine that it purports to replace, into an existing airframe by simply "declaring" an operational weight increase for the aircraft.

Did the engine mount attachment points on the airframe suddenly become capable of supporting twice as much weight just because you bolted double the engine weight up to it?

When the airframe's CG was drastically shifted by doubling the engine weight on the nose or tail of the airframe, is it still within the design CG limits for that airframe?

Will landing and aero loads on the airframe become less with twice as much engine weight?

Will a prop designed to transmit significantly more power become significantly lighter?

Was the airframe designed to handle a power increase that's likely produce level flight speeds in excess of its previous Vne?

No?

Well...  Then, in the real world, which happens to be the only world we actually live in (clearly quite different from the world in our heads), that won't work!

Why is stuff like that not painfully obvious?

Why is it not obvious that quadrupling the power input that a piece of equipment has to handle not a simple design requirement, and certainly not one that's likely to come without a significant weight increase or some other significant trade-off?

Why is it not obvious that steady and predictable power input makes it so much easier to design a reliable propellant plant?

Obviously steady and predictable power input is an advantage of the nuclear option. I am not denying that. Not sure how relevant the rest of your rant is!

Perhaps you actually believe what you're saying, but that still doesn't change how what you're asking for will actually work in the objective world.  Your proposal is in direct opposition to very well established physics and electrical engineering principles that were empirically arrived at, meaning through gathering of evidence, not gathering of assertions.  All the engineers here with first-hand knowledge and experience seem to directly oppose your assertions.  Is it possible that they're all trying to tell you something that you don't want to hear?

All of the electrical engineers I know would refuse to design anything that they know won't work.

What I'm getting is the feeling that some people are looking for objections, like when I used to state that you could land on Mars with retro rockets, without parachutes...people came up with all sorts of objections to that, based they claimed on physical laws, but now those objections have been quietly dropped. It was the same with slowing from hypersonic speed with a planetary pass - I was told that was physically impossible, but now that is precisely what Space X are proposing.

I presume you do accept that Space X have first rate engineers on their team.  If they opt for a solar solution will you accept it then?

Small portable fission reactors are the best that we can do, given the "not-so-benign" Martian surface environment and the requirement to produce 1,100t of propellant in less than two years time using power we can guarantee rather than power we could potentially get.  I'd love to have magic solar panels and batteries, too, but we seem to be all out of those.

And yet the pro-nuclearists here seem reluctant to admit how much they will mass.

So what if we have 300Wh/kg batteries?

A 20% energy density improvement over the batteries we're currently using means exactly what in the grand scheme of things?

You realize that when we start talking about the energy density of batteries that we're talking about the mass of the battery itself, irrespective of any packaging or other kind of required ancillary hardware or wiring to use the individual cells, right?

The greatest mass associated with battery systems used for space flight applications is not batteries.  It's packaging.  The batteries are heavy on their own for the energy they store, but the packaging is typically at least twice the mass of the batteries.

Well if that is the case then, I guess that explains your 79 t figure, but I've never come across that sort of relation between batteries and packaging before.

Batteries seemed the better option, rather than increasing the size propellant plant facility but if that is indeed the case, then it might make more sense to increase the size of the propellant plant facility.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#38 2019-10-11 22:36:49

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 84

Re: Nuclear power is safe

"The fact you might require 100 KP Units to power propellant production on Mars is a game changer I think."

Using 100 small reactors, each with their own subsystems, is not an efficient way of exploiting nuclear power.  If you want 1MWe say, them you build a 1MWe reactor.  You don't build a hundred smaller ones.


Interested in space science, engineering and technology.

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#39 2019-10-11 23:07:24

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 16,181

Re: Nuclear power is safe

The large quantity is more due to the BFR refueling requirements than actual power. I used the numbers and scaled in the other topic for insitu fuel production and its even higher for the BFR which even with 6 ships could not bring the total mass in one mars cycle and there was nothing left for the crews to survive with as that was just fuel and oxygen to breath as a surplus.
So the question was what amount of fuel is really required for an earth return from mars. Which even if we do have 2 crews and ships still means more energy than what we can do easily due to quantity of people.

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#40 2019-10-12 06:06:17

tahanson43206
Member
Registered: 2018-04-27
Posts: 1,072

Re: Nuclear power is safe

For Calliban re #38 ...

A reason to divide nuclear power into separate, independent smaller units is to dramatically improve resiliency of the system taken as a whole. 

In addition, the licensing and regulation problems you cite are likely to be even more severe as power increases.

The contributors to this discussion have (so far) not identified a potential national supplier who is positioned to offer nuclear fission devices at a price investors can afford.

The NASA sterling engine design is a working demonstration of a concept that can certainly be replicated by competent engineers. 

There is no reason to "steal" the design (as someone in this forum suggested a few days ago).  The demonstration of a workable concept should be enough for someone with the appropriate education to replicate it.

In fact (as I think about it) there is at least ONE nation which has the means, the population with appropriate education, and the incentive to replicate the NASA design in short order.

I would like to see initiatives by Canada and other Western nations along these lines as soon as possible.

(th)

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#41 2019-10-12 07:05:38

louis
Member
From: UK
Registered: 2008-03-24
Posts: 4,924

Re: Nuclear power is safe

Are you suggesting these local units be buried or on the surface?   If you are talking about the 10Kwe units, we will need in the UK something like 6,000,000 to provide the same amount of electricity as we have now from other sources. So that would be 6.5 million tons of material required, without any concrete bunkers or the like - just for the machines. I suspect big concrete bunkers or lead surrounds would be required - so it will probably end up more like 60 million tons.

tahanson43206 wrote:

For Calliban re #38 ...

A reason to divide nuclear power into separate, independent smaller units is to dramatically improve resiliency of the system taken as a whole. 

In addition, the licensing and regulation problems you cite are likely to be even more severe as power increases.

The contributors to this discussion have (so far) not identified a potential national supplier who is positioned to offer nuclear fission devices at a price investors can afford.

The NASA sterling engine design is a working demonstration of a concept that can certainly be replicated by competent engineers. 

There is no reason to "steal" the design (as someone in this forum suggested a few days ago).  The demonstration of a workable concept should be enough for someone with the appropriate education to replicate it.

In fact (as I think about it) there is at least ONE nation which has the means, the population with appropriate education, and the incentive to replicate the NASA design in short order.

I would like to see initiatives by Canada and other Western nations along these lines as soon as possible.

(th)


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#42 2019-10-12 07:20:29

louis
Member
From: UK
Registered: 2008-03-24
Posts: 4,924

Re: Nuclear power is safe

So how do you get this reactor on a Starship or are you seriously talking about building it from scratch ...How do you protect the crew from the radiation? If it's going on another Starship, how is the human passenger Starship powered?

If you are building it on the Mars surface, where does the energy for the building process come from? Do you bring all the building materials with you or do you use ISRU materials?

Who has specific plans for building a 1 Mwe reactor on Mars as part of Mission One? Anyone? I've never heard that suggested.

