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

[Lampyridae]

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?

I have a slightly insane idea for this.

You have a common lander - ye olde Zubrin tuna can habitat and ye olde SpaceX Dragon on top. Return vehicle is sent first: empty tin can with fuel tanks + engine + Dragon. Hab vehicle is sent second when the RV is topped up with metholox. It has LH2 feedstock onboard, useful as radiation shielding. The metholox tanks are turned into two hab compartments. Otherwise pretty much identical to the 1st lander. Standard Zubrin mission, swap over into the RV and away you go.

Now, the trick is the 1st crew, before they leave, strip the 2nd lander's habs of all their innards, plumbing etc and turn them into metholox tanks. So the abandoned hab now becomes another RV. If something goes south with the first RV, the crew can cannabilise their own lander and turn it into an RV. Also, the crew benefits from LH2 shielding from GCR on the way in, has 100% commonality with the RV in terms of spares and can turn the spent RV stage into a (rather Spartan) habitat for the voyage home, possibly using parts from their original lander.

It would mean a bigger lander of course and depend on whether the tanks could be converted to living spaces and back again. But it's an idea.

EDIT: and the LH2 feedstock has to be put somewhere.

ANOTHER EDIT: and of course you still need a separate cargo lander... but you could use the same mouldline and store the heavier cargo in the "Dragon" section to keep CoG similar.

[Sohl]

It would ... depend on whether the tanks could be converted to living spaces and back again.

Oof!  And to think I have trouble stopping O2 + N2 leaks at 1 ATM around my house's doors and windows.   I just guessing sealing up a LH2 or even LCH4 tank would be a bit tougher.   

[CuddlyRocket]

... you need to allow for sufficient propellant for a powered return, slightly reducing the total mass to Mars ...

Thinking in terms of a steady-state transport system to and from a Mars Colony - which would be what SpaceX is aiming for eventually, even if there's some modifications in the early stages - you'd want your return vehicle to obtain all its propellant on Mars rather than bring any or all of it from Earth.

That does imply a dedicated ISRU plant sent separately, but it makes sense to send large items of infrastructure and equipment separately, at least in the early stages of any colony.

[Lampyridae]

It would ... depend on whether the tanks could be converted to living spaces and back again.

Oof!  And to think I have trouble stopping O2 + N2 leaks at 1 ATM around my house's doors and windows.   I just guessing sealing up a LH2 or even LCH4 tank would be a bit tougher.   

Well, the idea is filed under insane.  Life support modules have to hold 1 ATM O2+N2 pressure and be sealed anyway, that's not an issue. The way I envision it is each tank is a separate deck, with a floor section that doubles as a baffle. Tanks have maintenance hatches anyway for cleaning + inspection. Downside is, no windows. Maybe a separate cupola? The main problem is whether you can convert a living space to a tank again. Can you get it to an acceptably clean state or will tomato sauce stains render the engines inoperable? Plus there's all the work involved.

[ciscosdad]

Given the structures inside the tank/habitat (floors etc) I doubt you could get it clean enough.
Anything organic in LOX os a serious hazard (high explosive mixture, very sensistive to friction, shock and almost anything else). LH2, probably less of a hazard, but muck in the filters might be a problem.

[R7]

Tanks could have strengthened areas for window flanges. Once on surface saw the window hole and bolt a window in place. The idea of converting back to propellant tank should stay firmly in the insane cabinet  Or is there doubt that the people suddenly decide the colony was a bad idea and everyone wants back to Earth 

[Joel]

Or is there doubt that the people suddenly decide the colony was a bad idea and everyone wants back to Earth 

Well, -50 degrees temperatures, no beaches in sight, air less healthy than in Los Angeles and the worst internet connection imaginable, might force Musk and other California expats to rethink.

[mlindner]

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

The Musk-Tinker exchange no longer exists, Elon deleted it, so can we forget about it? Tinker's design was arbitrary and vague as you could be, not much better than an elementary school student's drawing of a rocket launching from earth to Mars. His "design" hardly excludes any design from possibility, and with Elon's comment of "pretty much," it makes it even more vague. Then, by definition, his design is not a design. Basically we have _zero_ information gain from that now non-existent conversation.

[meekGee]

awww.. That's too harsh.

We can rule out with reasonable certainty, and only for the manned version, a large Mars-Earth cycler, probably any in-earth-orbit assembly, and anything in orbit around Mars.

On Hyperloop, otoh....  <ducks>