US scramjet hits Mach 5

Jet fuel-powered test flight

US defence contractor Alliant Techsystems has successfully tested a rocket-launched scramjet at Mach 5.5. The project, in association with the Defense Advanced Research Projects Agency (DARPA) and Office of Naval Research (ONR) - and which forms part of the Freeflight Atmospheric Scramjet Test Technique (FASTT) programme - did not reach the heady Mach 10 achieved by the hydrogen-fuelled X-43A back in November 2004, but it is the first "freeflight of a scramjet-powered vehicle using conventional liquid hydrocarbon jet fuel".

The FASTT vehicle was launched from the Wallops Flight Facility, Wallops Island, Virginia, on Saturday 10 December. The 106-inch, 11-inch diameter vehicle was blasted to 60,000 feet by its booster rocket, at which point it separated from the booster and "the Scramjet engine ignited and propelled the vehicle at approximately 5,300 feet per second - or Mach 5.5". After around 15 seconds of propelled flight during which "critical engineering data was captured via on-board sensors and tracking radars", the FASTT descended for an Atlantic splash-down.

According to Alliant Techsystems: "The ground-launched flight test demonstrated a viable and cost-effective flight-test method for future hypersonic Scramjet initiatives."

The X-43A is also rocket-boosted before the scramjet kicks in, but is launched from beneath a B52 at around 40,000ft. Some scientists have high hope for the technology, given that its use of atmospheric oxgen to mix with the fuel represents a considerable weight saving. Furthermore, it has relatively few moving parts compared with a traditional jet turbine.

However, and as we previously noted, a scaled-up X-43C programme - part of the HyperX project to develop alternative space launch technologies - was canned back in January 2004 when the US "committed to conventional rocket-powered space vehicles currently being planned as part of NASA's Constellation project". ®