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#201 2022-03-03 16:00:27

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 1,955

Re: Nuclear vs. Solar vs. Others

Terraformer, in part yes.  But if you are starting with depleted Uranium or Thorium, the accelerator would need to run for a long time to build up enough fissile isotopes to begin generating power.  It would sit consuming power all that time and the cladding would be taking damage from the neutron flux.  So the fuel load will probably need to include a load of fissile isotopes.  Though not necessarily 235U.  You might use spent light water reactor fuel.  If the neutrons were fast enough, like those yielded from fusion reactions, then 238U will fast-fission without need for breeding.  That would allow good power yields from DU blanket material without having to wait for fissile buildup.  When burn up reaches about 10% HM atoms, we could dispose of the blanket as waste without reprocessing and begin with fresh DU.  Or the heavy metal could be processed to remove fission products and used to produce LWR fuel.

Most of the flux comes from the accelerator, so no control rods are needed.  The power density of the blankets can therefore be high.  A dense heavy metal shell with sodium cooling channels.  Compact reactors with inherent safety features have economic benefits.

Last edited by Calliban (2022-03-03 16:09:08)


"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."

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#202 2022-03-03 20:24:25

SpaceNut
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Posts: 25,943

Re: Nuclear vs. Solar vs. Others

So it sounds like you need an isotope that breaks down faster than for half life to feed the reaction to convert the material.

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#203 2022-03-06 07:24:32

Mars_B4_Moon
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Registered: 2006-03-23
Posts: 3,212

Re: Nuclear vs. Solar vs. Others

China aims to build 450 GW of solar, wind power on Gobi desert - almost equal to half of the world's entire installed capacity today

https://www.reuters.com/world/china/chi … 022-03-05/

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#204 2022-03-13 11:34:33

Mars_B4_Moon
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Registered: 2006-03-23
Posts: 3,212

Re: Nuclear vs. Solar vs. Others

Thailand plans world's largest solar-hydro hybrid 2,725 MW plant to be built by 2027

https://techxplore.com/news/2022-03-tha … power.html

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#205 2022-04-11 15:05:04

Mars_B4_Moon
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Registered: 2006-03-23
Posts: 3,212

Re: Nuclear vs. Solar vs. Others

Could high-flying kites power your home? Companies are betting on computer-controlled, airborne wind energy for future power.

https://arstechnica.com/science/2022/04 … your-home/

Quest for nuclear fusion is advancing – powered by scientific grit
https://uk.style.yahoo.com/quest-nuclea … 53967.html

China determines over 40 elements in Chang’e-5 lunar samples, ‘significant for Moon formation studies’
https://www.globaltimes.cn/page/202203/1256907.shtml

The Holy Grail of Energy Generation Might Finally Be Within Our Grasp. We’ve been on a quest to unlock the potential of nuclear fusion...
https://www.thedailybeast.com/nuclear-f … ugh-moment

Nuclear fusion hit a milestone thanks to better reactor walls – this engineering advance is building toward reactors of the future
https://news.yahoo.com/nuclear-fusion-h … 52145.html

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#206 2022-04-12 06:06:10

Mars_B4_Moon
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Registered: 2006-03-23
Posts: 3,212

Re: Nuclear vs. Solar vs. Others

In 'project of the century', Swiss seek to bury radioactive waste

https://techxplore.com/news/2022-04-cen … ctive.html

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#207 2022-04-17 10:15:04

Mars_B4_Moon
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Registered: 2006-03-23
Posts: 3,212

Re: Nuclear vs. Solar vs. Others

Power stations in orbit?
https://www.aerosociety.com/news/power- … -in-orbit/

3D Printing Nuclear Reactors For Fun And Profit
https://hackaday.com/2020/06/08/3d-prin … nd-profit/
'In an effort to once again make the US nuclear industry competitive with nations like Canada, Russia and South Korea, the US Department of Energy tasked Oak Ridge National Laboratory (ORNL) to lead the Transformational Challenge Reactor (TCR) program. It aims to ‘demonstrate a revolutionary approach to deploying new nuclear power systems’. Essentially, the goal is to 3D print as much of a micro reactor as possible'



These guys use the words 'Nuclear' and 'Fusion' in the press release but it seems to be mostly chemical rockets?

Pulsar Fusion Ltd, a UK nuclear fusion company based in Bletchley, is developing green rocket technology that could eventually send humans to distances further than our Solar System.
https://bigworldtale.com/science/ground … ed-energy/
The rocket tests have been using a process where a ‘green’ (non-toxic) hybrid engine combusts nitrous oxide (N2O) oxidiser and high-density polyethene (HDPE) fuel and oxygen.


