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#1 2017-06-04 18:00:25

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,652

Going Solar...the best solution for Mars.

OK here's my more detailed proposal for a solar-based energy system to power Mission One on Mars. [In view of recent comments on other threads, I hope people can address the calculations, architecture and assumptions rather than making ad hominem attacks. I have made it quite clear before that a nuclear proposal is doable. I don't doubt the integrity of people who make the proposal. I just doubt that it will be as a good as solar and here are the reasons why...]


SOLAR ENERGY SYSTEM ON MARS (SESOM)

1.    Some  8 years prior to the arrival of humans,  LZ (Landing Zone) Robots land at the base site ans SESOM implementation begins. The robots deploy a 1200 sq metre PV system that delivers around 427 KWehs each sol. The robot rovers (powered by the PV syestem) clear and mark out the landing zone.

2.    6 years prior to the arrival of humans on Mars the MWO  (Methane, water and oxygen) plant is landed together with a further 2400 sq. metres of PV panelling - averaging 854 KwHs per sol.  This automated machine concentrates and condenses water  out of the atmosphere (3 kgs per sol over summer months – 200 sols, so about 600 kgs every two years). In the run up to humans landing it produces 1800 Kgs of water.  From the water, 234 kgs of hydrogen is harvested. 

3.    The 234 kgs of hydrogen is combined with carbon and oxygen (processed from the atmosphere and water) to create methane, 1026 Kgs in total, amounting to around 11000 KWhs of energy,  capable of producing about 5000 KWehs.  This can provide for the basic functioning of the base over about 100 sols. Large amounts of carbon and oxygen are also produced - 2 tonnes of oxygen at a minimum.

4.    At Year 1 Humans land with 7000 sq metres of PV panelling.

5.    On arrival the pioneers prioritise further methane and oxygen production, collecting thousands of kgs of water and CO2 for processing. The methane is stored in plastic bladder - lined trenches with regolith cover.  After three months, they have an additional 2000 Kgs of methane and 3000 Kgs of oxygen.

6.     Thereafter, water and CO2 continue to be processed. A further 5000 kgs of oxygen for combustion purposes is produced over the remained of Mission One.  By the end of Mission One, assuming no major dust storms, the settlement will have a store of  about 3000 Kgs of methane, with enough oxygen for its combustion, an energy reserve  of about 15000 KweHs.  In the event of dust storms,  this storage will be made use of and so may be depleted in part by the end of the mission.   

7.    The pioneers arrive with 500 Kgs of hydrogen, enabling them to make methane immediately in the event of a dust storm coinciding with their arrival.

8.     Once the base is well established, the pioneers will work to produce their own ISRU batteries so that power storage is further enhanced.


MASS BREAKDOWN

Total solar cells:                          3.0 tonnes.  (See Note 1)

Associated solar
power equipment
(converters, cabling and
so on)                                       1 tonne (see Note 2)


Methane/oxygen                          2 tonnes (see Note 3)
plant.

Inflatable gas bladders:                 1.5 tonnes      OR

Titanium gas tanks:                      3 tonnes

Batteries                                    2 tonnes (mostly Rover/mobile robot batteries)

Two 20 Kw generators                  500 kgs.


TOTAL MASS: 11.5 tonnes or (using titanium gas tanks) 13 tonnes.

To be noted: batteries are dual use, providing power back up for life support etc but also powering Rovers. If we split the 2 tonnes of batteries between transport and energy, the overall tonnage of the system could be as low as 10.5 tonnes.

[NB - Since I posted, SpaceNut has supported Kbd's figure of 250W per kg for the ATK Megaflex, posting some back up on that. If 250 W per Kg is accurate, then of course these mass estimates for a solar energy system are too high - you can probably take off 1.5 tonnes...so the lowest estimate would then be 9 tonnes.]


IMPORTANT ASSUMPTIONS AND DUST STORM AMELIORATION

Water ice melting, oxygen production and heating of water to provide hot water and heating of internal hab air, can (when necessary) take place during hours of light.

Lap tops are powered from batteries that are charged during the day.

Cooking takes place during the day using slow cookers or is heated during hours of darkness by microwave ovens using minimal power e.g. (0.04 KwH for one meal).

Hot water for showers and kitchen use is kept hot in aerogel lagged tanks.  Boiling of water for hot drinks will not require much additional energy.

During dust storms,  the following will action will be taken:

-    More cleaning of solar panels will take place to ensure maximum levels are maintained.

-    Even during the worst dust storms, the minimum obtained should be about 1600 KWehs (68% reduction on a summer time low of 5000 Kwehs).  1600 Kwehs is way more than the 294 Kwehs required to maintain basic functioning and life support (12 Kwes constant over the sol). If it is not, the settlement can call on its methane/oxygen reserves to provide power. (See Note 4) In a severe dust storm situation 600 KWhes could be used to provide 30 Kwes constant for 16 hours of night/low light and for the remaining 8 hours, there would be an average 125 Kwes available. Note - Edited from previous suggestion of 40 Kws for the 16 hours which I have now noted 2 tonnes of battery could not actually supply...but of course the 30 Kw can be topped up to 40 Kwe if desired through use of the methane powered generator.

-    The methane powered generators can  be used at full power, which should give 40 Kws constant. The generators can be used to top up the batteries as well to provide power flexibility.

ADVANTAGES OF A SOLAR POWER SYSTEM

1.    Flexibility. You can power explorations to mining areas a few Kms away. You can power mini rocket hoppers to undertake exploration.
2.    High power periods in the sol when industrial experiments such as smelting and brick firing can be undertaken.
3.    Back up available through different delivery systems, so no need to have a doubling up of capacity as with a single nuclear reactor system.
4.     A much larger KWehs ouput per sol in comparison with similar tonnage nuclear systems, allowing for a more sophisticated mission.

