programs has elements that address some portion of the critical technologies, and each has a funding line. The collective funds, if properly applied, may be sufficient in the near term for a significant critical technologies program; however, as configured, it is not clear that the collected programs cover all critical hypersonics technologies. What is more, NAI has not projected funding after existing program budgets run out. The committee observes that sharply higher budgets will be required to support technology scale-up (i.e., beyond presently planned small-scale demonstrations), especially flight demonstration programs aimed at maturing air-breathing hypersonics technologies to the point where decisions can be made about the development of large-scale Global Strike/ISR aircraft and air-breathing space access vehicles. A realistic budget must be projected consistent with answering the critical technology challenges, and existing programs should be more closely aligned, taking advantage of the synergistic potential championed by NAI, so they can provide critical hypersonics technologies to the nation.

This chapter begins by presenting the committee’s findings and recommendations, with brief discussions as appropriate. Technical and financial issues associated with the technologies that are critical to hypersonic flight are then discussed, together with recommended directions for future research and development.


Finding 2-1. The U.S. Air Force, the U.S. Army, and the U.S. Navy all see the possible benefits of applying air-breathing hypersonic propulsion technology to a broad range of warfighting missions, but none has yet developed formal requirements for such technology. Similarly, NASA sees potential in applying air-breathing hypersonics propulsion technology to space launch systems. Together, the DoD services and NASA are investing in the development of near- and mid-term hypersonics technologies under the NAI and are looking to 20181 as a point at which to assess whether hypersonic propulsion has sufficient system and/or operational benefits to warrant applying the technology to space launch missions (Sega, 2003a). The DoD services see air-breathing hypersonics technology as applied to hypersonic missiles and/or aircraft as tangible products along the path to 2018 (see Chapter 1 for more discussion of warfighter requirements).

Discussion 2-1. Although they recognize the potential benefits of applying hypersonic air-breathing technology to weapon systems, the DoD services are expressing a wait-and-see attitude, keeping an eye on hypersonics technology development, and continuing to explore concept of operations (CONOPS) for hypersonics systems employing air-breathing propulsion (Morrish, 2003; Graff, 2003; Hickman et al., 2003; Walker, 2003). For example, the Air Force recognizes that its space access requirements (as well as its time-critical strike and global reach requirements) may someday be met by hypersonic air-breathing propulsion, but only after the technology has been sufficiently matured. In the meantime, the greater maturity of rocket technology allows it to develop near- and mid-term (~2010 and 2015, respectively) rocket-based solutions to satisfy Operationally Responsive Spacelift (ORS) requirements. By 2018, hypersonic air-breathing technology may be sufficiently mature and understood, under a properly developed and executed NAI plan, to make a full-scale development (FSD) decision on whether to promote air-breathing hypersonics technology to the next block or spiral of space access system development, one with an initial operational capability (IOC) no sooner than about 2025.


This date and others that appear in the report were established by NAI participants prior to the President’s announcement of a new mandate for NASA. How these dates will be affected by the new NASA mandate is not yet clear; however, some NAI schedule objectives might be significantly delayed. See “NASA’s New Space Exploration Mandate” in the preface.

The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement