Fastest Air-Breathing Rocket Tested

Australia’s Defense Science and Technology Organization (DSTO) recently announced the successful testing of an experimental scramjet based craft which was rocketed to an altitude of 530 km and reached a speed of Mach 10 during re-entry. This test launch is part of an ongoing effort, which began several years ago, in collaboration with the U.S. Defense Advanced Research Projects Agency (DARPA). These experiments could someday lead the way to a functioning hypersonic space plane, long range ultra-fast cruise missiles and even low-cost satellite launching technology.

The historical flight of the HyCAUSE (Hypersonic Collaborative Australia/United States Experiment) Australian scramjet-engined rocket took place at the Woomera Test Facility in South Australia under the HyCAUSE project. The vehicle reached speeds of Mach 10 or ten times the speed of sound – the fastest speed a craft of this sort has ever reached.

The supersonic combustion ramjet (or scramjet) is a variant of the ramjet engine. Despite the extensive research conducted in this area in the last several decades, it has not yet reached operational stage. All ramjet engines are supersonic, but scramjet operates at hypersonic speeds, from approximately Mach 5 up to Mach 10-12 (NASA’S X-30 National Aerospace Plane, or NASP, was designed to reach speeds of up to Mach 25 in order to reach orbit, but the program was terminated in 1993 and the concept was never tested). Previously, the fastest scramjet ever tested was NASA’s X-43A, which reached Mach 9.6 in a test flight on November 16th, 2004.

A scramjet generally operates in a very similar way to a conventional ramjet, with the exception that the flow of air in the combustion of the fuel-air mixture through the engine happens at supersonic speeds, allowing the scramjet to achieve ultra-high speeds. A scramjet engine – just like a ramjet – cannot start operating until it attains a sufficiently high initial speed and so the Australian test included a conventional rocket engine booster for attaining the necessary height before the scramjet engine could kick in. 

In 2006 TFOT covered the test launch of another experimental air-breathing platform called Ramtech, which was built and tested by students from the Technion in Haifa, Israel. The Ramtech used two stage rocket-ramjet technology developed by the students and reached a speed of Mach 2 and an altitude of 30,000 feet before plummeting to the Mediterranean Sea.  

More on ramjet/scramjet history and technology can be found in our Ramtech article. More information on the recent Australian scramjet experiment can be found here.

Image:  TALOS rocket carrying the HyCAUSE scramjet experimental payload lifts off the launch pad at Woomera (Credit: Australias Defence Science and Technology Organisation).

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