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China Builds World's Fastest Hypersonic Wind Tunnel To Simulate Flight At 27,000 MPH (scmp.com)
schwit1 quotes a report from South China Morning Post: China is building the world's fastest wind tunnel to simulate hypersonic flight at speeds of up to 12 kilometers per second (~27,000 miles per hour). Zhao Wei, a senior scientist working on the project, said researchers aimed to have the facility up and running by around 2020 to meet the pressing demand of China's hypersonic weapon development program. "It will boost the engineering application of hypersonic technology, mostly in military sectors, by duplicating the environment of extreme hypersonic flights, so problems can be discovered and solved on the ground," said Zhao. The world's most powerful wind tunnel at present is America's LENX-X facility in Buffalo, New York state, which operates at speeds of up to 10 kilometers per second -- 30 times the speed of sound. Hypersonic aircraft are defined as vehicles that travel at speeds of Mach 5, five times the speed of sound, or above.
In the new tunnel there will be a test chamber with room for relatively large aircraft models with a wing span of almost three meters. To generate an airflow at extremely high speeds, the researchers will detonate several tubes containing a mixture of oxygen, hydrogen and nitrogen gases to create a series of explosions that can discharge one gigawatt of power within a split second, according to Zhao. The shock waves, channelled into the test chamber through a metallic tunnel, will envelope the prototype vehicle and increase the temperature over its body to 8,000 Kelvins, or 7,727 degrees Celsius, Zhao said. The new tunnel would also be used to test the scramjet, a new type of jet engine designed specifically for hypersonic flights. Traditional jet engines are not capable of handling air flows at such speeds.
In the new tunnel there will be a test chamber with room for relatively large aircraft models with a wing span of almost three meters. To generate an airflow at extremely high speeds, the researchers will detonate several tubes containing a mixture of oxygen, hydrogen and nitrogen gases to create a series of explosions that can discharge one gigawatt of power within a split second, according to Zhao. The shock waves, channelled into the test chamber through a metallic tunnel, will envelope the prototype vehicle and increase the temperature over its body to 8,000 Kelvins, or 7,727 degrees Celsius, Zhao said. The new tunnel would also be used to test the scramjet, a new type of jet engine designed specifically for hypersonic flights. Traditional jet engines are not capable of handling air flows at such speeds.
Low Earth orbital velocity is a little under 8 km/sec, so if you're moving faster than that, you're going to be spending a lot of fuel trying to stay down, close to the Earth. In other words, much of your thrust will be needed to add extra centripetal acceleration to supplement the pull of gravity. Earth escape velocity is about 11.2 km/sec, so moving anywhere at 12 km/sec would put you at risk of never coming home again if something went wrong with your vehicle. The amount of energy required to move at these speeds is huge, and would require tremendous amounts of fuel to achieve: note the size of a rocket necessary to accelerate a satellite up to orbital velocity. This hypersonic research is weapons related. The researchers are undoubtedly interested only in small payloads going at these speeds for very brief periods of time. One application might be getting a small warhead past a warship's defenses. Another application might be ICBM reentry.