5 ms·

The goal is to maximize re-use in order to minimize cost, for a tanker to fuel a tanker in orbit you'd need two tankers. So 1 booster + 1 transporter + 1 tanker

The goal is to maximize re-use in order to minimize cost, for a tanker to fuel a tanker in orbit you'd need two tankers. So 1 booster + 1 transporter + 1 tanker, vs. 1 booster + 1 transporter + 2 tankers. If the trip takes 100 days, adding 3 weeks is 20% longer, and you might get it 20% cheaper by saving one spacecraft ... I can see it going either way.

Grishnakh 10y ago
Why not just save a bunch of time and use new boosters? Then reuse those boosters for other missions? Reusing rockets is great for saving money, but that doesn't mean you need to reuse the same rocket for this one mission; if you have a business going with, say, 30 missions over the next year, you're probably going to need a lot more than one booster in stock anyway. Or, instead of new boosters, use a bunch of reused boosters for the Mars mission, letting other commercial customer who insist on brand-new boosters help subsidize your Mars mission.
- elevensies 10y ago
  With only one tanker, you can launch the tanker first and then launch the transporter, so it isn't any faster than launching a tanker and transporter simultaneously. To go any faster you'd need more tankers as well. I don't forsee the tanker having commercial value short-term, so this would still increase the cost. With two tankers though, you can just have a full tanker waiting in orbit which is the fastest possibility, so there is no need of extra boosters in that case. I agree with the premise of multiple boosters though. I wonder if a spacecraft could be made that could do both commercial earth orbit satellite missions, and serve as a tanker. This could finance a larger number of tankers. I think you'd need a 3rd stage on top of the tanker in this case to get the satellite in position. [EDIT: I mean either carry the extra fuel, or carry a 3rd stage + satellite, not both at the same time.]
- deftnerd 10y ago
  I personally think it makes sense for SpaceX to offer to take over Tiangong I, the Chinese space station that's going to be deorbited soon. It's older and not suitable for safe habitation anymore. If SpaceX could use their launch capacity to bring up fuel tanks and to boost the orbit, it could do well as an orbiting fueling station. Just launch tankers and fill up tanks on Tiangong and then the space craft with passengers would just have one trip to the space station to fuel up and then go to Mars. China is going to throw away the station anyway, so might as well give it (or lease it) to SpaceX for a good price in exchange for at-cost refueling for their own ambitions.
  - Pinckney 10y ago
    What would they use it for? If you're going to Mars, your vessel has a reasonable crew habitat, so you don't need Tiangong I for that. Tiangong I is more payload than spaceship. Its tanks can only hold about 1000kg of propellant. Mr. Musk's proposed transfer stage has a propellant budget that's nearly 2,000,000kg. Having to maintain compatibility with it may be hard (comms, docking, etc). There might be some hardware you could loot off it, but it's not worth flying a mission just for that, and launch windows mean visiting on a trip somewhere else would be prohibitively expensive.

Grishnakh 10y ago

Why not just save a bunch of time and use new boosters? Then reuse those boosters for other missions? Reusing rockets is great for saving money, but that doesn't mean you need to reuse the same rocket for this one mission; if you have a business going with, say, 30 missions over the next year, you're probably going to need a lot more than one booster in stock anyway. Or, instead of new boosters, use a bunch of reused boosters for the Mars mission, letting other commercial customer who insist on brand-new boosters help subsidize your Mars mission.

elevensies 10y ago
With only one tanker, you can launch the tanker first and then launch the transporter, so it isn't any faster than launching a tanker and transporter simultaneously. To go any faster you'd need more tankers as well. I don't forsee the tanker having commercial value short-term, so this would still increase the cost. With two tankers though, you can just have a full tanker waiting in orbit which is the fastest possibility, so there is no need of extra boosters in that case. I agree with the premise of multiple boosters though. I wonder if a spacecraft could be made that could do both commercial earth orbit satellite missions, and serve as a tanker. This could finance a larger number of tankers. I think you'd need a 3rd stage on top of the tanker in this case to get the satellite in position. [EDIT: I mean either carry the extra fuel, or carry a 3rd stage + satellite, not both at the same time.]
deftnerd 10y ago
I personally think it makes sense for SpaceX to offer to take over Tiangong I, the Chinese space station that's going to be deorbited soon. It's older and not suitable for safe habitation anymore. If SpaceX could use their launch capacity to bring up fuel tanks and to boost the orbit, it could do well as an orbiting fueling station. Just launch tankers and fill up tanks on Tiangong and then the space craft with passengers would just have one trip to the space station to fuel up and then go to Mars. China is going to throw away the station anyway, so might as well give it (or lease it) to SpaceX for a good price in exchange for at-cost refueling for their own ambitions.
- Pinckney 10y ago
  What would they use it for? If you're going to Mars, your vessel has a reasonable crew habitat, so you don't need Tiangong I for that. Tiangong I is more payload than spaceship. Its tanks can only hold about 1000kg of propellant. Mr. Musk's proposed transfer stage has a propellant budget that's nearly 2,000,000kg. Having to maintain compatibility with it may be hard (comms, docking, etc). There might be some hardware you could loot off it, but it's not worth flying a mission just for that, and launch windows mean visiting on a trip somewhere else would be prohibitively expensive.