Pulsar Fusion was founded by Richard Dinan in 2011 and based in Bletchley, United Kingdom.In July 2020, Pulsar tested its first commercial plasma spaceflight engine achieving 26km/second in plasma exhaust velocity.
https://en.wikipedia.org/wiki/Pulsar_Fusion
In November 2021, Pulsar demonstrated its hybrid launch rocket engines at the MOD COTEC base in the UK followed by an international rocket demonstration in Gstaad, Switzerland

Last edited by Mars_B4_Moon (2022-04-17 10:19:08)

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#208 2022-04-18 13:02:09

Mars_B4_Moon
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Registered: 2006-03-23
Posts: 3,212

Re: Nuclear vs. Solar vs. Others

Scientists Have Developed Liquid Solar Energy System That Can Store Electricity For 18 Years

https://www.indiatimes.com/technology/s … 67282.html

The tech can be added to smartwatches and headphones to power them.

As of now, this technology has only been used for creating small amounts of electricity, however, researchers claim the results are very promising and can allow them to tweak the system further to allow more energy to be extracted.

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#209 2022-04-22 06:41:19

Mars_B4_Moon
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Registered: 2006-03-23
Posts: 3,212

Re: Nuclear vs. Solar vs. Others

You've got a Full Moon?

Stanford Develops Solar Panels That Work at Night
https://www.cnet.com/home/energy-and-ut … -stanford/

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#210 2022-04-25 14:46:18

Mars_B4_Moon
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Registered: 2006-03-23
Posts: 3,212

Re: Nuclear vs. Solar vs. Others

How a new heat battery can quickly make millions of homes gas-free

https://techxplore.com/news/2022-04-bat … -free.html

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#211 2022-04-27 07:09:29

Calliban
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From: Northern England, UK
Registered: 2019-08-18
Posts: 1,955

Re: Nuclear vs. Solar vs. Others

Interesting study.

Photovoltaics-driven power production can support human exploration on Mars
https://arxiv.org/abs/2110.14757

Worth our collective scrutiny, I would suggest.


"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."

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#212 2022-04-27 10:49:43

Void
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Registered: 2011-12-29
Posts: 4,662

Re: Nuclear vs. Solar vs. Others

Interesting that you are willing to give this a chance.

I would note that it talks about exploration.

I have no problem with nuclear, particularly that which can help set up and maintain bases on Mars.

I would make note that while both Nuclear and Solar could help work their way to Mars, Nuclear already used is hard to get safely to the surface of Mars.  Solar might work better.  I am of course suggesting electric drive hardware to Mars.  I like that they might "Work for their passage".

The idea that several Starships would contain cargo prior to humans going to Mars by Hohmann transfer, makes sense.  However, sending further cargo only by that method seems silly to me.  My current pet is Magnetic Bubble propulsion.

Here is an example: http://www.niac.usra.edu/files/studies/ … 0structure.
This is similar: https://www.centauri-dreams.org/2017/12 … nd-beyond/

I believe that the fault on this propulsion is it will take more time to get the load to Mars.  But do we have to care that much?
This would be like sending logs down a river some time ago.  You would not dump people directly into the river to have them travel.

So, with this a "Barge" would bring large mass of cargo to Mars orbit, so you would want to have a "Bring-Down" process to land this stuff from orbit to the Martian surface.

------

Once on the ground, I would suggest that mirrors can be of great value also.  Solar Panels are best cooled, for efficiency.  However, a hybrid method could extract heat with a heat pump method and store the heat.  For Mars this will be even more valuable that for on Earth.

So, the solar flux being less than half that at Earth, then mirrors can boost it up, without damage to the solar panels.  If you have a good heat pump system, then you can even make it four times the natural solar flux on Mars, (When no dust storm).  Maybe even Eight.

Going beyond exploration, a good place to look into would be the Mariner Rift Valley.  A wet spot may exist in it's central zone, and lately some Mars quakes have been identified in the valley.  Mars quakes might indicate geothermal.  Wetness/Ice, in the valley, may indicate a sort of cryovolcanic/artesian process.  Maybe eventually then some geothermal power.

If ground mirrors and heat pumps can work with solar panels, we have some "Dead-Time", at night.  But if you can have mirrors in orbit, then you may use your ground installation to receive even more energy.  I am very interested in also promoting a orbital community for Mars.  This then can work with the ground community.  In realty they would be one community.

My opinion, of course.  And like everyone else I also have a rectum smile.

Done.

Last edited by Void (2022-04-27 11:08:41)


Done.

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#213 2022-04-27 11:46:49

Calliban
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From: Northern England, UK
Registered: 2019-08-18
Posts: 1,955

Re: Nuclear vs. Solar vs. Others

I have never had an ideological bias against solar power.  I have always thought solar power satellites were a good idea and still do.

I tend to react against the idealism of people like Louis, because their position is based on emotional prejudices for some things and against others.  A lot of people that advocate renewable energy do so because they are seduced by the elegance of the idea of powering society with 'natural' energy sources.  It is never about approaching the problem with a open mind and finding the best solution.  When idealistic people like that debate, they are trying to validate a predetermined position.  Some will go so far as to lie and deliberately sabotage alternatives to produce the result that they want, exactly what has happened to nuclear power in the OECD.  That is what ideology does to people that are vulnerable to idealistic thinking.  In all too many ways, ideologies have ruined our world.

