I’m researching for a book – if it were possible, using the spacecraft that we have today, to fly to Mercury and orbit that planet, how long would it take to get there?
The most recent mission to Mercury took about three-and-a-half years to get there. It didn't take a direct route, for technical reasons -- if you want I can go into these in a bit more detail but, broadly speaking, it's because heading to Mercury in a straight line would mean that current spacecraft would just zoom past it at too fast a speed to get into an orbit.