Author Topic: SpaceX: Mars Colonial Transporter "MCT" -- Speculation (not Raptor)  (Read 708056 times)

Offline xanmarus

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There is very promising technology - magnetoshell.
https://docs.google.com/file/d/0Bx2cC35KJTwsYU5rblJ1UGVWVEk/edit?pli=1

Online meekGee

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There is very promising technology - magnetoshell.
https://docs.google.com/file/d/0Bx2cC35KJTwsYU5rblJ1UGVWVEk/edit?pli=1

I think this one deserves a thread of its own.
a) It looks, well, almost too good to be true.  Obviously of enormous value if it works as advertised.  (Which is not to say it doesn't!)
b) Anyone knows of this company or research staff?

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Offline joek

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There is very promising technology - magnetoshell.
https://docs.google.com/file/d/0Bx2cC35KJTwsYU5rblJ1UGVWVEk/edit?pli=1
I think this one deserves a thread of its own.
a) It looks, well, almost too good to be true.  Obviously of enormous value if it works as advertised.  (Which is not to say it doesn't!)
b) Anyone knows of this company or research staff?

MSNW is the same company involved in development of FRC + Imploding Plasma Liner Fusion for the Fusion Rocket (NIAC2).  Little indication they have pursued magneto-shell since that initial publication (see here), although IIRC there have been similar proposals by others.

edit: p.s. yes, should be a separate thread.
« Last Edit: 07/23/2013 04:52 am by joek »

Offline xanmarus

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Offline Lobo

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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.



Why would you need a cargo carrier to drop off a cargo lander and then return?
If it's cargo, you can just send the cargo lander directly.  The only reason to have something come back to Earth is to return a crew.

Online meekGee

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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.



Why would you need a cargo carrier to drop off a cargo lander and then return?
If it's cargo, you can just send the cargo lander directly.  The only reason to have something come back to Earth is to return a crew.

That's why I said "either"....

If you don't need the tanks on Mars, and the carrier can free-return, then a) your lander's heat shield might be smaller and lighter since it has to protect a compact cargo lander, not a large empty tank with engines on the far end, and landing propellant mass is also reduced b) your cargo doesn't end up 30' off the ground and c) you get back an integrated deep space carrier 3.5 years later - that's gotta have value. The flip side is that you pay by having to have a second propulsion system for landing.

It's a trade, and I don't have enough information to call it...
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Offline sheltonjr

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I am having a hard time picturing what the MCT/Mars Lander configuration would look like. Suppose SpaceX wants to land 50 tons on Mars and with propulsive landing and return to Earth with ISRU refuelling.

If it lands tail first like the first stages booster will land, with the tanks/engines at the bottom. That puts all the cargo & habitat at the top of the lander. some of the cargo will be heavy and would need to roll off. I cannot think of a good configuration that inverts this.

Next configuration would be to use the big engines in the tail to retro-brake ALOT. Then flip for Horizontal re-entry for the biggest cross-section and with nearly empty tanks it should be very light with respect to its cross-section. Then land horizontal using much smaller methane engines or Super Dracos. 4 SDs would have the thrust of 71MT on Mars.  Two problems though. This configuration would make it very front/top heavy and once fully loaded with fuel it would not be able to launch this way. Need a way to distribute the fuel tanks throughout the vehicle but still allow cargo ramp access to the cargo bay.

Has anyone seen any designs that address this problem space. It is much bigger than anything I know of that NASA has even planned or thought of. Only science fiction.

Online meekGee

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I have a problem seeing such giant rockets landing right next to each other, since any crash would be catastrophic to the colony.

Imagine a cargo lander that is like a very large unpressurized dragon, and let's imagine it enters separately.  It aims a safe distance away, and then once it's at low speed, gear deployed, etc, it does the "last mile" burn and lands right next to all the other landed infrastructure, close enough that it can be linked to them. (meter precision).  So no stuck-on-top-of-a-pole problem.

In such a case, there's little motivation to land the TMI cargo stage, and it really can free-return.

I think the Mars-earth capsule won't become a habitat.  I mean, if the crew capsule becomes a ground habitat, would you really want to use it as a return vehicle?  Tear up the colony?  Also, as a future habitat, such a crew capsule would be more elaborate than is needed for a trip back home.  I think ground habitats will be part of the cargo transfer.

The manned MCT would look like that diagram diagram.  And it would land a safe distance away.  And people might have to actually use a ladder to get down.  The capsule stays where it is, it might be a contingency habitat, but otherwise it unused until the rocket flies back.
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Offline Lobo

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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).