The reality is, there are times when solar power provides the most sensible option for energy and there are times when nuclear power works a lot better.  We need to approach engineering problems with an open mind to find the best practical solutions.  But the ideological obsession with renewable energy runs deep in some people.  It is why I have to take papers like the above with a pinch of salt, until I can validate the assumptions behind their analysis.  As an engineer, I try to be as objective as I possibly can.

Last edited by Calliban (2022-04-27 11:52:30)


"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."

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#214 2022-04-27 19:35:06

SpaceNut
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Posts: 25,943

Re: Nuclear vs. Solar vs. Others

Mars_B4_Moon wrote:

'Why solar energy can be a more effective way to power a mission on the surface of Mars than nuclear'

https://www.universal-sci.com/article/s … rs-mission

barely at equator

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#215 2022-04-27 20:45:32

Void
Member
Registered: 2011-12-29
Posts: 4,662

Re: Nuclear vs. Solar vs. Others

I would say do both.  Historically mass has been limited so you would have to make a choice.

However, Starship will either work or not.  If it works, an extra one could likely hold at least 5 solar setups, and 5 reactors.

8.3 x 5 = 41.5 Tons

9.3 x 5 = 46.5 Tons

No point in being cheap with electrical power.  It is useful for just about everything after all.

Certainly, to have success is the difference between profit and loss.  Going cheap at that point would be silly.

And then you could test the reality of each system 5 times each.

Done.

Last edited by Void (2022-04-27 20:49:06)


Done.

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#216 2022-04-27 21:50:39

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 25,943

Re: Nuclear vs. Solar vs. Others

The data was for the KRUSTY kilowatt reactor and the 3 junction solar cells.
In other topics we have said to not rely soulfully on one or the other without a backup which means just as you have put it take both...

I believe the tonnage for the power was for the 40kwe output units but will keep looking for the exact document unless some one has it.

https://ntrs.nasa.gov/api/citations/202 … Design.pdf

https://ntrs.nasa.gov/api/citations/201 … 007389.pdf

https://nuke.fas.org/space/krusty.pdf

https://www.osti.gov/pages/servlets/purl/1648084

https://en.wikipedia.org/wiki/Kilopower

http://local.ans.org/trinity/pdf/mcclure-181012.pdf

10kw is 1500 kg

https://yellowdragonblogdotcom.files.wo … 2-1-17.pdf

https://www.simplerockets.com/c/L89b44/ … ng-Reactor


The per power output for a 1 meter square is just under 160w at the equator and drops off fast.

so for the hour to get 40kw we need 250 panels but since we need 25 hr to match power we need lots more

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#217 2022-04-28 12:11:18

kbd512
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Registered: 2015-01-02
Posts: 5,842

Re: Nuclear vs. Solar vs. Others

SpaceNut,

The KiloPower reactor's thermal output is 43kWt.  Electrical output is 10kWe, or 240kWh over a 24-hour time period.  There are ways to improve upon that output level, most notably using multiple turbine stages with re-heat of the thermal power transfer fluid running through the reactor core.  That would drastically reduce the total weight of the reactor since there's as much or more mass tied up in the radiator panels as the entire rest of the core.  The as-tested working fluid temperatures are sufficient to produce up to 480kWh over a 24-hour time period is doable.

Each square meter of solar panel area on Mars Insight generated about 592Wh/day at BOL.  I can't find enough detail on whether or not single-axis or dual-axis tracking were used, but I believe it was fixed / stationary.  Let's use 600Wh/m^2 as a nice round number.  That means we need about 800m^2 (a little over 28m by 28m square) to generate 480kWh.  NASA's exploration class mission planned to use a series of 5 KiloPower reactors to provide life support and return propellant.  Assume KiloPower never uses any more advanced power generation technology.  That means 5 reactors supply 1,200kWh over 24 hours.  Now you need 2,000m^2 of solar panel area to provide equivalent power output (about 45m by 45m).  That's still doable, but now you need to store about 75% of the power, and certainly no less than 50%.  That's also the bare minimum required for survival.  If you get any less than that, you either die there or you don't come home.  If you store 50% of the power using ISS ORUs which have the lifespan required to supply reliable power, then 26.6t of batteries.  Alternatively, for batteries that will only be 50% discharged so they actually last for thousands of cycles, you need 53.2t of batteries.  That grossly exceeds the weight devoted to all 5 KiloPower reactors and a vehicle to move and emplace them, even if they're using LEU instead of HEU.  You can see how fast it becomes impractical to use batteries for everything.

