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

[Aerospace Dilettante]

... but I would think that LOX would be a bigger concern ...

Mars has plenty of easily-processed Oxygen, in the convenient form of Co2 gas. All that is needed to make LOX is some plumbing and a heap of energy.

Making methane is very much more difficult. The problem being sourcing hydrogen. There simply isnt enough of it in the atmosphere, in any form, to use as feedstock for fuel-making. One would need to either import the H2 (all the way from earth!!!), or mine it as water-ice from the surface.
Mining is *much* more complicated than simply using the atmospheric gasses.

I think that if the only readily accessible source of water on Mars is the polar caps, Elon's dream of making man multi-planetary is totally impossible in the foreseeable future.   

[MikeAtkinson]

I think the following would be an efficient use of "MCT" as we have been imagining it.

1st opportunity

2 cargo MCT, carrying 45 tonnes of supplies each. No robotic construction, but robotic deployment of a small solar plant (say 10kW), this provides keep alive power to the MCT and produces CO + O2 at a low rate.


2nd opportunity

2 cargo, 2 crew MCT (crew and cargo MCT almost identical, but crew MCT have life support, air lock, etc.), 6-10 crew, they live in the crew MCT while they construct the base.

After landing the crew burn the CO+O2 produced for power until they can deploy enough solar panels for crew MCT power (including life support).

At this stage there should be ~250 tonnes of supplies, which should be enough for the initial ISRU unit, power supply, pressurised and unpressurised rovers and enough food and other supplies to last the crew for a decade or so.

The crew spend their time mainly building the base, but also do some exploration and general science. Obtaining a suitable water supply, drilling into brine aquifers or mining icy soil will probably require quite a bit of effort.


3rd opportunity

2 cargo, 2 crew MCT, 6-10 crew.

Now 4 crew MCT are connected together for living quarters.

Continue to expand the solar arrays.

The get the greenhouse(s) up and running for food supply, the greenhouses are probably quite power intensive (fans, lighting?, etc.)

There is enough power and ISRU resources to refuel one cargo MCT over the next 18 months.


4th opportunity

2 cargo, 2 crew MCT, 6-10 crew.

Base now consists of 5 crew MCT and some locally built structures, continue to expand the locally built structures and expand the solar array.

There is enough power and ISRU resources to refuel 2 cargo MCT and one crew MCT over the next 18 months. They return to Earth (crew MCT does not contain crew).


5th opportunity

2 cargo (one reused), 2 crew MCT, 6-10 crew.

Base now consists of 24-40 crew.

Base now self sufficient in basic foodstuffs, water, air, basic building material (bricks), and some plastics.

There is enough power and ISRU resources to refuel 2 cargo MCT and 2 crew MCT over the next 18 months. They return to Earth (one crew MCT contains crew).


[obviously, there are lots of details missing from this, but I can't see any showstoppers.]

[R7]

If you produce Methane from local water and CO2 you produce the correct amount of O2 in the same process as byproduct out of the water and CO2 used. So no separate production required.

If you want to produce O2 for breathing in the habitat, it is easiest to split CO2 into CO and O. That process requires the least energy input. That be the easiest process too, if you want to produce storable fuel, 2CO and O2 to burn to produce heat and electricity at night.

Methane from local water also produces excess oxygen because engines burn it at ~3.5 O/F ratio instead stoichiometric 4.

How Mars-storable LOX and LCH4 are? Do you have to factor in vacuum insulation for MCT tanks and/or active cooling?

[Chris Bergin]

Guys. You need to get this back on to the thread title, or I'll have to trim the thread.

[Roy_H]

Guys. You need to get this back on to the thread title, or I'll have to trim the thread.

Chris, I argued before that this was on topic, based on estimating mass requirements for transport. This does deviate from SpaceX (maybe, depends on whether you think SpaceX is going to create a Mars colony or only provide transportation for it). So what is your recommendation? A new thread within "SpaceX General" or a new thread on Mars Colonization Requirements under "General Discussion"?

