Base Impellers for Roll Control of Reentry Vehicles

摘要

A roll-control concept is considered for ballistic reentry vehicles that have small, but not negligible, configurational asymmetries. The control system consists of a number of blades or fins attached to the base of the vehicle in a manner to form an impeller that is integral with the body. The fins are located within the recirculation zone, and so oriented that their reaction the radial component of flow produces a rolling moment. Three impeller configurations were evaluated aerodynamically on a conical body in exploratory wind-tunnel tests at hypersonic speed, and the results are correlated with a generalized fin parameter. A simple criterion is derived for the magnitude of the control moment required to prevent steady roll resonance at small angles of attack. Finally, it is shown that the maximum rolling moment produced by these first impeller designs is sufficiently large to prevent resonance on, for example, a 1-foot-radius conical RV with an 0.1-degree aerodynamic trim angle acting in combination with an 0.048-inch out-of-plane displacement of the center of mass. Vehicles with larger configurational asymmetries, and vehicles which are smaller in size, require proportionally larger control moments. (Author)