Despite never progressing to what Leland describes as a planned HTV-3X follow-on demonstrator that “never was,” called the Blackswift, the conceptual design work led to “several key accomplishments which we didn't advertise too much,” he notes. “It produced an aircraft configuration that could controllably take off, accelerate through subsonic, supersonic, transonic and hypersonic speeds. It was controllable and kept the pointy end forward,” adds Leland.
Fundamental lessons were learned, particularly about flight control systems that could maintain stability through the transonic speed regime. Lockheed Martin's work proved the configuration could “take off without departing,” Leland notes. “We were able to drive down the takeoff speed and keep it stable and controllable. We proved all that in a whole series of wind-tunnel tests.”