SR-72?

SR-72?  Aviation Week is reporting that a successor to the SR-71 “Blackbird” reconnaissance aircraft is under development.  While retaining the ability to take off and land from airports, the SR-72 would have twice the SR-71's speed, and apparently would be unmanned.  Also different than the SR-71 (which so far as I know was strictly reconnaissance): the SR-72 would have strike capability.

The key to the speed of this beast is a hybrid turbine/ramjet power plant that would have both engines running in parallel during the transition to hypersonic speed.  There's a presentation on the power plant here.  Despite having dual engines, there's only a single intake and exhaust nozzle, thanks to some clever plumbing.

Way back in the early '70s, toward the end of the Vietnam War, I spent some time on a U.S. Navy ship on the South China Sea, off the coast of Vietnam.  The ship I was on (USS Long Beach CGN-9) had PIRAZ duty, and as part of that we tracked air targets over and near Vietnam.  Several times we tracked an air target crossing North Vietnam at an impossible speed – and we were told to say nothing at all about it.  Back then, the SR-71 was still a classified program. They've long since been declassified and retired, and now can be found in quite a few aerospace museums.  That's a bit of an odd feeling for me :)