High-Speed Investigations

High-speed studies of dynamic stability were very active at Wallops. The scope and contributions of the Wallops rocket-boosted model research programs for aircraft configurations, missiles, and airframe components covered an astounding number of technical areas, including aerodynamic performance, flutter, stability and control, heat transfer, automatic controls, boundary-layer control, inlet performance, ramjets, and separation behav­ior of aircraft components and stores. As an example of test productivity, in just 3 years beginning in 1947, over 386 models were launched at Wallops to evaluate a single topic: roll control effectiveness at transonic conditions. These tests included generic configurations and models with wings repre­sentative of the historic Douglas D-558-2 Skyrocket, Douglas X-3 Stiletto, and Bell X-2 research aircraft.[471] Fundamental studies of dynamic stability and control were also conducted with generic research models to study basic phenomena such as longitudinal trim changes, dynamic longitudi­nal stability, control-hinge moments, and aerodynamic damping in roll.[472] Studies with models of the D-558-2 also detected unexpected coupling of longitudinal and lateral oscillations, a problem that would subsequently prove to be common for configurations with long fuselages and relatively small wings.[473] Similar coupled motions caused great concern in the X-3 and F-100 aircraft development programs and spurred on numerous stud­ies of the phenomenon known as inertial coupling.

More than 20 specific aircraft configurations were evaluated during the Wallops studies, including early models of such well-known aircraft as the Douglas F4D Skyray, the McDonnell F3H Demon, the Convair B-58 Hustler, the North American F-100 Super Sabre, the Chance Vought F8U Crusader, the Convair F-102 Delta Dagger, the Grumman F11F Tiger, and the McDonnell F-4 Phantom II.

High-speed dynamic stability testing techniques at the Ames SFFT included studies of the static and dynamic stability of blunt-nose reen­try shapes, including analyses of boundary-layer separation.[474] This work included studies of the supersonic dynamic stability characteristics of the Mercury capsule. Noting the experimental observation of nonlinear varia­tions of pitching moment with angle of attack typically exhibited by blunt bodies, Ames researchers contributed a mathematical method for includ­ing such nonlinearities in theoretical analyses and predictions of capsule dynamic stability at supersonic speeds. During the X-15 program, Ames conducted free-flight testing in the SFFT to define stability, control, and flow-field characteristics of the configuration at high supersonic speeds.[475]