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 >>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://archives.simplelists.com >> > > >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 >