ISS Lithium-ion battery lifecycle testing performance and achieved on-orbit performance results aboard ISS:
International Space Station Lithium-Ion Battery Status

The issue with photovoltaics is not the weight of the panels at a small scale, although as the power requirement scales up the weight of the panels alone will dramatically exceed that of any nuclear power solution that produces equivalent output.  If you require gigawatts to terawatts of continuous power, then photovoltaics become increasingly impractical.  The weight of the batteries, however, remains an intractable issue with no good solutions.  If photovoltaics / electronics are used, there are radiation degradation issues over time, as well as dust accumulation on the panels which drastically reduces output in less than a year.  Using solar power for everything is merely another fantasy-based ideological belief with no grounding in good engineering practices.  Use case also matters greatly.  A photovoltaic panel on a robotic spacecraft with minimal power consumption can be exceptionally light and compact, as compared to an equivalent nuclear power solution.  Attempting to power an entire city that requires gigawatts of continuous power is an absurdity.

If there's a good method for cleaning the panels that does not scratch or craze them, then that solves the dust issue.  I think dust is solvable, but for whatever reason, no practical dust removal solutions have been implemented.  The radiation degradation issue is not solvable in any practical sense.  Matter is broken down at an atomic level by high energy proton strikes from the Sun and from Galactic Cosmic Rays (relativistic protons from supernova events).  Photovoltaics are exceptionally thin to make them lightweight and efficient.  We do not have any ultra-thin "self-healing" materials that convert photons into electrons.  The battery energy density problem is not solvable in any practical sense.  The gravimetric energy density of electrochemical reactions are an order of magnitude less energy-dense than chemical reactions involving Oxygen, Hydrogen, and Carbon.  The ultra-thin layers of materials used in modern Lithium-ion batteries are also subject to rapid high-energy proton degradation mechanisms.

There are long-term feasible solutions to the battery energy density problem, but they do not use batteries.  All human-lifetime durable energy storage systems use heat, rather than electrons.  Flow batteries are not batteries as such.  It's possible to make them last much longer than Lithium-ion batteries, but they suffer from even more severe volumetric and gravimetric energy density issues, which means they are feasible for stationary power plants but not vehicles.

Latest Lithium-ion batteries: 500Wh/L - 700Wh/L *Note1
Latest 3D Lithium-ion batteries: 1,000Wh/L *Note2
Latest flow batteries: 350Wh/L *Note3
Diesel fuel: 10,700Wh/L

*Note1: can vary significantly by form factor and cell chemistry; there are primary cells such as Aluminum-air that have up to double or triple the energy density of Lithium-ion, but those cells must be re-manufactured after a single-use so they are not included here (and it takes at least one order of magnitude more energy to "recharge" them than you can ever get out of them)
*Note2: 3D batteries, varies by technology, and they're either no better or little better than standard Lithium-ion cell chemistries made the traditional ways (potential for improvements exists here, but to think they're going to double or triple in gravimetric and volumetric energy density within our lifetimes is very optimistic)
*Note3: aqueous flow batteries that are not made from Unobtanium

Head-to-head, modern electric vehicles are or can be 50% more energy efficient than combustion engines, but that is near or at the practical limit.  That's fantastic, but they will never become significantly more energy efficient.  The electric motors are 95% efficient or better, the power converters are 95% efficient or better, and Lithium-ion batteries are about 99% electrical efficiency (charging and discharging without converting input or output electrical energy into heat).  Since you can't become more energy efficient in any practical sense, the only "improvements" to batteries will be cycle life, charge / discharge rates, and the ease with which the batteries can be recycled after they degrade unacceptably.  The trade-off for the increased energy efficiency is all those other aforementioned functional areas where batteries are decidedly less functional than combustion engines or fuel cells.

There are no reactive metals lighter than Lithium.  We've discovered other lower cost and more abundant materials that can do the same job as Lithium, but none are actually better than Lithium as it relates to performing the same function within the battery cell.  There are definitely much better anode and cathode materials available than the ones we presently use, but most have cost or service life issues due to swelling.  The wrapped layers of battery material, aka the "jelly roll", is already thinner than a human hair.  There's very little that can be done to make the active materials substantially thinner.  Graphene can be atomically "thin", but nothing that is only one atom thick can be easily rolled up into a cylinder at high speed, without breaking it in the process (largely negating its otherwise magical electrical properties).  Increasing the surface area of the materials is required to increase gravimetric and volumetric energy density, which implies 3D technology of some kind.

I can see batteries that use all-new technology that could double or maybe even triple the energy density of current Lithium-ion batteries, but then you run into diamond-hard technology limits.  Worse still, such batteries will have even more severe thermal control issues due to increased power density.  Heating them up and cooling them down rapidly will cause cracking, because they're made from solid materials.  Recycling them will be even more difficult, definitely uneconomical, and perhaps entirely impractical.  Suppression of dendrite growth that electrically short-circuits the battery becomes progressively more difficult as well.

Heat engines, as inefficient as they superficially appear, still hold a dramatic edge over all forms of electron storage in the gravimetric and volumetric energy density departments.  Heat engines are also vastly more durable over the long term than any type of battery.  They do not require sophisticated electronics that can and will fail catastrophically at the speed of light.  For powering moving vehicles with a given mass of input materials, batteries are another technological dead-end.

