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#51 2017-06-09 17:10:08

Oldfart1939
Member
Registered: 2016-11-26
Posts: 1,805

Re: Going Solar...the best solution for Mars.

I stand corrected! smile

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#52 2017-06-09 17:11:01

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 18,195

Re: Going Solar...the best solution for Mars.

Parameters for this is approximately 5 hrs solar to provvide power to produce all the needed fuel and oxygen to be consumed in a 20 hour period with the life support power being untouched form the panels for the 5 hours activly in use by crew.

Liquid Propane or gaseous natural gas are very simular to what we would be doing on mars for liquid or gaseous methane use.

So would someone please calculate the size of the fuels gaseous and liquid as well as the liquid Oxygen tank needed to satisfiy the burn time of 20 hours. Once we know these volumess then I will or others can search for the standard mass and volume for tanks to hold each on mars. Which leaves each day a 5 hr period to do any maintenance on the generator. Or should we have more of them?

http://www.propane-generators.com/propane_usage.php

http://www.booneyliving.com/906/how-muc … rator-use/

Not Saying that the commercial provides will be all that different than what we can find at the local links that follow and not endorsing them either as there are other providers in the world, just using for numbers for standby generator setup to which is what we would be doing.

Since we need 2k watts for life support and probably the same fr other cycled uses we would want for a 75% rating of the generator output would be 2k x 6 x 2 =24kw during the day or for shifts pretty much continous. So thats a 32kw generator.

This product fits that bill Generac liquid cooled generators or from competitor Generac Protector Qs 38000-Watt (Lp) / 38000-Watt (Ng) Standby Generator this one has specifications on its page.

The Full Load Fuel Consumption gallons per hour (GPH) 5.4 is for the max output in watts with a Fuel Consumption 1/2 Load liquid propane (LP)1.7 and for Fuel Consumption 1/2 Load natural gas (NG) 260

http://www.generac.com/all-products/gen … w-rg038-qs
http://gens.lccdn.com/generaccorporate/ … w-48kw.pdf

  • Natural Gas                                   Liquid Propane
                             (ft³/hr) (m³/hr)         (gal/hr) (l/hr) (ft³/hr)
    75% of rated load    361.7 10.2               4.2     16.2    153

The cooling for mars would need alteration depending air or liquid cooling.
The generator mass is on page 8

  • WEIGHT DATA ENGINE/KW ENCLOSURE MATERIAL
    2.4L             38KW          AL
    WEIGHT GENSET ONLY KG [LBS] WEIGHT SHIPPING SKID KG [LBS] SHIPPING WEIGHT KG [LBS]
    560 [1235]                              44 [98]                                  605 [1333]

So based on methane being in a gaseous state or liquified the changes are to the delivery pressure, and orifice size into the same unit.

The stoichiometric ratio of fuel and oxidizer is 1:2, for an methane:oxygen engine.

CH4 + 2O2 → CO2 + 2H2O

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#53 2017-06-09 17:33:43

Oldfart1939
Member
Registered: 2016-11-26
Posts: 1,805

Re: Going Solar...the best solution for Mars.

What are we really attempting to do here? Is all this thought going towards a first mission, or a colonization effort?

If it's about a crew of 4, 6, to 10 scientist astronauts, everything is becoming far too complex and infrastructure heavy. I can't see NASA or Musk buying into, going to such extremes to avoid use of nukes. The original Mars Direct scheme required 85 kWe, subsequently upped to 100 kWe, including fuel for return flight production.

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#54 2017-06-09 17:47:05

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 18,195

Re: Going Solar...the best solution for Mars.

Either, neither, both as I am trying to supply numbers to prove out just a direction of thought as to show how much mass needs to be delivered in chucks that we can do now not some far off future for some 100 plus colony to which is not happening anytime soon until the ground work has been done to make it possible.

If the ISS is any sort of simulated condition for power even the 100 kw would seem to be to low, the size of its parts for there mass and what it takes to be in near mars conditions where what we are supplying is what we would need from insitu use.

I am not sure but I think also a misconception for solar to a methane lox storage for later power generation is that we still need some batteries to handle the daytime solar useage and to control the power during surges of use.

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#55 2017-06-09 18:32:46

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,615

Re: Going Solar...the best solution for Mars.

I started the thread Oldfart and was quite explicit that I was referencing Mission One, the first arrival of humans on Mars. I took the claimed 100Kwe of the SAFe 400 design (discontinued as a project?)  as a reference point.




Oldfart1939 wrote:

What are we really attempting to do here? Is all this thought going towards a first mission, or a colonization effort?

If it's about a crew of 4, 6, to 10 scientist astronauts, everything is becoming far too complex and infrastructure heavy. I can't see NASA or Musk buying into, going to such extremes to avoid use of nukes. The original Mars Direct scheme required 85 kWe, subsequently upped to 100 kWe, including fuel for return flight production.


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

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#56 2017-06-09 18:55:59

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 18,195

Re: Going Solar...the best solution for Mars.

1,000 gallon propane tank....
ASME Propane Tank Dimensions

a local suppliers page
https://eastern.com/residential-propane/propane-tanks

http://www.propane101.com/propanetankdimensions.htm

It is said that its only 80% full for the size. Is boiloff rate the means to pressurization?
http://www.missiongas.com/1000gallontank.htm

http://www.missiongas.com/undergroundtanks.htm

http://www.dvorsons.com/Magikitchen/pdf … elines.pdf

http://www.npga.org/files/public/Facts_ … ropane.pdf

How much does a liquid propane tank 1000 gallon tank weigh? 2350lbs. on average
What is the required distance away from a building for a 1000 gallon propane tank? NFPA 58 generally requires above-ground LPG tanks having capacities greater than 500 gallons to be located at least 25 feet from a building. More as the size gets larger.

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#57 2017-06-09 19:11:05

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 3,806
Website

Re: Going Solar...the best solution for Mars.