[meekGee]

Guys. You need to get this back on to the thread title, or I'll have to trim the thread.

yup - some of this, fun as it was, did wander.  (surprise!)

But overall, it did a good job painting a picture of what MCT has to do.

I think it's clear that there needs to be a cargo variant, with multiple runs of 30-50 tons.  Even with GaAs panels, still a large fraction will be dedicated to power generation and ISRU.

It's not clear to me whether the cargo carrier should be reusable. I like the idea of each outbound carrier being used multiple times, since it works with the concept of an open-ended, "ever growing" colony.  It of course matters less if you're just thinking about the value of retrieving just a single carrier.

Tinker's dialog with Musk on MCT is important.  It shows that we can take in-space assembly, Mars-orbit, and exotic propulsion off the table.  For manned, it's probably as simple as launch, fuel, go, land, ISRU, fly back.  (except non-symmetrical)  For cargo, launch, fuel, go, and then either land and be done, or drop off the cargo and free-return.

yay hyperloop! 

[Lobo]

I don't think that a minimalistic transport architecture (in its very first iteration) means that the base has to have somehow low ambitions, or consist of people sitting in tin cans. I just think that the most reasonable is to get something working that has the potential of evolving into something sustainable.

Zubrin's Mars Direct was about as simple as you can get, yet faily capable at that same time.  There's a certain "sweet spot" of minimal/cheap, and capable/productive.  Something more than two guys sitting in a capsule for two years, and something less than NASA's Mars DRM 5.0.
I'd think Mars Direct or Mars Semi-direct or a hybrid of the two will be what we'll see from Musk as the preliminary goal anyway. 

I think in the first phase we'll see probably reusable boosters, but I'd be amazed if we seem much more than that, although the pieces might be put in place to have some more reusability later.
I think we'll maybe see a dual use lander than lands on Raptor engines, refuels on the surface, and uses them again to do Mars ascent and the TEI burn directly.
A Dragon capsule (mounted on the MAV/ERV) will probably be all that actually comes back to Earth because it would be pretty darn hard to bring the whole MAV/ERV into Earth EDL. 

I think there will be a methalox upper stage on the MCT system that is expended after doing TMI. 
There can be a Hab/lander vehicle that the crew habitates in the Earth-Mars trip, then lands on methalox engines, but jettisones it's heat shield.  (Which would be gone and thus unable for this vehicle to return to Earth's atmosphere).
The lander lands near a previous uncrewed lander so both are refueled and available to the crew. Both have some equipment on them.  Rovers, solar arrays, inflatable hab tents, and of course the Sabatier ractors.

The crew then boards one of these and returns directly to Earth, but does EDL at Earth in a Dragon capsule. 

THey can do "colonies" with these common landers by landing more landers with crews.  Once they've refueled themselves, any one of them could be used to return a crew to Earth at the 2 year launch window. 

Uncrewed landers can be used and stocked with extra supplies, as they won't have had a crew on it using consumables for the 6 month trip out.  So they could land some extra equipment mass.  Or one of these landers could be modified to be a permanent ground station and not lift off.  In which case it could be a larger hab, or a large heavy equipment lander. 

Everything uses the same engines, the same basic lander, etc.  Only one vehicle is actually needed to be designed, only one Mars EDL system is necessary to develop.

The crew could launch on a Dragon/F9R to rendezvous with the MCT lander in LEO prior to TMI, and that capsule returns to Earth and is reused.
The lander has a Dragon capsule integrated into it that is used for Earth reentry.  This Dragon could be reused as well.

I just don't see how Musk can launch a large lander, have it land on Mars, take back off, come back to Earth...and then also land on Earth.  I just don't see how to make it have Earth EDL abilities as well as Mars ones....and have a chance to get it back off the surface of Mars.
Despite may who seem to think that's exactly what he'll have. 

