Author Topic: SpaceX: Mars Colonial Transporter "MCT" -- Speculation (not Raptor)  (Read 676390 times)

Online meekGee

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Assume for a second that the MCT is coming back mostly empty.  The reason it's coming back is just re-use.  It might carry some science samples, but that's negligible.

Let's be more realistic. First of all, there won't be many trips going to Mars in the foreseeable future, if any. And if any spacecraft will return, it will do so so to carry people back. Bringing back spacecrafts just for reuse is way further into the future.

Let me argue this:

A) I think SpaceX has more than 1 ship in mind, even on the first manned flight.

B) Consider cargo. I'm hesitant to wager a guess here, but I think you'll need easily 20-50x in mass in (solar panels or other power sources, ISRU reactors, habitats, consumables) compared with the mass of the people. You still want the ship back for re-use, but nothing's coming back from that upmass.

C) SpaceX is planning a colony, not a base.  People are coming back after some time on the surface, and it's a total waste to ship them back after 2 years.  Experience counts for everything in a new colony.  I'll figure a tour of duty is 6 years minimum.  Meanwhile, the colony is growing (every 2 years).   And so the volume of people coming back is only a small fraction of the people going out.

For B, you have to reason that there's enough ISRU, and therefore enough power, to support the steady-state consumption of the people you sent, plus the fuel for the rockets going back.  I'll do the calc again over the weekend, but it came out as a LOT of solar power. And if you know solar, you need to carry with you the equipment to clean it, and the equipment to get the water in order to clean it...   There's a lot of critical mass before you can bootstrap.
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Offline simonbp

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Good stuff Joel, I think you're definitely on the right track.

Though, there is nothing to say that MCT leaves from/returns to LEO. A departure point at an L point would lower the requirements on MCT, shifting a bit more of the burden to the Earth launch vehicles...
« Last Edit: 07/18/2013 04:49 pm by simonbp »

Offline Joel

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Though, there is nothing to say that MCT leaves from/returns to LEO. A departure point at an L point would lower the requirements on MCT, shifting a bit more of the burden to the Earth launch vehicles...

I think the question of whether to depart from LEO or wherever is secondary. The key is that you want to use a vehicle with maximum communality with a reusable upper stage. If you can perform atmosphere reentering, precision landings, rapid reuse etc. on Earth, getting it to work on Mars will be less of a hurdle. So, my guess is that MCT will first see day's light as an upper stage, but with the future Mars use in mind.

Online Rocket Surgeon

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Tinker, I think your architecture is spot on. It is, at a first glance, the simplest way to do things...though I think the only difference might be that the MCT is the 'Payload' of a ‘Falcon X Heavy’ rather than an integrated second-stage

I.E. your architecture, except with a second stage (separation progression: boosters, 1st stage, second stage, MCT) so that it is easier to return the 1st Stage (Core Stage) back to the launch site, or to help increase payload.

I believe that the next generation of SpaceX rockets that use the Raptor (with the exception of possibly using them on upper stages for the Falcon 9R and Falcon Heavy) would essentially be super-sized Falcon 9R's working in a similar way to the Falcon 9R/Falcon Heavy’s, except in this case, the single core version may lift on the order of 50 tonnes. This could also be advantageous from a commercial stand point, as the Falcon Heavy may create a market for a 50 tonne LEO lifter, that the Falcon X could use to help keep the costs of going to Mars down, and make it easier to get said 50 tonne payloads up (only having to deal with one core, as oppose to three, less handling, fewer engine issues etc.)

So the only change to your flow chart would be to have that the small ‘tag’ at the bottom of the Mars stage disconnects and returns to Earth from LEO, the rest continuing on to Mars, then returning. I should point out that in this scenario, the MCT still has a Raptor and associated fuel tanks, though would probably land with other rockets, possibly a number of SuperDraco's at least at Mars.

Also, I was wondering what people think of how these launches would be staged. Would you send out one first, refuel it then get the ball rolling with people Mars Direct style? (The difference being full reuse and a common hab/ERV design) or would they launch, refuel and return in the same MCT?

