An alternative — and much less expensive — path to a US moon landing

[ecarfan]

V2 Starship would help, of course.

It seems like V2 Starship would be a fairly straightforward vehicle to since it is primarily stretched tanks and then 3 additional RVacs.

Also, a lunar Starship has no flaps and no TPMS so that helps.

 

[JB47394]

It seems like V2 Starship would be a fairly straightforward vehicle to since it is primarily stretched tanks and then 3 additional RVacs.

I believe that additional engines don't provide any benefit for HLS once its on orbit. In fact, they're a penalty because they have significant dry mass. They increase how quickly the ship can change velocity, but that's not all that important.

A V2 Starship would need to have roughly double the tank capacity of the V1 Starship for the full round trip, and it could only do it with perhaps 20 tons of cargo.

It would all be helped tremendously if the returning vehicle used aerobraking (like the Apollo missions did). That reduces the return delta-v requirement significantly. This is why Starliner is being used to return to Earth; it has enough delta-v to get from LLO to Earth's surface by using aerobraking. Another possibility is getting to LEO using aerobraking. This topic was briefly discussed in the NASASpaceFlight forums in 2022.

 

[ecarfan]

It would all be helped tremendously if the returning vehicle used aerobraking (like the Apollo missions did). That reduces the return delta-v requirement significantly.

So, a V2 Starship with TPMS and flaps, returning from the Moon, could use aerobraking to re-enter LEO, and then the crew would transfer to a Dragon for return to Earth?

 

[JB47394]

So, a V2 Starship with TPMS and flaps, returning from the Moon, could use aerobraking to re-enter LEO, and then the crew would transfer to a Dragon for return to Earth?

That's the idea, but we don't know if a V2 Starship could do it because we don't know its dry mass and propellant load. If it can do it, there's the question of how much cargo it could take on such a trip.

I was thinking that, instead of sending propellant to the Moon, can we use an orbital booster to get the Starship moving? I'm thinking of another Starship as the booster here, not a ground launch booster. The idea is to get the stack going on a free return trajectory (perhaps just a highly-elliptical orbit) so that the booster will come back and be able to aerobrake back into LEO. The Starship then stages and fires its engines to go wherever it's going, retaining its full delta-v at the point of staging. The boosted path of the Starship should obviously be as compatible with the Starship's intended path as possible.

I don't know enough about orbital mechanics to know if it's practical or even possible.