A typical home in the US needs about 1-2 kw at night when everything but heat and air conditioning is "off",  and about 5-6 KW in the afternoon when everything is "on".  Anywhere from 2 to 6 people live in such a home.  The energy requirement might be higher on Mars,  since it is colder there. 

My guess is that we need about 1-2 KW "base load" power,  regardless of light or dark,  and regardless of whether the sky is clear or obscured by dust.  Some of that can come from solar,  at reduced delivery if dusty in the daylight,  and from batteries at night,  regardless.  The rest comes from somewhere else,  and that has to be nuclear.  Period.  End of issue.

You will need both types of power on Mars,  and there is NO way around that fact of life.  Facts of life are often ugly,  and this one certainly is. 

I would suggest about 3-4 KW electric worth of solar power for a crew 2-6,  plus a nuclear source for 1-2 KW worth of power.  That entirely excludes any powering of ISRU,  greenhouses,  or any of the other experimental things we'd like to do while there.  Those just add to the total.  From there it is a trade-off of battery mass versus nuclear mass.  But you have to have both,  just to survive at all,  even if you don't accomplish anything else at all. 

There is NO WAY around that conclusion,  not at this time in history with the ways we know to do things.  That will not sit well with either Louis or Kbd512,  but tough shit,  there it is.  Deal with it. 

As for actually doing a mission,  neither the right solar nor the right nuclear is receiving adequate attention to support that which we would like to do.  Flexible-film solar is polymer,  and we already know plastics are degraded by UV light:  look at your car's dashboard materials.  UV is worse on Mars. 

As for nuclear,  in every western country,  it is a government monopoly.  None of those governments are seriously trying to develop anything that would actually work on Mars,  beyond the oddball technology program such as SAFE-400.  No technology program like that actually results in usable hardware on a timescale exceeding 20 years. 

I make that statement because what is needed to reject waste heat on Mars is not the same thing as is needed to reject waste heat in space.  On Mars you bury coolant pipes to reject heat far more efficiently in the cold regolith than any possible radiation-to-space scheme.  No one is actually doing that kind of design,  and that is how I know no government is yet serious about actually doing the Mars mission thing. 

With nuclear being a government monopoly pretty much universally,  there is no way for a private concern to develop what is needed for a Mars mission.  And that explains entirely why I think a fast trip to Mars is nonsense.  Until we the people change out these governments,  even exploration is unlikely in our lifetimes,  and any attempt at colonization is nonsense. 

There I went and said something true,  but extremely unpopular.  You all will have to change the way you vote before this impasse will change. 

Sorry.

GW

Last edited by GW Johnson (2017-06-09 19:17:27)


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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#58 2017-06-09 19:31:11

Oldfart1939
Member
Registered: 2016-11-26
Posts: 1,805

Re: Going Solar...the best solution for Mars.

GW-

You are, unfortunately, correct. The way around the impasse of the U235 monopoly of governments is possibly through use of Thorium.

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#59 2017-06-09 19:44:27

Oldfart1939
Member
Registered: 2016-11-26
Posts: 1,805

Re: Going Solar...the best solution for Mars.

At one time about 5-6 years ago while I was still actively ranching, I explored the possibility of a combined solar and wind system for getting my ranch off the power grid. That was before Elon Musk was starting up Solar City with the Solar Panel Roofs, and wind power in Wyoming was the "in" thing. I had a wind power consultant look at my requirements and concluded that I needed a 13 kWe wind turbine at a basic cost of $65,000, and Solar Panels capable of generating 8 kWe. This would have powered all my operation...except when the wind didn't blow and the Sun didn't shine. The total system was going to cost me around $120,000 including a big battery bank with a 5 year lifespan. Every 5 years, I would be looking at ~ $20,000 replacement cost. The DOE was at the time, offering to underwrite 30% of the cost, and the USDA another 10%. I was still looking at having to spend ~$80,000 to get off the grid--sort of. The anticipated lifetime of the Solar system ultimately decided me against doing it, and the neighbors objected to the big 50 foot diameter wind turbine.

What does this have to do with Mars? Just the fact that having a turn-key nuclear reactor is similar to being on the grid; anything else is somewhat frivolous.

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#60 2017-06-10 02:29:40

kbd512
Moderator
Registered: 2015-01-02
Posts: 3,280

Re: Going Solar...the best solution for Mars.

louis wrote:

kbd, I guess we’ll have to differ as to whether Space X will have any problems putting humans into space. I doubt it. Human space flight followed on v. quickly from the inauguration of the space era in the late 50s. Musk isn’t performing party tricks. He’s navigating a path to Mars.

I never said Mr. Musk wasn't an exceptionally bright and talented individual.  He's surrounded by capable and like-minded people.  Even so, in his own words he states that nothing about what SpaceX does is simple, easy, or guaranteed to work.  A commercial launch services provider sending humans into space will be a truly momentous occasion that I look forward to.  That said, nobody is sending humans to Mars until the gravity, radiation, and life support reliability issues are adequately resolved and it'd be foolish to try.

louis wrote:

It’s not magical thinking to believe Musk and Space X are in all likelihood already working on the challenges of operating in 0.38 gravity. It’s reasoned speculation. Making a bogeyman out of low gravity is not the way to get to Mars. Likewise extracting water vapour from the Mars atmosphere will not be an amazing technical feat. As far as I can see it involves some pretty standard technology.

The only way to determine what happens to humans in .38g is to build an artificial gravity space station to determine what health effects .38g produces.  It's not inordinately complicated, but it's expensive and potentially dangerous.  That's why nobody's done it yet.

louis wrote:

So for a six person mission, you would be taking 6 x 10 KWe KiloPower reactors providing (a mere) 60 Kwe. In addition you would have some batteries/homopolar generator (couple of tonnes?).  So it looks your mass for six people would be around 6x 1.54 tonnes plus 2 tonnes. 11.2 tonnes in total. Obviously, if the solar energy system was trimmed from a 100 KWe equivalent to a 60 KWe equivalent,  it would probably be coming in at around 7.5 tonnes, certainly much lower than 11.2 tonnes.