In addition, where would I go to find any theories on how SpaceX intends to return/reuse the core stage of the Falcon Heavy…seems like it would be a bit tricky to get it back to the launch site to me.


Edit: X-post from the SpaceX Party Thread, which seems to have disappeared...probably should have put it here in the first palce :)
« Last Edit: 07/18/2013 11:32 pm by Rocket Surgeon »

Offline go4mars

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higher T/W. So, a MCT used as US would probably need shorter tanks than a MCT going to Mars.
I'm not clear on what you mean by MCT.  Do you mean the middle core with an integrated spaceship that goes to Mars, refuels there and comes back?  Do we know that 80 tonnes is specifically relevant or limiting to the eventual Mars Colonial Transport architecture?  I don't know what you are assuming. 
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Offline Joel

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higher T/W. So, a MCT used as US would probably need shorter tanks than a MCT going to Mars.
I'm not clear on what you mean by MCT.  Do you mean the middle core with an integrated spaceship that goes to Mars, refuels there and comes back?  Do we know that 80 tonnes is specifically relevant or limiting to the eventual Mars Colonial Transport architecture?  I don't know what you are assuming. 

Well, it was just a thought experiment based on tinker's schematic that Musk did confirm was "pretty close" to what he had in mind (which doesn't mean much, admittedly).

The starting point was that "MCT" be an integrated spacecraft powered by a single Raptor with 2.5 MN thrust. Furthermore, the assumption was that it would be refueled with in-situ CH4/LOX on Mars and be able to return to Earth as a SSTO vehicle, with no refueling in Mars orbit or elsewhere. In the schematic, the same "MCT" was also used as hab module, reusable upper stage and earth-departure stage of the launch vehicle, which would certainly minimize the number of components to be developed. The conclusion is that such an architecture could very well make sense, provided that the "MCT" is refueled in LEO (or L-point) on its way to Mars.
« Last Edit: 07/19/2013 11:19 pm by Joel »

Offline Jim

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Tinker, I think your architecture is spot on. It is, at a first glance, the simplest way to do things...though I think the only difference might be that the MCT is the 'Payload' of a ‘Falcon X Heavy’ rather than an integrated second-stage

That isn't spot on.  That is a very significant difference, so much that it isn't compatible

Offline Joel

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B) Consider cargo. I'm hesitant to wager a guess here, but I think you'll need easily 20-50x in mass in (solar panels or other power sources, ISRU reactors, habitats, consumables) compared with the mass of the people. You still want the ship back for re-use, but nothing's coming back from that upmass.

I can't see that they would want to bring cargo ships back for a long time. Certainly not in the first iteration of the architecture. Produce all that propellant in-situ just to get a 2 year old cargo spaceship back?

C) SpaceX is planning a colony, not a base.  People are coming back after some time on the surface, and it's a total waste to ship them back after 2 years.  Experience counts for everything in a new colony.  I'll figure a tour of duty is 6 years minimum.  Meanwhile, the colony is growing (every 2 years).   And so the volume of people coming back is only a small fraction of the people going out.

Realistically it will be a small base to begin with. And you probably want to come up with the simplest possible architecture to serve it. A transportation system that can bring ~45 tons to Mars and ~20 tons back is probably close to the most minimalistic approach possible. I think it all adds up very well for a first iteration of a Mars transportation system.

Offline GalacticIntruder

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I am trying to understand the concept. I understand the human transport, but what about cargo landers?

If MCT is considered a human transport, reusable SSTO, Earth and Mars, and maybe even habitat as well, then what will be used the for cargo. Zubrin always says send cargo first, then people, kind of like Mars One. Even Elon has stated the first several missions would be mostly cargo going to Mars and not much coming back to Earth. I don't think sending a single MCT craft for cargo and humans makes sense, so what will be for cargo? A FH and 5m lander could do some, but more is needed. Will be there be a new, unknown, spacecraft for the upper stage of FX, one 10-15m cargo module, and one 10-15m MCT for humans?

