Aerodynamics and Stealth of the Low-observability RQ-3 DarkStar

Abstract

Marques P. (2013). Aerodynamics and stealth of the low- observability DarkStar vehicle. International Journal of Unmanned Systems Engineering. 1(S3): 1-5. The RQ-3 DarkStar high-altitude endurance UAV has an unusual shape that represents a compromise between aerodynamic efficiency and stealth constraints for low detectability in heavily guarded airspace. This technical note examines the aerodynamic and stealth characteristics of the rare RQ-3 DarkStar configuration. The distinctive flying-saucer fuselage and slightly-forward-swept rectangular wings present a challenge in aerodynamic design. The vehicle's lifting body sheds a leading edge vortex that triggers flow separation in the wing root region at high angles of attack. Also, the disk-shaped body generates upwash in the inboard wing area, increasing the angle of attack and the likelihood of flow separation. CFD played an integral role in the rapid prototyping environment in which the DarkStar was designed, built, and fight- tested. A wing root insert was devised using CFD that decreased the lift generated by the body, and attenuated the strength of the leading edge vortex and flow separation. Therefore, CFD was essential in diagnosing the complex aerodynamics and preventing the pitch up tendency of the initial DarkStar prototype. The turbo engine is mounted above the fuselage to shield the compressor and exhaust noise and heat signatures. The small size and low-profile airframe of the DarkStar is the result of shaping for radar concealment at the expense of downgraded aerodynamic performance. © Marques Aviation Ltd - Press.