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Copyright © 2004 National Academy of Sciences
All right reserved.
THE BOTTOM LINE
The committee believes that the National Aerospace Initiative (NAI) is an effective instrument for assisting the Department of Defense (DoD) and the National Aeronautics and Space Administration (NASA) in their pursuit of technologies for our nation's future military systems and its future space launch needs, both crewed and uncrewed. The NAI goals directly address issues of national concern. NAI has fostered collaboration between the DoD and NASA in research and technology areas-hypersonics, access to space, and space technology-that can benefit both organizations. It has increased the visibility of the two agencies' related research and technology development efforts and has made it easier for them to work together to achieve overlapping objectives. It has increased the probability of achieving synergistic results. It offers opportunities to achieve efficiencies that would not be possible if each agency were to work in isolation. The committee recommends that DoD and NASA, through NAI, continue to advocate, communicate, and facilitate the nation's endeavors in hypersonics, access to space, and space technology.
The stated mission of NAI is to "ensure America'saerospace leadership with an integrated, capability-focused, national approach that enables high speed/hypersonics flight; affordable, responsive, safe, reliable access to and from space; and in-space operation by developing, maturing, demonstrating, and transitioning transformational aerospace technologies." For hypersonics and space access, NAI goals are stated as follows:
Hypersonics. Flight demonstrate increasing Mach number capability each year, reaching Mach 12 by 2012.
Space access. Demonstrate technologies that will dramatically increase space access and reliability while decreasing costs.
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 addition, the committee was asked to consider two Air Force budget scenarios-one assuming that no additional NAI funds are allocated and one corresponding to optimal NAI development timelines. Finally, the committee was asked to suggest initiatives to ensure a more robust aerospace science and engineering workforce.
THE NATIONAL AEROSPACE INITIATIVE
The National Aerospace Initiative is a joint technology initiative begun in 2001 by the DoD and NASA. The goals of NAI are to renew American aerospace leadership; push the space frontier with breakthrough aerospace technologies; revitalize the U.S. aerospace industry; stimulate science and engineering education; and enhance U.S. security, economy, and quality of life. The initiative focuses on science and technology advances in three areas, or "pillars"-high speed/hypersonics flight, access to space, and space technologies. The high speed/hypersonics flight goal is to demonstrate Mach 12 by 2012. The access-to-space goal is to demonstrate technologies to dramatically increase space access and reliability while decreasing costs. Leveraging the full potential of space is the goal of the space technology pillar, an area that, by agreement with the sponsor, the committee did not address.
Air-breathing hypersonic vehicles have potential application as missiles, cruise missiles, long-range strike aircraft, and/or space launchers. Technology development and demonstration are required to mature critical hypersonic technologies to the point where a decision could be made to fund any or all of these applications. The technical challenges of air-breathing hypersonics increase dramatically as the speed of the vehicle increases, through scramjet speeds that could reach Mach 4 to Mach 14. The military departments and NASA have ongoing technology development and demonstration programs in air-breathing hypersonics. The Army and Navy programs are directed toward missile applications. The Air Force is interested in nearer-term missile applications and is also working with NASA to pursue the longer-term possibilities of reusable launch vehicles for space access.
During the past 45 years, space access capability has been developed for low-launch-rate applications from low Earth orbits to beyond the solar system. Rocket-based vehicles have operated as missiles, long-range strike missiles, or space launchers for 50 years. The Air Force and NASA are both investing in technology for rocket-based, reusable launch vehicles. While their final systems may be very different, they share many common technologies, for which NAI is facilitating related collaboration. The Air Force has credible emerging needs for a rapid rate, operationally responsive spacelift capability that might utilize a reusable rocket-powered vehicle. NASA needs a replacement for its Space Transportation System (the space shuttles) that might be implemented in the next decade using reusable, rocket-based propulsion. Both DoD and NASA are planning new rocket-based systems for the near term but are at the same time working on capabilities in air-breathing hypersonics for possible application to launch vehicles in about two decades.
Advances in space technology are desired to provide national security decision makers with the most current and complete information made available through on-demand intelligence, surveillance, and reconnaissance. In addition, space technology advances are desired to benefit other warfighter mission areas such as navigation, weather, communications, missile warning, space control, and force application. Satellite systems using advanced space technologies are seen by NAI participants as a vital element of space, air, and ground systems that are so well networked and integrated that they provide revolutionary capabilities. The nonmilitary benefits of advanced space technology include the scientific study of Earth, leading to improved capabilities for predicting climate, weather, and natural hazards.
During 2002, workshops and meetings were held to further develop NAI definitions, goals, and plans. Planning teams were formed around the three NAI pillars. They included participants from the three military departments, NASA, and staff of the Director of Defense Research and Engineering (DDR&E). The teams used a structured process to go from the high-level NAI goal statements to project-level technology roadmaps. The process combined layered analysis (goals were analyzed to determine objectives, which were analyzed to determine technical challenges, and so on) and planning (projects were identified and roadmaps developed to address the challenges). By the time of this study, NAI participants had undergone the first iteration of this process and had developed initial roadmaps that included project-level details. The initial roadmaps included many DoD and NASA NAI-related projects that had already been under way or planned when NAI was established.