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#218 2022-04-28 16:54:13

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,858
Website

Re: Nuclear vs. Solar vs. Others

The wh/L comparison between various energy storage things is quite good.  The heat engine fuel (diesel fuel) requires a bit of attention if you wish to use it off Earth.  That heating value of 10,700 Wh per L of diesel fuel ONLY obtains when burned with free air,  or really the oxygen derived from the air.  You cannot burn it on Mars without also supplying the oxygen to react with. 

Dividing by the density gets you something near 12,000 Wh/kg.  It will take just about 3.9 kg of oxygen to burn each and every kg of that diesel fuel in some sort of heat engine.  So,  on Mars,  that 12,000 Wh gets released from reacting about 4.9 kg of fuel + oxygen,  and on Mars,  you have to have both available in tanks to pump into the engine inlet. So that's closer to 2400-2500 WH/kg-of-reactants on Mars. 

Multiply that by the mass-averaged density of the reactants,  gets you somewhere near 2000 WH released per liter of the total reactants.  If you don't have free ambient oxygen,  you have to figure it that way,  because that is the only way you can actually use it. 

It's really only crudely about a factor of 2 better than the best batteries,  as dense energy storage,  on Mars (or anywhere else without Earthly air). Earth is the anomaly that makes it look so much better,  and ONLY because free ambient oxygen is available at a reasonably-high gaseous density.

Factor 2 is dramatic enough of an improvement,  but not so dramatic that other considerations besides energy density might not intervene in your choice.  Besides,  the only heat engines we humans have ever built that used a hydrocarbon fuel and pure oxygen are rocket engines. 

All the other heat engines use air,  with the oxygen very strongly diluted.  At stoichiometric,  that is the difference between 5000-5500 F and 4000-4500 F flame temperatures.  We have no real experiences handling the higher flame temperatures in piston engines. 

And in turbines,  you are limited to about 2000 F turbine inlet temperature,  which means you run very,  very lean. That drastically raises the air (or oxygen) required for each kg of fuel.  You lose your factor of 2 energy density advantage pretty quickly,  when you have to store the oxidant as well as the fuel.

GW

Last edited by GW Johnson (2022-04-28 16:56:01)


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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#219 2022-04-28 17:13:56

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 10,760

Re: Nuclear vs. Solar vs. Others

For GW Johnson re #218

All the other heat engines use air,  with the oxygen very strongly diluted.  At stoichiometric,  that is the difference between 5000-5500 F and 4000-4500 F flame temperatures.  We have no real experiences handling the higher flame temperatures in piston engines.

In the past, this forum has considered the use of CO/O2 on Mars, for internal combustion engines.

The obvious convenience of making and using that combination of fuel and oxidizer, compared to anything else, seems (to me at least) to be an argument in it's favcor.

However, your post contains this item:

All the other heat engines use air,  with the oxygen very strongly diluted.  At stoichiometric,  that is the difference between 5000-5500 F and 4000-4500 F flame temperatures.  We have no real experiences handling the higher flame temperatures in piston engines.

On Earth, CO/O2 ** has ** been tested, and links (or at least ** a ** link) is/are available in the forum archive.

My question is: By any chance, would the temperature of CO/O2 be within the known range of capability of existing internal combustion engine designs?

The ability for a stock engine to run without modification on Mars would seem to be worth investigating.

An engine could be tested on the ISS (or another suitable orbital location) at (relatively) modest cost.

I bring this up because there are more than a small number of well established manufacturers of internal combustion engines on Earth right now, and a few might be interested in funding a CO/O2 test in orbit, for bragging rights if it works, and for a contribution to science if it doesn't.

(th)

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#220 2022-04-29 00:43:01

kbd512
Administrator
Registered: 2015-01-02
Posts: 5,842

Re: Nuclear vs. Solar vs. Others

GW,

Oxygenated Fuels for Oxidizer Mass Reduction

While what you say about fuels and oxidizers is true, there are synthetic chemicals like diglyme (C6H14O3; flashpoint 57C) or butyl-diglyme (C12H26O3; flashpoint 117C) that contain some of their own oxidizer within the fuel.  These synthetics are produced by combining dimethyl ether (DME) plus ethylene oxide over an acidic catalyst.  Diglyme is 35.8% Oxygen, by weight, which is 32.17MJ/kg.

Oxy-Fuel Combustion Tecnology
Burning anything with pure O2 also increases the heat of combustion, which reduces the quantity of fuel required, but you inject less fuel or include inert diluent gas to keep combustion temperatures within tolerable limits.  There's Nitrogen to expand on the power stroke to increase engine power output from a piston engine, but CO2 exhaust gas can be recirculated into the intake charge since the diesel engines are direct-injected, and that has the ability to increase power output without requiring as much onboard / "stored" diluent gas.

Oxy-fuel combustion is also used in coal-fired power plants and large gas turbine power plants.  These applications are definitely not rocket engines and they're used every single day at power plants around the world, in order to reduce NOx emissions.  I presume we'd use the same very high temperature technology at stationary power plants on Mars, in order to reduce the mass of the thermal power transfer equipment.

