Floating launchpad

phoebos@... wrote:

> If a payload could
> be launched from a floating platform miles above the Earth's
> surface, could that significantly cut launch costs in the long run?

Depends on your definition of significant. 7% of the energy
necessary to get into orbit involves going up. 93% involves
going sideways fast till the rate that you fall matches
the curvature of the earth.

Therefore a floating platform doesn't help very much. It
does however get you out of the really thick bit of the
air and it helps improve the efficiency of your rocket
nozzles because they see less variation in pressure
so there are some subtle advantages.