SpaceX: Mars Colonial Transporter "MCT" -- Speculation (not Raptor)

[Joel]

Let's keep the discussion on "MCT" only in this thread. Why not start a new thread for discussing the first base/colony?

[meekGee]

Actually, ok - since there's no way to keep it focused on MCT requirements, really.

There's probably more than one over at advanced concepts.  We can talk about it here in the SpaceX section if and when there's a significant bit of information from SpaceX about their plans.

[MP99]

How about if the first step is entirely robotic, with the goal of collecting water and assembling a solar panel array ? We know ice is close to the surface at the poles and likely at other places as well. Processing dirty ice should not be too difficult. What is the lowest latitude that water has been found?

Then: Given that there is a supply of water already collected in  tanks, what would the early manned missions be doing? Greenhouse? Solar power system? Oxygen production? methane? What architecture would best support this? If you have water, oxygen is easy, and well over half the propellent needs.

Could the early stages of the transport system have the oxygen propellent only produced at the Mars end?

If you want robots to prospect for and mine water, you're gonna need to get JPL, and they'd need to build robots way more capable than MSL.

Multi-billions, right there. More than Musk is planning for the whole effort, I'd say. Huge lead time as well.

NASA has it's own plans for Mars based around SLS & Orion. I don't see them going in with Musk unless those get canned, and that's still looking pretty unlikely at the moment.

Cheers, Martin

[Occupymars]

Well let's just say for one moment here that the Mars ascent vehicle is also the descent vehicle could it be used for tank storage of ISRU to produce CH4 & LOX for the next MADV since it would be the same size tank's?

Ill take it one step further and ask is it possible to land this stage with everything it would need to produce CH4 & LOX over a period of 2 half years   given the payload to mars is 40 tonnes ?

Would producing these liquid's need considerable infrastructure and power relative to a 40 tonne payload? and how much hydrogen are we talking about here to produce a considerable amount of CH4 & LOX?

[Jcc]

How about if the first step is entirely robotic, with the goal of collecting water and assembling a solar panel array ? We know ice is close to the surface at the poles and likely at other places as well. Processing dirty ice should not be too difficult. What is the lowest latitude that water has been found?

Then: Given that there is a supply of water already collected in  tanks, what would the early manned missions be doing? Greenhouse? Solar power system? Oxygen production? methane? What architecture would best support this? If you have water, oxygen is easy, and well over half the propellent needs.

Could the early stages of the transport system have the oxygen propellent only produced at the Mars end?

If you want robots to prospect for and mine water, you're gonna need to get JPL, and they'd need to build robots way more capable than MSL.

Multi-billions, right there. More than Musk is planning for the whole effort, I'd say. Huge lead time as well.

NASA has it's own plans for Mars based around SLS & Orion. I don't see them going in with Musk unless those get canned, and that's still looking pretty unlikely at the moment.

Cheers, Martin

Actually I would not rely on JPL for robots, a construction robot does not need all the scientific instruments on curiosity that make it so expensive. This company claims to have more practical designs: http://www.astrobotic.com/

[ciscosdad]

You are correct, this is off topic, but you will have trouble nailing down the architecture without some assumptions about whats going on at the martian surface.
Too little information.

[Jcc]

You are correct, this is off topic, but you will have trouble nailing down the architecture without some assumptions about whats going on at the martian surface.
Too little information.

We need a moderator to splice these posts into a thread such as
http://forum.nasaspaceflight.com/index.php?topic=32201.90

I will cross post my last one there.

[Joel]

NASA has it's own plans for Mars based around SLS & Orion. I don't see them going in with Musk unless those get canned, and that's still looking pretty unlikely at the moment.

There is still no successor to Altair, right? Or corresponding lander for Mars? Could MCT ("you can land with the whole thing") be used for that?

Another observation: The Apollo lunar module and command/service module had combined delta-v of around 7500 m/s. So could perhaps MCT (using the earlier assumptions) be used for fully reusable trips to the moon, replacing the LM and CSM? In addition for going to Mars?

[MikeAtkinson]

Using a general purpose construction robot/rover to build the solar array will be very slow due to the long round trip signal delay. But, this is off topic.

On-topic: how much power is required for refueling the MCT assuming 380 tonnes of fuel and 18 months for the MCT on the surface (actually the stay time is likely to be a bit longer than that, but lets assume 18 months to allow a bit of margin)?

ISRU would need to include extraction of CO2, extraction of water (including mining it, moving it to the ISRU plant, melting purification), reacting water and CO2 to get CH4 and O2, compression and cooling of the propellants, leakages and other losses.

[MikeAtkinson]

Another observation: The Apollo lunar module and command/service module had combined delta-v of around 7500 m/s. So could perhaps MCT (using the earlier assumptions) be used for fully reusable trips to the moon, replacing the LM and CSM? In addition for going to Mars?

Probably yes. What we surmise of the MCT design would also make a fine Lunar lander. It probably will not have enough delta-v to do LEO-Moon-Earth without refueling somewhere, but starting in low lunar orbit or L1/L2 it should have enough delta-v. Lots of minor problems would need to be sorted out though.

