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> Even if SpaceX will do orbital re-fueling, it's just two-three launches, why would you need more? Wikipedia says Starship weights 120 ton empty and 1320 ton
by avmich 2y ago
> Even if SpaceX will do orbital re-fueling, it's just two-three launches, why would you need more?
Wikipedia says Starship weights 120 ton empty and 1320 ton fueled, plus 100 ton payload (approximate numbers). That means fuel weights 1200 ton. So to carry fuel to LEO to fuel up a Starship you need 1200 / 100 = 12 flights. You can change this number maybe 2 times into both directions, but I doubt you'll fuel Starship with just 2 or 3 flights of tankers. Would be glad to err here.
- vl 2y agoBut you don’t have to fuel it fully to go to the moon and back. It’s a bit hard to compare to Apollo since Apollo dropped stages at every step of the process, but it seems they used 70 tons of fuel in the third state of Saturn V for original trans lunar injection of 45 ton Apollo. Apollo itself was 2/3 fuel. So it’s ratio of 15 tons to 90 tons. I.e. 1/6.
- avmich 2y ago> But you don’t have to fuel it fully to go to the moon and back. Numbers: from LEO (low Earth orbit) to TLI (translunar injection) - approx. 3.1 km/s; from Moon hyperbolic to LMO (low Moon orbit) - approx. 0.8 km/s; from LMO to the Moon surface - 1.6 km/s, back to LMO - 1.6 km/s, total - 7.1 km.s . Numbers are optimistic, no errors. You absolutely, positively have to add delta-V for landing, Apollo LEMs, for example, had ~0.6 km/s, and also for docking - about the same, so total is already 8.3 km/s . This is more than Starship needs to get to LEO after SuperHeavy boosted it from the Earth. So... no, if you're planning to get to the Moon anything near the Starship regular payload - 100 ton - you absolutely have to fuel it up fully.
- vl 2y agoYes, you are correct, I forgot about payload. With payload my estimate produces full refueling as well.