"Fastest Gun In The West”

Press, Volume CVI, Issue 31139, 16 August 1966, Page 11

"Fastest Gun In The West”

)) Scientists at the Ames Research Centre, Mountain ) I View, California, are now ; able to fire “bullets” at speeds ; of 20.000 miles an hour, or six , miles a second. This is twice as fast as any previous speed of a projectile in a laboratory i and by firing into a 10,000 . mile an hour air-stream head- ) on, a relative speed of 30,000 ( miles an hour is obtainable. . The centre has three huge , gas guns which fire into I special wind-tunnels driven by . gas guns firing in the opposite ) direction. Each pair of , opposed gas guns is 460 feet ■ long including the length of the wind tunnel in the middle. The “bullets” are one-inch diameter scale models of 1 spacecraft and the 30,000 mile ■ an hour combined speed of ' model and airstream matches ; the conditions that will be met ; by spacecraft returning to the 1 earth’s atmosphere after I missions to other planets. The new gas guns use ordinary gun-powder which drives a plastic piston down a long tube. The piston com- | presses a charge of hydrogen gas so quickly that its temperature rises to 8000 degrees Fahrenheit at a pressure of I 100 tons a square inch. The | hot hydrogen pushes the model down the tube and

accelerates it to the required velocity. Hydrogen is used because it is the lightest gas and needs only a small portion of its energy to accelerate itself, leaving ample energy for pushing the model to superhigh speeds. After passing through a blast chamber the model enters the wind tunnel and flies into a jet of gas produced in a similar manner. In the test section of the wind tunnel the model is photographed many times with exposures measured in millionths of a second. Shadowgraph techniques reveal the pattern of the air-flow and shock waves around the model as it decelerates during its artificial “re-entry.”