This article on testing satellite shielding against space debris is a good reminder that even if NASA solves the foam problem, or someone comes up with a new reusable vehicle concept that isn't subject to debris during ascent, that space vehicles will always be vulnerable to orbital debris:

An object less than 0.05 inch across blew a hole through a section near the payload door of the shuttle Atlantis during its mission last September, according to the July edition of NASA's Orbital Debris Quarterly News journal.

The damaged section was replaced.

Had the object, which investigators think was a piece of a circuit board, hit the thinnest part of the wing edge, "There is a question whether the vehicle would have survived re-entry," said Eric Christiansen, a NASA engineer specializing in debris shielding.

A spacefaring nation will have the capability to do repairs on orbit to mitigate the hazard of such events, but to do that requires the development of a orbital infrastructure, something that NASA's current plans strenuously avoid.

I agree wholeheartedly. Any if anyone thinks the hazard is unlikely, Endeavour suffered an even larger hit during it's mission last month. Here's the details:

http://www.nasaspaceflight.com/content/?cid=5214

Keeping a launcher in orbit for very long may be a bad idea. I also wonder if damage-resistant TPS may be a good idea (tranpiration cooled systems that can route more coolant to compromised areas, say).

Keeping a launcher in orbit for very long may be a bad idea.

Or an entry vehicle. Orion isn't a launcher...

In fact, you wouldn't want to keep a reusable launcher in orbit very long--that's not very good utilization of it (yet another one of the mistakes of the Shuttle program).

Or an entry vehicle. Orion isn't a launcher...

That would be more justifiable, for an escape system if nothing else. A entry vehicle may be easier to protect (say, in a protective enclosure) than a full-up launcher, partoularly if the latter has a larger integrated set of propellant tanks.