And with a rudimentary supersonic drag model (over Mach 1.4, Cd is 0.95, between Mach 0.95 and Mach 1.4 it is 1.25, and below Mach 0.95 it is 0.47:

https://i.imgur.com/bules7a.png
​
This has the effect of lowering peak dynamic pressure to around 10 kPa.

​

-------- Original Message --------
 On January 30, 2018 9:12 PM, Caleuche <xxxxxx@sudnadja.com> wrote:

>So, this with 0.7 meter radius, for a reference area of 1.54 m^2, mass now 204 kg for real, initial orbit parameters had a semimajor axis of earth's radius + 150km, eccentricity 0.0103.
>
>https://i.imgur.com/cF9bq6S.png
>
> and the data:
>https://i.imgur.com/2Fs7zdO.png
>
> Dynamic pressure does get above 20 kPa (about 22 kPa). Acceleration due to drag at that point is 80.8 m/s^2 (8.2g), altitude at 38818 meters, velocity 3087.51 m/s (Mach=9.80), molecular density at that point 0.165927 mol/m^3, static pressure 0.34087 kPa. Drag coefficient is still assigned to be 0.47 and should be more like 0.95 at in those conditions at that velocity. Temperature 247.1 Kelvins.
>
>
> ​
>
> ​
>
> -------- Original Message --------
> On January 30, 2018 4:40 PM, Tim xxxxxx@little-possums.net wrote:
>
>>On Tue, Jan 30, 2018 at 05:07:40PM -0500, Caleuche wrote:
>>>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
>>>That's not possible.  Drag = dynamic pressure * coefficient * area, so
>> with your figures the drag should be 2.2 MN, acting on a 204 kg object
>> thus yielding a deceleration of 1100 gee.  If you're getting 8 gee,
>> then you must be using a mass of 28 tonnes (or some similarly far-out
>> number elsewhere in the calculation).
>>A chunk of solid rock of the same size might have a mass of 28 tonnes,
>> and it would be physically reasonable for it to get down to 20 km
>> altitude before slowing significantly, but an astronaut in a bubble
>> won't.
>> - Tim
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