NOTES

Note 1 Based on ATK Megaflex:

See the following link:

http://www.lpi.usra.edu/opag/meetings/a … uchamp.pdf

In earth orbit this delivers 150 Watts per kgs. For Mars, 43% of that figure and take off a further 5% for atmospheric effects = 57 watts.
57 watts x 3000 (for 3 tonnes of PV) =  171 Kwes. The average for hours of light would be 342 Kwes.  Total KWehs per sol would on average be 12.5 x 342 = 4275 KWehs.

Seasonal variation would likely be of the order of 4107 to 5363 KWehs per sol. See following link (page 856):

http://www.uapress.arizona.edu/onlinebk … rces30.pdf

The 4257 KWehs average  compares with the 2450 KWehs [Edited from 1000 Kwhes - calculation error] constant of the SAFe 400 design, the most commonly cited nuclear power option. Each sol, a portion of this solar energy would be assigned to methane/oxygen production and a portion to battery storage. In order to provide 30 Kwes constant for 16 hours of night and low light hours, 600 KWehs could be used as battery storage, if necessary.

Note 2 Difficult to establish an estimate for the additional electrical equipment required for the PV system (excluding batteries). I have made an allowance of 33% which is probably on the generous side.

Note 3 Estimate based on 885 Kg machine for water concentration from Mars atmosphere producing around  3 kgs of water per sol at Chryse Planitia latitude. See following link:

http://www.lpi.usra.edu/publications/re … ington.pdf

Note 4

See page 860 - graph (a):


http://www.uapress.arizona.edu/onlinebk … rces30.pdf

VARIATIONS AND COMMENTS

I am not saying this is the perfect design for a solar-based system. It is debatable whether it's better to bring hydrogen feedstock to begin methane manufacture (as in Mars Direct). Perhaps it is. However, I do like the failsafe feel of a machine being there that can concentrate constituent parts of the atmosphere.

[PS I should have added I finished this off in something of a hurry as it appeared some other posters here wanted to close off this debate. I wasn't able to justify all my numbers e.g. gas tanks and so on. Will be happy to add detail as required.]

Last edited by louis (2017-06-05 09:47:40)


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#2 2017-06-04 21:15:39

RobS
Member
From: South Bend, IN
Registered: 2002-01-15
Posts: 1,701
Website

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

This is very thorough, Louis, but I don't have access to data to correct or improve it.

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#3 2017-06-04 22:13:59

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 18,346

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

This sort of sounds like a corporate or consortium funded mission and seem quite complete with preloaded planning.

Not sure of the hydrogen gaseous loss rate but we do know of LH2 to which even on mars we would be lossing even in a Titanium tanks.

It might be best to just collect for processing once man is there for not only the CO2 but Water.

I think the Plastic blatter tanks for water are the way to go for sure as we can build the trench with soft cushoin for blatter to rest on, cover with a protective casing to keep from punchering lay the blatter within it as its covered and then filled as we go from water collection.

Sure would go with a metal tank for the gaseous or Liquified Co2 collection and holding.

Man can always process the water and co2 upon arrival for refueling as the collection of both is complete before man evens starts out.

That said for all the supplied plan we still need a Mars lander capable of landing the tonnage without changing its design for every payload brought to mars.

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#4 2017-06-05 03:15:36

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,652

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

SpaceNut,

Thank you for the reminder. I need to look into gas loss rates as that will affect the required production rates.

Once we arrive at somewhere like north east Chryse Planitia where water makes up something like 6% of the regolith, water supply should not be a problem. We should simply be able to dig up the regolith, heat it and condense out the water. However, I think for Mission One we probably want as much "failsafeness" built in, so it would be desirable to have an alternative means of water extraction. 

Yes, a good point, the plastic bladder tanks will need some sort of protective top layer. If the tanks were say metre wide inflatable cylinders we might rest granite/basalt slabs on the top edges of the two sides and then lay over regolith.

Yes - an "all purpose lander" would be nice, but I am guessing we might need maybe three variations (one for mobile equipment, one for static operational equipement and one for supplies like food).

SpaceNut wrote:

This sort of sounds like a corporate or consortium funded mission and seem quite complete with preloaded planning.

Not sure of the hydrogen gaseous loss rate but we do know of LH2 to which even on mars we would be lossing even in a Titanium tanks.

It might be best to just collect for processing once man is there for not only the CO2 but Water.

I think the Plastic blatter tanks for water are the way to go for sure as we can build the trench with soft cushoin for blatter to rest on, cover with a protective casing to keep from punchering lay the blatter within it as its covered and then filled as we go from water collection.

Sure would go with a metal tank for the gaseous or Liquified Co2 collection and holding.

Man can always process the water and co2 upon arrival for refueling as the collection of both is complete before man evens starts out.

That said for all the supplied plan we still need a Mars lander capable of landing the tonnage without changing its design for every payload brought to mars.


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

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#5 2017-06-05 09:46:32

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,652

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

louis wrote:

OK here's my more detailed proposal for a solar-based energy system to power Mission One on Mars. [In view of recent comments on other threads, I hope people can address the calculations, architecture and assumptions rather than making ad hominem attacks. I have made it quite clear before that a nuclear proposal is doable. I don't doubt the integrity of people who make the proposal. I just doubt that it will be as a good as solar and here are the reasons why...]


SOLAR ENERGY SYSTEM ON MARS (SESOM)

1.    Some  8 years prior to the arrival of humans,  LZ (Landing Zone) Robots land at the base site ans SESOM implementation begins. The robots deploy a 1200 sq metre PV system that delivers around 427 KWehs each sol. The robot rovers (powered by the PV syestem) clear and mark out the landing zone.

2.    6 years prior to the arrival of humans on Mars the MWO  (Methane, water and oxygen) plant is landed together with a further 2400 sq. metres of PV panelling - averaging 854 KwHs per sol.  This automated machine concentrates and condenses water  out of the atmosphere (3 kgs per sol over summer months – 200 sols, so about 600 kgs every two years). In the run up to humans landing it produces 1800 Kgs of water.  From the water, 234 kgs of hydrogen is harvested. 