The NAI executive office, staffed by DoD and NASA personnel, acts as an advocate and facilitates collaboration in the development of goals, plans, and roadmaps for the three pillars.
Late in the budget cycle, DDR&E succeeded in having new NAI funding (in addition to that for existing or planned projects) included in the President's budget request (PBR) for fiscal year (FY) 2004. No new NAI funding was included in the PBR for FY 2005 and beyond; however, DDR&E expected the FY 2005 PBR to add new out-year funding.
THE NAI ROADMAPPING PROCESS
The committee believes that DoD and NASA have made a positive start; however, it also noted some weaknesses in what has been done so far. It was not clear to the committee that the process used to develop the NAI roadmaps was effective in defining a comprehensive and compelling technology development program that would mature all of the critical enabling technologies in time to meet the various NAI schedule goals, one of them being a milestone decision in 2018 on hypersonic access to space. For example, NAI brought together essentially all existing U.S. programs and attempted to use them to lay out a high speed/hypersonics technology roadmap. However, this roadmap is more a collection of existing programs than a logical and complete plan to achieve military strike, global reach, and space access objectives. Each of the collected programs has elements that address some portion of the critical technologies, and each program, owing to its very existence, has a funding line. The collective funds, if properly applied, perhaps are 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 hypersonic technologies. The low level of basic and applied research in the NAI plan is also conspicuous.
The committee recommends that, starting with a defined and articulated vision, DoD and NASA use a top-down process based on sound system engineering principles to determine the objectives, technical challenges, and enabling technologies and to plan the fundamental research, technology development, ground testing, and flight demonstrations required to mature the enabling technologies to levels sufficient for application. The result should be a comprehensive, integrated roadmap that ensures all technologies are sufficiently matured to support the multitude of decision milestones scheduled during the NAI time frame of interest. This roadmap may include preexisting projects; however, the roadmapping process should closely examine how each project contributes to achieving NAI goals and assess the trade-offs with other needed technology efforts. The roadmap should include detailed plans for fundamental research and clearly defined exit criteria for each of the critical technologies. The committee recommends that DoD and NASA clearly communicate the plan, once it is complete, to decision makers and stakeholders, including the public.
The committee recommends that DoD and NASA complete an end-to-end cost estimate for the top-down program through the period of interest and then work to secure funding commitments consistent with this cost. This plan and its funding estimates should then be exposed to competition from other DoD and NASA requirements to see if they are realistic. For example, if the national plan to complete and begin initial operational capability of a multibillion-dollar new and revolutionary two-stage-to-orbit, reusable launch vehicle is achieved in 2015-2018, how likely is it that at the same time Congress and the nation will be willing to approve an even more expensive follow-on air-breathing hypersonic launcher?
To help assess the realism of the resulting roadmaps, the committee recommends that DoD and NASA set up their planned NAI advisory panels, steering groups, and revolutionary concepts panels to review the NAI program on a continuing basis. The committee believes that the progress NAI has made in facilitating coordination of activities among participants would benefit from periodic oversight by independent groups of experts.
The committee identified four critical enabling technologies for air-breathing hypersonic flight that must be matured: air-breathing propulsion and flight test; materials, thermal protection systems, and structures; integrated vehicle design and multidisciplinary optimization; and integrated ground test and numerical simulation and analysis.
Propulsion is foremost among the critical technologies that will enable air-breathing hypersonic flight, both for the dual-mode ramjet/scramjet engines that will achieve hypersonic speeds and for the lower speed engines that will accelerate the ramjet/scramjet to takeover speeds (typically Mach 3-4). Several challenges exist for scramjet engines, among them performance and operability across a broad range of operating speeds, especially above Mach 8; management of the extreme thermal environment encountered by such engines; and durability of engine structures and systems for long life and low maintenance. Challenges for low-speed engines include thrust-to-weight ratio (i.e., high thrust at low weight while maintaining high efficiency), thermal management, and integration with both the airframe and the high-speed propulsion system.
Excerpted from EVALUATION OF THE NATIONAL AEROSPACE INITIATIVE Copyright © 2004 by National Academy of Sciences. Excerpted by permission.
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|1||The National Aerospace Initiative||9|
|3||Access to space||53|
|4||Enabling a more robust aerospace workforce||87|
|App. A||Biographical sketches of committee members||99|
|App. B||Guest speaker presentations to the committee||104|
|App. C||National Aerospace Initiative hypersonics programs and technologies||109|
|App. D||National Aerospace Initiative access-to-space programs||116|
|App. E||Fuels research||122|