Yea, I picture something like this, with powerful methalox engines supplying dV rather than a huge parachute.  If there's a big circular heat shield, then the engines wouldn't have to ignite into a supersonic slipstream, they could ignite behind the shield and then begin to slow the descent as they throttled up towards terminal landing. 

And, it would appear that Musk is at least aware of Zubrin's work.


Offline Lobo

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But rather than two different landers like Mars Direct, have one common lander, that could be used either as the crew hab, or as a cargo lander.  The lander part would be common though. 
Inflatable descelerators could be used as well, but I'm just wondering if there would be a problem igniting engines into a supersonic slip stream.  So having a big circular shield on the bottom could give protection to the engines until they are ready to ignite.  The thrust would jettison the shield while slowing the lander letting the shield fall away. 
Then the whole lander, once refueled, would lift off and burn directly for TEI.  A Dragon capsule would be mounted on top, and that's what would be used to land the crew back on Earth along with samples and such. 
That same Hab is then used fro the Earth-Mars Transit, the surface stay on Mars, and then back to Earth.

Mars Direct had the crew occupy a Hab lander on the way out, and on the surface, but then a much smaller hab area on the ERV for the return home.  Two different landers altogether.

I'm wondering if it can be done in one common lander platform?

Offline QuantumG

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Why would you need a cargo carrier to drop off a cargo lander and then return?
If it's cargo, you can just send the cargo lander directly.  The only reason to have something come back to Earth is to return a crew.

No, it's so you can fly it again and not have to build another rocket.

It's about cost.
Human spaceflight is basically just LARPing now.

Offline Joel

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Assuming that a methalox MCT is designed to be able to land propulsively on Mars, how big of a technological challenge would it be to avoid propellant boil-off during a 6-month transfer?
« Last Edit: 07/23/2013 09:53 pm by Joel »

Offline Lobo

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Why would you need a cargo carrier to drop off a cargo lander and then return?
If it's cargo, you can just send the cargo lander directly.  The only reason to have something come back to Earth is to return a crew.

No, it's so you can fly it again and not have to build another rocket.

It's about cost.


Huh?  I'm not sure what you mean.  How is having a cargo carrier going to save anything?  You would need to accelerate the lander to redenzvous with it, and descelerate it at Mars.  How does it docking with a cargo carrier in a cycler save anything?

Offline Lobo

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Assuming that a methalox MCT is designed to be able to land propulsively on Mars, how big of a technological challenge would it be to avoid propellant boil-off during a 6-month transfer?

I believe methalox stores in space passively essentually indefinately.  Which is why it's better behaved than LH2.

Online meekGee

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Why would you need a cargo carrier to drop off a cargo lander and then return?
If it's cargo, you can just send the cargo lander directly.  The only reason to have something come back to Earth is to return a crew.

No, it's so you can fly it again and not have to build another rocket.

It's about cost.


Huh?  I'm not sure what you mean.  How is having a cargo carrier going to save anything?  You would need to accelerate the lander to redenzvous with it, and descelerate it at Mars.  How does it docking with a cargo carrier in a cycler save anything?


I wasn't talking about a cycler.

The carrier does TMI, splits off from the lander before EDL, and does a single free-return trajectory and re-enters at Earth, so does not need any dV beyond the original TMI.

You just get to use it again.  You need to launch it again, but then again you'd have needed to launch the propellant anyway, so you're not losing much by having it re-enter.
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Offline Lobo

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Why would you need a cargo carrier to drop off a cargo lander and then return?
If it's cargo, you can just send the cargo lander directly.  The only reason to have something come back to Earth is to return a crew.

No, it's so you can fly it again and not have to build another rocket.

It's about cost.


Huh?  I'm not sure what you mean.  How is having a cargo carrier going to save anything?  You would need to accelerate the lander to redenzvous with it, and descelerate it at Mars.  How does it docking with a cargo carrier in a cycler save anything?


I wasn't talking about a cycler.

The carrier does TMI, splits off from the lander before EDL, and does a single free-return trajectory and re-enters at Earth, so does not need any dV beyond the original TMI.

You just get to use it again.  You need to launch it again, but then again you'd have needed to launch the propellant anyway, so you're not losing much by having it re-enter.

Ahhhh...that makes more sense.  Basically an EDS stage that is capable of returning through the Earth's atmosphere and being recovered, is what you are talking about?

Interesting to find out if there's actually any cost advantage in doing that. 

Offline Mongo62

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It seems to me that it would be more cost-efficient for the TMI booster to boost back to Earth after supplying the delta-vee for the cargo lander.

