[AR] Re: supersonic retro (was Re: Re: Falcon 9 flight today)
- From: Henry Spencer <henry@xxxxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Wed, 2 Oct 2013 15:35:24 -0400 (EDT)
On Wed, 2 Oct 2013, Chris Jones wrote:
> > The Apollo LM did supersonic retro-propulsion down to landing, but that
> > was in vacuum.
>
> Nor were they the first to use "retro-propulsion" to effect a landing on
> the moon (both Lunas and Surveyors preceded them). But doesn't the
> "sonic" part of supersonic imply non-vacuum conditions?
There's vacuum, and then there's vacuum. :-) The solar wind is pretty
damn thin by aerodynamic standards, but the speed of sound in it *is* a
meaningful concept -- although not usually a useful one for anything
except plasma physics.
Agreed that it's rather stretching the definition.
Henry Spencer
henry@xxxxxxxxxxxxxxx
(hspencer@xxxxxxxxxxxxx)
(regexpguy@xxxxxxxxx)
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