All you need to know is that it's already impossible WITHOUT drag. Atmospheres just make it worse.

You could simulate atmospheric drag in an excel spreadshhet with a crude finite-difference scheme based on linearised equations of motions and Cd.

If you don't understand those terms, you're already in too deep.

I'm sorry, but I have a job and a life and my own projects to work on. Do your own work...

And if you want to understand why NASA is working on it there are several possible reasons:-

1) Launch assistance could replace the heavy first stage
2) The researchers could be working to launch payloads but selling it as a man-launcher
3) The researchers might just be taking the money to keep their careers going, any way they can
4) NASA may be doing (2) or (3) for themselves
5) NASA may not know what it's doing
6) This may be technology enabling for the far future, like launching from the Moon

(Happy New Year)