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Originally Posted by Hemi-Cuda
So in For All Mankind season 2, they launch an advanced version of the shuttle that launches into space on it's own after piggy backing off a 747. Can someone more knowledgeable on space stuff than me explain why it's preferable to keep using rockets vs a more advanced shuttle setup?
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Getting into orbit is all about getting enough speed than it is about getting high enough.
Getting high enough, which a 747 can help with, is pretty easy, it's the going fast enough part that is really hard, and why the fuel tank for the shuttle is larger than the shuttle itself.
Same thing for all the other rockets we see.
Most of the mass/volume is fuel to get you going fast enough.
In FAM, the shuttle they were using was using "Nuclear engines", which are probalby meant to be ion engines/thrusters which are a thing, and do require a lot less fuel mass, so kind of on track, but the ones we have now aren't really suited to what they were doing in FAM. Ion thrusters use electricity to accelerate a small amount of mass/fuel to a very high speed, so you get better thrust/kg of fuel vs a chemical rocket, but you need enough electricity to get it going, so I guess that's the premise of the nuclear engine is at least kind of correct.
But for now, it's not really feasible, so using a plane doesn't do you any good.
Virgin uses the plane/rocket setup because it's a sub orbital flight. They get high enough to be in space, but not fast enough to be in orbit, so for them using a plane to start at a higher point means they need a smaller rocket with less fuel, it's more efficient for them that way.
If you want to go to orbit with anything larger than a small satellite, the plane doesn't do you any good.