Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!munnari.oz.au!uniwa!cc.curtin.edu.au!tcliftonr
From: tcliftonr@cc.curtin.edu.au
Newsgroups: rec.skydiving
Subject: Re: Skydiving at supersonic airspeeds
Message-ID: <1991Jun28.195615.8833@cc.curtin.edu.au>
Date: 28 Jun 91 11:56:15 GMT
References: <1991Jun24.135815.8781@cc.curtin.edu.au> <996@lhdsy1.chevron.com> <1265@keele.keele.ac.uk>
Organization: Curtin University of Technology
Lines: 35

In article <1265@keele.keele.ac.uk>, csa18@seq1.keele.ac.uk (R.J. Husmo) writes:
> I always wanted to skydive from ORBIT, myself.
> Would anybody like to comment on the problems with such an undertaking?
> 
> Radar.

Why not do a mini shuttle trick?

Start with a low circular orbit.  Then v2/r = g  so v = sqr(g*r) = 8 km/s

Now nudge down (with a retro burn of your remaining rocket of course)
so that you hit enough atmosphere for one gee of drag.

It would be good to design a flight path so that one gee of drag is maintained 
throughout the descent.  Then that 8 000 m/s is reduced at 10 m/s per second over
800 seconds, which shouldn't be too much oxygen to carry!

If you have enough flying control, 
you can nose down for increased drag and nose up for reduced drag.
This will be pretty sensitive at the hoigh speeds, so I for one would prefer 
an automatic control.

There is a mean amount of KE to be gotten rid of as heated, eddying air.
Power = force*vel = 10 N/kg * 8 km/s = 80 kW/kg at height, decreasing. 
This would need tiles on your feet and some sort of refractory control surface.

Since the compression cones would be tight, arcsin(v/c) = arcsin(250/8000) = sfa
it might be wise to keep your nose out of the wind.  That requires a shell around 
your feet-first hurtling body, a mini-shuttle.

What slowed-down velocity is cool and smooth enough for skydiving?  We might 
know more when the 120 000 ft experiment is performed - they will reach 0.3 km/s 
supersonic.  

We wish you luck, brave traveller.