And just the one reactor? So, if that reactor fails or is shut down for maintenance, you have absolutely no power?

Calliban wrote:

"The fact you might require 100 KP Units to power propellant production on Mars is a game changer I think."

Using 100 small reactors, each with their own subsystems, is not an efficient way of exploiting nuclear power.  If you want 1MWe say, them you build a 1MWe reactor.  You don't build a hundred smaller ones.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#43 2019-10-12 09:15:57

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 16,181

Re: Nuclear power is safe

Connecting multiple stations of power is already being performed by the companies owning the wires to every home world wide in the form of the electrical grid. Its not as rodundant that we would have on mars but its the same concepts for power distribution and load control for the utilities which generate the power.
The size of the kw units make for the ability to power a small group of homes without interuption to the grid and if there is excess the grid takes it in for others to make use of in net metering.

For starship crew what is the power required for a flight to make life comfortable and still provide for active cooling of propellant for the journey. If its 1 or 2 units then we alter the construction to provide room for them further away from crew with a shield plate between them and the system as is done even on submarines. The heat pipe radiators can be added to the outer wall as is being done on the service module for Orion. These are behind panels on the way up and once on orbit these are jetisoned so the units can move to a fin mode away from the ships same as a solar panel would be.

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#44 2019-10-12 10:44:46

tahanson43206
Member
Registered: 2018-04-27
Posts: 1,072

Re: Nuclear power is safe

For SpaceNut re #43

Thanks for helping Louis with this observation << grin >>

The situation faced by Californians right now is on my mind, because I have relatives and friends who live there.

If there were an entity within the United States that ** might ** have the clout to overcome resistance to multiple small nuclear fission reactors, it ** might ** be California.

The inability of a single large utility to safely deliver power throughout a region as large as California should be instructive to those who are entrusted with responsibility for delivery of utilities to citizens.

A cluster of small reactors in a secure community facility would (should) be capable of serving the needs of a community, and (with proper planning) the used fuel should be easier to manage than the waste from larger facilities.

There may be a sweet spot in sizing, between the minimal/demonstration system designed and tested by NASA, and a practical version that would be mass produced for the California market, never forgetting for a minute the need for security with live personnel at each and every power site.

The "live personnel" positions could be made attractive, by requiring a minimum of a masters degree in nuclear engineering, as well as mastery of security procedures including live action scenario training.  The positions could be made even ** more ** valuable to the community as a whole, if the position holders were expected to teach a senior level course on engineering at the local high school.

(th)

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#45 2019-10-12 12:29:49

louis
Member
From: UK
Registered: 2008-03-24
Posts: 4,924

Re: Nuclear power is safe

The point about domestic reactors, leaving aside the very real terrorist threat for one moment, is whether they have to be buried or on the surface. If they are going to be buried in tons of concrete I really can't seem them ever being economic. Think of the manufacturing costs, the maintenance costs, the construction costs...and meanwhile you are maintaining a grid that isn't going to be used except for maybe 0.001% of the time when a KP unit fails. Sounds like madness to me.

I'm getting different stores from the nukists here. Some say "Don't be ridiculous, you've never activate a KP unit on a Starship! It will be activated on the surface of Mars. " but then there are others, like yourself who say "No problem, fire it up on the Starship." How heavy would this plate have to be? Surely you 'd have to shield it entirely, otherwise the Starship steel itself would become radioactive, and a hazard to humans...and what about the rest of the cargo?

Fin actuation I'm guessing might take 200 Kwe, so you'd need at least 20 Kilopower units on board for that. 

SpaceNut wrote:

Connecting multiple stations of power is already being performed by the companies owning the wires to every home world wide in the form of the electrical grid. Its not as rodundant that we would have on mars but its the same concepts for power distribution and load control for the utilities which generate the power.
The size of the kw units make for the ability to power a small group of homes without interuption to the grid and if there is excess the grid takes it in for others to make use of in net metering.

For starship crew what is the power required for a flight to make life comfortable and still provide for active cooling of propellant for the journey. If its 1 or 2 units then we alter the construction to provide room for them further away from crew with a shield plate between them and the system as is done even on submarines. The heat pipe radiators can be added to the outer wall as is being done on the service module for Orion. These are behind panels on the way up and once on orbit these are jetisoned so the units can move to a fin mode away from the ships same as a solar panel would be.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#46 2019-10-12 14:30:52

kbd512
Moderator
Registered: 2015-01-02
Posts: 2,962

Re: Nuclear power is safe

louis wrote:

The reason we don't do it on Earth is that it could be blown away, or washed away. Another reason is that a solar farm is an economic enterprise and it makes sense to create a long-life facility, maybe 20 years or more, which then justifies the infrastructure required to protect the panels. Likewise it makes sense to aim for high efficiency, to produce high output per panel. The PV system for Mars is not an economic investment. It is simply the energy solution for Mission One. The main requirements for an energy system are reliability and failsafeness, low mass and ease of installation.

You mean we couldn't just put tent stakes through the corners of the things, the way we do with nylon tents that somehow survive gale force winds in the mountains, and stake it to the ground in the middle of a desert?

It doesn't have anything to do with the fact that if we laid a solar panel on the ground, it'd get dirty or dusty and stop producing power?

louis wrote:

I see no reason why flexible PV on Mars can't be laid out almost as quickly as Rapid Roll on Earth.

So an array that produces megawatts of power is going to be unfurled and connected in mere minutes, no matter the terrain?

If it was so easy and fast to do this, then why not just use these panels here on Earth and roll them up and store them during storms?

louis wrote:

We know a lot about dust levels on Mars at various locations.  Dust levels do vary a lot on Mars. One of the criteria for landing sites is low dust levels. I have always advocated robotic cleaning of the PV facility.

They do, but if the places where there's very little dust are also very far away from a good water source, then what?

louis wrote:

Benign to PV panels, which is why they have worked so well on Mars. We know electronics and batteries have survived out on the surface of Mars for 14 years.  Mission One is for two years and most batteries and electronic equipment will be accommodated in aerogel habs.

Was there anything functionally wrong with the solar panel, apart from the fact that it was covered in dust that reduced useful power to zero (which would be why the battery drained and the rover died)?

louis wrote:

This is accepted and accounted for in my proposals. But a dust storm does not reduced insolation to zero as nukophiles like to suggest. The solar powered robot survived six dust storms. We'll see how the nuclear power robot does.

I've never stated that the insolation levels will drop to zero.  I've stated repeatedly that equipment that has to deal with insane power fluctuations of multiple megawatts is neither easy to design nor likely to be long-lived.  It's also unlikely to be as efficient as it otherwise could be if it had constant input power.

What's the state of development for all this equipment intended to account for the environment?

Can you point to any progress beyond PowerPoint presentations?

Is SpaceX really afraid that someone will steal their technology and "beat them" to Mars?

It's so super-secret, that nobody's even bothered to file any patents, right?

louis wrote:

It doesn't make sense to protect the PV facility from hail, rain, hurricanes and tornadoes if those things don't exist on Mars.