3.    The 234 kgs of hydrogen is combined with carbon and oxygen (processed from the atmosphere and water) to create methane, 1026 Kgs in total, amounting to around 11000 KWhs of energy,  capable of producing about 5000 KWehs.  This can provide for the basic functioning of the base over about 100 sols. Large amounts of carbon and oxygen are also produced - 2 tonnes of oxygen at a minimum.

4.    At Year 1 Humans land with 7000 sq metres of PV panelling.

5.    On arrival the pioneers prioritise further methane and oxygen production, collecting thousands of kgs of water and CO2 for processing. The methane is stored in plastic bladder - lined trenches with regolith cover.  After three months, they have an additional 2000 Kgs of methane and 3000 Kgs of oxygen.

6.     Thereafter, water and CO2 continue to be processed. A further 5000 kgs of oxygen for combustion purposes is produced over the remained of Mission One.  By the end of Mission One, assuming no major dust storms, the settlement will have a store of  about 3000 Kgs of methane, with enough oxygen for its combustion, an energy reserve  of about 15000 KweHs.  In the event of dust storms,  this storage will be made use of and so may be depleted in part by the end of the mission.   

7.    The pioneers arrive with 500 Kgs of hydrogen, enabling them to make methane immediately in the event of a dust storm coinciding with their arrival.

8.    Once the base is well established, the pioneers will work on producing their own batteries to further enhance power storage.


MASS BREAKDOWN

Total solar cells:                          3.0 tonnes.  (See Note 1)

Associated solar
power equipment
(converters, cabling and
so on)                                       1 tonne (see Note 2)


Methane/oxygen                          2 tonnes (see Note 3)
plant.

Inflatable gas bladders:                 1.5 tonnes      OR

Titanium gas tanks:                      3 tonnes

Batteries                                    2 tonnes (mostly Rover/mobile robot batteries)

Two 20 Kw generators                  500 kgs.


TOTAL MASS: 11.5 tonnes or (using titanium gas tanks) 13 tonnes.

To be noted: batteries are dual use, providing power back up for life support etc but also powering Rovers. If we split the 2 tonnes of batteries between transport and energy, the overall tonnage of the system could be as low as 10.5 tonnes.

[NB - Since I posted, SpaceNut has supported Kbd's figure of 250W per kg for the ATK Megaflex, posting some back up on that. If 250 W per Kg is accurate, then of course these mass estimates for a solar energy system are too high - you can probably take off 1.5 tonnes...so the lowest estimate would then be 9 tonnes.]


IMPORTANT ASSUMPTIONS AND DUST STORM AMELIORATION

Water ice melting, oxygen production and heating of water to provide hot water and heating of internal hab air, can (when necessary) take place during hours of light.

Lap tops are powered from batteries that are charged during the day.

Cooking takes place during the day using slow cookers or is heated during hours of darkness by microwave ovens using minimal power e.g. (0.04 KwH for one meal).

Hot water for showers and kitchen use is kept hot in aerogel lagged tanks.  Boiling of water for hot drinks will not require much additional energy.

During dust storms,  the following will action will be taken:

-    More cleaning of solar panels will take place to ensure maximum levels are maintained.

-    Even during the worst dust storms, the minimum obtained should be about 1600 KWehs (68% reduction on a summer time low of 5000 Kwehs).  1600 Kwehs is way more than the 294 Kwehs required to maintain basic functioning and life support (12 Kwes constant over the sol). If it is not, the settlement can call on its methane/oxygen reserves to provide power. (See Note 4) In a severe dust storm situation 600 KWhes could be used to provide 30 Kwes constant for 16 hours of night/low light and for the remaining 8 hours, there would be an average 125 Kwes available. Note - Edited from previous suggestion of 40 Kws for the 16 hours which I have now noted 2 tonnes of battery could not actually supply...but of course the 30 Kw can be topped up to 40 Kwe if desired through use of the methane powered generator.

-    The methane powered generators can  be used at full power, which should give 40 Kws constant. The generators can be used to top up the batteries as well to provide power flexibility.

ADVANTAGES OF A SOLAR POWER SYSTEM

1.    Flexibility. You can power explorations to mining areas a few Kms away. You can power mini rocket hoppers to undertake exploration.
2.    High power periods in the sol when industrial experiments such as smelting and brick firing can be undertaken.
3.    Back up available through different delivery systems, so no need to have a doubling up of capacity as with a single nuclear reactor system.
4.     A much larger KWehs ouput per sol in comparison with similar tonnage nuclear systems, allowing for a more sophisticated mission.

NOTES

Note 1 Based on ATK Megaflex:

See the following link:

http://www.lpi.usra.edu/opag/meetings/a … uchamp.pdf

In earth orbit this delivers 150 Watts per kgs. For Mars, 43% of that figure and take off a further 5% for atmospheric effects = 57 watts.
57 watts x 3000 (for 3 tonnes of PV) =  171 Kwes. The average for hours of light would be 342 Kwes.  Total KWehs per sol would on average be 12.5 x 342 = 4275 KWehs.

Seasonal variation would likely be of the order of 4107 to 5363 KWehs per sol. See following link (page 856):

http://www.uapress.arizona.edu/onlinebk … rces30.pdf

The 4257 KWehs average  compares with the 2450 KWehs [Edited from 1000 Kwhes - calculation error] constant of the SAFe 400 design, the most commonly cited nuclear power option. Each sol, a portion of this solar energy would be assigned to methane/oxygen production and a portion to battery storage. In order to provide 30 Kwes constant for 16 hours of night and low light hours, 600 KWehs could be used as battery storage, if necessary.

