On question B, the answer is yes, such a craft can definitely be built and attached to either ISS or the Hubble. It's basically a propulsion module, and those things have been built for years. Although it'll need to be designed and built and paid for, the technology is basically there.<br /><br />The problem is the propellant. You'll need to feed this propulsion module, and ISS is very big, which means it takes a lot of prop to move it. That's the part that ultimately makes this impractical, at least with the thrust levels and specific impulse currently available. (Ion drives are currently too small to really be useful for this; they haven't got the thrust.)<br /><br />The most practical idea I've seen for this came from Martin Lo. I started a thread about it with "Lagrange" in the title. It's one of those schemes where "it's so crazy, it just might work," except that he's got the mathematical genius to prove it. (Plus, the basic concept was proven by Genesis, believe it or not.) It only works for very specific locations, however. You can exploit Lagrange (or libration) points to move even very massive objects around, as long as you're really patient.<br /><br />It's not really useful in low Earth orbit, however. Lo's scheme (called the Interplanetary Highway) really only works if you're near a Lagrange point, like Earth-Moon L1, which is much closer to the Moon than it is to Earth. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em> -- The Tenth Doctor, "Blink"</font></p> </div>