The path toward a hypersonic space plane has been a slow one, filled with twists and turns one would expect given the technological leap involved. Speeds of Mach 8+ place tremendous heat and resistance stresses on a craft. Building a vehicle that is both light enough to achieve the speeds desired at reasonable cost, and robust enough to survive those speeds, is no easy task.
Despite the considerable engineering challenges ahead, the potential of a truly hypersonic aircraft for reconnaissance, global strike/ transport, and low-cost access to near-space and space is a compelling goal on both engineering and military grounds. The question, as always, will be balancing the need for funding to prove out new designs and concepts, with risk management that ensures limited exposure if it becomes clear that the challenge is still too great. In October 2008, the US Congress decided that FALCON/Blackswift had reached those limits. That decision led to the program’s cancellation, though some activities will continue.