US to begin new phase of hypersonic flight program

The Falcon HTV-2 is an arrow-shaped aircraft that launches in a rocket, separates and then glides at hypersonic speeds of 13,000 mph through the Earth’s atmosphere. (DARPA)

The Defense Department's research arm will seek proposals next month for solutions to technology hurdles in super high-speed flight with a goal of testing a full-scale hypersonic X-plane in four years.

The Defense Advanced Research Projects Agency said Friday it will host a so-called Proposers' Day on Aug. 14 to lay out technical areas for which proposals are being sought.

DARPA has tested highly experimental versions of a rocket-launched unmanned glider designed to fly at speeds 20 times the speed of sound, or Mach 20. The goal is to give the U.S. a defense capability of reaching any spot on Earth in an hour.

But such aircraft have to endure blast-furnace heat and require extraordinary controls.

The last test launch from California ended with the glider's skin peeling away.