[I also don't expect Elon to say more about MCT or whatever it is, anytime soon. He has too much going on for the next several months, and it makes no sense to me to reveal his new Mars ideas without the rocket it will need, ie FX, and its methane engines.  I think we might have to wait two more years. The question is, on what order will he start leaking all of his Mars hardware]
« Last Edit: 07/20/2013 02:08 am by GalacticIntruder »
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Online meekGee

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B) Consider cargo. I'm hesitant to wager a guess here, but I think you'll need easily 20-50x in mass in (solar panels or other power sources, ISRU reactors, habitats, consumables) compared with the mass of the people. You still want the ship back for re-use, but nothing's coming back from that upmass.

I can't see that they would want to bring cargo ships back for a long time. Certainly not in the first iteration of the architecture. Produce all that propellant in-situ just to get a 2 year old cargo spaceship back?

C) SpaceX is planning a colony, not a base.  People are coming back after some time on the surface, and it's a total waste to ship them back after 2 years.  Experience counts for everything in a new colony.  I'll figure a tour of duty is 6 years minimum.  Meanwhile, the colony is growing (every 2 years).   And so the volume of people coming back is only a small fraction of the people going out.

Realistically it will be a small base to begin with. And you probably want to come up with the simplest possible architecture to serve it. A transportation system that can bring ~45 tons to Mars and ~20 tons back is probably close to the most minimalistic approach possible. I think it all adds up very well for a first iteration of a Mars transportation system.

I think what we're discussing here is the single most important thing - what kind of base does SpaceX plan?  From there, everything else is derived.  You can't really speculate on the transport system until you understand what is driving the requirements for it.

My thinking is that since this base is the seed for a colony, there's very little value in just having people there for two years, sitting in tin cans.  For a colony seed, the only job of the first base is to enable the construction of a bigger base.

So these (10 or so?) people will need to have the minimal habitat that will support them, but also support activities such as assembling habitats, power units, and ISRU for more people.  So you need extensive surface activities, with all this entails - suits, heavy tools, vehicles (how are you going to move and install all those solar panels? )...  So the on-surface mass requirement, even for 10 people, will be much larger than the mass of the crew carrier.

Again, it is possible to construct a much more minimalist base, just a bunch of landed capsules, but such a base won't have any value from a colony point of view.  It will just eat up whatever resources were produced in the years preceding it.  This is the difference between a manned Mars mission and a colony seed.

So from a rocketry point of view, the cargo transport issue dwarfs the manned transport issue.

One idea is to have a cargo carrier that kicks off from Earth, separates from the cargo lander near Mars, free-returns, aero-brakes, and lands to be used again.

But whatever the cargo strategy is, it is tied to the MCT design.  SpaceX here is the owner of the colony, which is driving the requirements for the vehicles.
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Offline Joel

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I don't think you should take Musk too seriously when he says "Mars Colonial Transporter". If everything works out really well, he'd be able to establish a very small base using a spacecraft design that with time could evolve into something reusable and affordable.

If you want to have any chance of success, you want to come up with the cheapest possible architecture. I think that means spacecraft of 2-5 people, as much ISRU as possible. And cargo spacecraft will reasonably be crewed spacecraft minus life support.

Offline Jcc

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meekGee: "I think what we're discussing here is the single most important thing - what kind of base does SpaceX plan?  From there, everything else is derived.  You can't really speculate on the transport system until you understand what is driving the requirements for it."

This makes perfect sense of course. The structures, supplies and people needed to construct the colony should define the requirements for the transport system needed to deliver them.

But the reality is that the limitations of the transport system resulting from limited budget, current technology and a desire to get started with the basic technologies we have, rather than waiting 20 years for nuclear, VASMIR, or whatever might be developed on the future. As a result, there will be trade offs between designing rockets to carry the desired payloads and designing the payloads to fit the rockets available.
« Last Edit: 07/20/2013 12:48 pm by Jcc »

Online meekGee

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I don't think you should take Musk too seriously when he says "Mars Colonial Transporter". If everything works out really well, he'd be able to establish a very small base using a spacecraft design that with time could evolve into something reusable and affordable.

