S
StewartB
Check this out. 7000 mph, mach 9.6, and they think they can squeeze mach 15 out of it. That's some serious giddy-up. This isn't a rocket, it's a jet.
http://www.nasa.gov/missions/research/x43-main.html
SB
http://www.nasa.gov/missions/research/x43-main.html
SB