I mistakenly ran the model with 1.4 meters radius rather than 1.4 meters diameter, but otherwise modeled a sphere with radius 1.4 meters, subsonic drag coefficient 0.47 and transsonic drag coefficient 0.55, and supersonic drag coefficient 0.47 again (I need to fix that, spheres have very high supersonic drag coefficients), mass was modeled to be 104 kg for the sphere and 100 kg for the astronaut+spacesuit (the same as the traveller reentry kit) but going on with it:

Here is the plot from entry interface to touchdown:
https://i.imgur.com/APikZcR.png

And some of the extracted data:
https://i.imgur.com/zdxUmZG.png

Peak acceleration is just over 8g at around 20,000 meters altitude, and dynamic pressure peaks at that time too, at around 650 kPa (thanks to the fairly high mach number at that point). I'm using Mathematica's StandardAtmosphereData[] for pressure, temperature, atmospheric molecular density and speed of sound data. I'm presuming the air is an ideal gas.

Dynamic pressure remains below 12 kPa until altitude is ~58 km, though. I suppose the astronaut could "bail out" at that point but it's still over Mach 25.
​

​

-------- Original Message --------
 On January 30, 2018 5:41 AM, Tim <xxxxxx@little-possums.net> wrote:

>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
>
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