Tom Merkle wrote:

[snip]
I think it's a great idea, although I have some serious doubts about
any NASA-led selection process for 'finalists.'

I think there should be no selection process except the drop tests. If you
have a selection process that is not based on actual flights, it is not a
good prize.

So if you have too many competitors, just repeat the drop tests until some
competitors fail. Or put them on a vibration table for launch simulation or
in a vacuum chamber for space simulation.

But I don't think that this will be a problem. For the X-Prize there are
only a few (definitely less than 10) participants that have a decent chance
of winning. And with the DARPA grand challenge, most participants failed
within the first mile.

I would expect maybe 20 or 30 teams to show up for the airplane drop tests.
Since they will probably have done some airplane drop tests on their own,
most reentry vehicles will survive this. But the high altitude drop tests
where the vehicles will reach supersonic speed will result in many craters
in the ground and only a few remaining teams.