[Roy_H]

Let's keep the discussion on "MCT" only in this thread. Why not start a new thread for discussing the first base/colony?

I don't agree. A new thread would be in itself off-topic to SpaceX General. This is on-topic as long as it is primarily focused on determining mass requirements.

I don't think that Elon expects SpaceX to be the prime driver of building a colony on Mars. Just an enabler. He is hoping that if transportation can be proven reliable and cost-effective, other companies/groups/space agencies will provide the planning, equipment, and financing of a colony.

[Joel]

On-topic: how much power is required for refueling the MCT assuming 380 tonnes of fuel and 18 months for the MCT on the surface (actually the stay time is likely to be a bit longer than that, but lets assume 18 months to allow a bit of margin)?

With a (fuel-rich) mixture ratio of 2.77 (http://www.braeunig.us/space/propel.htm), 380 tonnes of propellant means 101 tonnes of methane.

The world's largest plant for producing methane from water and atmospheric CO2 was inaugurated in Germany in 2012:

http://www.zsw-bw.de/infoportal/presseinformationen/presse-detail/weltweit-groesste-power-to-gas-anlage-zur-methan-erzeugung-geht-in-betrieb.html (in German)

It requires 250 kW(electric) to produce 300 m3, or about 197 kg, CH4 per day. So 101 tonnes would take 512 days, a bit less than 18 months. Add liquefaction and cooling losses.

Anyway, 300 kW is probably a reasonable guess.

Mars Direct planned a 100 kW(electric) nuclear reactor for producing 107 tonnes of propellant, but assumed that the H2 was brought from Earth:
http://wp10988215.server-he.de/MSE/wp-content/uploads/2011/10/Mars-Direct-Scenario_Zubrin_19911.pdf

[meekGee]

Let's keep the discussion on "MCT" only in this thread. Why not start a new thread for discussing the first base/colony?

I don't agree. A new thread would be in itself off-topic to SpaceX General. This is on-topic as long as it is primarily focused on determining mass requirements.

I don't think that Elon expects SpaceX to be the prime driver of building a colony on Mars. Just an enabler. He is hoping that if transportation can be proven reliable and cost-effective, other companies/groups/space agencies will provide the planning, equipment, and financing of a colony.

Roy - put yourself in Elon's shoes.  Do you really think, that with Mars colonization being his life's dream, that it is in his character to be just and enabler?  Why leave all the fun to others?  and to whom?   And to keep it on topic - how do you think they are setting up the requirements for the Mars transportation system - just build it and they will come?

What's probably true, however, is that further down-field, he's banking on more companies joining in.

[Occupymars]

On-topic: how much power is required for refueling the MCT assuming 380 tonnes of fuel and 18 months for the MCT on the surface (actually the stay time is likely to be a bit longer than that, but lets assume 18 months to allow a bit of margin)?

With a (fuel-rich) mixture ratio of 2.77 (http://www.braeunig.us/space/propel.htm), 380 tonnes of propellant means 101 tonnes of methane.

The world's largest plant for producing methane from water and atmospheric CO2 was inaugurated in Germany in 2012:

http://www.zsw-bw.de/infoportal/presseinformationen/presse-detail/weltweit-groesste-power-to-gas-anlage-zur-methan-erzeugung-geht-in-betrieb.html (in German)

It requires 250 kW(electric) to produce 300 m3, or about 197 kg, CH4 per day. So 101 tonnes would take 512 days, a bit less than 18 months. Add liquefaction and cooling losses.

Anyway, 300 kW is probably a reasonable guess.

Mars Direct planned a 100 kW(electric) nuclear reactor for producing 107 tonnes of propellant, but assumed that the H2 was brought from Earth:
http://wp10988215.server-he.de/MSE/wp-content/uploads/2011/10/Mars-Direct-Scenario_Zubrin_19911.pdf

What would the weight of their proposed 100 kW nuclear reactor be? can't find it in the paper.

[meekGee]

On-topic: how much power is required for refueling the MCT assuming 380 tonnes of fuel and 18 months for the MCT on the surface (actually the stay time is likely to be a bit longer than that, but lets assume 18 months to allow a bit of margin)?

With a (fuel-rich) mixture ratio of 2.77 (http://www.braeunig.us/space/propel.htm), 380 tonnes of propellant means 101 tonnes of methane.

The world's largest plant for producing methane from water and atmospheric CO2 was inaugurated in Germany in 2012:

http://www.zsw-bw.de/infoportal/presseinformationen/presse-detail/weltweit-groesste-power-to-gas-anlage-zur-methan-erzeugung-geht-in-betrieb.html (in German)

It requires 250 kW(electric) to produce 300 m3, or about 197 kg, CH4 per day. So 101 tonnes would take 512 days, a bit less than 18 months. Add liquefaction and cooling losses.

Anyway, 300 kW is probably a reasonable guess.

