Can anyone suggest a commercial code capable of modelling hypersonic flow and simulate deformed flow separation generated by drag reduction devices, ie. aerospike. Is this an area where one would be better off developing their own code? I've been looking at Aerosoft, Fluent...etc but I don't know much about any of them. Any suggestions are appreciated.

I can tell you from personal experience that the Aerosoft GASP code has been used for a lot of hypersonic applications. It would be one useful option for you.

If you are in the U. S., there are several government codes available which might be useful (the NPARC Alliance WIND code, the VULCAN code from NASA Langley, etc.). Both of these are good codes and have been used for a number of hypersonic applications.

Of course, the accuracy of your answers will depend on a lot of factors (turbulence modeling, chemical reaction rates, grid resolution, etc.). You definitely need to understand the models you are using and their potential shortcomings.

If you are a student, you might want to try writing you own code. It is a lot of work, but the insight you obtain can be invaluable in understanding CFD. If you are just trying to solve a particular problem, then maybe GASP, WIND, or VULCAN would be the best options.