Note 2 Difficult to establish an estimate for the additional electrical equipment required for the PV system (excluding batteries). I have made an allowance of 33% which is probably on the generous side.

Note 3 Estimate based on 885 Kg machine for water concentration from Mars atmosphere producing around  3 kgs of water per sol at Chryse Planitia latitude. See following link:

http://www.lpi.usra.edu/publications/re … ington.pdf

Note 4

See page 860 - graph (a):


http://www.uapress.arizona.edu/onlinebk … rces30.pdf

VARIATIONS AND COMMENTS

I am not saying this is the perfect design for a solar-based system. It is debatable whether it's better to bring hydrogen feedstock to begin methane manufacture (as in Mars Direct). Perhaps it is. However, I do like the failsafe feel of a machine being there that can concentrate constituent parts of the atmosphere.

[PS I should have added I finished this off in something of a hurry as it appeared some other posters here wanted to close off this debate. I wasn't able to justify all my numbers e.g. gas tanks and so on. Will be happy to add detail as required.]


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

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#6 2017-06-05 14:41:21

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

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

Well Louis, you seem to be having fun.  So I won't bore you with any inconvenient facts :-)

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#7 2017-06-05 16:04:13

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,652

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

100% fact-free comment from Antius.  Why do facts, when you can do ad hominem?

Antius wrote:

Well Louis, you seem to be having fun.  So I won't bore you with any inconvenient facts :-)


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

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#8 2017-06-06 00:38:42

kbd512
Moderator
Registered: 2015-01-02
Posts: 3,338

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

Louis,

What kind of continuous and peak power does the plant require?

WAVAR alone requires 12kWe to 15kWe continuous power and peak power is 25kWe.

I would skip the plastic bladders and Titanium tanks and just use Aluminum.  It's not that heavy and it's what we typically store rocket propellants in when mass matters.

Why do you need so much battery tonnage for the rover?

Your storage quantities for LOX and LCH4 don't make much sense to me.  An optimum O/F ratio for LOX/LCH4 should be between 3 and 3.5 in a vacuum.  Wikipedia says 3.45.  I thought Raptor was 3.5, but I could be wrong.  Your stored masses for combustion in a rocket engine are way off.  You should have something like 6,900kg or more of LOX to burn 2,000kg of LCH4 since Mars is so close to a vacuum.

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#9 2017-06-06 02:02:48

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,652

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

Thanks kbd for those useful comments.

I knew the WAVAR requirement but I didn't have time to research in detail the other power requirements so that was a bit of a guesstimate. I will try and get a more accurate fix on that. I found this:

At 100% efficiency, electrolysis would require close to 40 kWh per kilogram of hydrogen—a number derived from the higher heating value of hydrogen, a physical property. However, today’s systems have an efficiency of about 60-70%, with the DOE’s future target at 75%.

https://phys.org/news/2007-10-analysis- … y.html#jCp

So maybe 55 Kwhs for one kg = 165 Kwhs for 3 Kgs. Not sure if that has to be continuous...I don't think it would, so makes it easier to manage.

So far we have 367 Kwhs for WAVAR and 165 Kwhs for electrolysis. 529 Kwhs in total.               

3600 s. metres of PV panelling should be producing an average of 1281 Kwehs per sol.

The power requirement for the Sabatier reaction involves minimal power it seems if Wikipedia is to be believed.

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

I will look into the other aspects of the process but I think the PV panelling budget may just about cover it.   

I haven't seen any aluminium gas tanks advertised when I researched this...isn't there an issue over pressurisation? I need to look into that more.

The PV panelling for Rover operation may be a bit excessive. But I am envisaging them being fairly active clearing the site of stones and boulders.  They would be clearing quite a large area - maybe something like 250 x 250 metres or even larger. Before they could clear the landing zone they would have to explore and identify any v. large obstacles that could not be removed to make sure they had the capability to clear the zone, and they would be checking ground conditions. They would be laying transponders and communicating with Earth regularly. All in all I am envisaging quite a bit of power usage.


kbd512 wrote:

Louis,

What kind of continuous and peak power does the plant require?

WAVAR alone requires 12kWe to 15kWe continuous power and peak power is 25kWe.

I would skip the plastic bladders and Titanium tanks and just use Aluminum.  It's not that heavy and it's what we typically store rocket propellants in when mass matters.

Why do you need so much battery tonnage for the rover?

Your storage quantities for LOX and LCH4 don't make much sense to me.  An optimum O/F ratio for LOX/LCH4 should be between 3 and 3.5 in a vacuum.  Wikipedia says 3.45.  I thought Raptor was 3.5, but I could be wrong.  Your stored masses for combustion in a rocket engine are way off.  You should have something like 6,900kg or more of LOX to burn 2,000kg of LCH4 since Mars is so close to a vacuum.


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

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#10 2017-06-06 08:52:04

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

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

louis wrote:

100% fact-free comment from Antius.  Why do facts, when you can do ad hominem?

Antius wrote:

Well Louis, you seem to be having fun.  So I won't bore you with any inconvenient facts :-)

Louis, the problem is that we have gone over the facts, over and over again.  Many hours of time were invested.  We have done a lot of analysis in other threads and the thin-film based power supply has been shown to be highly problematic.  So why start a new thread presenting it as a viable mission scenario, without answering any of the fundamental problems that have been uncovered?  How many times do I need to kill this white elephant?

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#11 2017-06-06 09:36:57

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,652

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

Problems so fundamental that Elon Musk intends using solar power on Mars?

https://www.youtube.com/watch?v=_J4RxDZJ6Vg

Musk is the only guy on the planet who has shown he has the determination and the wherewithal to get humans to Mars. He clearly sees solar as eminently "straightforward" as he says, and doable. So why are you so eager to diss solar?

All you mean by we've "gone over the facts over and over again" is that you haven't been able to put forward a convincing case as to  why nuclear is better than solar. I suggest you set up a separate thread and show how nuclear would work in all scenarios.

