I was thinking it as a reaction drive with independent thrust and ISP throttling - it goes low-isp, consuming about 60% of fuel for the first and last 10 Km's to minimize the damage, and blasting on full power once up safe.
Hmmm... this might actually work out for the ground.
As for the whole implications, i'd suggest that you make your genius member of a third or at best second world country. Someone from the african continent, maybe, or from an undeveloped asian nation, or somewhere in south america. They have lots of empty plains where he could build the thing unnoticed and where noone would get disturbed too much at launch. Legal procedures aren't that tough either.
If he is American, stuff gets way too complicated. Of course you'd have to make sure that he can somehow get his hands on the needed parts in an underdeveloped nation, but it might actually be easier than in a first world nation, where gouvernement will immediately notice and get veeery suspicious when someone buys large amounts of alloys, electronics and chemicals to build a spaceship.
As for how the whole story would play, I think a lot of attention has to be given to radar officers. First confusion, then alarm, since the rocket is launched with rather "normal" energy output it might get mistaken for an ICBM. Gouvernemant panic, defcon X, wild accusing and arguing on international lines, then suddenly the call "the thing is accelerating at impossible rates!" everyone halts, wild speculation, general confusion in politics as well as the public (when the ship lights up its engines at full power, most people living on the hemisphere should be able to see it, if it's dark even exceptionally well). Talk about extraterrestrials having infiltrated the earth and now making off with their data, E.T. going home, etc.
Now would be a good time for people to start radioing. I'd guess the first one to make contact in such a case would be amateurs, bacause they'll probably have gotten on their radios first second they heard about something unidentified launching.
Then comes the excited "the object has reached orbital velocity and stopped accelerating. I repeat, object has entered stable orbit!"
Some sort of radio contact will now certainly be established, the nature of the object is clear, and most Gov-leaders from around the world will want to talk to the pilot. That's when the whole negotiating would start on where the thing is going to land. Gouvernements will outdo themselfes with offers for the technology, some might even threaten to shoot it down if it doesn't land in their country, or if it lands in a country they consider specifically hostile (imagine for example the U.S. if the guy says he's going to land in Iran...).
From there on, I guess it would get more and more complex. Depending on the character of your genious, he might decide to land in a neutral nation which he believes would make the technology public, or he might land in the country of the highest bidder, or he might land somewhere where he deemes his chance of not getting locked away for live as a "valuable asset" highest.
Or, he pulls it Perry Rhodan style lands somewhere in the desert, errects his Deflector SHield which he also happened to construct to keep the artileries of the nations at bay, found a new nation and start his quest for unification of the earth... :lol:
