Eventually we'll have to use some combination of extreme ship armor (meter-thick plating of expired uranium?) and lasers that detect and zap all particles (that aren't human shaped) within 1 km of the spacecraft.
Boosting the kind of armor into orbit that would be necessary to deal with at least the worse scenarios is unfeasible. If you think that cost-to-orbit is high now...
True, and probably we'd have to either mine/manufacture the armor in space, or else develop some less expensive heavy lifting technologies (which is pretty much necessary anyway, if we're going to put up more manned space stations and interplanetary craft).
