Evaluation of the Low-Speed Stability and Control Characteristics of a Mach 5.5 Waverider Concept

The use of trademarks or names of manufacturers in this report is for accurate reporting and does not constitute an official endorsement, either expressed or implied, of such products or manufacturers by the National Aeronautics and Space Administration. Summary Static force and moment tests of a 0.062-scale model of a hypersonic vehicle study concept known as the LoFLYTE™ 1 configuration were conducted in the Lan-gley 12-Foot Low-Speed Tunnel. These tests looked primarily at the low-speed static stability and control characteristics of this configuration. Data were obtained over an angle-of-attack range of –5° to 22° at sideslip angles that ranged between –10° and 10°. Supporting flow visualization tests were also conducted. Two primary concerns before the test were whether the configuration had adequate pitch control and adequate directional stability for low-speed operations. The tiperons were sized to provide enough pitch control to trim the vehicle to α = 16° with no more than 10° of surface deflection; however, there still was some concern about achieving this capability. The data obtained in this test showed that 10° of tiperon deflection was nearly sufficient to trim the configuration to the desired angle of attack. Because of the pitching-moment characteristics of the LoFLYTE™ configuration, there is a reasonably high level of unpowered trimmed lift at nominal takeoff and approach to landing angles of attack that should allow for acceptable takeoff and landing speeds for this vehicle. Initial evaluation of the directional stability characteristics of this configuration showed a significant instability between α = 10° and about α = 18°. This test determined that the cause of this instability was the interaction of the wing leading-edge vortex with the vertical tails. Moving the vertical tails either inboard or outboard from the baseline location eliminated this unfavorable interaction. The inboard location, however, is more desirable because it also places the tails in a position where they do not interfere with the tiperons. This location allows for the lower portion of the rudder to be extended (the baseline rudders have a cutout to allow a full 30° of tiperon deflection) and for the vertical tails to be moved farther aft, thus resulting in an additional increase in rudder power.