Nobody here even brought up any of that except you.  The stuff we send into space doesn't deal with things that can't and don't happen in space.  I've talked about environments with abrasive blowing dust scratching plastic and the effects of mildly cryogenic temperatures on electronics without proper heat sources to protect them.

Are we really going to sit here and pretend that that's not exactly what happens when we see it here on Earth and places like the moon and Mars?

louis wrote:

So what's your tonnage for a nuclear solution based on a deliverable system, say Kilopower, rather than some fantasy reactor?

Well, it's incredibly likely that they're going to weigh 1,500kg each, which would be the mass of a functional reactor with top shielding intended to reduce radiation levels received by the electric generators.

Why is that so incredibly likely?

There are computer programs that can tell you exactly what a block of metal of a given alloy with a given set of dimensions will weigh.  KP is very nearly 100% metal of various alloys with well known mechanical properties, which includes mass.  That's why the design team is so sure about what it will weigh.  The only thing they're still playing with are the diameter of the heat pipes (3/8" vs 1/2" heat pipes for every possible variant of KP, presuming that nobody is interested in reactors producing less than 1kWe output levels) and the brands of Stirling engines used (Qnergy / Qinetiq / etc).  None of those tweaks represents a substantial change in mass.  IIRC, NASA and LANL are using ANSYS for design.  That software can tell you exactly what a block of a particular type of alloy weighs, and yes, it's exceptionally accurate.

That's rather odd, seeing as how that statement runs directly counter to what the people who send things to Mars have to say about that.

Do you have access to data to support your assertion that they don't?

louis wrote:

I didn't say angling won't increase the amount of insolation captured - I said it was less important than on Earth. You yourself said Mars is a very dusty planet. Dust diffuses sunlight. Or do you dispute that? If it's more diffuse, attempts to capture direct beam insolation will be less productive than on Earth.

So far as I'm aware, all photovoltaics produce the greatest amount of output via direct beam power from the Sun.  Sure, they can still produce power from diffuse sunlight, but it's certainly not optimal.  Every piece of scientific literature I've ever read states that unequivocally.

louis wrote:

Yet again you're reading across from Earth to Mars. Nuclear power is too expensive compared with rival energy systems on Earth. That is irrelevant as to whether it is the right energy choice for Mars. So yes, I saying cost is essentially (within reason) not a factor for the Mars Mission.

Nuclear power has been made artificially expensive for purposes that having nothing to do with the viability of the technology.

If solar and wind power were ever required to be as pharmaceutically grade "clean" as nuclear power plants, there wouldn't be any solar or wind farms.  They consume obscene amounts of resources for the meager output they provide and despite the fact that the market for them is growing, we keeping pumping out CO2 at an astronomical rate.  You know something, bubba, you can win every battle and still lose the war.

What's the cost associated with not having power available?

louis wrote:

There has been some research into capturing infrared radiation on the underside of solar panels at night, so it's not impossible you could capture energy at night, but probably not worth doing.

Sure, and it does work, just not well enough to be terribly useful, as you've already noted.

louis wrote:

Is suction really not feasible?  Well if not, then I guess blowing it will have to be. I guess you would work in the direction of prevailing winds, to reduce redistribution.  A robot travelling along a 50,000 metres array with 2 metre strips, could probably complete the job in one sol - about 25 Kms at 3 kms an hour.

How much power are you willing to devote to creating the proper amount of suction?

louis wrote:

Systems degrade at different rates but Mission One will be for two years. There is no requirement to establish a long-life array.

So the next mission will require more solar panels?  And the one after that?

Are you beginning to understand at all why it's not really a feasible solution?

If we can't bring our people back in 2 or even 4 years because we didn't get enough power, then what?

Leave them there to die?

louis wrote:

What are you on about? Space X have already announced they will be using Tesla batteries on the Starships. Those batteries exist.

I'm "on about" the fact that NONE of the required supporting technologies have been properly test AT ALL.

Do space-rated versions of the battery packs exist?

We already have those cells in space in every laptop aboard ISS, but we don't use them as primary power yet.

Why is that?

Packaging, maybe?

louis wrote:

Methane generators exist and meth-ox generators have been tested.

Then post a link to a space-rated Methalox generator, not some natural gas home backup generator that we all know is never going into space.

louis wrote:

Flexible PV exists, PV panels that have been used on Mars exist.

True.

louis wrote:

You don't seem to understand just how detailed surveying on landing sites areas on Mars can be. Space X with help from NASA will  be able to measure the terrain with great exactitude, every bump and crack. I think you are finding objections for the sake of it now.

No, Louis, I'm pointing out the fact that you don't always get to choose the precise spot where you'd like to set up shop.  NASA doesn't have a landing system with the precision you think we'll have and they're the only ones who send things to Mars every 5 to 10 years.  There's no SpaceX anything that's been to Mars one silly time, so there's no landing beacons, no GPS, no nothing but inertial guidance and terrain maps, which really aren't a good substitute for making sure you're in position before you smack into the atmosphere at hypersonic velocity.

louis wrote:

A 50,000 sq. metre array (223 x 223 metres) might cover an area of 223 x 350 metres. I have read proposals to site Kilopower reactors well away from the hab - but I don't know how far that would be. Which option might use most cabling is open to debate.

The KP team's plan has been to put the reactors between 1km and 2km away from the hab in a worst case deployment scenario (you land on a plain that's as flat as a pancake for as far as the eye can see).  If there's a mound of regolith between the reactors and the habitat, then they can be a lot closer, meaning just over a hill.  Some of us also want to use the solar panels, reactors, or whatever for more than one lousy mission.  SpaceX is also big on reusability because it drastically reduces ongoing operational costs.

louis wrote:

Well two reasons I can see: 1. To avoid any problems with dust contamination and 2. you might as well make use of the waste heat for other heating e.g. the rover hab, a science and tech hab.

Well, the inverters will most likely be encased in Aluminum heat sinks which would eliminate any dust issues, as the ones aboard ISS are, and the Aluminum is required to radiate heat away from the power conversion electronics and electrical components.  I guess if you could convert enough of the waste heat to electricity then that would be worth doing, but those devices are generally horribly inefficient.  It'll be generating heat during the day, though, when you really need to get rid of whatever you can't use.  Maybe we could use it to heat water for later use or perhaps supply heat to the Sabatier reactor?  Maybe.  If it could stay "hot" or at least "warm" 24/7, that'd be really beneficial to the life of the inverter.  Power electronics deal with staying warm or even hot (to a point) a whole lot better than they do with daily thermal cycling.

louis wrote:

There hardly any point is there? Trying to second guess experts!  I would trust NASA and Space X to know how to keep electronics alive on Mars.

The "experts" are testing new fission reactors because those electronics still need power whether or not the Sun is up, down, or sideways, precisely because they'd like their electronics to live long enough to do as much useful work as possible.

louis wrote:

I never suggested putting the batteries in the accommodation hab.  Large battery stations would have their own dedicated hab would be my suggestion. This might be a discrete part of a science and tech hab.

