Scramspace I's primary role is to test the design and operation of the scramjet engine which operates on the principle of radical farming. In this design, hydrogen fuel is injected from holes in the inlet, rather than in the combustion chamber. Leading-edge shocks are deliberately ingested into the inlet where they interact with other shock waves and expansion fans in the constant-area combustor. The combination produces an area of localized higher pressure and temperatures where “radicals” are formed.
This process not only helps accelerate the ignition process but combustion is achieved at lower mean static temperatures and pressures than would be created in a larger combustion chamber. As radical farming injects fuel in the intake, this reduces the mixing length needed in the combustor, therefore enabling the use of a smaller chamber which also reduces skin friction drag.
Secondary experiments will include a tunable-diode laser flight instrument to measure flow, temperature and possibly angle-of-attack data, as well as the thrust nozzle. Tertiary experiments include ultra-high-temperature ceramic materials made by the Italian aerospace research agency CIRA, as well as temperature-sensitive paints from the University of New South Wales on the inside of the vehicle to provide thermal loads and distribution data post-flight.
Additional materials and propulsion-related flowpath testing continues with international partners. Other Scramspace members include the Universities of Adelaide and Southern Queensland, while government and industry members include the Australian Defense Science and Technology Organization (DSTO); BAE Systems, Aimtek and Teakle. International partners also include the Japanese Aerospace Exploration Agency (supporting optics for the laser experiment), and the University of Minnesota.
To make testing affordable, the project is “piggybacking” off the joint Australian-U.S. HIFiRE fundamental hypersonic research program (see page 42) which is around the halfway point in a multi-year effort involving nine flights between 2009 and 2014. The first opportunity for launch was originally expected to be the seventh HIFiRE experiment in May/June 2013. However, DSTO is now thought to be reviewing the possibility of launching instead on the repeat run of HIFiRE 5 around March-April 2014.
Scramspace will be launched on an S30-Improved Orion two-stage sounding rocket to around 100 km (62.5 mi.) when the deployment sequence will start with a de-spin maneuver and payload separation. The nose cone and starting door covers will then eject, and the vehicle reaction control system activated to position it for reentry and starting the scramjet as it hurtles down at Mach 8 through a test window between 32 km and 27 km altitude.
Testing and assembly is expected to be completed by March 2013, after which the vehicle qualification will take place. Pending a successful effort, the payload will be finalized by the end of May.