Yes, you need to allow for sufficient propellant for a powered return, slightly reducing the total mass to Mars, but you get the booster back a LOT sooner than with a free-return trajectory to Mars.  So you would need a lot fewer boosters to handle all the flights (assuming they are reusable of course).

The actual cargo carriers could certainly be designed for ISRU refueling and return to Earth, but a lot of the savings could be due to keeping the total mass going to Mars (with its multi-year return time) to a minimum.

Musk has stated (see earlier this thread) that he wants to land 50t loads on Mars.  Gwynne Shotwell has also stated that they are looking at a heavy lifter in the 180t range to LEO.  Assuming methalox engines, can that size of lifter throw a package to Mars capable of landing 50t of cargo on Mars?  Or will it need to be refueled in LEO first?

Offline R7

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Assuming that a methalox MCT is designed to be able to land propulsively on Mars, how big of a technological challenge would it be to avoid propellant boil-off during a 6-month transfer?

I believe methalox stores in space passively essentually indefinately.  Which is why it's better behaved than LH2.

Things are even easier during interplanetary trip than low orbit depots because there's no warm celestial body covering half the sphere around you. JWST sun shield cools passively below 50K, even oxygen would freeze. Also LH2 boil off rate would be miniscule thanks to fourth power in the thermal radiation laws.

But things get different if the ISRU plant takes 18 months to fill the MCT tanks on the surface.
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Offline MikeAtkinson

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Why would you need a cargo carrier to drop off a cargo lander and then return?
If it's cargo, you can just send the cargo lander directly.  The only reason to have something come back to Earth is to return a crew.

No, it's so you can fly it again and not have to build another rocket.

It's about cost.


Huh?  I'm not sure what you mean.  How is having a cargo carrier going to save anything?  You would need to accelerate the lander to redenzvous with it, and descelerate it at Mars.  How does it docking with a cargo carrier in a cycler save anything?


I wasn't talking about a cycler.

The carrier does TMI, splits off from the lander before EDL, and does a single free-return trajectory and re-enters at Earth, so does not need any dV beyond the original TMI.

You just get to use it again.  You need to launch it again, but then again you'd have needed to launch the propellant anyway, so you're not losing much by having it re-enter.

I don't think it is advantageous to do that.

SpaceX would then have to design, build and operate 3 vehicles:
    1. cargo stage (with its own heat sheild)
    2. cargo carrier (including descent stage)
    3. crewed MCT

It results in saving a bit of IMLEO (fuel), but in my opinion leads to higher costs. Potentially it allows more cargo stages to be returned and reused, but does not allow any reuse of the cargo carrier which is likely to be where the bulk of the value is.

It also reduces safety, as the cargo and crewed versions are different EDL experience from the cargo version cannot be directly transferred to the crewed version.

The advantage of having a separate cargo carrier is that potentially larger modules/structures/vehicles could be landed assembled.

Offline Lampyridae

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I am having a hard time picturing what the MCT/Mars Lander configuration would look like. Suppose SpaceX wants to land 50 tons on Mars and with propulsive landing and return to Earth with ISRU refuelling.

If it lands tail first like the first stages booster will land, with the tanks/engines at the bottom. That puts all the cargo & habitat at the top of the lander. some of the cargo will be heavy and would need to roll off. I cannot think of a good configuration that inverts this.

Next configuration would be to use the big engines in the tail to retro-brake ALOT. Then flip for Horizontal re-entry for the biggest cross-section and with nearly empty tanks it should be very light with respect to its cross-section. Then land horizontal using much smaller methane engines or Super Dracos. 4 SDs would have the thrust of 71MT on Mars.  Two problems though. This configuration would make it very front/top heavy and once fully loaded with fuel it would not be able to launch this way. Need a way to distribute the fuel tanks throughout the vehicle but still allow cargo ramp access to the cargo bay.

Has anyone seen any designs that address this problem space. It is much bigger than anything I know of that NASA has even planned or thought of. Only science fiction.


Why mount rockets at the base? The main engines could be mounted amidships with a slight angle offset for the plumes to pass the hull. Slight cosine losses but that's all. Or else mount the engines on pylons, Skylon style.

One of the biggest problems for landing a truly large vessel on Mars would be all the dirt+debris kicked up by the descent motors. That could damage the motors as well as the heatshield.

You could minimise the exposure of engines and heatshields by landing base first with the main engines in clustered by the midsection (your main body being your usual biconic or whatever). Cargo is located in the base for easy access and of course the landing gear is there, so CoG helps make the vehicle stable. Engines are far away from dust and debris. This at least allows you to make only one set of engines + thrust frames.

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