Slashdot Mirror
Air Force to Test Aeroelastic Wings
firegate writes "The New Scientist is reporting that the US Air Force is planning to test a variant of the Wing Warping steering system used on the original Wright Brothers plane to steer new supersonic jets. They've invested $41 million in the project so far, and the first test flight will take place next month at NASA's Dryden research center in California."
It's extremely hard to test at supersonic speeds because supersonic wind tunnels are designed for a specific mach number. The geometry of the wind tunnel must be changed if a new supersonic mach speed is desired. Most supersonic wind tunnels have multiple test sections, each designed for a specific speed. Because of the nature of supersonic flow, the wind tunnel geometry must be "right" at each supersonic speed in order to ensure wave-free, "clean flow". Otherwise, any data collected is useless. As for testing at a sonic speed (mach = 1), that is extremely hard. The *only* place in a wind tunnel where the mach number can be one is at the throat (in a converging/diverging nozzle). Note that adding heat will always drive flow towards mach 1 (regardless of supersonic or subsonic flow). The only way to accelerate flow once it has reached mach one in a wind tunnel is a cross secional area increase. Wind tunnels are not developed so that one could place a test piece at the throat of the tunnel (I've never heard of one that is.)