The US Air Force Research Laboratory is making final preparations for a four-flight scramjet test programme that it hopes will prove that achieving hypersonic thrust is more than "just luck".

First flight of the expendable X-51A vehicle is set for 13 December, with three subsequent 300s flights to follow at four- to six-week intervals, barring failures. The flights will examine scramjet performance in acceleration from Mach 4 to M6 after launch from the wing of a Boeing B-52H.

The $246.5 million, six-year programme is a year behind schedule, but carries high hopes for the hypersonics community. USAF X-51A programme manager Charlie Brink told the American Institute of Aeronautics and Astronautics' 45th Joint Propulsion Conference in Denver: "We want more flight success to show [achieving hypersonic thrust] isn't just luck. There is no plan for a follow-on programme [to X-51A]. It is a question of when not if, but [the hypersonics community] have to be successful."

The research laboratory and its partners, Boeing and Pratt & Whitney, are building four identical X-51As. The first should be complete by the end of this month, the second had its Inconel scramjet engine installed at the beginning of August and the fourth X-51A has been sent to a facility in Palmdale, California to have its thermal protection system added.

The fourth is the static test vehicle that recently finished testing. Captive carry flights will take place in October and mating tests with a B-52 wing pylon have already taken place.

The X-51A is one of a number of demonstrator vehicles planned. The first of the US Defense Advanced Research Projects Agency's expendable Hypersonic Technology Vehicle demonstrators will also be launched in the third quarter, while the international HiFire project will see an experiment launched in October 2010.

Source: Flight International