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The turbojet designs to get up out of most of the
atmosphere to launch a space rocket are horizontal winged
affairs because that's the most efficient way to get off the
ground with that kind of engine. However, launching a
rocket from an airplane has the disadvantage of having to
carry the
rocket horizontally, launching it and having it
twist its course and fly upwards.
This isn't a huge deal but if I were a rocket, I'd rather just
sit upright and take a nice ride up to the edge of the
atmosphere and launch from a jet propelled launch pad.
Yes, you'd need more engines than with an airplane but it
could be done and then you don't need all those bulky
wings and control surfaces. It would also be fully modular
in that you add as many engines as you need to make the
thing fly.
Plus it's easier to launch a rocket standing vertically than
horizontally since you have to hold its stages together until
it gets up to speed. When a rocket is standing vertically
gravity does that job.
It would be huge, but it would be completely re-usable.
No ridiculously long runway either. Use any existing space
port.
[link]
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a very large quadcopter could do it with the rocket at the
center. Not sure it would be cost efficient on the energy
tradeoff. |
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In terms of efficiency, wings are a lot better than vertical
jets. Even the Harrier (the first practical VTOL jet aircraft)
would only use VTOL when there was no other option,
because it drank fuel. |
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In a rocket, everything is about exponentials and keeping
them under control. If you need an extra 1000kg of engine
plus fuel, you also need an extra 700kg of engine and fuel
to lift the 1000kg, and then an extra 500kg to lift the
700kg... If you can reduce your engine mass by using
aerodynamic lift (which requires only some lightweight
wings), you've effectively won the lottery. |
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If I remember correctly, the Shuttle was originally
conceived as a horizontal take-off machine (winged orbiter
piggybacked on a winged first stage), but then endless
budget cuts reduced it to a glider strapped to the back of a
giant fuel tank and a couple of huge booster rockets. If
they'd stuck with the original HTOL concept it'd really have
been something. |
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