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.

Comments

Re:Strike

[ClickOnThis]

Low earth-orbit velocity is about 17,500 mi/hr. Escape velocity is about 25,000 mi/hr. They're testing at speeds above the earth's escape velocity.

Yes, anywhere in the world in under 30 min, but you'd need to burn lots of fuel not just to fly that fast, but also to keep yourself following the curvature of the earth, so you don't fly out into space and never come back..

Not very realistic for transportation

[dlleigh]

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.

Re:Not very realistic for transportation

[Strider-]

Well, the other bit to consider is that when you're testing scale models in a wind tunnel, depending on what you're testing you also need to scale the wind/air conditions to achieve accurate results. Often this means scaling up the airspeed and/or air pressure as you scale down the object being tested.

Let's say I'm testing out a new design for an airliner wing. At full scale, the air flowing over it will exert a certain amount of force per area (PSI or Newtons/m^2, take your pick). Now, since it's not practical to put a full sized airliner wing into a wind tunnel, I build a 1/4 scale model, and put that in the wind tunnel. Here's the rub: if I ran the air over my 1/4 scale model at the same conditions as I were to test the full sized wing, I would be applying 1/16th the scale force. To make up for the difference, I need to either scale up the airspeed, the air pressure, or both. There are also a whole host of other weird effects that need to be taken into account.

Anyhow, it's not just that this thing is designed to test a vehicle/weapon capable of operating at 27,000mph, but rather that it can provide realistic conditions to a scale model of the craft under test.

Re:First?

[Strider-]

Supersonic/Hypersonic wind tunnels are tremendously expensive and power hungry. There's pretty much no way to hide them. Yeah, there might be small scale versions out there (say the hypersonic helium gas guns etc...) but we're talking really small scale. This kind of testing is why NASA was given/assigned an SR-71; they could use the drone attachment points to carry tests and essentially use the atmosphere as a high super-sonic wind tunnel. Look at the pictures of the NASA SR-71 carrying the linear aerospike engine during testing.