One could say there is nothing new in feedback control for vertical flight. It has even been coupled with GPS for precision motion and landing in rockets already many years ago by Armadillo Aerospace and others.
All this could have been done in the seventies, bar the GPS part, which would have required some more costly alternatives.
But even the V-2 had gyros on a free rotating platform that was connected to the thrust vectoring vanes that kept the rocket pointed to where the flight program required. The sensors weren't so good and you probably could not have throttled the V-2 to hover accurately, but maybe with radio guidance (that they actually used with some of the flights) it could have worked. Mechanical PID controllers date to late 1800s already (warship steering) so it was a totally straightforward thing to do, and was done by Goddard already. Nobody cared but the Germans...
All this could have been done in the seventies, bar the GPS part, which would have required some more costly alternatives.
But even the V-2 had gyros on a free rotating platform that was connected to the thrust vectoring vanes that kept the rocket pointed to where the flight program required. The sensors weren't so good and you probably could not have throttled the V-2 to hover accurately, but maybe with radio guidance (that they actually used with some of the flights) it could have worked. Mechanical PID controllers date to late 1800s already (warship steering) so it was a totally straightforward thing to do, and was done by Goddard already. Nobody cared but the Germans...