1 or SAOehGHnGEBB:I8WSPOEE
speeds, greater than Mach 5. or five times the speed of sound. ③⑤ Propelled by _a special
type of "air-breathing jet engine. a highperformance hypersonic craft might even be able
to "Hiy' into orbit 一一 a possibilityirst considered more than four decades ago. Recently。
。as the technology has maturedAN'ey人ie qemand for more efficient Earth-tororbit
ES