high altitude pressure.

s4177112

hi i'm new here and i need some help regarding atmospheric pressures.
i have a way of calculating it up until about 50 km above sea level.
is there a way to accurately model the pressure at an altitude up to 300km?

E=ML^2

Hi there, I hope I can be of assistance. i don't know how to model the pressure at an altitude up to 300 km. But remember that the pressure declines quite rapidly, I don't recall if it was an logarithmic scale proportional to the heigh above sea level, or perhaps an exponential scale, but above the stratosphere there is no weather (in the general terms we are accustomed to) and above the mesosphere you can pretty much say that you are in space, imo. Of course, it depends on how accurate you want the model to be, perhaps that is still of interest to your project.

I hope I helped, at least somewhat :P

s4177112

thanks for your help.
i'll give you a bit more background to the problem.
i am actually trying to calculate the surface pressure of a vehicle that has been shot up in a rocket and detaches. it reaches a height of 300km and begins its descent. i have already modeled its velocity with python and wanted to do the same for the surface pressure for the entire trajectory.
i'm using the equation:

p-p1 = rho*v^2*sin^2theta

where p1 is the upstream pressure.
i have said that p1 is:

p1 = p0(1-(L*h/T0))^(g*M/R*L)
this only holds true up until 50 km.

all of this has been simplified down especially the fluid dynamics as the 'real' equations are far too complex and i think to solve it properly computation fluid dynamics is needed.

i am not sure what i should assume for altitudes above 50 km? i will also need to do the same with the density.
any ideas?
thanks again

Astronuc

Here are some formulations.

http://www.grc.nasa.gov/WWW/K-12/airplane/atmosmet.html

NASA is planning to measure the earth's atmosphere up to 400 km.
http://cddis.nasa.gov/lw13/docs/pape...icholas_1m.pdf

See also
http://www.brodo.de/space/nrlmsise/index.html
http://ccmc.gsfc.nasa.gov/models/mod...hp?model=MSISE

This may provide useful links
http://en.wikipedia.org/wiki/NRLMSISE-00

s4177112

thank you very much.
it is exactly what i needed.