The University of Queensland has launched a new plan to use scramjets as satellite launch vehicles.
Scramjets – aka supersonic combusting ramjets – require air to pass through an engine at supersonic speeds. Fuel is added to that supersonic air, then ignited, with the result being a supersonic plume of hot gas capable of propelling an aircraft to speeds of between Mach 12 and Mach 24.
Scramjets are still experimental, and temperamental; in 2013, the University of Queensland's Centre for Hypersonics tested a Mach 8 craft but the engine didn't fire as required. US efforts to fly a scramjet have seen three crashes before a modest Mach 5 success.
Those setbacks haven't stopped the Centre for Hypersonics stepping up with a new plan, namely “a three-stage transformational space project called SPARTAN, designed to deliver satellites weighing up to 500kgs into orbit and allowing them to be monitored nationally or internationally.”
The idea is to launch satellites atop a vehicle dubbed the Austral Launch Vehicle (ALV) that takes off like a plane but then stows its wings and engages a rocket engine. Once the ALV hits Mach 5, it returns to Earth like a conventional plane and hands over to the SPARTAN scramjet. That craft will accelerate to Mach 10 and hoist the satellite to a height from which a third vehicle can finish the job of leaving the atmosphere. Both the ALV and scramjet are re-usable, which should make for cheaper launches.
There's a long way to go before this idea becomes reality: the Centre for Hypersonics says a “subscale demonstrator [of the ALV] with a three-metre wingspan will be flown by the end of 2015.” Large-scale test craft await funding to enable their development. As do scramjets of sufficient reliability to fly regularly, never mind be entrusted with delicate payloads. ®