A system that has one common and "mass produced" Hab/lander/MAV/ERV vehicle per mission, an expendable upper stage, two reusable dragon capsules, and reusable boosters would be a pretty darn good partially reusable and potentially relatively low cost system.  And i think Elon would be given a lot of credit for just that.



 

[Lobo]

... but I would think that LOX would be a bigger concern ...

Mars has plenty of easily-processed Oxygen, in the convenient form of Co2 gas. All that is needed to make LOX is some plumbing and a heap of energy.

Making methane is very much more difficult. The problem being sourcing hydrogen. There simply isnt enough of it in the atmosphere, in any form, to use as feedstock for fuel-making. One would need to either import the H2 (all the way from earth!!!), or mine it as water-ice from the surface.
Mining is *much* more complicated than simply using the atmospheric gasses.

Importing feedstock LH2 from Earth was what Zubrin proposed, and he worked out the details of it.  It's feasible and required less power than cracking CO2.  A CO-O2 rocket isn't very efficient. 
Water ice can and will work at some time, but that's putting the cart before the horse.  They really need an -assured- way to make the return propellants before sending a crew there.  The crew and other crews can then experiment with ice mining.  (in fact, I'd guess that would be one of their primary goals in the early missions, as well as scientific exploration via rovers).  Once ice mining is proven, then the ice can be used as the source of hydrogen to make CH4.  But you won't want to start with that.

[go4mars]

Elon already said at some some Q&A at a college a few years ago, it's on youtube, that he wants to be able to land 50 tonne infrastructure elements.  That implies a downmass of more (descent propellant, engines, structures, etc.), in order to get a 50 tonne piece down. 

It's a debate for a different thread whether the undivisible 50 tonnes is a "base in a box", a drilling rig, nuclear back-up, bull-dozers, dump trucks, solar farm, rail ties, smelter/foundry elements, wire, or power broadcaster's, a case of Tesla's, or what-have you.  It looks like there is sufficient interest to start one.  I think it's reasonable to do so within the SpaceX section of this forum, as it is their stated goal, and we know the SpaceX specific 'landing 50 tonne indivisible elements to the surface' constraint.  We also know the goal for methane MCT is tens of thousands of people.  Work from that, otherwise the thread will go all over the place. 

[RocketmanUS]

Elon already said at some some Q&A at a college a few years ago, it's on youtube, that he wants to be able to land 50 tonne infrastructure elements.  That implies a downmass of more (descent propellant, engines, structures, etc.), in order to get a 50 tonne piece down. 

It's a debate for a different thread whether the undivisible 50 tonnes is a "base in a box", a drilling rig, nuclear back-up, bull-dozers, dump trucks, solar farm, rail ties, smelter/foundry elements, wire, or power broadcaster's, a case of Tesla's, or what-have you.  It looks like there is sufficient interest to start one.  I think it's reasonable to do so within the SpaceX section of this forum, as it is their stated goal, and we know the SpaceX specific 'landing 50 tonne indivisible elements to the surface' constraint.  We also know the goal for methane MCT is tens of thousands of people.  Work from that, otherwise the thread will go all over the place. 

The first crew transporter to Mars most likely would send about four crew members. Test the design out on a smaller scale , then build the much larger version when there would be a demand for it and the infrastructure to handle it at Earth and Mars.

Edit:
I believe they would send two crewed MCT's to Mars at the same time. If one has a problem then crew could transfer to the other. So I believe the MCT would be able to handle up to 8 crew if needed ( this comes from the t/Spacex's Lunar CEV crew concept ).

[Joel]

Tinker's dialog with Musk on MCT is important.  It shows that we can take in-space assembly, Mars-orbit, and exotic propulsion off the table.  For manned, it's probably as simple as launch, fuel, go, land, ISRU, fly back.

Yes, that's also my impression. And I would add that solar arrays shipped from Earth would be the natural power source. H2 could be brought or locally sourced.

[Robotbeat]

I've got reason to believe that Musk likes solar electric propulsion for his Mars mission concept.

