[AR] Re: SpaceX Single Stage to Orbit
- From: Nels Anderson <nels.anderson@xxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Tue, 28 May 2019 10:05:12 -0400
On 5/27/19 2:50 PM, Keith Henson wrote:
The not-so-obvious thing they do is using the wings to unload gravity
drag. They do this even after the switch to rocket mode. The wings
save an incredible amount of delta-v compared to a rocket that took as
long to get to orbit.
How incredible could the savings be? Total losses, not just gravity,
for a conventional rocket to LEO might be 1000 m/s out of a total ideal
delta-V of about 9000 m/s. Saving a significant fraction of that 1000
m/s ain't peanuts if you're operating well into the rocket equation's
exponential regime, where a rocket-powered SSTO . But given how lousy
hypersonic L/D's, I would think it's almost as much a matter of trading
gravity losses for drag losses as saving gravity losses.
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