I have been asked a number of questions about how solar would work and I was asked to set out a detailed mass budget. I've done that. If you can't be bothered to challenge it factually, that's your concern.


Antius wrote:
louis wrote:

100% fact-free comment from Antius.  Why do facts, when you can do ad hominem?

Antius wrote:

Well Louis, you seem to be having fun.  So I won't bore you with any inconvenient facts :-)

Louis, the problem is that we have gone over the facts, over and over again.  Many hours of time were invested.  We have done a lot of analysis in other threads and the thin-film based power supply has been shown to be highly problematic.  So why start a new thread presenting it as a viable mission scenario, without answering any of the fundamental problems that have been uncovered?  How many times do I need to kill this white elephant?

Last edited by louis (2017-06-06 09:37:37)


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#12 2017-06-06 10:20:08

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

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

Elon Musk is also promoting Solar technology through his Solar City business, as well as promoting the Tesla automobiles. Yes, he has the wherewithal to take us to Mars with his rockets, but so far has done little to explain what happens after we get there. He has yet to offer anything regarding infrastructure or continued support for those his company wants to transport there. Solar City is financially on the ropes, and Tesla is also fraught with difficulties.

I agree that Elon is a remarkable individual with a great deal of vision, but he too, can make mistakes.

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#13 2017-06-06 11:33:57

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

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

Oldfart1939 wrote:

Elon Musk is also promoting Solar technology through his Solar City business, as well as promoting the Tesla automobiles. Yes, he has the wherewithal to take us to Mars with his rockets, but so far has done little to explain what happens after we get there. He has yet to offer anything regarding infrastructure or continued support for those his company wants to transport there. Solar City is financially on the ropes, and Tesla is also fraught with difficulties.

I agree that Elon is a remarkable individual with a great deal of vision, but he too, can make mistakes.

Agreed.  There is of course the inescapable fact that purchasing a small nuclear reactor would be an absolute administrative and legal headache for a privateer like Elon Musk.  He may have decided that it was easier and cheaper to work with a more massive and less efficient energy system than to attempt to pick his way through the legal minefield of trying to procure and launch an SP-100.  It is politics and legal skulduggery that has crippled the nuclear power industry here on Earth.

That said, the difference in mass between a small fast reactor and an encapsulated (UV protected) solar power system, both capable of delivering the same end use power output, is more than a factor ten.  There is no way around that.  Even on Earth, thin-film PV is typically encased between glass panels to prevent rapid UV degradation.  Even then, efficiency declines at ~1%/year.  Imagine taking thin-film solar cells into an environment with a UV damage rate hundreds of times worse than Earth’s with no encapsulation at all?  That is essentially Louis’s scenario.  That is before we get into issues like energy storage and deployment of the system on Mars.

In the long run, we will need to build power systems on Mars using energy and resources from Mars.  The analysis in previous threads on this topic shows that that is unlikely to be energetically favourable to do that using solar power systems, with energy payback times of ten years or more.

These problems are a direct result of the poor energy density of sunlight on Mars.  Sunlight is a time-averaged energy flux of about 140W/m2 on Mars.  Compare that to a fast reactor core, which has power density of 300MW/m3.  That's a difference of six orders of magnitude.

Last edited by Antius (2017-06-06 11:40:31)

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#14 2017-06-06 11:50:17

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,652

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

I agree he's not incapable of making mistakes.  I have criticised him for what I consider his lack of understanding of what it will take to build a successful culture that works well on Mars - his open migration policy sounds like the height of folly to me and will be exploited by people's who aims and objectives contradict Musk's.

He's really a technical man. I think it highly unlikely that he hasn't thought long and hard about providing energy on Mars because he will know that is the ground on which everything else is built. The fact he talks about how Space X have been considering solar panel roll out devices for Mars shows his technical team must be on the case. My prediction: he'll be able to do it twice as effectively as NASA and at half the price.


Oldfart1939 wrote:

Elon Musk is also promoting Solar technology through his Solar City business, as well as promoting the Tesla automobiles. Yes, he has the wherewithal to take us to Mars with his rockets, but so far has done little to explain what happens after we get there. He has yet to offer anything regarding infrastructure or continued support for those his company wants to transport there. Solar City is financially on the ropes, and Tesla is also fraught with difficulties.

I agree that Elon is a remarkable individual with a great deal of vision, but he too, can make mistakes.


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#15 2017-06-06 13:06:16

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,652

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

You haven't shown that a workable nuclear power solution is less massive than a solar solution.  Where are your detailed proposals? Where are anyone's detailed proposals for a nuclear option?

Solar City and Tesla are nothing to do with Space X legally.  If they go down, it has no bearing on Space X. I doubt Space X solar and batteries will be those of Solar City and Tesla in any case, though I suppose it's not impossible. You claim:

That said, the difference in mass between a small fast reactor and an encapsulated (UV protected) solar power system, both capable of delivering the same end use power output, is more than a factor ten.

I note you phrase this carefully by using the misleading phrase "same end use power output"  which no doubt you will interpret to mean a constant power output. What good is a power output of 100 Kws if we need a power output of 500 Kws to undertake a range of activities? Let's see a nuclear system match solar's peak power...to do that, you'll need to quintuple your mass.

Leaving that aside, you will have  read what Kbd and SpaceNut have stated about the ATK Megaflex system - it's space-rated and delivering 250 watts per kg (I used a lower figure of 150w, 57w for Mars,  in the above). Your 100 Kw nuclear reactor will need to mass less than 1.3 tonnes to match that. No way are you going to get close to that if a 10 Kw KiloPower unit clocks in at 1.5tonnes.

I am not sure why you are going on about encapsulation. Have you seen Megaflex?

https://www.youtube.com/watch?v=3dZuiYqcbXI

The idea that Megaflex will fall apart on Mars doesn't seem v. likely to me.

