Author told me, it's a distant descendant of the project Neva It utilizes MHD technology to boost chemical engine's exhaust to plasma. Also, it uses lasers and generators of external EM-waves to smoothly dissipate shock waves on subsonic speed.
I don't know does this piece of cake either uses gravizappa or not
like the thought that's behind this. vectoring rocket engines on the back i'd imagine. thoughtful detailing! i imagine this as something coming out of a secret Russian air force program. very well done.