If you want to have any chance of success, you want to come up with the cheapest possible architecture. I think that means spacecraft of 2-5 people, as much ISRU as possible. And cargo spacecraft will reasonably be crewed spacecraft minus life support.

Well, yes and no...

I agree that the initial base will be small in manpower and very spartan, but I think there will be a requirement that it's net use of resources be negative.

That is - for a "mission-type" base, you can accumulate resources for several years, and then have the crew deplete them in two years of stay. (while conducting science, etc)

By saying that you want your stored resources to actually increase during the stay, you raise the bar considerably, but you must do that if you utter the word "colony" or "permanent".


So back to the rocket. We sometimes discount talk of "giant rockets flying regularly" as being "too grandiose", but then we say there's a limit to what the first base can look like, since there's a limit on the amount or rocketry.

I'd say that both the talk about the size of the infrastructure, and the talk about the flight rate, are pretty consistent.

I'd be a lot more suspicious if Musk said he can set up a colony with an FH, or with a couple of flights of MCT.

But he's not doing that - he's got the size of the colony and rocket effort matched pretty well, at a level a lot higher than ever been contemplated by NASA or even organizations like the Mars Society
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Offline Joel

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But he's not doing that - he's got the size of the colony and rocket effort matched pretty well, at a level a lot higher than ever been contemplated by NASA or even organizations like the Mars Society

Source? As far as I've understood, he wants first flights to Mars to be in a partnership with NASA. Don't mix up long-term (crazy?) ambitions like $500k tickets, moving 80k ppl per year etc. with stuff they are actually working on now, like reusability, Raptor, MCT.

This is not a direct quote, but sounds reasonable to me:

Quote
In Musk's vision, the ambitious Mars settlement program would start with a pioneering group of fewer than 10 people, who would journey to the Red Planet aboard a huge reusable rocket powered by liquid oxygen and methane.

http://news.yahoo.com/huge-mars-colony-eyed-spacex-founder-elon-musk-120626263.html

Online meekGee

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But he's not doing that - he's got the size of the colony and rocket effort matched pretty well, at a level a lot higher than ever been contemplated by NASA or even organizations like the Mars Society

Source? As far as I've understood, he wants first flights to Mars to be in a partnership with NASA. Don't mix up long-term (crazy?) ambitions like $500k tickets, moving 80k ppl per year etc. with stuff they are actually working on now, like reusability, Raptor, MCT.

This is not a direct quote, but sounds reasonable to me:

Quote
In Musk's vision, the ambitious Mars settlement program would start with a pioneering group of fewer than 10 people, who would journey to the Red Planet aboard a huge reusable rocket powered by liquid oxygen and methane.

http://news.yahoo.com/huge-mars-colony-eyed-spacex-founder-elon-musk-120626263.html

I agree about discounting the $500k/person comment.  That's very far field.

10 people for first base - I'm ok with that.

But now the big question is what the 10 people are doing over the course of two years.

If your goal is have them survive and come back, then you have one type of mission.  If your goal is to have them prepare the groundwork so you can send more people next time, then it's an entirely different ballgame.

I don't have a source for this, I'm just adding up what I think it will take, mass wise.  Will you need, oh, 100 kWatt-hr per day per person?  (An average person in the western world consumes about 25, depending on what you count in, which usually does not include food production or ISRU)  Will you need to do daily surface activities, so ample airlocks/surface suits/clean-up equipment?  Will you have to go get your own water?  Will you need food supplies for 2 years?

So unless your goal is just to sit inside the landed capsule for 2 years just to claim that you did, I don't see how a single rocket shot does the trick.

Again, without a source, I do see how Musk is approaching the Mars transport architecture.  Why emphasize reusability for such an architecture where clearly there's little value in getting your launch vehicle back if you're only doing a one-shot?

His attitude is of flying often (way before those $500k numbers) and I think this means that his intent is on a surface effort like I'm describing.

Again, I'm not aware of any explicit statements from him in this regard - I'm speculating here, trying to match what little we know about the transport system, about Musk's intention, and some basic constraints that are a result of common sense.
« Last Edit: 07/20/2013 07:46 pm by meekGee »
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Offline Joel

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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.