I want to send three pairs of astronauts to different locations per opportunity.  Each pair of astronauts receives a pair of fission reactors because they're not co-located.  I want to cover as much surface area as possible over a campaign of three exploration missions.  If water resources are located and no other show stoppers arise, then we can move on to construction of a Mars base.  If no show stoppers arise during a six year surface stay at the Mars base, then we can move on to colonization.  If the first colony is generally successful, then we can move on to construction of a fleet of ITS type vehicles to facilitate mass movement of people and cargo to Mars.  That is the logical progression of activities from initial exploration, to outpost, to permanent colony, to creation of a second branch of human civilization.

Opportunity #1 (Cargo Manifest for Every 2 Astronauts):

Falcon Heavy #1 - 3.5t - 2 Kilopower 10kWe fission reactors (with power cables and towing wheels for the rover to tow into place)
Falcon Heavy #2 - 5t - 1 Small electrically powered tracked rover (powered with PV panels and Lithium-ion batteries or homopolar generators and Silicon-graphite permanent batteries)
Falcon Heavy #3 - 4t - 1 Standard Cygnus module
Falcon Heavy #4 - 5t - 1 Ascent vehicle (with an unpressurized capsule)

Opportunity #2 (Astronaut and Cargo Manifest for 2 Astronauts):
Falcon Heavy #5 - 6t - 1 Enhanced Cygnus module with SEP service module
Falcon 9 #1 - 6.4t - 1 Dragon 2 capsule to deliver the astronauts to Cygnus

If the delivered tonnages seem tiny, that's because that's what Falcon Heavy can deliver to the surface of Mars using every trick in JPL's book of smoking crater avoidance tricks.

louis wrote:

I have never said nuclear can’t do the basic job, so your comments about Curiosity are not relevant.

Continuous power was relevant enough to JPL that they're using nuclear power instead of solar power on Mars for small robotic rovers that only require a small fraction of the electrical power necessary for an exploration mission involving humans.

louis wrote:

If Megaflex is 250 w per Kg, I am not sure if you are right about Curiosity’s RTG weighing less than a solar energy solution.  The fuel alone weighs 4.8 Kgs. It’s in a graphite shell and sits in some kind of container (another Kg or so?).  There is also a heat rejection system – not sure if that would be necessary if it was solar powered. The RTG pumps out 100W – so about 2.5 KWhs per day.  .Curiosity has batteries because the 100W is not sufficient for peak demand (precisely the point I was making).  There are 2x 40 ampere-hour batteries. Sounds like around 2kg for those batteries. Looks like the whole system could well be 8 kgs or more. I couldn’t find the mass of the stirling engine.  But I note the MMRTG is designed to produce 125 W electrical power at the start of mission, falling to about 100 W after 14 years. With a mass of 45 kg  the MMRTG provides about 2.8 W/kg of electrical power at beginning of life.  Is this the true amount of energy mass in the Curiosity Rover? A solar version might have 3 Kgs of Mageflex generating 6Kwhs compared with just over 3 Kwhs for the nuclear system. You might have 12 Kgs of batteries on board for the solar energy system.

Both MegaFlex and Kilopower are still in development, Louis.  By definition, that means neither system is space flight qualified.  NASA does Mars missions using the technology they have, not what they might one day have after development has been completed.  You keep ignoring this point about how real versus imagined missions will be executed.

I would absolutely love to have PV panels and batteries that provide more continuous power than a nuclear reactor for equivalent mass, but no such solution presently exists.

The batteries are continuously charged by the MMRTG and the heat from the MMRTG also provides thermal control.  Predictable and continuous output is the primary advantage of using nuclear power at this time.  The Mars 2020 rover is also using a MMRTG for that reason.  This is what the director of JPL, at the time that Curiosity was developed and delivered to Mars, has stated was the primary reason for using RTG's instead of PV panels.

louis wrote:

We can test human ability to cope with 0.38 G with a moon-based experiment. After a zero G flight of 8 months the test crew would live on the Moon for a substantial period, while wearing gravity compensation clothing to make up for the 0.16 G environment.  We can then see how their bodies react. The fact that NASA have conducted no such test shows they are not yet serious about getting to Mars.

Apparently I was wrong about NASA not working on a .38g simulator space station.  NASA's contractors are working on this problem using funding allocated for the express purpose of building a rotating space station capable of providing varying amounts of artificial gravity.

louis wrote:

Making methane on Mars is more about efficient energy storage not propellant production, but we could of course eventually move into propellant production.

It's another aimless development program of the kind you chastise NASA over until we conclusively determine whether or not humans can live in .38g without serious health effects related to lower gravity.  Until then, Mars is scientifically interesting and nothing more substantive than that.

Here's what NASA thinks is required for an ISRU lander demonstrator to produce 1/5th of the LOX quantity required for a Mars Ascent Vehicle:

1. PV Day-Only ISRU using 4 of the 5.6m diameter UltraFlex PV arrays: 1,098 days to make 4,400kg of LOX

2. PV ISRU using 4 of the 7.5m diameter UltraFlex PV arrays and 1,100kg of Lithium-ion batteries (presuming no dust storms): 527 days to make 4,400kg of LOX

3. A 43.3kWt (10kWe) Kilopower fission reactor operated at 70% power: 407 days to make 4,400kg of LOX

I know you'll inevitably come back with some claim about NASA's figures not being "correct", but since you didn't know what the O/F ratio of LOX/LCH4 for was before I told you, we're taking NASA's assessment of electrical power requirements over yours.  Incidentally, the nuclear powered ISRU lander doesn't deploy anything, unlike the PV powered variant, because the reactor is simply built into the lander.  The 40kWe requirement for surface power came from NASA's desire to make ISRU LOX for the MAV and to support 4 crew members for a 500+ day surface stay.  I thought it was to grow food on Mars, but I was mistaken.

louis wrote:

JPL are also working on solar power satellite systems but for some reason that is not considered a viable technology by many here.

