Hypersonic Countdown

An Australian team is here at the Andøya Rocket Range near the top of Norway, north of the Arctic Circle, in the final preparation stages for launching Scramspace – one of the most novel air-breathing hypersonic free-flight experiments ever undertaken.

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Scramspace is prepared for mating with the 2-stage rocket booster (Donald Cook)

Over the next few days the University of Queensland (UQ)-led team will send the Scramjet-based Access-to-Space Systems (Scramspace) vehicle rocketing out of the atmosphere high over the Norwegian Sea. The $12.9 million ($14 million Aus) three-year research project will culminate when the scramjet-powered craft powers back down through the atmosphere at a speed close to Mach 8. Hurtling to a watery grave at around 2.4 km/second, Scramspace will pass through the experimental altitude zone between 19 and 16 miles in just over 2 seconds.

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The rocket range is nestled at the base of spectacular coastal mountains (Guy Norris)

While 2 seconds may not seem long, it is an eternity to hypersonic researchers who rarely have the opportunity for flight test.  To get some idea just how valuable 2 second can be it is interesting to note that the scientists and engineers at UQ who, along with Australia's Defence Science and Technology Organization (DSTO), have helped give the nation a pre-eminent reputation in high Mach number hypersonics, have amassed only around 30 seconds of total hypersonic run time over 23 years and 11,000 shock tunnel tests.  

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Rockets can travel significant distances downrange from Andoya, although Scramspace will fall closer to the launch site. (HobbySpace.com)

Although a number of experiments are planned, the test is focused on the performance of a free-flying axisymmetric inlet-injection scramjet.  Unlike the recent U.S. Air Force-led X-51A hypersonic tests which were powered by a scramjet burning hydrocarbon fuel injected into the combustor section of the flow-path, Scramspace will be a key flight test of a concept called ‘radical farming’.  In this process 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 flows 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.The hydrogen-fuelled vehicle will be boosted by a two-stage S30/Improved Orion sounding rocket to an apogee of 200 miles (320 km) and re-oriented exo-atmospherically by a cold gas reaction control system, before reaching a gravity-assisted Mach 8 on its descent.

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HF-3 launches from Andoya (Andoya Rocket Range)

The team, which includes consortium of partners in five countries, Australia, Germany, Italy, Japan and USA, is more confident after the success of a similarly configured  scramjet combustor on HF-3, a recent flight of the US-Australian HIFiRE program. The test, conducted  from Andoya on Sept 13, 2012, was “110%” successful says DSTO, and was the first Australian scramjet flight since the HyCause (U.S-Australian hypersonic experiment) in 2007. Although the HF-3 axisymmetric hydrogen-fueled scramjet remained attached to the booster throughout the test (and was not a free flyer like the Scramspace), it also used the ‘radical farming’ method during a ballistic Mach 8 re-entry.

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...and finally. Impressive view of the Northern lights in the night sky close to launch day (Matthew Taylor/University of Queensland)

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