Are we just talking about a tent of some kind or a full-blown pressurized "battery habitat"?

If it's the former, why bother?

If it's the latter, how much extra packaging mass are you trying to add to the batteries?

louis wrote:

In theory, yes. But it depends what you are proposing. Are you creating berms of digging ditches for your reactor(s). I'm struggling to visualise what you are proposing. Is the Kilopower reactor going to have any packaging? How will it be handled with or without packaging. Are you proposing humans working in EVA suits? I think a roll of flexible PV could be automatically rolled off the Starship by chute onto an inflatable bed to bounce off on to the surface. Nothing like that could be attempted with a KP unit.

I imagine that the reactors would be partially disassembled for shipping, meaning the Aluminum alloy radiators and Beryllium Oxide reflectors would be removed for launch.  Reflector removal precludes the possibility of the reactor "going critical", no matter what.  There's a significant amount of mass in those components, so that's make it easier to transport them to the surface.  The cores would most likely be bolted to the floor of the cargo deck.  Taken together, the mass of the top shielding / reflector / core / aluminum radiator panels represent roughly 200kg loads on Mars.  The radiator panels are light enough to move by hand, but the rest of the components require small hand cranes to move around the cargo bay, essentially being equivalent in weight (on Mars) to all-Aluminum LS type V8 engines.  After landing, the cores would be unbolted and transported to the cargo hatch using hand cranes or hoists, no different than moving an engine in a garage.  From there, a winch would lower the reactors to the surface using a system of ropes and pulleys.  It's not "high tech" because it doesn't need to be.

Once on the ground, a small rover would take each reactor to an emplacement site, located up to 2km away in a worst case scenario or just over a hill in a best case scenario.  After that, a hole .5m in diameter and 1.5m in depth would be bored into the regolith.  If you're able to drill to a depth of 3m, then you could put the reactors much closer to the habitat.  As a function of the mass of material between you and the reactor, you have to get pretty close to the reactors if they're 3m below ground before radiation becomes an issue, even with constant exposure.  The 0.5m x 1.5m bore hole is essentially a post hole, no different than the kind I've dug by hand with a pick axe and post hole digger through Texas limestone in two hours or less.  That said, we're going to use an electric drill to speed up the process.  The electric drills can chew through rock in a matter of minutes.  If we can't drill to at least 3m, then we're obviously not assured of getting any water which may be found much deeper than that.

Each emplacement site would contain multiple reactors.  If we did exactly what you previously brought up as a potential problem and ran Aluminum utility wire (1350-H19 aluminum conductor / core with PE insulation; 44lbs per 1,000ft; 29,040lbs per 660,000ft / 200km) with more than double the Ampacity rating (600V and up to 108A) of what each reactor's Stirling engines could actually produce, then each 2km long power cable would weigh 290.4lbs / 132kg, for a total of 13.2t of wiring for 100 reactors.  Assuming cost is not an issue, we'll substitute conventional PE insulation for the aircraft-rated / space-rated CNT tape insulation used in military aircraft and satellites, saving approximately 70% of the insulation mass, or 13.3 pounds per 1,000ft of wiring / 92.1kg per 2km, which would bring our wiring mass down to 20,262lbs / 9.21t.

That's certainly not ideal from a mass perspective, as we could likely economize on wiring mass and runs through the use of step-up and step-down transformers, but it would certainly work, it's stupidly simple, and would weigh no more than an insulated tank holding 12t of LCH4 that you planned on taking, once again completely ignoring the 43t of LOX required to actually burn 12t of LCH4 and the cryocooler power requirements to keep both cryogens cold at all times to prevent boil off.

Dropping any sort of power generation equipment from 50m in the air is, quite frankly, pretty dumb.  The slide idea could certainly work for lighter cargo, but I'd counter with the fact that synthetic rope is much easier to work, likely to be significantly lighter, requires no inflation if using inflatables or erection if using fabric and trusses, and has lots of other uses for movement of cargo on the ground.  Therefore, I'm assuming all rolls of thin film panels and all reactors will be hand-craned off the ship using hand cranes, pulleys or winches, and synthetic rope under direct human control.  Each item of cargo will use some form of inflatable jacket surrounding it for protection, not of the cargo itself, but of the Starship's delicate heat shield.

louis wrote:

My proposal is for something like 70% of PV power to be stored in batteries. I think you might need to allow for up to 3 Mwes. That would be the limit.

Storing 70% of daily production would likely result in batteries that weigh as much as the payload allocation for a single Starship.

louis wrote:

Where do you get the 79 t figure from?

Actual Lithium-ion battery packs that are actually providing power to ISS as I write this.

louis wrote:

Everything I've read about space rated batteries is that they are giving you state of the art performance - the highest charge per kg.

Again, packaging.  Lithium-ion batteries in motor vehicles have liquid cooling systems that don't reject heat through radiation.  Remember your favorite "read across" fallacy?  You're not going to regulate temperature in a near vacuum by running a fan blowing across a heat exchanger.

louis wrote:

Obviously steady and predictable power input is an advantage of the nuclear option. I am not denying that. Not sure how relevant the rest of your rant is!

Is it, though?

Because what I keep reading from you exactly sounds like what I've heard from people who think they're going to put much heavier car engines in aircraft without any modifications and SOMEHOW the entire rest of that flying system that we call an "airplane" is just supposed to accept those drastic changes without any other changes.

louis wrote:

What I'm getting is the feeling that some people are looking for objections, like when I used to state that you could land on Mars with retro rockets, without parachutes...people came up with all sorts of objections to that, based they claimed on physical laws, but now those objections have been quietly dropped. It was the same with slowing from hypersonic speed with a planetary pass - I was told that was physically impossible, but now that is precisely what Space X are proposing.

I get the feeling that you've done zero / zip / zilch / nada in the way of math to determine how well what you're proposing would work in practice.  Since Elon Musk said it, it must be true.  Smooth sailing from here on out.  Good grief, man.

louis wrote:

I presume you do accept that Space X have first rate engineers on their team.  If they opt for a solar solution will you accept it then?

If someone from SpaceX actually designs / builds / tests a megawatt-class solar / battery power system (or even just a sub-scale system to demonstrate the feasibility of the concept) that runs for 2 years in temperatures colder than any encountered on Earth and in an abrasive blowing dust environment, without major issues, then yes, I'll accept that.  I've seen zero / zip / zilch / nada in the "actual evidence" department to support that idea (meaning the idea that someone is actually working on this problem).  If you have any actual evidence of that, beyond someone making a PowerPoint to a group of cheerleaders who know nothing about space flight or power engineering, then please post it here so everyone else can benefit.

louis wrote:

And yet the pro-nuclearists here seem reluctant to admit how much they will mass.

I keep giving you masses for equipment used by NASA, their contractors, and industry.  You keep bloviating about not getting real numbers.