[meekGee]

I've got reason to believe that Musk likes solar electric propulsion for his Mars mission concept.

Extraordinary claims require extraordinary evidence?   

[JasonAW3]

Anybody ever thought that they might be considering some sort of Mars Cycler system similar to what has been suggested in the past?

     A system similar but larger than teh ISS, made up of Rad hardened Bigelow style modules, with a strongback spun up to produce sufficent G to avoid physical problems, being able to pick up and drop off landers and cargos as needed.  Food could be grown on the cycler for air recycling, food and to help avoid bordom.

     A fifty ton craft should have enough power to get a crew of eight to and from such a cycler, assuming areobraking on each end to slow down the landing craft.  50 ton supply modules could be boosted into rendevous orbits at fairly regular intervals, providing additional consumables and equipment as needed.

     A larger cycler could eventually be made out of a NEO asteroid, that occupies an orbit similar to what is needed, or slightly altered to what is needed as an eventual replacement.  Such a ficlity could house hunderds of colonists at a time, as well as a few hundred residents, who'd maintain the facility as needed.

Just a thought...

Jason.

[meekGee]

Not according to the Musk-Tinker exchange, not for the manned transport at least.

A cargo carrier can drop off a cargo lander, and continue empty on a free-return path, which will bring it back less than 4 years after it was launched.  Either that, or stay on Mars and serve as ISRU tanks or some other use of the structure.

[MikeAtkinson]

Anybody ever thought that they might be considering some sort of Mars Cycler system similar to what has been suggested in the past?

A cycler is very capital intensive, to get any benefit (artificial gravity and enhanced radiation protection) they need to be big. To give regular flybys of the Earth and Mars you really need two or more. They also do not reduce the cost of the transfer stages much, which still need the same (or probably higher delta-v) and to be able to do Mars EDL and ascent.

[Robotbeat]

I've got reason to believe that Musk likes solar electric propulsion for his Mars mission concept.

Extraordinary claims require extraordinary evidence?   

Unfortunately, all I have is some comments by Tom Markusic, who was a propulsion guy at SpaceX for quite a while. He seemed to think Musk really liked the idea of some combination of SEP and chemical for manned trips to Mars.

[Jcc]

NASA has been fretting over how to land a payload bigger than 1 ton (Curiosity-class) on Mars. The Russians also.

I think the assumptions are that 1) there will be too little fuel available to do a fully propulsive landing, 2) you can't make or launch  a heat shield big enough to dissipate the energy to slow enough for parachutes, 3) you can't make hypersonic parachutes that will work for a Mars descent.

So what is the secret that will allow a 50 ton MCT to land, which NASA doesn't know about?

[meekGee]

NASA has been fretting over how to land a payload bigger than 1 ton (Curiosity-class) on Mars. The Russians also.

I think the assumptions are that 1) there will be too little fuel available to do a fully propulsive landing, 2) you can't make or launch  a heat shield big enough to dissipate the energy to slow enough for parachutes, 3) you can't make hypersonic parachutes that will work for a Mars descent.

So what is the secret that will allow a 50 ton MCT to land, which NASA doesn't know about?

Smaller heat shield, more fuel spent on retro-braking, thus reduced payload fraction.  Thus requirement for a larger rocket to begin with, in-orbit fueling, and thus the requirement for cheap LEO launch.  Thus requirement for fully and rapidly reusable VTVL system.

So not a secret really. Just thinking about a persistent transportation system and not a single mission at a time.

[Robotbeat]

Well, a smaller heatshield can be good enough to bleed away vast majority of delta-v and you can use propulsive landing instead of using a ginormous parachute. A big issue about the delta-v normally used for terminal propulsive landing on Mars is that they've been heavy and perhaps even monopropellant. The propulsive systems at that level would benefit quite a bit from a scale-up (unlike the aerodynamic systems).

If MCT uses a pump-fed methalox system, it can get far, far better performance than historical landing schemes (usually pressure-fed, often monopropellant).