Space-Rated Battery Energy Density
ISS Battery Orbital Replacement Units (ORUs) are good for storing 4kWh of power, but they weigh 520 pounds each, or 16.95Wh/kg.  We can obviously increase that quite a bit by sacrificing battery service life in favor of gravimetric energy density, but therein lies the trade-off.  We are greatly sacrificing battery service life performance to achieve increased battery energy density performance.  ISS batteries have achieved many thousands of charge / discharge cycles, as the linked document from my Post #217 shows, at the expense of batteries that store less total energy than Lead-acid batteries per unit weight.  If they completely discharge the batteries or discharged them at a faster rate, battery service life drops like a rock.  The graphs within the NTRS document I linked to very clearly illustrate that relationship.

Electronic Vehicle Battery Energy Density and Tradeoffs
The Tesla Model 3 Long Range version has a 480kg 82kWh battery, so it achieves 170.83Wh/kg.  However, Tesla's battery will never achieve the tens of thousands of charge / discharge cycles that ISS batteries achieve without a dramatic loss in total capacity.  That Wh/kg figure also ignores the weight of the cooling system required to keep the battery from cooking itself, which should be included unless the battery can charge and discharge at a rate that's useful to us without it.

Hydrocarbon Fuel Energy Density, with Oxidizer Mass Included
If a diesel-type fuel is still achieving 2,000Wh/kg after Oxygen is supplied as well, then we're still talking about an energy source that's 11.7X lighter, which is still more than 1 order of magnitude better than any kind of rechargeable battery.  The greater the total continuous energy output requirement, the more impractical all types of batteries become.  If there's a practical way around that problem, then hundreds of billions of dollars of investment in batteries of all types have yet to discover what that would entail.  A pragmatically-motivated person would accept that there's a fundamental technological limitation there, whereas an ideologically-motivated person would not.

But no, diesel is not "more energy dense" by a factor of 2.  It's more than a factor of 10 more energy dense, or at least a factor of 5 after heat losses are accounted for.  That's why there are no practical battery powered airplanes, but there are plenty of airplanes that use diesel or kerosene fuels.  Modern turbocharged gasoline engines can be over 40% thermally efficient within their power band (meaning, not "at idle").  Modern turbocharged diesel engines can be near 50% thermally efficient within their power band.  Large simple cycle gas turbine engines are already closing in on 50% thermal efficiency, and 65% or more is achievable using recuperators.  Fuel cells readily achieve 70% energy efficiency, to as high as 85% in high temperature models that use distillate fuel oils like kerosene and diesel.  No existing battery technology comes within a country mile of liquid hydrocarbon fuels, here on Earth or anywhere else for that matter.

Aircraft used here on Earth adequately illustrate how dramatic the difference is when no onboard oxidizer is carried.  A battery powered aircraft of equivalent weight can fly for 45 minutes to 1 hour before the battery is completely drained.  If reserve power is retained for emergencies, then a functional battery electronic transport aircraft with equivalent weight to one powered by gasoline or kerosene will fly for 15 to 30 minutes at most.  If the Sharp Nemesis NXT was as heavily laden with fuel as Rolls Royce's battery powered facsimile, then it could easily fly for 8 hours.

Practical Land-based Mars Vehicles and Why We Need Nuclear Power
Nuclear power is the only form of power generation that allows any type of land-based vehicle to literally circle an entire planet several times over, without ever stopping to refuel.  We have far less atmospheric drag to overcome on Mars and only 38% of Earth's gravity, but the very rough and sandy nature of the terrain partially negates those advantages, assuming we're discussing a heavy duty land transport vehicle that must overcome greatly increased rolling resistance associated with off-road use.  Since there are no roads on Mars, that's exactly what we're talking about.  If we're going to assert that weight is not an issue, then the weight of small nuclear reactors will easily achieve what no battery or hydrocarbon fuel ever could, in terms of total vehicle range / power output for a given mass of delivered equipment.  Nuclear power is the only form of power generation that requires little to no further energy input after the reactor has been built and transported to Mars.  Using hydrocarbons, you must supply the oxidizer and fuel.  Using batteries, you must supply the electrical power to charge the battery.  I will readily accept the argument that batteries are logistically simpler to "refuel" than combustion engines (no storage or transport of volatile or reactive liquids), but not that the total mass of equipment transported to Mars will be significantly lower (since all of the fuel and oxidizer comes from Mars).  If that argument is attempted, then nuclear power easily wins that argument as well.

Nuclear power using supercritical CO2, combined with thermal energy storage, provides a complete power generation and power backup solution.  This type of power generation scheme does not rely upon micro electronics to control it, either.  The turbo machinery is positively tiny compared to using steam.  For a land vehicle using 1MWe of power, we're talking about a sCO2 gas turbine that you can easily pick up with one hand.  You can close your hand around a 250kWe sCO2 turbine.  The use of printed circuit heat exchangers, essentially carved steel plates with tiny coolant passages that have been diffusion bonded together, are also about 8X smaller than traditional heat exchangers using flat metal plates or tubes bonded to metal plates.