Post the mass of an actual solar power system, something that works in space rather than Flat Holm Island, and then we'll go from there.  Since I've already provided that information, which I took directly from NTRS, you shouldn't have to look anywhere else on the internet other than this forum to find it.  I didn't make anything up for sake of argument.  I took the data they provided, a pocket calculator, and started running numbers on masses and sizes using the best case scenario for solar power (the all-time record output achieved to date).

louis wrote:

Well if that is the case then, I guess that explains your 79 t figure, but I've never come across that sort of relation between batteries and packaging before.

I'd love to "turn a corner" in space-rated battery systems using advanced materials to reduce the mass of the packaging, which I would agree is horrendous.  NASA has done far more work on this than any other entity, to include SpaceX and Tesla.  If it were up to me, I'd take all the technology advancements from the Orion program and transplant them into the Starship program so that SpaceX doesn't have to design absolutely everything from scratch.  The friction stir weld tools would be at SpaceX's disposal, for example.

louis wrote:

Batteries seemed the better option, rather than increasing the size propellant plant facility but if that is indeed the case, then it might make more sense to increase the size of the propellant plant facility.

It's possible to use batteries to buffer power input, provided you have sufficient capacity.  The disadvantage is obviously the weight increase of the batteries.  Charge or discharge them too quickly and bad things happen.  It's not even the power transients that concern me so much, it's the fact that you have to increase the capacity of everything by half an order of magnitude to cover the fact that you don't get to pick and choose when you make propellant.  If power is available, then you have to use it.  I'm not telling you it's utterly impossible to do.  I'm telling you that it's not practical to do for a reasonable weight and complexity penalty.

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#47 2019-10-12 15:16:08

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 16,181

Re: Nuclear power is safe

Keep in mind the size and scale are not the same so the numbers in it will not be as well as the reactor type is not of the same type.

https://science.howstuffworks.com/nucle … arine5.htm
https://fas.org/man/dod-101/sys/ship/eng/reactor.html

rx5.gif

stmplt1.jpg

warning 800 pages
https://www.nrc.gov/docs/ML1000/ML100070680.pdf
Reactor shielding for nuclear engineers

494 page count
https://www.energy.gov/sites/prod/files … mplete.pdf

https://fas.org/nuke/space/krusty.pdf
pg 9 table has the kg mass for shielding and material make up
Shielding mass goes down with power output

http://anstd.ans.org/NETS-2019-Papers/T … t-96-0.pdf
radiator is a titainium water heat pipe

https://www.sciencedirect.com/science/a … 3318309355
Thermal-hydraulic analysis of a new conceptual heat pipe cooled small nuclear reactor system

https://deepblue.lib.umich.edu/bitstrea … sAllowed=y
Low Power Thermal Reactor for Deep Space Probes

https://beyondnerva.com/2017/11/19/krus … r-part-ii/

https://space.stackexchange.com/questio … -shielding

http://fiso.spiritastro.net/telecon16-1 … 2-1-17.pdf
Kilopower: Small Fission Power Systems for Mars and Beyond

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#48 2019-10-12 16:31:45

kbd512
Moderator
Registered: 2015-01-02
Posts: 2,962

Re: Nuclear power is safe

SpaceNut,

Yes, this is what people think of when they think of nuclear reactors.  It's also nothing at all like Kilopower (KP).

KP is a liquid Sodium metal heat-pipe cooled ("cooled" being something of a misnomer here since it requires no cooling apart from natural thermal radiation to remain at its equilibrium temperature at "full power", meaning the control rod is completely removed and only thermal radiation is actively "cooling" the reactor) reactor regulated using a single control rod located in the center of the reactor.  The core consists of a single solid chunk of cast Uranium metal alloy, with holes in it for the heat pipes to take thermal power off of the reactor for conversion to electrical power, surrounded by a larger and heavier chunk of Beryllium Oxide to reflect enough neutrons to "go critical" / cause the Uranium to start fissioning.  The "fuel" is a cylinder of Uranium-Molybdenum alloy that's nowhere close to melting if you turned it on and completely removed the thermal power transfer equipment.  If you did remove the power transfer equipment (Sodium filled stainless steel heat pipes / Aluminum radiators / Stirling engines ), then it would stay at an equilibrium temperature of 800C.

That act of "heating up" much past its equilibrium temperature causes thermal power output to drop, which is why you need the Stirling engines and heat pipes to consume the thermal power, turn it into electricity, and radiate the excess thermal power into space.  That is what the KP design team means by "self-regulating".  If you completely remove the thermal power transfer equipment while the reactor is operating at full power, then the temperature briefly spikes to a temperature that's still below the melting point of the UMo alloy and then it returns to its 800C equilibrium temperature because the temperature increase causes the fuel to swell, with an attendant reduction in neutron activity (less fissioning).  That was derived through actual testing (intentionally trying to kill the thing), not someone "supposing" that that's what would happen.  KP's surface area to volume ratio is so high that it can't "melt down" in the same way that reactors with much higher power densities do.  Similarly, without the reflector in place, there's also insufficient neutron activity to "go critical", no matter where the control rod happens to be.

Before KP is turned on for the first time, there's something like 3 orders of magnitude less radiation than the radiation produced by a RTG, meaning KP is much less of a potential radiological hazard to handle in comparison to Pu238 fueled RTG's.  The KP unit is also at room temperature before it's turned on, unlike a RTG, so there's less potential for thermal burns at that point.

A lot of this stuff is contained in the documentation and testing reports, but I doubt many people are actually reading those.

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#49 2019-10-12 17:58:54

louis
Member
From: UK
Registered: 2008-03-24
Posts: 4,924

Re: Nuclear power is safe

You mean we couldn't just put tent stakes through the corners of the things, the way we do with nylon tents that somehow survive gale force winds in the mountains, and stake it to the ground in the middle of a desert?

It doesn't have anything to do with the fact that if we laid a solar panel on the ground, it'd get dirty or dusty and stop producing power?

I'd like to see your nylon tent with pegs last 20 years' worth of rain storms, lightning, floods, high winds, tornadoes and all the rest. I would be happy to test a ground PV system in Mars like conditions, subject to a robot rover cleaner going up and down the PV strips once a day. It would be v. interesting to see what the result was. It would have to be Mars analogue conditions. I am not convinced that the reduction in power compared with a conventional PV panel on Earth would be that bad. I base that on the low power of wind on Mars. The reason dust storms occur is because in the summer season sometimes the wind force becomes strong enough to kick up fine particles of dust. But apart from those situations, the ground on Mars seems to be v. settled, judging by photos taken a few sols apart.
So, I think if we have robot cleaners around, dust accumulation will be pretty minimal.

So an array that produces megawatts of power is going to be unfurled and connected in mere minutes, no matter the terrain?

If it was so easy and fast to do this, then why not just use these panels here on Earth and roll them up and store them during storms?

