My mistake ! I should have taken a look at Richard Garwin’s briefing and also at the 2010 MDA doc before putting in my two cents about that…

The FY10 MDA document draws a distinction between the two phases, and indicates interest in new ideas that would apply to the post-boost “ascent phase.”

I think Allen is right to be skeptical about this. If the boost window is small, the “ascent” window — post-boost, pre-deployment of midcourse countermeasures — is liable to be much smaller. Garwin recently touched on this, and I suspect we’ll hear more about it in the years to come.

The whole point in developing boost-phase MDs is that the intercept would occur while the propellant is burning, and so while its infrared signature is extremely visible, much more than during mid-course. The other reason would be to destroy a large, single target instead of having to cope with countermeasures.

So of course, the whole job would be extremely difficult and time-sensitive (the window of opportunity may be as small as 4 or 5 minutes) but I don’t think “traditional” countermeasures would be a problem here. At least, it doesn’t seem to be the biggest one.

Ascent phase strikes me as iffy, since countermeasures or bomblets would probably be deployed immediately after booster burn-out, like within a minute or so.