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perrochon t1_j1w2fcy wrote

Fuels is a big part of weight, and any Mars bound craft will not carry it's fuel up from Earth. It will get to orbit (or be assembled there) and other ships will bring up fuel to orbit and transfer to the Mars bound craft. Then those other ships will go back down to get more fuel and supplies.

SpaceX is changing the economics of rockets drastically. Starship has so much capacity and power at low cost that it opens up more flexibility. Spaceship is lifted off earth on a booster. Then gets refuled by more Starships. But it is designed to take off from Mars or Moon on it's own (after refueling). There is a graph here:

https://www.spacex.com/human-spaceflight/mars/

One big topic for discussion is whether we should go to the Moon first, and then from there to Mars, or straight to Mars. If we could lift fuel from the Moon, it might be more efficient. But with Starship, that discussion is less critical. We can do both :-)

Rocket Science has never been more interesting. Your daughter gets it :-)

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gbbloom OP t1_j1wbzae wrote

My daughter is so into it. She's a bit young to talk "career" but I think she'd love to have something to do with space one day. I actually just remembered that I said she could have a new telescope for Hanukkah... so we'll call that the "bonus" present.

This is utterly fascinating. Wondering if picking up fuel from the moon is viable... if there are other things we could use for fuel beyond what we've always considered, if we don't have to escape Earth's gravity well first.

So, I'll challenge you: what if we headed for, say, Ceres first, and then on to Mars?

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ADSWNJ t1_j1wqdu0 wrote

This is where Musk and SpaceX have been planning for years. Where other rockets have used space grade kerosene (RP1) and liquid oxygen, or liquid hydrogen + oxygen, Musk knew he wanted to refuel natively from the Martian atmosphere, which is CO2 rich, then the best fuel would be methane and oxygen. Hence the new raptor engine burns methane amd oxygen. Plus the Starships can be configured as fuel browsers, freighters, human-rated travel or as "Pez" dispensers fir hundreds of Starlink satellites per launch. The goal is to fund interplanetary missions from massive commercial benefits of launching satellites around Earth, then to build a fleet of vehicles capable of hundreds of trips each ship, then refuel in Earth orbit to allow much bigger missions to Mars than could launch direct from Earth. And so on... its incredible really.

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