No of course not. I gave an estimate originally for how long it would take to unroll flexible PV on Mars. Can't recall what I arrived at but Rapid Roll claim they lay 11 kw (presumably max capacity) in 2 mins. I think on that basis it would take a few sols, maybe 3 or more. But feel free to assume10 sols. That's no problem at all.

I don't think the terrain will be a big issue. The terrain will be fairly flat. The robot rover might well be moving more slowly than a big tractor on Earth.

They do, but if the places where there's very little dust are also very far away from a good water source, then what?

I think NASA has already identified potential landing sites on Mars which meet both criteria in Accidia Planitia/Amazonis Planitia

Was there anything functionally wrong with the solar panel, apart from the fact that it was covered in dust that reduced useful power to zero (which would be why the battery drained and the rover died)?

You seem determined to ignore the fact it survived for 50 plus more times than its planned life! If so, I can't help you.

I've never stated that the insolation levels will drop to zero.  I've stated repeatedly that equipment that has to deal with insane power fluctuations of multiple megawatts is neither easy to design nor likely to be long-lived.  It's also unlikely to be as efficient as it otherwise could be if it had constant input power.

What's the state of development for all this equipment intended to account for the environment?

Can you point to any progress beyond PowerPoint presentations?

Is SpaceX really afraid that someone will steal their technology and "beat them" to Mars?

It's so super-secret, that nobody's even bothered to file any patents, right?

I accept you have not suggested that insolation levels will drop to zero but other pro-nukers here have.  But what do you think insolation drops to in a worst case dust storm scenario. Again, the nuke community seem reluctant to discuss that. From my researches it seems that a figure of around 36% is the lowest. And that seems to translate (with extra dust accumulation in dust storms) to a figure of around 20% as the lowest for actual PV generation as a % of the norm.  I have never seen any records to suggest that such low points last longer than a few sols. I think that's because dust storms are self-regulating - whilst initially they act like a heat trap, beyond a certain point they being to reduce the atmospheric temperature and so the storm subsides.

I am not suggesting megawatt fluctuations in power input as I am proposing a v. large amount of battery storage.

Nobody here even brought up any of that except you.  The stuff we send into space doesn't deal with things that can't and don't happen in space.  I've talked about environments with abrasive blowing dust scratching plastic and the effects of mildly cryogenic temperatures on electronics without proper heat sources to protect them.

Are we really going to sit here and pretend that that's not exactly what happens when we see it here on Earth and places like the moon and Mars?

Well quite...but it may not have been you but pro-nuclearists here have referenced how long it takes to create a solar farm on Earth as an indication of how long it would take on Mars. Even if we didn't use ground flexible PV we could string it on wires on Mars due to the benign weather.

Abrasion did not seem to greatly affect the performance of the solar powered rover over 14 years. The dust on Mars would feel soft to the touch - so not like bits of gravel being thrown about as on Earth.

Well, it's incredibly likely that they're going to weigh 1,500kg each, which would be the mass of a functional reactor with top shielding intended to reduce radiation levels received by the electric generators.

Why is that so incredibly likely?

There are computer programs that can tell you exactly what a block of metal of a given alloy with a given set of dimensions will weigh.  KP is very nearly 100% metal of various alloys with well known mechanical properties, which includes mass.  That's why the design team is so sure about what it will weigh.  The only thing they're still playing with are the diameter of the heat pipes (3/8" vs 1/2" heat pipes for every possible variant of KP, presuming that nobody is interested in reactors producing less than 1kWe output levels) and the brands of Stirling engines used (Qnergy / Qinetiq / etc).  None of those tweaks represents a substantial change in mass.  IIRC, NASA and LANL are using ANSYS for design.  That software can tell you exactly what a block of a particular type of alloy weighs, and yes, it's exceptionally accurate.

That's rather odd, seeing as how that statement runs directly counter to what the people who send things to Mars have to say about that.

Do you have access to data to support your assertion that they don't?

I don't really follow your argument there.  As far as I can see we agree they will weigh a minimum of 1.5 tons per 10 Kwe.  But those are not units that would allow humans to work in close proximity. If I am wrong on that, let me know.

So far as I'm aware, all photovoltaics produce the greatest amount of output via direct beam power from the Sun.  Sure, they can still produce power from diffuse sunlight, but it's certainly not optimal.  Every piece of scientific literature I've ever read states that unequivocally.

So far as I am aware, a photon is a photon.  Yes, direct beam insolation will always be best if you have the right angle, but (assuming two planets A and B at the same distance from a star) if there is less direct beam insolation on Planet A than Planet B then, all else being equal,  clearly the productivity of equipment designed to maximise direct beam capture will be less on Planet A than on Planet B.  That means that simply laying PV on the ground will be less detrimental to electricity production on Planet A than would have been the case if there was as much direct beam insolation as on Planet B.

Nuclear power has been made artificially expensive for purposes that having nothing to do with the viability of the technology.

If solar and wind power were ever required to be as pharmaceutically grade "clean" as nuclear power plants, there wouldn't be any solar or wind farms.  They consume obscene amounts of resources for the meager output they provide and despite the fact that the market for them is growing, we keeping pumping out CO2 at an astronomical rate.  You know something, bubba, you can win every battle and still lose the war.

What's the cost associated with not having power available?

Well as I have said elsewhere, no nuclear facility anywhere on the planet could get private insurance against third party claims on the open market. The verdict of the open market is normally pretty sound.  That suggests to me that nuclear power has not been discriminated against but mightily indulged ie in every country where it is allowed to operate it does so with a state guarantee to pick up the tab if things go wrong (as we see in Japan where it is the state picking up the tab for all the homeless people and loss of agricultural and other production).

Anyway we shouldn't read across between the two planets! I have never said that nuclear power could not be used on Mars Mission One.
I have said it is not as good an option as solar.

Sure, and it does work, just not well enough to be terribly useful, as you've already noted.

Well there you go, we can agree!  Infrared PV panels are unlikely to be much help on Mars.

How much power are you willing to devote to creating the proper amount of suction?

I'm a pragmatist. If suction uses too much power, use blowing. Have the PV rolls laid out one against the other then a metre gap for the rover to pass down. It could have angled blowers on either side blowing the dust accumulation forward of the rover which would then scoop up most of the dust using a mechanical system, rather than suction. Once full, the rover could deposit the rover could deposit the dust in a dedicated bin which would be periodically transported out of the location and deposited e.g. in a small crater.

So the next mission will require more solar panels?  And the one after that?

Are you beginning to understand at all why it's not really a feasible solution?

If we can't bring our people back in 2 or even 4 years because we didn't get enough power, then what?

Leave them there to die?

I am giving you the minimum requirement for Mission One. Of course, if only for failsafeness you are going to design them to last 4 years, I would suggest.

I certainly don't think we should be trying to design a long life PV system for Mission One. Mission One is all about establishing the base.