I have repeatedly stated that solar power is coming along for every mission.  It's the most mass-efficient solution in deep space where there is always line-of-sight to the Sun.  There is such a thing as suitability to task.

louis wrote:

NASA is unfocussed and spreads itself too thin in my view.

What are all the other government-sponsored space agencies working on right now?

louis wrote:

For me colonisation, or settlement, starts with the first human on Mars. We know a huge amount about ground conditions somewhere like Chryse Planitia and we can build on the current knowledge with pre-landing.  No reason to expect anything that will endanger the setting up of a base.

After we have solutions to the gravity, radiation, and closed-loop life support technical problems, then we can build a base.

louis wrote:

You claim we've already proven that your proposed solution is not more mass efficient than Kilopower.  See above. I dispute that. The 2 Kwe per person level can easily be supplied by solar energy system, even in the worst dust storm.

You dispute whatever doesn't support your argument, but the data collected by JPL and NASA does not contradict what I've stated because they've actually sent solar and nuclear powered rovers to Mars.  The data they've collected has been reviewed by hundreds of scientists and understanding what they've recorded and written about it is trivial.  It's freely available online.

louis wrote:

Nuclear black magic! lol I can understand that the “coffee can” is actually a lot bigger and a lot heavier than your description suggests. We could easily keep an ATV powered with solar panels, had we gone down that design route.  NASA simply chose not to.  Rovers are not to be compared to settlements in any meaningful sense. There is no problem in organising back up power at a static settlement. Why don’t you eat some plutonium…that would be more convincing than the bananas. smile

The "coffee can" is that part of the reactor that must be shielded with regolith.  The 43.3kWt (10kWe) Kilopower core diameter is 6 inches in diameter and 11 inches in length.  The 43.3kWt (10kWe) Kilopower BeO reflector increases the core diameter to 12 inches in diameter and 16 inches in length.  The reactor is 3.3m in length (top of radiator panels to bottom of reflector) and 1.5m in diameter (radiator panel tip to radiator panel tip, when stowed for transit).  Someone needs to dig a hole a foot wide and a couple yards deep.  The exclusion zone is 200m in diameter with 2m of regolith shielding.  Radiation decreases exponentially with distance from the emission source.  A 200m power cable would weigh an estimated 415kg for a 10kWe Kilopower reactor.

NASA chose not to use ATV's because those types of vehicles will never adequately protect their occupants from CME's.  That'd be why I proposed sending a small tracked rover that's properly shielded.  If you want to travel somewhere far away from your habitat module and can't predict CME's far enough in advance to avoid being caught unprotected on the surface of Mars, then the solution is a vehicle with proper radiation shielding.  The people ESA tasked with design of a Mars exploration rover also incorporated a radiation shelter into their vehicle design concept.  All of the same basic themes were present in both rover designs, but I think the Europeans designed a better vehicle from a basic functionality standpoint.

louis wrote:

A reactor has to be deployed and cabled up.  There may be ways to deploy it without human contact but that will mean more mass I expect. I don’t think maintenance is such an issue with smaller RTGs, especially if you build in some redundancy by bringing in several. Maintenance and back up is more an issue with single nuclear reactor proposals.

If the astronauts have to connect a power cable to the solar arrays, then this is not an advantage of solar power over nuclear power.

So what if the astronauts have to dig a hole the same diameter as a ruler?  I've dug four foot deep post holes in Austin in places where the ground was solid limestone six inches down using a post hole digger.  It's a little obnoxious, but it doesn't take that long.

Since nobody has ever done more than simple assembly of a RTG after launch and there's never been a RTG failure on any mission, you're right about maintenance not being an issue for small nuclear power systems.  There won't be any maintenance on a small fission reactor, either.

louis wrote:

I don’t think you’ve established the case that the nuclear/RTG reactor is a lower mass option than solar energy system with methane and chemical batteries.

It's hard to establish a case for something with someone who doesn't read anything that doesn't support their opinion.  I do this stupid little thing I learned in grade school called basic math.  I have repeatedly demonstrated to you, using basic math, why it is that a PV panel and battery solution alone doesn't produce more continuous electrical power output than a spectacularly inefficient fission reactor like Kilopower.  I've made no attempt whatsoever to conceal, obfuscate, or omit any information about what I proposed.  The mass figures I provided are representative of what things would actually weigh.

The only people who have ever sent anything the size of a car to Mars seem to think that nuclear power is the best option as a function of the mass required to assure a given level of output using current or advanced development electrical power production technologies.  You seem to think that since Elon Musk proposed using solar power, then that must be the best way to do it.  After he sends something to the surface of Mars and it arrives in one piece, I'll pay more attention to what he proposes.  Until then, the word of NASA and JPL on this subject is just a tiny bit more authoritative than that of Elon Musk.

If PV panels and batteries become mass-competitive with fission reactors, as it pertains to providing continuous electrical output, I'll make the exact same arguments to anyone who proposes using fission reactors.  I'm not for or against what you want to do.  I showed you how the math works out and you ignored it.  Scratch that.  NASA showed you how the math works out and you ignored it.  I merely repeated what they stated.

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#61 2017-06-10 04:13:18

kbd512
Moderator
Registered: 2015-01-02
Posts: 3,280

Re: Going Solar...the best solution for Mars.

Elon Musk has proposed using nuclear power on Mars shipped from Earth "if the public is receptive to it" and further stated that nuclear power plants will "certainly be built on Mars".  It seems that Louis cherry-picks the parts of what Elon Musk has stated about about providing power to Mars colonists and ignored what was stated that he didn't want to hear.