A core is a core - it's not a the whole system, so another irrelevance.

Antius wrote:
Oldfart1939 wrote:

Elon Musk is also promoting Solar technology through his Solar City business, as well as promoting the Tesla automobiles. Yes, he has the wherewithal to take us to Mars with his rockets, but so far has done little to explain what happens after we get there. He has yet to offer anything regarding infrastructure or continued support for those his company wants to transport there. Solar City is financially on the ropes, and Tesla is also fraught with difficulties.

I agree that Elon is a remarkable individual with a great deal of vision, but he too, can make mistakes.

Agreed.  There is of course the inescapable fact that purchasing a small nuclear reactor would be an absolute administrative and legal headache for a privateer like Elon Musk.  He may have decided that it was easier and cheaper to work with a more massive and less efficient energy system than to attempt to pick his way through the legal minefield of trying to procure and launch an SP-100.  It is politics and legal skulduggery that has crippled the nuclear power industry here on Earth.

  There is no way around that.  Even on Earth, thin-film PV is typically encased between glass panels to prevent rapid UV degradation.  Even then, efficiency declines at ~1%/year.  Imagine taking thin-film solar cells into an environment with a UV damage rate hundreds of times worse than Earth’s with no encapsulation at all?  That is essentially Louis’s scenario.  That is before we get into issues like energy storage and deployment of the system on Mars.

In the long run, we will need to build power systems on Mars using energy and resources from Mars.  The analysis in previous threads on this topic shows that that is unlikely to be energetically favourable to do that using solar power systems, with energy payback times of ten years or more.

These problems are a direct result of the poor energy density of sunlight on Mars.  Sunlight is a time-averaged energy flux of about 140W/m2 on Mars.  Compare that to a fast reactor core, which has power density of 300MW/m3.  That's a difference of six orders of magnitude.


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#16 2017-06-06 16:35:50

kbd512
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Registered: 2015-01-02
Posts: 3,338

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

MegaFlex and Kilopower are not flight qualified yet, Louis.  NASA is still working on both systems and both system are in an advanced state of development.  MegaFlex was principally developed to power for SEP and Kilopower was developed to replace inordinately expensive RTG's and to provide surface power for NASA's proposed human missions to Mars.  They seem to recognize that certain power systems are more suitable for specific tasks than others.

1kWe for a MegaFlex array in LEO is only 430We on Mars under ideal conditions.  That can and does drop to 140We, under less than ideal conditions, on a regular basis.  1kWe MegaFlex array weighs 7kg.  That means 51kg of solar array mass is required to guarantee 1kWe of output under all conditions or 510kg for 10kWe.

The power production and storage problems don't end there.  Mars has a day/night cycle.  You need at least 120kWe to provide power for the 12 hours when you get no power from the PV array, which means a 600kg battery.  In all reality, it's 16 hours, which means a 800kg battery.  That's just the mass of the 250Wh/kg cells.  The ISS ORU's add another 91kg of packaging for 15kWh packs.  There would be 8 individual packs required for a 120kWh battery if each individual pack stored 15kWh.  That's 728kg of additional mass.  On top of that, we actually have to guarantee that 10kWe during the day in addition to charging the batteries, which means another 510kg of solar panels.

The battery packs alone would weigh two thirds as much as Kilopower.  If some sort of composite is substituted for aluminum, which is what I would do, maybe we can cut that packaging mass by third.  Even so, any deep space capable 120kWh Lithium-ion battery using current technology would weigh about 1t.

The fact that you can produce more power than you can using Kilopower, on a fair weather day, is not what mission planners care about.  They want to know, with a high degree of certainty, that they've achieved minimum output targets.  I have never claimed nor thought that I couldn't potentially produce more power with PV panels than with Kilopower using a mass of PV panels equal to Kilopower.  I know this is possible, but neither NASA nor SpaceX operate equipment built for best case scenarios.

If the battery capacity and PV panel output both improve by about a factor of 2, then we can guarantee equivalent performance for equivalent mass.  NASA and many others are still working on this.  Unfortunately, we're just not there yet.  I'm confident that one day we will be, but there's no reason to wait for that day to come when workable solutions exist using existing technologies.  As continuous power requirements go up, next generation PV panel and battery technology still can't compete with energy sources that contains 70 to 80 million mega joules per kilogram when burn up rates greater than 1% are achieved (and they are achievable because they have been achieved).

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#17 2017-06-06 17:02:06

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,652

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

Have you read my original post on this thread?   It doesn't sound like you have.

Why are you only considering chemical batteries - why not methane storage as well?  Why are you assuming you can only make energy post-landing of humans? Why are you assuming the pioneers can't make chemical batteries themselves on Mars?  Why, in short, are you trying to fix the rules so nuclear comes out on top, despite the fact that Musk, who probably knows more about the demands of Mars than anyone else on the planet sees solar as a very viable choice?

I've covered all the points in my original post. Solar can provide all this cover. But it can also provide peak power of several hundred watts on most sols. For a nuclear facility to produce the equivalent it would have be about 80 or more tonnes of mass. Peak power is next in importance to the required baseload. It allows us to do all sorts of things like smelting, conducting a wide range of experiments,  electrolysis, exploration, and fuelling up rocket hoppers.

Musk is clearly talking about solar arrays being deployed for Mars missions and it is Musk's Space X not NASA who are the serious contenders for being first to put humans on Mars.


kbd512 wrote:

MegaFlex and Kilopower are not flight qualified yet, Louis.  NASA is still working on both systems and both system are in an advanced state of development.  MegaFlex was principally developed to power for SEP and Kilopower was developed to replace inordinately expensive RTG's and to provide surface power for NASA's proposed human missions to Mars.  They seem to recognize that certain power systems are more suitable for specific tasks than others.