Mars Direct planned a 100 kW(electric) nuclear reactor for producing 107 tonnes of propellant, but assumed that the H2 was brought from Earth:
http://wp10988215.server-he.de/MSE/wp-content/uploads/2011/10/Mars-Direct-Scenario_Zubrin_19911.pdf

300 kW continuous, or 7.2 MWh/day.

I estimated about 4 kW per person average continuous, so for 10 people, that's only 40 kW continuous, or 10% of the ISRU requirement.

So no surprise - ISRU power costs dominate.

If implemented as non-tracking solar, you'll need about 1.5 - 2.0 MWatt rated field.  Which will be more than 2x its size of Earth due to lower insolation and higher inclination.

Let's use 100W/m2 as a ballpark number for panel peak output, so 15000 - 20000 m2.  If each m2, installed, plus foundation, wiring, etc weighs 10 kg, we're looking at 150-200 tons of power equipment.  To support ISRU.

The plant itself doesn't look lightweight, but can probably be made lighter.  So another 200 tons?

What do you need in order to deploy/maintain 20,000 m2 of solar power?

If you don't plan to wash the panels, you need more of them, since power production will diminish.  Maybe you can get away with dry cleaning, since there are no organics in the air.  ("dry dust" doesn't stick - see how the MER panels got cleaned up by mere wind)


Anyway - suppose power and ISRU mass can be bound at 500-1000 tons.

What about habitats that allow for extensive surface work?

A BA2100 (70 tons, 2000 m3) designed for zero-g of course, has a design crew of 16.
15 Dragon-like capsules weigh about the same, and provide 150 m3.

Bracketing between those two obviously extreme numbers, still at under 100 tons, it seems habitat mass will be less than the power/ISRU mass.

What about food and other consumables for 2 years?  Assume minimal water requirements, so everything is dry.  Even at 1 kg per person per day, that's only 35 tons per year for 10 people.  (I'm sure there are very good estimates for that)

Is it reasonable to say that SpaceX need to have around 1000 tons on the surface before they land a crew of 10 people there?

What does that say about MCT?

[Joel]

What would the weight of their proposed 100 kW nuclear reactor be? can't find it in the paper.

No idea, but a TOPAZ-II reactor http://fti.neep.wisc.edu/neep602/SPRING00/lecture35.pdf weights 1061 kg and produces 6 kW electric. Scaling that up to 300 kW would mean some 50 tonnes.

I would prefer solar power anyway. Should not be too hard to make it in-situ. It is also much less controversial. Thin film solar cells can be made at home:
http://www.prlog.org/10270892-homemade-solar-cells-how-to-make-solar-cell.html

[Joel]

What does that say about MCT?

I think it just tells you that you cannot reasonably transport the solar arrays from Earth, they have to be made in-situ. The ISS solar arrays produce 84 kW and have much higher availability. So several times the ISS solar arrays transported to the surface of Mars? I'd forget that.

Maybe some part of them could be transported from Earth, such as the metal in thin-film solar cells (if the glass is made in-situ).

My proposal is to fund an X-price for in-situ solar array manufacturing:)

[meekGee]

What would the weight of their proposed 100 kW nuclear reactor be? can't find it in the paper.

No idea, but a TOPAZ-II reactor http://fti.neep.wisc.edu/neep602/SPRING00/lecture35.pdf weights 1061 kg and produces 6 kW electric. Scaling that up to 300 kW would mean some 50 tonnes.

I would prefer solar power anyway. Should not be too hard to make it in-situ. It is also much less controversial. Thin film solar cells can be made at home:
http://www.prlog.org/10270892-homemade-solar-cells-how-to-make-solar-cell.html

Eventually, sure.  But at MWatt-scale fields, it will weigh more to build the fab needed to produce 1 MW/yr then it is to bring a MW over with you.

You need to make production-level modules, not lab demonstrators - they need to have high (and consistent!) efficiency, have a a lifetime of at least several years (with high confidence), etc.   Google "solar fab line" and you'll see what it takes to make cells, and then go from cells to installation-ready modules.

Also, the efficiency of local cells will be lower, which means you'll need more of them, and therefore more wiring, more framing and foundation, etc.

My guess is that local solar cells production is a "ten years down the road" item, at least.

[meekGee]

What does that say about MCT?

I think it just tells you that you cannot reasonably transport the solar arrays from Earth

... or, that you need to build a cargo infrastructure that will fly 40 tons payloads on a regular basis, so you can do 25 flights over the course of maybe 6 years?

[Joel]

What does that say about MCT?

I think it just tells you that you cannot reasonably transport the solar arrays from Earth

... or, that you need to build a cargo infrastructure that will fly 40 tons payloads on a regular basis, so you can do 25 flights over the course of maybe 6 years?

No way. It makes no sense whatsoever. If you cannot produce the solar arrays and don't want to ship a nuclear reactor, you should not attempt to produce the  propellant in-situ. Change the mission instead with low Mars orbit rendezvous and use propellant brought from Earth.