On Tue, Jan 30, 2018 at 12:31:26AM -0500, Caleuche wrote:
> I'm not clear about some of the reentry procedure, the patent states
> that the sphere is under very low absolute pressure and is obviously
> not rigid, the returning astronaut will know it's safe to depart the
> "vehicle" once the sphere starts to collapse under the higher
> outside pressure of Earth's atmosphere. But reentry itself will
> result in fairly high pressures at times

Not for something this light.  Even if it came in steeply enough to
peak at 10 gee deceleration, the dynamic pressure would still be less
than 20 kPa.  You can run the numbers on a (say) 100 kg sphere with
about 1.4 m diameter to see that the expected peak deceleration for a
typical shallow entry will be quite a bit less than that.

The patent document states that it was designed to support up to
8.5 gees deceleration, with an internal pressure of 1.75 p.s.i.a (about
12 kPa).  So their figures are comparable with my back of the envelope
numbers.  The bladder pressure was chosen to be that low so as not to
exceed the internal pressure of a space suit and possibly restrict air
flow during descent.

- Tim