GRAHAM WARWICK / WASHINGTON DC
US Department of Defense looks at new ways of quickly putting spy payloads into orbit
Fighters could be converted to launch vehicles as the US Department of Defense looks for ways to send spy satellites into orbit at short notice. Six teams are studying launching payloads from high-performance aircraft under the US Defense Advanced Research Projects Agency's (DARPA) Responsive Access, Small Cargo and Affordable Launch (RASCAL) programme.
If the concept is found to be feasible when the studies are completed next January, DARPA will select two teams to continue system design, with the winner to conduct a flight demonstration in 2006. The demonstration is planned to result in a residual operational capability to launch small satellites at short notice.
The $75-90 million programme is intended to demonstrate the delivery of a 75kg (165lb) payload into a 500km (310 mile) sun-synchronous orbit with 24h notice and a cost per launch under $75,000. The RASCAL vehicle combines a reusable air-breathing first stage able to operate from normal runways with an expendable rocket-powered upper stage. Most of the teams are basing their designs on an existing military aircraft, which could be operated manned or unmanned.
The teams led by Coleman Research, Delta Velocity, Northrop Grumman, Pioneer Rocketplane, Space Access and Space Launch have received contracts worth between $1 million and $2 million for the nine-month first phase. Many participants are small companies that have been struggling to develop low-cost launchers commercially for several years.
DARPA requires the reusable launch vehicle (RLV) to use mass injected, pre-compressor cooled turbojet technology. Injecting water and oxidiser into the inlet to cool and densify the air flowing into an existing afterburning engine will increase thrust at high altitude for a short period. This will let the RLV, whether based on an existing fighter or clean-sheet design, to zoom-climb to speeds of over Mach 3 and altitudes over 100,000ft (30,500m) to release the upper stage.
Exo-atmospheric release of the expendable rocket vehicle eliminates the weight and cost of a payload fairing, but requires the upper stage to be carried internally or otherwise protected during the ascent through the atmosphere. The expendable vehicle would be handled and launched like a missile, DARPA says.
Northrop Grumman RASCAL programme manager Mark Gamache says the concept is similar to the 1980s US Air Force anti-satellite (ASAT) weapon, which was to have been launched from a Boeing F-15 in a zoom climb. "It's like ASAT, but with a bigger payload," he says.
Source: Flight International
