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 > >The Traveller Mailing List > Archives at http://archives.simplelists.com/tml > Report problems to xxxxxx@simplelists.com > To unsubscribe from this list please go to >http://www.simplelists.com/confirm.php?u=0og3DHdoRHgL9lI7peOXYWnk6UF4c1zE >
