Hey, nice thread for a first post, eh? I've been making solar-powered ion shuttles for several months now and in order to land an asteroid... it would be nearly impossible. It's not the thrust of the engine or amount needed that's the obstacle, it's the electric charge needed that is. To make a plane that can take off and achieve very high altitude Kerbin flight, I've had to plaster the entire wing span with solar panels for the 9 thrusters installed in order to keep them at maximum thrust. For my orbital craft and Mun missions, I've used 6 retractable Gigantor arrays. If that isn't problem enough, anytime you enter a shadow, you lose power. You need batteries... lost and lots of batteries to maintain thrust while the engines/panels are in shade. In addition to all of that, you need xenon gas containers. It might burn more efficiently than liquid fuel but you still need a whole lot of it. In a Mun-and-Back mission, I've burned through about 10,000 units of it. Most of the craft would just end up being a mash-up of gas containers, solar panels and batteries. Anything left would be engines. And the more mass you take up with utilities, the more engines you need; the more engines you need, the more utilities you need.