Here's the link to the video where Elon Musk makes the statements quoted below (skip ahead to 2:15:36):

Nuclear Power - Dr. Helen Caldicott - Visions of the Future

Incidentally, it's a clip from another video I've watched several times where Elon Musk outlines his plans for taking humans to Mars.

Elon Musk's exact quote from the video:

"The main thing about Mars is actually going to be energy.  If you have energy, there's plenty of water because there's massive amounts of ice.  So, it's really just about getting a huge number of solar panels out there and I think, assuming the public is receptive, you know, there might be nuclear and I think certainly if you build nuclear on Mars.  As to whether you transport nuclear to Mars, you know, it would kinda be up to the public to decide."

I find myself in agreement with JPL, NASA, Jeff Bezos, Elon Musk, and Dr. Zubrin on the matter of using nuclear power on Mars and in space, where appropriate.

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#62 2017-06-10 04:18:09

kbd512
Moderator
Registered: 2015-01-02
Posts: 3,280

Re: Going Solar...the best solution for Mars.

Oldfart1939 wrote:

GW-

You are, unfortunately, correct. The way around the impasse of the U235 monopoly of governments is possibly through use of Thorium.

Thorium is fertile, not fissile.  You still need fissile material to initiate and continue the fission process.  You just need a lot less Uranium to do it.

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#63 2017-06-10 04:38:39

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,615

Re: Going Solar...the best solution for Mars.

I also agree nuclear should be used where appropriate.  I just don't think it's very appropriate either for early or later settlements at the sort of latitudes we will be talking about. I can see a case for nuclear power at polar bases, or maybe in some other difficult environments where you might want to mine. Longer term, we might even use nucleap power to melt the ice caps. Though by the time that is on the table we will have solar power satellites that will probably do the job more efficiently and at less risk.

I really do doubt there will be much of a role for nuclear. I accept Musk may be looking more to building nuclear on Mars at a later stage.  But remember, he's thinking big.  He knows he can pack a cargo ITS with 450 tonnes of PV panelling (a 42 MWe plant on Mars)  and no one will complain. But trying to put a 450 tonne nuclear power station in one of those craft will raise a lot of issues.




kbd512 wrote:

Elon Musk has proposed using nuclear power on Mars shipped from Earth "if the public is receptive to it" and further stated that nuclear power plants will "certainly be built on Mars".  It seems that Louis cherry-picks the parts of what Elon Musk has stated about about providing power to Mars colonists and ignored what was stated that he didn't want to hear.

Here's the link to the video where Elon Musk makes the statements quoted below (skip ahead to 2:15:36):

Nuclear Power - Dr. Helen Caldicott - Visions of the Future

Incidentally, it's a clip from another video I've watched several times where Elon Musk outlines his plans for taking humans to Mars.

Elon Musk's exact quote from the video:

"The main thing about Mars is actually going to be energy.  If you have energy, there's plenty of water because there's massive amounts of ice.  So, it's really just about getting a huge number of solar panels out there and I think, assuming the public is receptive, you know, there might be nuclear and I think certainly if you build nuclear on Mars.  As to whether you transport nuclear to Mars, you know, it would kinda be up to the public to decide."

I find myself in agreement with JPL, NASA, Jeff Bezos, Elon Musk, and Dr. Zubrin on the matter of using nuclear power on Mars and in space, where appropriate.


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

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#64 2017-06-10 07:07:45

Terraformer
Member
From: Lancashire
Registered: 2007-08-27
Posts: 3,222
Website

Re: Going Solar...the best solution for Mars.

How much mass are we looking at for solar?

The best Lithium-ion batteries get 0.265 kWh/kg. Therefore, in order to provide 10 kW continuous for 25 hours (approx. 1 sol), we're looking at 25 * 10 / 0.265 = 943 kg, which is around 1 tonne of batteries. Huh, that's not too bad. Assuming we get 100 W/kg (the 250 W/kg was for Earth orbit, wasn't it?) on a sunny sol, assuming five hours of peak production then to generate that 250 kWhrs we'd need (250 / 5) / 0.1 = 500 kg.

So solar, assuming a best case scenario, could just about break even with kilopower according to my very crude calculations. As soon as you account for dust storms, battery degradation, solar panel degradation, seasonal changes etc, it becomes significantly worse. If sunlight drops by 2/3 due to a dust storm, you'll need 3x as much to produce the same power as a small reactor. Louis seems to be assuming that the Aresnauts would be doing all their work during the 5 hours of peak sunlight.

Of course, for later stages where the settlement can build nickel-iron batteries and protective filters for imported solar cells, the math changes. On the other hand, they'd also be able to make most parts of a nuclear power system at that point.


"I guarantee you that at some point, everything's going to go south on you, and you're going to say, 'This is it, this is how I end.' Now you can either accept that, or you can get to work." - Mark Watney

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#65 2017-06-10 07:29:59

Oldfart1939
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Registered: 2016-11-26
Posts: 1,805

Re: Going Solar...the best solution for Mars.

Since the "There be Dragons" of radiation and effects of microgravity issues have been again raised, here is the latest from Dr. Zubrin on the recent scare tactic employed by the "let's keep doing research on the radiation problem" hucksters.

http://mailchi.mp/marssociety/48wet1x6j … ce9cd02e34

Going on my own research from ~2007, while I was still gainfully employed, I spent quite a bit of effort on the microgravity problems. I concluded that there is one helluva big difference between deep space zero g conditions and the reduced gravitation on Mars of just 0.38g. The effects of reduced but non-zero g conditions may give rise to slow development of a disease resembling osteoporosis here on Earth, a condition for which hormonal regulation therapy is available. So...simply taking along injectable Calcitonin, the hormone responsible for regulation of skeletal Calcium uptake...should alleviate 90% of the effects of reduced but non-zero gravity concerns.

Putting aside these "Dragons," we should return to the engineering problems facing us.

