Caided
Aero
AERO is primarly a nozzle calculator. Input a gas temperature and NPR and the program will calculate a nozzle area from a given mass flow

Pressure at altitude can used and ram conditions due to a flight velocity can also entered

It is still in beta form, so there may be a couple of bugs. You can contact me at nick at caided.co.uk if you find any bugs or want to request feature enhancements. 
 
It aimed at CFD user who needs quick access to some simple values, i.e. pressure and temperature at altitude. 

It is freeware for use on the windows desktop.