Mission Two will have habs and rovers available. So Mission Two, assuming it was also a six Starship mission,  will have more room available for other cargo.  I would certainly be looking to taking more PV and longer-life PV at that. Energy is the basis of human survival on Mars, so it is a priority A cargo. I am fairly confident that within a decade we could be looking at shipping out automated PV panel manufacturing equipment to utilise ISRU materials in making PV panels. More than that, within a few years after the Mars Community will be able to 3D print, using Mars ISRU materials, the PV panel manufacturing equipment itself. That will essentially make Mars energy-independent.

I'm "on about" the fact that NONE of the required supporting technologies have been properly test AT ALL.

Do space-rated versions of the battery packs exist?

We already have those cells in space in every laptop aboard ISS, but we don't use them as primary power yet.

Why is that?

Packaging, maybe?

I accept this is not verified yet.  This requires further investigation. I am a bit puzzled by your use of "space rated". What does that mean?  Does it mean a battery pack operating in a space vacuum? Well if so, that's not necessarily what we are talking about with the Tesla batteries.

Then post a link to a space-rated Methalox generator, not some natural gas home backup generator that we all know is never going into space.

Again, I need to know what you mean by "space-rated". If you mean "floating in space by itself" then that is not what I mean. I am talking about a methox generator on the Mars surface in a pressurised hab.


No, Louis, I'm pointing out the fact that you don't always get to choose the precise spot where you'd like to set up shop.  NASA doesn't have a landing system with the precision you think we'll have and they're the only ones who send things to Mars every 5 to 10 years.  There's no SpaceX anything that's been to Mars one silly time, so there's no landing beacons, no GPS, no nothing but inertial guidance and terrain maps, which really aren't a good substitute for making sure you're in position before you smack into the atmosphere at hypersonic velocity.

Well when the human passenger Starship comes in there will be Starships with radio beacons already landed and the HP Starship will be able to get a lock on a precise landing position from them. I don't think it's just inertial guidance and terrain maps. I think it's laser guidance systems and Mars statellite coms as well.

The KP team's plan has been to put the reactors between 1km and 2km away from the hab in a worst case deployment scenario (you land on a plain that's as flat as a pancake for as far as the eye can see).  If there's a mound of regolith between the reactors and the habitat, then they can be a lot closer, meaning just over a hill.  Some of us also want to use the solar panels, reactors, or whatever for more than one lousy mission.  SpaceX is also big on reusability because it drastically reduces ongoing operational costs.

Well 1 Km is a fair old distance.

I think the energy system for Mission One is essentially expendable (although I don't expect it to be expended)

Well, the inverters will most likely be encased in Aluminum heat sinks which would eliminate any dust issues, as the ones aboard ISS are, and the Aluminum is required to radiate heat away from the power conversion electronics and electrical components.  I guess if you could convert enough of the waste heat to electricity then that would be worth doing, but those devices are generally horribly inefficient.  It'll be generating heat during the day, though, when you really need to get rid of whatever you can't use.  Maybe we could use it to heat water for later use or perhaps supply heat to the Sabatier reactor?  Maybe.  If it could stay "hot" or at least "warm" 24/7, that'd be really beneficial to the life of the inverter.  Power electronics deal with staying warm or even hot (to a point) a whole lot better than they do with daily thermal cycling.

Whatever serves the overall efficiency of the base.

The "experts" are testing new fission reactors because those electronics still need power whether or not the Sun is up, down, or sideways, precisely because they'd like their electronics to live long enough to do as much useful work as possible.

Maybe, but never underestimate the power of powerful lobbies. smile  This is why the USA has ended up with the silly situation of having a really top notch successful rocket company - Space X - that is not being backed 100% by NASA because American pork barrel politics has ensured NASA is glued to some underperforming industry giants.

Are we just talking about a tent of some kind or a full-blown pressurized "battery habitat"?

If it's the former, why bother?

If it's the latter, how much extra packaging mass are you trying to add to the batteries?

Much more the latter.  I suspect it's less packaging with an aerogel hab than with anything out there on the surface.
In terms of overal mass, I think it's not a huge percentage.


I imagine that the reactors would be partially disassembled for shipping, meaning the Aluminum alloy radiators and Beryllium Oxide reflectors would be removed for launch.  Reflector removal precludes the possibility of the reactor "going critical", no matter what.  There's a significant amount of mass in those components, so that's make it easier to transport them to the surface.  The cores would most likely be bolted to the floor of the cargo deck.  Taken together, the mass of the top shielding / reflector / core / aluminum radiator panels represent roughly 200kg loads on Mars.  The radiator panels are light enough to move by hand, but the rest of the components require small hand cranes to move around the cargo bay, essentially being equivalent in weight (on Mars) to all-Aluminum LS type V8 engines.  After landing, the cores would be unbolted and transported to the cargo hatch using hand cranes or hoists, no different than moving an engine in a garage.  From there, a winch would lower the reactors to the surface using a system of ropes and pulleys.  It's not "high tech" because it doesn't need to be.

Once on the ground, a small rover would take each reactor to an emplacement site, located up to 2km away in a worst case scenario or just over a hill in a best case scenario.  After that, a hole .5m in diameter and 1.5m in depth would be bored into the regolith.  If you're able to drill to a depth of 3m, then you could put the reactors much closer to the habitat.  As a function of the mass of material between you and the reactor, you have to get pretty close to the reactors if they're 3m below ground before radiation becomes an issue, even with constant exposure.  The 0.5m x 1.5m bore hole is essentially a post hole, no different than the kind I've dug by hand with a pick axe and post hole digger through Texas limestone in two hours or less.  That said, we're going to use an electric drill to speed up the process.  The electric drills can chew through rock in a matter of minutes.  If we can't drill to at least 3m, then we're obviously not assured of getting any water which may be found much deeper than that.

Each emplacement site would contain multiple reactors.  If we did exactly what you previously brought up as a potential problem and ran Aluminum utility wire (1350-H19 aluminum conductor / core with PE insulation; 44lbs per 1,000ft; 29,040lbs per 660,000ft / 200km) with more than double the Ampacity rating (600V and up to 108A) of what each reactor's Stirling engines could actually produce, then each 2km long power cable would weigh 290.4lbs / 132kg, for a total of 13.2t of wiring for 100 reactors.  Assuming cost is not an issue, we'll substitute conventional PE insulation for the aircraft-rated / space-rated CNT tape insulation used in military aircraft and satellites, saving approximately 70% of the insulation mass, or 13.3 pounds per 1,000ft of wiring / 92.1kg per 2km, which would bring our wiring mass down to 20,262lbs / 9.21t.

That's certainly not ideal from a mass perspective, as we could likely economize on wiring mass and runs through the use of step-up and step-down transformers, but it would certainly work, it's stupidly simple, and would weigh no more than an insulated tank holding 12t of LCH4 that you planned on taking, once again completely ignoring the 43t of LOX required to actually burn 12t of LCH4 and the cryocooler power requirements to keep both cryogens cold at all times to prevent boil off.