Louis- You and I must continue to agree to disagree on the role of nuclear power on Mars. The first mission(s) will be able to achieve a lot more basic research if they are not out setting up and depending on solar arrays; my insistence on a near turn-key nuclear system.

kbd512- We are more in agreement than disagreement on many of these issues. I for one, disagree about dispersing and diffusing the assets available over 3 different landing sites. Six astronauts working together will require a lot less infrastructure be sent, than on 3 essentially different missions. Believe it or not--money talks when paying for that many Falcon Heavy launches as you've described. The amount of base development 6 persons working together will be at least double that of the 3 pairs you propose working independently of one another.

Last edited by Oldfart1939 (2017-06-10 07:30:45)

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#66 2017-06-10 10:26:44

Antius
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From: Cumbria, UK
Registered: 2007-05-22
Posts: 1,003

Re: Going Solar...the best solution for Mars.

I referenced SP-100 as a representative space nuclear reactor in the 2500MWth range.  The project was cancelled in the 1990s when it became clear that NASA would not get funding for manned space flight projects beyond low Earth orbit.  This made it redundant for the foreseeable future.

150W/Kg is the potential power density of the solar cells without encapsulation.  It is not the power density of the whole system.  It remains to be seen whether Megaflex can produce solar power systems in the 100KWe range that compete on a mass and performance basis with a space nuclear reactor in the same power range.  These are cells that are literally as thin as paper.

I would be happy to see it happen, but I am sceptical.  There are a lot of complications that aren't being accounted for in your simple scenarios.  The need for encapsulation to avoid UV damage on Mars may be one.  Maybe I am over-egging it.  But I do know that radiation damage and oxidation are big enough problems here on Earth to require that all thin PV films be encapsulated in glass to prevent rapid degradation.  On Mars, the oxidation problem is less severe, but the radiation damage rate is hundreds of times greater.  How that will effect polymer lined PV cells is an unknown at present.

Another issue I can see is the breakdown voltage of silicon films that are literally microns thick.  This limits output voltage of the cells to a few tens of volts. For solar arrays spanning several thousand square metres, you either need solar cells clustered around local inverters and transformers or you need some thick cables delivering power back to your hab or propellant plant.  Either way, its more weight.  Significantly more weight.

And then there is storage.  As I have stated before, planning your mission around an intermittent power supply is likely to introduce significant problems.  So you need storage.  Li-ion batteries are more efficient than stored methane and oxygen, which reduces the area of cells needed and reduces both cell mass and surface deployment time.  They are also a lot more reliable than combined electrolysis fuel cell system, which must include numerous pumps, heaters, membranes and heat exchangers.  You were worried about the reliability of liquid metal cooled fission reactors with multiple independent power conversion loops.  How reliable do you think a fuel cell will be in comparison?  Batteries are more reliable and efficient, but they are heavy.  Dust storms and dust accumulation are other issues.

Maybe it is possible to solve these sorts of problems and produce a reliable system in the 100KW range with a mass power density superior to a nuclear reactor.  But wishful thinking won't get us there.

Last edited by Antius (2017-06-10 11:01:37)

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#67 2017-06-10 14:27:23

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 18,195

Re: Going Solar...the best solution for Mars.

1000 Gallons (US) = 3.78541178 Cubic Meter and that is 80% filled with NG (800 Gallons (US) = 3.02832943 Cubic Meter) which would be a use of 10.2m3/hr x 20hrs of run time would require 204 m^3 / 3 M^3 will = 68 tanks of the 1,000 gallon variety each having a mass of 2,350 Pounds = 1,065.94207 Kilograms each. or 72,788kg of empty steel...I have a feeling that the oxygen tanks would not be any different and that is 2 times as many to satify the useage. bringing the grand total of tanks to 204 minimum 1,000 gallon at a total mass of 217,464 kg or approximate 218mT....

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#68 2017-06-10 14:58:43

louis
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From: UK
Registered: 2008-03-24
Posts: 5,615

Re: Going Solar...the best solution for Mars.

I think you are, indeed, over-egging the problems with ATK's systems. These have been tested for use in space as I understand it, and so surely that covers the UV/radiation question. As I understand it they will be more protected from radiation on the surface of Mars. There might be an issue with dust and dust cleaning. As long as you can clean with blown gas, then I don't think that's a big problem.

SpaceNut and kbd have provided links suggesting 250 w/kg for Megaflex.  150w/kg was the starting point for my proposal. 

I don't accept that lithium-ion batteries are more efficient than a methane-oxygen production plant plus generator. I think you are just looking at energy density. The plant keeps on producing methane-oxygen. In principle there is no upper limit to how much energy can be stored as long as the plant is functional.  We will know if it is working before humans depart for Mars.

I've covered the risk factors. There is no evidence that in even the worst dust storms the percentage of solar radiation received falls by more than two thirds of the normal rate.

I haven't proposed fuel cell technology.

Basing a proposal on proven  ATK technology is hardly "wishful thinking".

Antius wrote:

I referenced SP-100 as a representative space nuclear reactor in the 2500MWth range.  The project was cancelled in the 1990s when it became clear that NASA would not get funding for manned space flight projects beyond low Earth orbit.  This made it redundant for the foreseeable future.

150W/Kg is the potential power density of the solar cells without encapsulation.  It is not the power density of the whole system.  It remains to be seen whether Megaflex can produce solar power systems in the 100KWe range that compete on a mass and performance basis with a space nuclear reactor in the same power range.  These are cells that are literally as thin as paper.

I would be happy to see it happen, but I am sceptical.  There are a lot of complications that aren't being accounted for in your simple scenarios.  The need for encapsulation to avoid UV damage on Mars may be one.  Maybe I am over-egging it.  But I do know that radiation damage and oxidation are big enough problems here on Earth to require that all thin PV films be encapsulated in glass to prevent rapid degradation.  On Mars, the oxidation problem is less severe, but the radiation damage rate is hundreds of times greater.  How that will effect polymer lined PV cells is an unknown at present.

