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.
-- doctorremulac3, Mar 02 2019

a very large quadcopter could do it with the rocket at the center. Not sure it would be cost efficient on the energy tradeoff.
-- theircompetitor, Mar 02 2019


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.

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.

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.
-- MaxwellBuchanan, Mar 02 2019



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