How Fast Is Fast Enough?

Two thousand years before the invention of the airplane, Sun Tzu said "Rapidity is the essence of war."1 Since the Wright Brothers' first flight, air power advocates strategized and innovators enabled air and space superiority through revolutionary leaps in speed and range. Airpower leaders pushed air and space strategy, capabilities, technology, and airframes to new levels as vehicles traveled from the subsonic regime (Mach lt; 0.7) through transonic ( 0.7 lt; Mach lt; 1) and supersonic (Mach gt; 1) regimes and on into the hypersonic realm (Mach gt; 5). However, in the 1970s and 1980s, the strategic and technological focus shifted towards stealth enabling capabilities. Since the 1990s, research and development investment has tilted toward "smart" multi-role morphing aircraft, hyper-spectral sensor platforms, directed energy weapons, and uninhabited capabilities. These recent advances have inspired revolutionary changes in the thought, organization, and structure of the USAF today. But there is one unanswered question airpower visionaries have ignored for more than forty years: How fast is fast enough? This paper begins by examining the historical context of speed and demonstrates its revolutionary impact on air and space operations. It then reviews past national hypersonic projects before summarizing current hypersonic efforts. The paper subsequently analyzes hypersonic options for Global Strike concepts. Mach 5+ flight is the natural progression of modern war and hypersonic platforms and weapons systems will have a revolutionary impact on USAF mission needs, operational requirements, and concepts of operation. The implications of hypersonics for responsive space access are left for future investigation. Technological hurdles must be overcome, the requirements must be vetted, and the decision making/planning process accelerated for hypersonic systems to enable and maintain U.S. air and space supremacy.