PAUL LEWIS / WASHINGTON DC
The US Department of Defense (DoD) has unveiled its research roadmap to increase progressively the speed of manned and unmanned vehicles to around Mach 12 over the next 10 years by cross-leveraging military and NASA hypersonic, space access and technology programmes under the National Aerospace Initiative (NAI).
The NAI technology framework identifies three critical areas to explore at speeds up to M12, encompassing high-speed expendable and reusable strike systems, reusable launch vehicles (RLV) and space launch payloads. The interconnected technology provides for a steady increase on the M3 sustained speed of the 1960s vintage jet-powered Lockheed SR-71 and North American XB-70 bomber.
"We can be on a path of a Mach number per year through to 2012," says Ronald Sega, DoD director of defence research and engineering. The programme includes a series of demonstrations such as the Defense Advanced Research Projects Agency's (DARPA) M4 turbine-powered Responsive Access Small Cargo Affordable Launch (RASCAL) system, the US Navy's ramjet-powered Hypersonics Flight effort, which was recently tested at NASA Langley up to M6.5, and M4-M7 hydrocarbon and M8-plus hydrogen scramjets.
NAI's three areas are linked by technology bridging the gap between endoatmospheric and exoatmospheric operations such as RASCAL, and which could benefit DoD and NASA. Hypersonic air breathing propulsion could be used by a long-range strike aircraft or as the first-stage of a two-stage-to-orbit space vehicle.
"You effectively cut across the chart of ongoing DARPA programmes from an aircraft-like first stage to second and third stage rockets to small spacecraft," says Sega.
He adds that the NAI roadmap is intended to provide "off ramps" to field systems along the way, rather than taking a "Mach 25 or bust" approach.
The USN is hoping the Hypersonics Flight initiative will produce a combined cycle 1,110km (600nm) range anti-ship missile designed to fit inside ship-board vertical launch systems. In the longer term, Sega sees even closer collaborative work between DoD and NASA, such as a third- generation RLV.