ch5-14

WIND TUNNELS OF NASA

Chapter 5 - The Era of High-Speed Flight

A Small Tunnel for Fast Missiles

[67] According to the Unitary Plan, Langley's new tunnel was to be devoted to the aerodynamic development of high-speed missiles. It had to be a supersonic tunnel, of course, but it could be relatively small because the missiles to be tested traveled at such high Mach numbers that their shock waves would sweep way back. The tunnel designers, under the leadership of Herbert A. (Hack) Wilson, chose a 4 x 4-foot cross section. Two separate test sections were built; one...

[68] The Ames Unitary Plan wind tunnel actually consisted of three separate test sections fed by a centralized power source. One test section was transonic; the other two were supersonic.

A 1 /6-scale model in the Ames 1 1-foot Unitary Plan tran sonic tunnel. Note the rows of wall perforations.

...covered the range from Mach 1.5 to Mach 2.9; the other, Mach 2.3 to Mach 4.6. The valves and ducts permitted tunnel operators to select one or the other section. Each test section was equipped with the Ames-developed asymmetric nozzle with a sliding block that varied the Mach number in the test section.

The major challenge in designing and building this tunnel was the power source: the compressors. The compression ratios needed varied from 1.3 to 16. The solution involved a complex of six commercially available compressors (the largest were normally used in blast furnaces) driven by a family of electric motors totaling 100 000 horsepower. Although small, the Langley Unitary Plan supersonic tunnel was something of a plumber's nightmare, with a maze of ducting,, valves, and drive motors.

A long series of missiles passed through the 4 x 4foot tunnel, where they were tested for high- speed performance, stability and control, maneuverability, jet-exhaust effects, and other performance factors. A novel feature of missile evaluation was the need to duplicate the extreme range of orientations that missiles pass through in normal flight; that is, they perform maneuvers that manned aircraft would never attempt. Despite the original dedication of this tunnel to missile development, it had been in operation....

[69] Under the Unitary Plan, Langley built a supersonic tunnel with two test sections that spanned Mach numbers 1.5 through 4. 6. Shown here is the battery of six compressors needed to supply compression ratios between 1.3 and 16. The corresponding family of electric-drive motors was rated at 1OO 000 horsepower.

...scarcely a year before the now-famous McDonnell F-4 Phantom was being tested in model form. Later, the X-15, the F-111, and various supersonic transport configurations, as well as models of space vehicles, could be found mounted in the test section.