1kWe for a MegaFlex array in LEO is only 430We on Mars under ideal conditions.  That can and does drop to 140We, under less than ideal conditions, on a regular basis.  1kWe MegaFlex array weighs 7kg.  That means 51kg of solar array mass is required to guarantee 1kWe of output under all conditions or 510kg for 10kWe.

The power production and storage problems don't end there.  Mars has a day/night cycle.  You need at least 120kWe to provide power for the 12 hours when you get no power from the PV array, which means a 600kg battery.  In all reality, it's 16 hours, which means a 800kg battery.  That's just the mass of the 250Wh/kg cells.  The ISS ORU's add another 91kg of packaging for 15kWh packs.  There would be 8 individual packs required for a 120kWh battery if each individual pack stored 15kWh.  That's 728kg of additional mass.  On top of that, we actually have to guarantee that 10kWe during the day in addition to charging the batteries, which means another 510kg of solar panels.

The battery packs alone would weigh two thirds as much as Kilopower.  If some sort of composite is substituted for aluminum, which is what I would do, maybe we can cut that packaging mass by third.  Even so, any deep space capable 120kWh Lithium-ion battery using current technology would weigh about 1t.

The fact that you can produce more power than you can using Kilopower, on a fair weather day, is not what mission planners care about.  They want to know, with a high degree of certainty, that they've achieved minimum output targets.  I have never claimed nor thought that I couldn't potentially produce more power with PV panels than with Kilopower using a mass of PV panels equal to Kilopower.  I know this is possible, but neither NASA nor SpaceX operate equipment built for best case scenarios.

If the battery capacity and PV panel output both improve by about a factor of 2, then we can guarantee equivalent performance for equivalent mass.  NASA and many others are still working on this.  Unfortunately, we're just not there yet.  I'm confident that one day we will be, but there's no reason to wait for that day to come when workable solutions exist using existing technologies.  As continuous power requirements go up, next generation PV panel and battery technology still can't compete with energy sources that contains 70 to 80 million mega joules per kilogram when burn up rates greater than 1% are achieved (and they are achievable because they have been achieved).


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#18 2017-06-06 18:10:47

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 18,346

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

Like the solar panels the batteries for mars temperatures and currents are still in the developing stages as to get more out of LION we will need to tweek the electrolyte for the colder temperatures which is using sulfur, chlorides and flourine mixes to accomplish. With this the outputs and storage currents are going up for more wattage for the mass. Also we will not need to expend wattage to keep them as warm which gives more power back for other uses with these batteries.

Laying the solar panels on the ground is a bad idea as the output will drop a lot. Solar cells want to align perpendicular to the incoming suns rays for maximum coversion.

http://www.solarpaneltilt.com/
http://solarelectricityhandbook.com/sol … lator.html

Experiments & Analysis of the Role of Solar Power in Limiting Mars Rover Range

SunAltitude.gif

You would get more than 100% gain from a tracker on the north or south pole in mid summer (or on a sattelite/ space station) as opposed to a fixed solar array at that location. On the equator, the gain in output is less than 5% (or so I believe). When fixed set at the proper angle.

http://www.builditsolar.com/SiteSurvey/site_survey.htm

SunChartMarked.jpg

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#19 2017-06-06 18:16:51

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 18,346

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

Let say we do have methane to burn with oxygen in a closed loop exhaust gas recapture system, even though we create power for the duration of running we still are going to loss alot of that burning energy as heat which is a loss from the original energy that started the process to make the methane. We get Co,Co2, H2O from the burning funtion to try and save the energy of the initial compression, electrolysis and sabitier reactor energy to reuse to start the process all over again.

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#20 2017-06-06 18:28:39

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,652

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

Trackers might in some cases make sense on Earth but as the cost of solar comes down they make less and less sense. As for Mars, well "Mass is King" and so mass-heavy tracking equipment. Personally I think you would just use boulders and the like to create a mix of desired attitudes  to get the most out of your array.


SpaceNut wrote:

Like the solar panels the batteries for mars temperatures and currents are still in the developing stages as to get more out of LION we will need to tweek the electrolyte for the colder temperatures which is using sulfur, chlorides and flourine mixes to accomplish. With this the outputs and storage currents are going up for more wattage for the mass. Also we will not need to expend wattage to keep them as warm which gives more power back for other uses with these batteries.

Laying the solar panels on the ground is a bad idea as the output will drop a lot. Solar cells want to align perpendicular to the incoming suns rays for maximum coversion.

http://www.solarpaneltilt.com/
http://solarelectricityhandbook.com/sol … lator.html

Experiments & Analysis of the Role of Solar Power in Limiting Mars Rover Range

http://www.builditsolar.com/SiteSurvey/SunAltitude.gif

You would get more than 100% gain from a tracker on the north or south pole in mid summer (or on a sattelite/ space station) as opposed to a fixed solar array at that location. On the equator, the gain in output is less than 5% (or so I believe). When fixed set at the proper angle.

http://www.builditsolar.com/SiteSurvey/site_survey.htm

http://www.builditsolar.com/SiteSurvey/ … Marked.jpg


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#21 2017-06-06 18:33:55

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,652

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

Depends where you are burning. Put the generator in a hab with the water heater and I think that will offset your losses.


SpaceNut wrote:

Let say we do have methane to burn with oxygen in a closed loop exhaust gas recapture system, even though we create power for the duration of running we still are going to loss alot of that burning energy as heat which is a loss from the original energy that started the process to make the methane. We get Co,Co2, H2O from the burning funtion to try and save the energy of the initial compression, electrolysis and sabitier reactor energy to reuse to start the process all over again.

Last edited by louis (2017-06-06 18:34:16)


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#22 2017-06-06 18:55:57

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 18,346

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

I agree trying to save the heat via a water heating unit wrapped around the generator system is one way to cut the losses and get something that we will use.

The solar tracking is built into the ATK orbital fan units, so its not heavy at all.