Another issue I can see is the breakdown voltage of silicon films that are literally microns thick.  This limits output voltage of the cells to a few tens of volts. For solar arrays spanning several thousand square metres, you either need solar cells clustered around local inverters and transformers or you need some thick cables delivering power back to your hab or propellant plant.  Either way, its more weight.  Significantly more weight.

And then there is storage.  As I have stated before, planning your mission around an intermittent power supply is likely to introduce significant problems.  So you need storage.  Li-ion batteries are more efficient than stored methane and oxygen, which reduces the area of cells needed and reduces both cell mass and surface deployment time.  They are also a lot more reliable than combined electrolysis fuel cell system, which must include numerous pumps, heaters, membranes and heat exchangers.  You were worried about the reliability of liquid metal cooled fission reactors with multiple independent power conversion loops.  How reliable do you think a fuel cell will be in comparison?  Batteries are more reliable and efficient, but they are heavy.  Dust storms and dust accumulation are other issues.

Maybe it is possible to solve these sorts of problems and produce a reliable system in the 100KW range with a mass power density superior to a nuclear reactor.  But wishful thinking won't get us there.


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

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#69 2017-06-10 15:16:14

louis
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From: UK
Registered: 2008-03-24
Posts: 5,615

Re: Going Solar...the best solution for Mars.

Not sure what your calculations are referencing SpaceNut. I was proposing titanium for any metal tanks - 3 tonnes in total, about 6 tonnes in steel equivalent or thereabouts. An alternative is lightweight gas bladders.

The 11,000 KWehs available as methane on the pioneers' arrival combined with the chemical battery storage and also the PV power available (even at reduced levels in a dust storm).

Once the pioneers are on Mars they can dig trenches, line them with cuboid gas bladders and lay over with regolith. These trenches can be used for gas storage. Under my proposals, you'd have about 40 days emergency supply available on arrival with no solar array input. I think that is enough for a failisafe scenario.


SpaceNut wrote:

1000 Gallons (US) = 3.78541178 Cubic Meter and that is 80% filled with NG (800 Gallons (US) = 3.02832943 Cubic Meter) which would be a use of 10.2m3/hr x 20hrs of run time would require 204 m^3 / 3 M^3 will = 68 tanks of the 1,000 gallon variety each having a mass of 2,350 Pounds = 1,065.94207 Kilograms each. or 72,788kg of empty steel...I have a feeling that the oxygen tanks would not be any different and that is 2 times as many to satify the useage. bringing the grand total of tanks to 204 minimum 1,000 gallon at a total mass of 217,464 kg or approximate 218mT....


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

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#70 2017-06-10 17:24:56

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,615

Re: Going Solar...the best solution for Mars.

In the UK I have seen figures suggesting that televisions can easily account for 25% of electricity usage. Other heavy usage can be accounted for by electric ovens or cookers,  increased space heating in poorly insulated homes, lavish lighting requirements, lawn mowers, power washers etc. In contrast, on Mars energy usage per capita, in terms of a domestic setting will be much lower. They will use low energy laptops not huge TVs. As for heating, the humans will be in a much more confined space and aerogel insulation will ensure that heat loss is very, very minimal. On the other hand we will have life support systems to power.

The consensus appears to be about 2Kwe per person baseload, so 12Kwes for a six person mission or 294 Kwhes per sol.

Have you actually read the post that I started this thread with? I explain how we cover all eventualities including night-time and dust storm  conditions.

No one has yet shown that a nuclear energy solution comes in at a lower mass than a solar energy system.



GW Johnson wrote:

A typical home in the US needs about 1-2 kw at night when everything but heat and air conditioning is "off",  and about 5-6 KW in the afternoon when everything is "on".  Anywhere from 2 to 6 people live in such a home.  The energy requirement might be higher on Mars,  since it is colder there. 

My guess is that we need about 1-2 KW "base load" power,  regardless of light or dark,  and regardless of whether the sky is clear or obscured by dust.  Some of that can come from solar,  at reduced delivery if dusty in the daylight,  and from batteries at night,  regardless.  The rest comes from somewhere else,  and that has to be nuclear.  Period.  End of issue.

You will need both types of power on Mars,  and there is NO way around that fact of life.  Facts of life are often ugly,  and this one certainly is. 

I would suggest about 3-4 KW electric worth of solar power for a crew 2-6,  plus a nuclear source for 1-2 KW worth of power.  That entirely excludes any powering of ISRU,  greenhouses,  or any of the other experimental things we'd like to do while there.  Those just add to the total.  From there it is a trade-off of battery mass versus nuclear mass.  But you have to have both,  just to survive at all,  even if you don't accomplish anything else at all. 

There is NO WAY around that conclusion,  not at this time in history with the ways we know to do things.  That will not sit well with either Louis or Kbd512,  but tough shit,  there it is.  Deal with it. 

As for actually doing a mission,  neither the right solar nor the right nuclear is receiving adequate attention to support that which we would like to do.  Flexible-film solar is polymer,  and we already know plastics are degraded by UV light:  look at your car's dashboard materials.  UV is worse on Mars. 

As for nuclear,  in every western country,  it is a government monopoly.  None of those governments are seriously trying to develop anything that would actually work on Mars,  beyond the oddball technology program such as SAFE-400.  No technology program like that actually results in usable hardware on a timescale exceeding 20 years. 

I make that statement because what is needed to reject waste heat on Mars is not the same thing as is needed to reject waste heat in space.  On Mars you bury coolant pipes to reject heat far more efficiently in the cold regolith than any possible radiation-to-space scheme.  No one is actually doing that kind of design,  and that is how I know no government is yet serious about actually doing the Mars mission thing. 

With nuclear being a government monopoly pretty much universally,  there is no way for a private concern to develop what is needed for a Mars mission.  And that explains entirely why I think a fast trip to Mars is nonsense.  Until we the people change out these governments,  even exploration is unlikely in our lifetimes,  and any attempt at colonization is nonsense. 

