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(In this question, Starship refers to the reusable 2nd stage, not the full stack w/ Super Heavy).

I was thinking about it the other day, and I realized that I'm not sure a reusable Starship actually has that much bearing on SpaceX's Mars plans (apart from funding the company).

For LEO and Earth-to-Earth, full reuse absolutely makes sense, and SpaceX is making a really smart choice pursuing it as aggressively as they are.

However, I would expect most Mars (or Moon) trips will be one-way, or maybe two-way without a second round trip. If they send a Starship to Mars and bring it back, I'd think they'd be more likely to disassemble and examine it for improving their LEO system than actually send it to Mars again. Given the fact that the Starship lunar edition lacks ailerons and therefore cannot reenter Earth's atmosphere (and survive, that is), a one-way-only design doesn't seem that farfetched.

At that point, it's an expendable 2nd stage really. It'd do the same principle as a Saturn V - send a lander, stay there for a while, come back and survive reentry, discard the capsule. Reusability of the 2nd stage doesn't save them much money in that case either.

Given this, why does Elon think full reusability (including the 2nd stage) is important for a Mars colony?

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    $\begingroup$ Might be useful to clarify 'serve a purpose for mars' as being actually using it to land on Mars, or just using it to lift fuel and payload for Mars departure. With the later pretty clear that a fleet of low(ish) cost heavy lifters is pretty critical purpose, even though most will never leave LEO. $\endgroup$
    – GremlinWranger
    Commented Apr 24, 2021 at 9:50

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Reusability is important because of the vast number of tanker Starships that will need to be flown into orbit. It is essential that these tankers can be used over and over again to ensure sufficient propellent is put into orbit to supply the cargo ships and the crewed ships that will be traveling to the Moon and to Mars. And to ensure this happens cheaply.

In addition the crewed Moon ships will certainly be bringing their crews back if NASA has anything to do with it. And as for Mars I doubt very much that the very early crews will be staying permanently as there will not be sufficient infrastructure at that point. It will take time before permanent settlers arrive - in my opinion.

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  • $\begingroup$ Do you think the Mars-bound Starships will be reused upon returning to Earth, or discarded/disassembled? Given SpaceX's willingness to have multiple renditions on the Starship, I could see a non-reusable Mars version existing, even if the tanker ships would be reusable. In the link I provided in the question, their lunar Starship render lacked ailerons, eliminating Moon-to-Earth reuse, so I could see a similar thing for Mars happening. $\endgroup$
    – Drake P
    Commented Apr 24, 2021 at 18:56
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    $\begingroup$ I don't think it is entirely clear yet. IMO the early cargo ships will stay on Mars the early crewed ships will return to Earth. I doubt the first ship to go to Mars will be used again. Beyond that it will depend on a lot of things like how quickly SpaceX settle on a stable design and how much it costs. In addition how expensive in terms of opportunity loss will it be to use the vast amount of Martian energy needed to create the propellants to return a Starship. It might make sense to restrict numbers of people until the base is ready. There will be ships returning and they may well be reused. $\endgroup$
    – Slarty
    Commented Apr 24, 2021 at 21:24
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Building a sustainable settlement on Mars will need hundreds of flights. Building tens of Starships and reusing them vs. building hundreds of Starships and throwing them away, is going to be much cheaper.

Given the fact that the Starship lunar edition lacks ailerons and therefore cannot reenter Earth's atmosphere (and survive, that is), a one-way-only design doesn't seem that farfetched.

The Lunar Starship (Moonship?) is very much going to be reused. That is a crucial element of SpaceX's bid, and makes it different from both Dynetics' and the National Team's bids, both of which were only partially reusable. (The National Team's lander leaves the descent element behind when it launches from the Moon, and Dynetics' lander has drop tanks that it drops during descent.)

While the current contract is only for two flights, in the future, there are going to be more contracts.

The fact that the Lunar Starship does not need the recovery hardware for atmospheric reentry, is a quirk in the Artemis mission architecture, which simply could not foresee a vehicle capable of from Earth to the Moon and back. Therefore, NASA only asked for a lander that can go from the Lunar Gateway to the Moon and back, and that is what SpaceX designed for them.

If, in the future, NASA decides that the whole SLS launches Orion, Orion docks to the Gateway, crew transfers from Orion to Gateway, HLS docks to Gateway, crew transfers from Gateway to HLS, HLS lands on the Moon, HLS launches back up to Gateway, crew transfers through Gateway to Orion, Orion goes back to Earth, meanwhile Gateway is re-supplied using Dragon XL dance is much too complicated, and they could just launch crew on Starship to the Moon and bring them back to Earth, then it is easy to put the recovery hardware back on and reduce the payload mass by 20 tons.

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    $\begingroup$ I feel this answer doesn't address Mars very much. Is your answer trying to imply that the reason reuse is important for Mars is because Elon is in fact planning for Mars Starships to make multiple roundtrips? Also, can you elaborate on how the lunar Starship is going to be reused? Without ailerons, I'm confused about the reuse you're suggesting is there since they cannot return to Earth. Or have they added the ailerons back on? $\endgroup$
    – Drake P
    Commented Apr 24, 2021 at 18:48
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    $\begingroup$ As I explain in the answer, NASA's Artemis architecture has the HLS only go between Gateway and Lunar surface. Starship will, IFF it gets selected for future contracts, do many flights from the Gateway to the Lunar surface, back to the Gateway, back down again, and so on, with trips to LEO for refueling in between. For Mars, the answer is simple: you need a huge amount of flights. It is trivially cheaper to fly multiple of those times with the same vehicle than to fly every flight with a new vehicle. $\endgroup$
    – Jörg W Mittag
    Commented Apr 24, 2021 at 19:12
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    $\begingroup$ As I also explained in the answer, it would be easy to not remove the flaps, if NASA decided to change the mission architecture to eliminate the use of SLS and Orion for launching crew from and returning them to Earth. The reason why the Lunar Starship doesn't have flaps is because the way NASA has specified the mission architecture, it doesn't need them. There is nothing inherent about Lunar Starship that prohibits it from having flaps. It simply doesn't need them. $\endgroup$
    – Jörg W Mittag
    Commented Apr 24, 2021 at 19:24
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    $\begingroup$ Starship may have the hardware to do Earth orbit -> Moon surface -> Earth reentry, but it doesn't have the fuel. The delta-V of that mission is about 8400 m/s, nearly as much as the 9200 m/s for Earth surface -> Earth orbit, and the practical limit for single-stage rockets is around 5000 m/s. It'll need to do a fuel stop somewhere (probably lunar orbit) in order to make the trip. $\endgroup$
    – Mark
    Commented Apr 24, 2021 at 23:52

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