A 250kWe aircraft-type electric generator is significantly larger and heavier than the power transfer turbine, yet you can still pick it up.  Siemens 16.5" diameter / 11" length 2015 model year SP260D electric aircraft motor produces 260kWe / 1,000Nm (737ft-lbs) continuous output at 2,500rpm motor-generator and weighs 50kg.  Siemens 2017 model year SP200D electric aircraft motor produces 204kWe / 1,500Nm (1,106ft-lbs) continuous output at 1,300rpm motor-generator and weighs 49kg.  Both motors are oil-cooled using "Syltherm 800" synthetic and are 3-phase type units.  Both motors do not use any type of gearing to generate their rated torque output.  A slightly larger axial-flux motor-generator could easily triple or quadruple that torque output.  MagniX has a 640kWe 3,020Nm continuous output electric motor at 2,300rpm and weighs 200kg.  The AGT-1500 that powers the M1 Abrams main battle tank produces 3,950ft-lbs at 1,000rpm and 2,768ft-lbs at torque output at 3,000 rpm, which produces its peak power output of 1,500hp.  A pair of MagniX motors could produce 4,422ft-lbs at 2,300rpm.  Siemens has also created a 2000D 2MWe motor-generator model, built using the same technology as the 200D, that weighs 261kg.

Nuclear powered heavy duty off-road mining, construction, and transport equipment is not only feasible but practical on Mars.  Such vehicles will be operable 24/7/365 since the vehicle never has to "plug in" to a fuel pump of any description, won't require as much routine maintenance as similar diesel-powered equipment used here on Earth, require fewer complex microelectronics for primary power and propulsion control as compared to batteries and solar panels, and there's no EPA or other regulatory agency to assert that nuclear power is "unsafe" simply because it's vastly more efficient and less consumptive than competing alternatives.  All power generation technology used on Mars comes at an incredibly steep "price of entry" due to the cost of transporting it there.  This is the most practical use of readily available technology for undertaking the types of activities we would have to do, in order to live on Mars long-term.

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#221 2022-04-29 08:42:29

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 1,955

Re: Nuclear vs. Solar vs. Others

A lot to think about here.  The things that a solar powered solution has in its favour are simplicity, technological readiness and relatively low development costs.  It cannot compete with fast reactors from a whole system power density viewpoint.  The only thing that limits power density of nuclear systems is heat transfer.  The more power you need, the greater the mass disparity becomes.

Attempts to improve power density of solar systems tend to focus on making solar panels thinner.  There are fundamental limits to how far this can be taken.  There are resistance losses that increase progressively the thinner they become.  Raising voltage is one way of reducing resistance losses, but in thin PV cells this is limited by breakdown voltage of PV materials.  The thinner PV structures become, the more fragile they become.  The more vulnerable they become to abrasion, to cracking due to bending, damage occurring during deployment, etc.  This is why thin film Systems here of Earth tend to use just as much material as monocrystalline cells.  What they actually reduce is the amount of PV material used.  PV Systems need storage using hydrogen, batteries or some other arrangement.  The sort of chemical reactor systems used in propellant production won't tolerate thermal cycling.

For scouting missions, requiring tens of kW of power for propellant production, it is entirely possible that solar power systems may have an edge over small reactors on a mass basis.  But these systems are fragile and include a lot of complexity for energy storage.  This will have a detrimental effect on mission reliability.  If things go wrong with the mission primary power supply, the entire crew die.  This is why most serious mission proposals tend to employ hybrid nuclear and solar systems, using a combination of both.

Last edited by Calliban (2022-04-29 08:47:22)


"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."

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#222 2022-04-29 09:19:21

kbd512
Administrator
Registered: 2015-01-02
Posts: 5,842

Re: Nuclear vs. Solar vs. Others

Calliban,

If I didn't like solar panels and batteries, then I wouldn't have 76 panels on my roof and 2 Tesla Power Walls next to my breaker box.  It works for powering a large house in Texas, land of unrelenting sunlight and far less dust than a desert.  It's hot and humid most of the time, and the heavy rainfall frequently cleans off the panels for me.  Despite the heat, I have never once watered the grass since I've lived in Houston and it has never died, unlike Austin.  I have not used a sprinkler one lousy time in more than 15 years!  That's clearly a very unique environment.  The rest of the world is not Houston or Louisiana or Alabama.

Solar power is fantastic when it's available and when the electronics work.  I've had 16 on-panel power inverter failures during the 1st year of operation, so no "commercial solar" solution would survive 2 years on Mars.  There's also a case to be made for plugging in electric vehicles to a long "extension cord" (catenary wiring system) since these vehicles will predominantly be working in one relatively small location at a time.  It's not outside the realm of feasibility.  However, if significant onboard energy storage is required for long distance transport, solar power immediately becomes impractical unless they're mounted on a train, not due to the solar panels themselves, but the batteries required to take you from Point A to Point B.  All of your payload becomes batteries rather quickly.  You have pointed that out more than once.