There I went and said something true,  but extremely unpopular.  You all will have to change the way you vote before this impasse will change. 

Sorry.

GW

Last edited by louis (2017-06-10 17:25:40)


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

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#71 2017-06-10 18:29:45

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 18,195

Re: Going Solar...the best solution for Mars.

Lious, what form is the methane that you have created? What form is the oxygen?

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#72 2017-06-11 08:39:45

Oldfart1939
Member
Registered: 2016-11-26
Posts: 1,805

Re: Going Solar...the best solution for Mars.

Louis-

I think you need to step back and take a realistic look at what you've been suggesting for the "first mission!" All  simply to avoid use of a nuclear reactor!
You've suggested that the explorer/astronauts spend a lot of time digging trenches for bladders without even suggesting how they are to accomplish this task, and with no equipment supplied through the weight allowances! Then you've suggested 3 metric tonne Titanium storage tanks for methane without a weight allowance for the massive Sabatier reactor (not yet built--even a pilot model), and a Moxie unit not yet tested.
This is pure fantasy! A lot of the equipment may be light weight, but is very bulky to transport, especially empty fuel tanks.
If your scheme were to be adopted, we'd be getting everything "in place" by the mid 2040s! The overall cost would be enormous, too!

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#73 2017-06-11 16:17:52

louis
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From: UK
Registered: 2008-03-24
Posts: 5,615

Re: Going Solar...the best solution for Mars.

A Rover with a digger attachment is - for me - a necessary part of the overall Mission One architecture. It isn't exclusively required for methane storage. Digging trenches for energy storage isn't actually a do-or-die element, it's just that I think it would be important to establish whether we can find low mass ways of storing methane on Mars. It doesn't form part of the calculations for total energy output that I have set out here. But it would be a fantastic technical achievement.  Remember, the pioneers are going to spend maybe 700 sols on the planet.  That's a lot of time.  I can't think of many more useful things they could do than master trench digging and mining techniques on Mars.

You've seen my mass calculations. They aren't huge - a max. of 13 tonnes but possibly much lower if we can use Megaflex-style 250 w/kg solar panels. That was to match a hypothetical constant 100 Kwe nuclear power solution.  So far no one has put forward a full mass account for a nuclear solution, although kbd has come close and, for a six person mission, appears to be coming in at 10.5 tonnes for 6 x 10 Kwe KiloPower units plus perhaps a couple of tonnes for solar panels, chemical batteries and homopolar batteries, but let's make it 11.5 tonnes. But that's 11.5 tonnes for a 60Kwe output. If you scale that up to 100Kwe output, which was my comparison point, the figure would be 19.1 tonnes, about 7 tonnes more.

I have included a mass allowance for the Sabatier reactor. That was contained in the 2 tonnes for the methane-oxygen plant. That overall figure included 885kgs  for the water extractor process, leaving 1.115 tonnes for the rest of the process. Remember, this is not a propellant production plant - the amount of methane and oxygen being produced is relatively modest (just over a tonne). My 2 tonne allowance is possibly too much as the following citation gives a production of 1kg of methane per sol from a machine massing at a tiny 50 kgs. So maybe my proposed plant would be closer to one tonne, in which case the solar-batteries-methane option could be anything between 10 and 12 tonnes.

From Wikipedia:

"A variation of the basic Sabatier methanation reaction may be used via a mixed catalyst bed and a reverse water gas shift in a single reactor to produce methane from the raw materials available on Mars, utilizing water from the Martian subsoil and carbon dioxide in the Martian atmosphere.[10] A 2011 prototype test operation that harvested CO2 from a simulated Martian atmosphere and reacted it with H2, produced methane rocket propellant at a rate of 1 kg/day, operating autonomously for 5 consecutive days, maintaining a nearly 100% conversion rate. An optimized system of this design massing 50 kg "is projected to produce 1 kg/day of O2:CH4 propellant ... with a methane purity of 98+% while consuming 700 Watts of electrical power." Overall unit conversion rate expected from the optimized system is one tonne of propellant per 17 MWh energy input."



Oldfart1939 wrote:

Louis-

I think you need to step back and take a realistic look at what you've been suggesting for the "first mission!" All  simply to avoid use of a nuclear reactor!
You've suggested that the explorer/astronauts spend a lot of time digging trenches for bladders without even suggesting how they are to accomplish this task, and with no equipment supplied through the weight allowances! Then you've suggested 3 metric tonne Titanium storage tanks for methane without a weight allowance for the massive Sabatier reactor (not yet built--even a pilot model), and a Moxie unit not yet tested.
This is pure fantasy! A lot of the equipment may be light weight, but is very bulky to transport, especially empty fuel tanks.
If your scheme were to be adopted, we'd be getting everything "in place" by the mid 2040s! The overall cost would be enormous, too!


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

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#74 2017-06-11 17:30:50

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 18,195

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#75 2017-06-11 18:19:54

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,615

Re: Going Solar...the best solution for Mars.

A standard 500 Gallon propane tank can carry about 0.93 ton of propane. The empty tank weighs about 400 kg but with titantium or other low mass materials we can probably get that down to the 250 kg mark.  Methane is a bit heavier than propane at 0.49 grams per cubic centimetre but is more energy rich I believe.

With 0.93 ton of methane you should be able to generate about 4600 Kwehs of electricity enough to provide power at 12Kwes (2 Kwes per person) for 15 days.  For the total of methane produced under my proposal I think there is about 17 sols' supply plus another 2 sols supply from chemical batteries.

I think if I revisit the figures I may be able to get the figure for guaranteed supply up because the mass for tanks can probably be reduced.  Need to investigate low pressure storage in lightweight bladders or possibly as clathrates on the surface. All worth investigating. Ideally, I'd like to get the power credit up a little more.

Apologies BTW,  I think I overstated the amount of electrical power available on landing earlier having temporarily forgotten to the conversion from energy to electrical power.



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