As I see it, the key to sustainability is ISRU, getting production of rocket propellant, food, building materials, photovoltaic cells before even sending the first people. A base that depends on having bulky and heavy stuff transported from Earth will never survive IMO.

Anyway, I think that the bits we've seen so far about SpaceX's Mars architecture (a SC engine of around 2.5 MN, chemical propulsion, methane instead of hydrolox, "land with the whole thing" instead of cyclers or habitats) is consistent with a minimalistic approach.

Online meekGee

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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.

As I see it, the key to sustainability is ISRU, getting production of rocket propellant, food, building materials, photovoltaic cells before even sending the first people. A base that depends on having bulky and heavy stuff transported from Earth will never survive IMO.

Anyway, I think that the bits we've seen so far about SpaceX's Mars architecture (a SC engine of around 2.5 MN, chemical propulsion, methane instead of hydrolox, "land with the whole thing" instead of cyclers or habitats) is consistent with a minimalistic approach.

... minimalist is relative...  But I think we're in agreement on the definition:
"The minimal base that can establish ISRU to the level where there's a net production of resources" - fair enough?   and about 10 people?

But let's flesh it out together then.  What power level do you think they need (kWatt-hr/day) and lets separate low-temp thermal (for heating) from electrical.  And do you think they'll use solar (thin film? non-tracking?) or nuclear?
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Offline Jcc

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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.

As I see it, the key to sustainability is ISRU, getting production of rocket propellant, food, building materials, photovoltaic cells before even sending the first people. A base that depends on having bulky and heavy stuff transported from Earth will never survive IMO.

Anyway, I think that the bits we've seen so far about SpaceX's Mars architecture (a SC engine of around 2.5 MN, chemical propulsion, methane instead of hydrolox, "land with the whole thing" instead of cyclers or habitats) is consistent with a minimalistic approach.

... minimalist is relative...  But I think we're in agreement on the definition:
"The minimal base that can establish ISRU to the level where there's a net production of resources" - fair enough?   and about 10 people?

But let's flesh it out together then.  What power level do you think they need (kWatt-hr/day) and lets separate low-temp thermal (for heating) from electrical.  And do you think they'll use solar (thin film? non-tracking?) or nuclear?

As a first cut at estimating power requirements I would look at Antarctic research stations. Most run on diesel generators, but McMurdo installed a 1.5 MW nuclear plant in 1962. It ran until 1972, when it was shut down for safety concerns. Many bases are now installing wind and solar. Solar is great for half the year there, not so much the other half but the summer staffing is probably over 10 times the number that overwinter, or more, so it make sense. Wind may be more available year round, but I don't suppose it would produce a lot of energy on Mars.

http://theenergycollective.com/taylenpeterson/40184/wind-and-solar-energy-power-antarctic-research-stations
http://www.awi.de/?id=140
http://en.wikipedia.org/wiki/McMurdo_Station

any way, if it were me on Mars, I would want to have as many redundant sources of power as possible, both solar and nuclear.

Online meekGee

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So 1 MWatt of continuous power for 1000 people is 24 kWh/day.

Wiki says the plant provided 1.8 MWatt, and that the station houses between 200 and 1000 people.  Power efficiency increases with the number of people, so for 10 people the requirement will be higher.

My estimate is probably low, in other words.

For non-tracking solar, you'll need about 5-6 times the average use, plus storage.  Plus, you don't get thermal power, so you will need to collect that separately. Thermal panels are more efficient than solar panels, but are pretty heavy.

Wiki has some mass estimates on the nuclear plant, btw - http://en.wikipedia.org/wiki/McMurdo_Station#Nuclear_power_1962-1972


Joel point out that this is a bit OT, but here's the thing - we're not discussing arbitrary Mars settlement here, but trying to derive the requirements for a very specific rocket system, that is designed to enable a very specific colony.  So as long as we don't pollute non-MCT threads, I think speculating on this specific colony, only for estimating mass transport requirements, is in-scope.
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Offline ciscosdad

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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?

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