Thin film panels work here on Earth because they're protected by a rather thick cover glass that is abrasion-resistant.  Glass is very heavy, so the thicknesses used would be impractical unless the glass was made on Mars.  Maybe some kind of very thin "Gorilla Glass" type iPhone / iPad screen protector could be used to make the transported panel mass more reasonable, but even those are rather theavy.  In any event, that means the panels can no longer be deployed from a long continuous roll the way NASA's ROSA technology is.  That also means you need rather small and light individual panel supports.  If you go to that trouble, then you may as well do single-axis sun tracking as well, which adds more weight and complexity.  The panels could use Apple-like "MagSafe" connectors to daisy chain them into strings, potentially electrically isolating the strings which would prevent static electricity power surges from hurting more panels.

You need a very sophisticated robot to emplace these delicate panels or a team of humans with a delicate touch and attention to detail.  Doable, yes, but someone needs to demo the technology first in a realistic desert-type environment with lots of fine abrasive blowing sand- much like Iraq.  After they're panels have been set up, then you really do need a maintenance robot to endlessly clean them off, especially during dust storms.

Even at the scale of scouting missions, solar power only provides a significant advantage if you ignore the mass of the batteries, which you cannot do, and the relative complexity of deploying a small solar power station.  The moment you try to do ISRU propellant production, the mass differential shifts very lopsidedly in favor of nuclear power.  If you don't do ISRU propellant production, then the IMLEO value increases to the point of making the mission unaffordable, especially without electric in-space propulsion.

I tend to agree that a hybrid approach covers more bases.  I'm not comfortable entrusting any single power generation and storage technology with the lives of our astronauts over 2 full years.  The mass of thin film panels could be quite reasonable.  The mass of significant battery energy storage capacity quickly becomes very unreasonable.  If you use regenerative fuel cells, then you get a rough 10X reduction in total energy storage system mass, even after accounting for very heavy CFRP 10,000psi O2/H2 reactant storage tanks.

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#223 2022-04-29 16:43:25

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 25,943

Re: Nuclear vs. Solar vs. Others

Article snippets

They based their calculations on the electricity needs of a crew of six people, including the weight of the equipment that would need to be transported from Earth to Mars.

solar-powered system would require transport of about 8.3 tons of mass to the red planet to generate the same amount of power that a mini nuclear power station would produce at 9.3 tons.


In the end, after weighing in the relevant factors, a photovoltaic array that utilizes compressed hydrogen for energy storage came out as the winner.

storage of surplus energy, the scientists lean towards hydrogen as hydrogen can also be used to create ammonia for fertilizers when combined with nitrogen.

Nasa crew size power number is 40 kwe continous

What is the electrical to support the crew not answered.

KRUSTRY is not 9.3 tons its only 1.5 ton no shield and with 2 ton but as power increase not to exceed 3.5 ton

The lunar reactor version of KRUSTY must weigh no more than 13,200 pounds (6,000 kilograms), and fit into a rocket with the dimensions listed above. The reactor will be assembled on Earth, then launched to the moon, where it must provide 40 kilowatts of continuous electric power for 10 years. The reactor must also have temperature controls to keep the device cool. The moon can reach more than 260 degrees Fahrenheit, or 127 degrees Celsius, during the day.

No source of hydrogen accounted for from water

No statement for oxygen tank

Electrical requires a fuel cell for conversion

No source of nitrogen without atmospheric unit to collect and separate

Junk science


https://youtu.be/FKhszB4E1_M

Solar concentration panel reflecting gain of at least 5x for same panel from 2x panels reflectors

Crew size and duration does have an impact on requirements

aseb-snip.png

conjunction-class mission launched in 2039 would take 916 days roundtrip: 210 days getting there, 496 days on the surface until the planets are correctly aligned again, and 210 days home. A comparison opposition-class mission would launch in 2037 and last 650 days: 217 days enroute, 30 days on the surface, and 403 days home via a Venus swingby.

The 7% RTG efficiency

The high decay heat of Plutonium-238 (0.56 W/g) enables its use as an electricity source in the RTGs of spacecraft, satellites and navigation beacons. Its intense alpha decay process with negligible gamma radiation calls for minimal shielding.
Americium-241, with 0.15 W/g, is another source of energy, favoured by the European Space Agency, though it has high levels of relatively low-energy gamma radiation.

where the sterling brings the same fuel up to 20% efficiency

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#224 2022-05-03 04:29:43

Mars_B4_Moon
Member
Registered: 2006-03-23
Posts: 3,212

Re: Nuclear vs. Solar vs. Others

Denmark says it will accelerate plans for artificial islands to harvest off-shore wind, to reduce the EU’s dependence on Russian energy, and thinks it can create 35GW of power from the developments.

https://www.offshorewind.biz/2022/04/20 … sil-fuels/

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#225 2022-05-11 19:56:07

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 25,943

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