The study committee was asked to answer three general questions—Is NAI technically feasible in the time frame laid out? Is it financially feasible in the same time frame? Is it operationally relevant? The committee’s answers are presented in the paragraphs that follow.
Concerning the technical feasibility of hypersonics, the NAI roadmap for integrated high speed/hypersonics and space access ground and flight demonstration outlines a series of development and demonstration programs resulting in a Mach 12 air-breathing capability in the 2014 time frame. While the committee believes that Mach 12 air-breathing vehicles may be technically feasible in that time frame, it recommends a more comprehensive approach addressing all requisite activities, from fundamental research to critical technology development to flight demonstration.
The NAI phased approach to space access with rocket propulsion envisions that technology investments will result in increasingly ambitious potential system payoffs by 2008 and 2015. The quantified payoffs include short turnaround time; high sortie numbers for airframe, propulsion, and systems; low marginal sortie cost; high reliability; and improved payload performance. The committee believes strongly in the general goal of demonstrating technologies to dramatically increase space access and reliability while decreasing cost but does not believe that all the payoffs will be available in the time frames suggested by the NAI.
Concerning financial feasibility, the committee believes that both pillars are underfunded in relation to current NAI planning. It believes that near-term NAI funding for the air-breathing hypersonics pillar might suffice for a significant critical technologies program that could support near-term warfighting applications such as missiles. However, sharply higher budgets will be required to achieve the currently stated, long-term NAI objective of air-breathing hypersonic access to space. The access-to-space pillar faces a similar funding issue. The NAI envisions a multiphase demonstration program with increasingly capable reusable rockets available in 2008 and 2015. The development of these vehicles is not supported by current budgets. Clearly, neither the goals of NAI nor the needs of the military services can be met without significant additional funding.
Finally, the committee found that NAI is operationally relevant. All the DoD operational commands contacted by the committee believe that NAI technologies and capabilities, if realized, could support, to a degree, their stated capability goals and missions, such as Prompt Global Strike, Global Missile Defense, and Operationally Responsive Spacelift. However, non-NAI approaches can also support these missions, and the operational commands recognize that many NAI technologies have yet to be developed and proven.
The committee strongly agrees with the operational commands, which, while they support the capabilities offered by NAI, believe that NAI must be balanced with other research and technology development efforts, priorities, and investments to ensure proper trades between current, near-term, and future combat capability.
As described in the preface, this study was undertaken in response to a request by the U.S. Air Force that the National Research Council (NRC) of the National Academies provide an independent evaluation of the feasibility of achieving the science and technical goals outlined by the NAI. To conduct the study, the NRC appointed the Committee on the National Aerospace Initiative under the auspices of the Air Force Science and Technology Board.
To answer the three general questions the study committee was asked—Is NAI technically feasible in the time frame laid out? Is it financially feasible in the same time frame? Is it operationally relevant?—the committee was asked to perform several tasks, including evaluating NAI in terms of warfighter capabilities and baselining the readiness of NAI technologies. The committee was also asked to recommend technologies that should be emphasized over the next 5 to 7 years as well as specific efforts to advance hypersonics and access to space over the next 20 years. In