D-21s are very cool!
A couple months ago I was on a business trip to NASA Dryden. While I was there, they allowed me to poke around with one of the D-21s that was stored next to a runway (maybe the one pictured here). The D-21 is wicked cool. Too bad they're only collecting dust in the Mojave Desert. Lots of neat old hardware is doing that at NASA Dryden....
Gary