Hypersonic proponents worldwide will eagerly watch two long-awaited technology demonstrations starting with the imminent first flight attempt for the X-51 Waverider, to be followed within a month by the first flight of the Falcon HTV-2 hypersonic test vehicle.

Successful flights for both are seen as critical to proving the practicality of hypersonic technology for high-speed weapon, reconnaissance and space-access applications. The X-51 is a Mach 6+vehicle powered by a hydrocarbon fuel-cooled scramjet, and could perform the longest duration air-breathing hypersonic flight in history. The HTV-2 is an unpowered hypersonic glider aimed at gathering rare performance data.

Researchers say success in at least one of the four planned X-51 flights, the first of which could come as soon as Mar. 18, will reinforce the case for follow-on development. The HTV-2 will be boosted on a Minotaur IV Lite from Vandenberg AFB, Calif., to an impact near the Reagan Test Site at Kwajalein Atoll in the Marshall Islands. A launch is planned within an 8-day window—Apr. 20-27.

Preparations for the first flight of the X-51, a joint effort involving the Air Force, Pratt & Whitney Rocketdyne and Boeing, are now complete, says Boeing X-51 program manager Joe Vogel. “The vehicle is ready to go and we’re ready to make it happen.” Originally expected to fly in late October 2009, the test has slipped mainly because of availability of the B-52H carrier aircraft that will launch the X-51 over the Pacific.

Two captive-carry tests were flown in December and January, the second of which “threaded the eye of the storm” through successive weather fronts to fly out over the Point Mugu, Calif.-controlled test range, from which the X-51 will be launched at 50,000 ft. “We can’t fly on a rainy day,” adds Vogel. That is not because of weather; it is done to control test parameters.