Dropping any sort of power generation equipment from 50m in the air is, quite frankly, pretty dumb.  The slide idea could certainly work for lighter cargo, but I'd counter with the fact that synthetic rope is much easier to work, likely to be significantly lighter, requires no inflation if using inflatables or erection if using fabric and trusses, and has lots of other uses for movement of cargo on the ground.  Therefore, I'm assuming all rolls of thin film panels and all reactors will be hand-craned off the ship using hand cranes, pulleys or winches, and synthetic rope under direct human control.  Each item of cargo will use some form of inflatable jacket surrounding it for protection, not of the cargo itself, but of the Starship's delicate heat shield.

Well I respect you taking seriously all the issues related to actually deploying KP units. Others here seem to assume they will fly to their locations by themselves and magically being producing power. 

The mass tonnages for cabling of KP units are not disastrous. But I do wonder about labour time required by the Mars pioneers and especially any EVA activity.

As for deploying a flexible PV drum - well I think the cargo hold would be further down...maybe 40 metres?  Then you have a cantilevered chute...that might get you another 25 metres down...so a 15 metre oblique drop on to an inflatable air bed. Why not?  Experiment!

Storing 70% of daily production would likely result in batteries that weigh as much as the payload allocation for a single Starship.

Actual Lithium-ion battery packs that are actually providing power to ISS as I write this.

Well I think that is what is at issue at the moment. I am not saying I accept your figures on batteries. We all know NASA doing things the least efficient and most expensive way...I am still laughing about their $400 billion figure for a Mars Mission back in whenever - 1980s?  - probably be a trillion dollars now in 2019 money. They went to every department and said "If money was no object what would you like to give us for a Mars Mission..."

Again, packaging.  Lithium-ion batteries in motor vehicles have liquid cooling systems that don't reject heat through radiation.  Remember your favorite "read across" fallacy?  You're not going to regulate temperature in a near vacuum by running a fan blowing across a heat exchanger.

I accept I need to do some research in this area! smile But you do say "near vacuum" and of course I am proposing batteries in pressurised habs.

I get the feeling that you've done zero / zip / zilch / nada in the way of math to determine how well what you're proposing would work in practice.  Since Elon Musk said it, it must be true.  Smooth sailing from here on out.  Good grief, man.

I do math but only off the back of other people! smile  I am not a religious Muskite, I am a Marsite.  Musk is the best bet for Mars at the moment. But I backed Space X at an early stage when they were back on Kwajalein in the Pacific trying out the Falcon 1. They always seemed to me to have the right stuff.

I think Ryan MacDonald ("Martian Colonist") in his latest video is right...Starship development has been phenomenal. If you get Starship right, then Mars colonisation is really just a lot of boxes to be ticked. The energy system is the big tick, but I think you will find in time that solar delivers that big tick.

If someone from SpaceX actually designs / builds / tests a megawatt-class solar / battery power system (or even just a sub-scale system to demonstrate the feasibility of the concept) that runs for 2 years in temperatures colder than any encountered on Earth and in an abrasive blowing dust environment, without major issues, then yes, I'll accept that.  I've seen zero / zip / zilch / nada in the "actual evidence" department to support that idea (meaning the idea that someone is actually working on this problem).  If you have any actual evidence of that, beyond someone making a PowerPoint to a group of cheerleaders who know nothing about space flight or power engineering, then please post it here so everyone else can benefit.

Well we know at a minimum that PV panels can survive for 14 years on Mars and still deliver close to optimal power. I've not evidence Space X have a feasible energy system plan, but equally I can't imagine Musk would be so daft as to produce top of the range world class rockets in pursuit of his Mars dream but forget about the energy system for the base and propellant production system. Let's at least allow he will be focussed on that along with a lot of other things.

I keep giving you masses for equipment used by NASA, their contractors, and industry.  You keep bloviating about not getting real numbers.

Post the mass of an actual solar power system, something that works in space rather than Flat Holm Island, and then we'll go from there.  Since I've already provided that information, which I took directly from NTRS, you shouldn't have to look anywhere else on the internet other than this forum to find it.  I didn't make anything up for sake of argument.  I took the data they provided, a pocket calculator, and started running numbers on masses and sizes using the best case scenario for solar power (the all-time record output achieved to date).

This makes no sense to me. You've already said the ATK space-rated systems are way too fragile for the Mars surface. So why do you want proof of something that works "in space". Surely we need to have something that works on Mars.

I'd love to "turn a corner" in space-rated battery systems using advanced materials to reduce the mass of the packaging, which I would agree is horrendous.  NASA has done far more work on this than any other entity, to include SpaceX and Tesla.  If it were up to me, I'd take all the technology advancements from the Orion program and transplant them into the Starship program so that SpaceX doesn't have to design absolutely everything from scratch.  The friction stir weld tools would be at SpaceX's disposal, for example.

It's possible to use batteries to buffer power input, provided you have sufficient capacity.  The disadvantage is obviously the weight increase of the batteries.  Charge or discharge them too quickly and bad things happen.  It's not even the power transients that concern me so much, it's the fact that you have to increase the capacity of everything by half an order of magnitude to cover the fact that you don't get to pick and choose when you make propellant.  If power is available, then you have to use it.  I'm not telling you it's utterly impossible to do.  I'm telling you that it's not practical to do for a reasonable weight and complexity penalty.

Your  79 ton battery figure takes me close to the 160 tons figure for KP units but not sure it takes it over.

But I think one could increase the propellant facility and reduce the battery tonnage accordingly and so come under your figure for KP of (at least) 160 tons. Because of course, you haven't said yet how you would activate fins on the Starship...would you be using batteries?


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#50 2019-10-13 08:46:35

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 16,181

Re: Nuclear power is safe

Test data for the 28hr no cooling run
https://gain.inl.gov/SiteAssets/Micro-R … shopV5.pdf

Kilopower can produce one kilowatt of electricity – just about enough for a toaster – with the prototype that LANL and NASA tested is about one meter tall and a half meter in diameter.

With the final design to generate up to 10 kilowatts when made to scale it will be three meter tall and one meter in diameter with small uranium core – about the size of a paper towel roll. With shielding, the entire 10-kWe reactor would likely weigh about 2,000 kilograms.

Four of those large reactors would match NASA’s estimated life support number of 40 kilowatts needed to sustain a four-person outpost on Mars or the moon. These devices will need to dump a lot of “extra” heat into the Red Planet air; a conversion efficiency of 30 percent means 70 percent of the fission heat remains, equipped with a wide, circular radiators at the reactors’ tops, giving them a beach umbrella look.

Radiation exposure
https://spaceradiation.jsc.nasa.gov/ref … inogen.pdf

https://spaceradiation.jsc.nasa.gov/irModels/

https://www.nasa.gov/centers/johnson/pd … ap_CPR.pdf

https://rocketrundown.com/us-revises-po … r-systems/

usnuclearenergy.org/PDF-Documents/11-04-16-Nuclear-Reactor-Test-In-NV-Next-Year.pdf

https://ncsp.llnl.gov/docs/NCSP_NEWSLET … L_2018.pdf

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