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#23 2017-06-06 19:02:18

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,652

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

Thanks for the info SpaceNut...I had wrongly assumed the ATK fan units were static judging from the video I saw.

SpaceNut wrote:

I agree trying to save the heat via a water heating unit wrapped around the generator system is one way to cut the losses and get something that we will use.

The solar tracking is built into the ATK orbital fan units, so its not heavy at all.

Last edited by louis (2017-06-06 19:02:35)


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#24 2017-06-07 04:00:17

kbd512
Moderator
Registered: 2015-01-02
Posts: 3,338

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

louis wrote:

Have you read my original post on this thread?   It doesn't sound like you have.

The activities you're proposing are things we should concern ourselves with after we explore a bit and have some confirmation of where the resources are.  Maybe solar and battery technology will be sufficiently advanced at that point to actually do what you want to do.

louis wrote:

Why are you only considering chemical batteries - why not methane storage as well?  Why are you assuming you can only make energy post-landing of humans? Why are you assuming the pioneers can't make chemical batteries themselves on Mars?  Why, in short, are you trying to fix the rules so nuclear comes out on top, despite the fact that Musk, who probably knows more about the demands of Mars than anyone else on the planet sees solar as a very viable choice?

I assure you that I do not control the state of development of solar panels, batteries, or nuclear reactors.  I didn't decide that nuclear power delivers more energy than solar power for less mass, the physical universe did.

louis wrote:

I've covered all the points in my original post. Solar can provide all this cover. But it can also provide peak power of several hundred watts on most sols. For a nuclear facility to produce the equivalent it would have be about 80 or more tonnes of mass. Peak power is next in importance to the required baseload. It allows us to do all sorts of things like smelting, conducting a wide range of experiments,  electrolysis, exploration, and fuelling up rocket hoppers.

I suppose if we ignore those little problems of mass, complexity, and thus cost, then you've covered everything.

Why would you use a rocket hopper to travel a few kilometers when electrically-driven tracked rovers can take you there for less cost and complexity, not to mention far less danger of becoming another impact crater?

Why devote tons of mass to a methane plant instead of a battery powered rover with solar panels on the roof or a permanent battery and generator?

louis wrote:

Musk is clearly talking about solar arrays being deployed for Mars missions and it is Musk's Space X not NASA who are the serious contenders for being first to put humans on Mars.

If NASA gives him billions of dollars, he might be able to put people on Mars.  SpaceX hasn't put anyone into space yet.  I'm rooting for Mr. Musk and SpaceX, but his ideas are not a replacement for NASA or DARPA which solve all those pesky engineering problems to make things like Mars missions possible to begin with.

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#25 2017-06-07 04:44:16

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,652

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

kbd512 wrote:

The activities you're proposing are things we should concern ourselves with after we explore a bit and have some confirmation of where the resources are.  Maybe solar and battery technology will be sufficiently advanced at that point to actually do what you want to do.

You haven't shown that we can't do these things with the current state of technology. Musk is clearly positive about solar energy, but you know better. I have set out one approach which I think covers all angles.

kbd512 wrote:

I assure you that I do not control the state of development of solar panels, batteries, or nuclear reactors.  I didn't decide that nuclear power delivers more energy than solar power for less mass, the physical universe did.

You are dodging the question - which is why are you only considering "solar plus imported chemical batteries" rather than solar plus chemical batteries plus methane storage/generation plus ISRU batteries".

kbd512 wrote:

I suppose if we ignore those little problems of mass, complexity, and thus cost, then you've covered everything.

Why would you use a rocket hopper to travel a few kilometers when electrically-driven tracked rovers can take you there for less cost and complexity, not to mention far less danger of becoming another impact crater?

Why devote tons of mass to a methane plant instead of a battery powered rover with solar panels on the roof or a permanent battery and generator?

What little problem of mass?  It's you who has the problem with mass since your 10 x 10 Kw KiloPower units come in at 15 tonnes and that is with NO batteries or cabling at all and with no explanation of how they are going to be used.

Complexity?  Solar is one of the most straightforward energy technologies going, as Musk points out. Lay it out and plug it in! smile  Methane power generation is one of the best established technologies on Earth.  V. little development required for Mars. Chemical batteries are well understood in a space context.  But "nuclear power plus humans on a planet 100 Kms away over a two year period"?  Well, that is a step into the unknown.  I think it can be done but it will be complex (particularly re deployment and monitoring) and I doubt it will be done without batteries.

Cost?  You haven't shown that delivering the sort of system I propose will be less costly than sending a nuclear-based energy system because you haven't shown it is less mass.

A small robot rocket hopper on Mission One would be invaluable in identifying the locations where the Rover should go, rather than randomly coming across such areas.  I am not saying it is definitely doable on Mission One, but the higher KWeh output of a solar energy system would at least make it a feasible option. How to power the main exploratory Rover is debatable. 

The methane plant allows you to expand your energy storage constantly seamlessly. You can't do that with chemical batteries, although chemical battery storage could be expanded through ISRU activity on Mission One. But I think there will be limited space for that (because any ISRU batteries will likely need to be made in the industrial hab), whereas creating gas storage will not be so difficult. We also have to think about the limited available labour time.

kbd512 wrote:

If NASA gives him billions of dollars, he might be able to put people on Mars.  SpaceX hasn't put anyone into space yet.  I'm rooting for Mr. Musk and SpaceX, but his ideas are not a replacement for NASA or DARPA which solve all those pesky engineering problems to make things like Mars missions possible to begin with.

You're talking about the company that has perfected retro rocket landing of first stage rockets!  Something NASA didn't achieve in 60 years and Space X achieved in 15 from a standing start with no government largesse at the beginning.

I cannot prove it but it is my judgement that Musk and his teams are well advanced in terms of Mission One planning and will be addressing all the problem areas. Taking along a nuclear reactor will just create a whole host of unnecessary problems for them.


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