Summary

THE BOTTOM LINE

Additional emphasis must be placed on propulsion research or the technological lead of the United States will almost certainly cease to exist. Competing demands for national resources, coupled with reductions in industry investments in propulsion research, have created a near crisis. Compounding the situation is the change in how the Department of Defense (DoD) determines requirements. This determination is now based on capabilities rather than on perceived threats, which means that developers have to spread resources over a broader range of potential systems. As a result, new systems may not get the needed funding to reach maturity.

The Air Force annual science and technology (S&T) investment in propulsion is about $300 million. This number reflects applied research (6.2) and early advanced development (6.3) funding; basic research funding (6.1) for propulsion is accounted for separately. In its recent budget requests, the Air Force did not project its level of propulsion S&T investment to change much in future years. Air Force funding accounts for roughly two-thirds to three-fourths of the overall DoD investment in this area, which is also fairly flat at around $400 million per year. But flatness is not indicative of the true picture, particularly in 6.2 budgets, which can cover laboratory payroll and administration costs as well as additional internal taxes, items that have increased significantly and squeezed funds available for real S&T.



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A Review of United States Air Force and Department of Defense Aerospace Propulsion Needs Summary THE BOTTOM LINE Additional emphasis must be placed on propulsion research or the technological lead of the United States will almost certainly cease to exist. Competing demands for national resources, coupled with reductions in industry investments in propulsion research, have created a near crisis. Compounding the situation is the change in how the Department of Defense (DoD) determines requirements. This determination is now based on capabilities rather than on perceived threats, which means that developers have to spread resources over a broader range of potential systems. As a result, new systems may not get the needed funding to reach maturity. The Air Force annual science and technology (S&T) investment in propulsion is about $300 million. This number reflects applied research (6.2) and early advanced development (6.3) funding; basic research funding (6.1) for propulsion is accounted for separately. In its recent budget requests, the Air Force did not project its level of propulsion S&T investment to change much in future years. Air Force funding accounts for roughly two-thirds to three-fourths of the overall DoD investment in this area, which is also fairly flat at around $400 million per year. But flatness is not indicative of the true picture, particularly in 6.2 budgets, which can cover laboratory payroll and administration costs as well as additional internal taxes, items that have increased significantly and squeezed funds available for real S&T.

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A Review of United States Air Force and Department of Defense Aerospace Propulsion Needs Because projected investments are flat—they do not even cover inflation—one can expect only incremental improvements in technology. Anything revolutionary could come only at the expense of existing programs or would require funding above and beyond projections. Research funding (6.1 and 6.2) is vital to the warfighter since such research is the source of new ideas and technologies and promotes the education of new engineers and scientists in aerospace propulsion. DoD future-force planning is immature and the S&T planning process is insufficient to identify short-, medium-, and long-term propulsion requirements to provide the warfighting capabilities needed for the late 2010s. The DoD Defense Science and Technology Reliance program does not address propulsion in a coherent manner; rather, propulsion efforts are subsets of other specialty areas. Further, products of the Reliance process are only recommendations and have no binding effect on service S&T priorities and investments. The study statement of task required the committee to “identify technical gaps and suggest rough order of magnitude (ROM), specifically applied S&T investments in these areas of propulsion.” The committee based its ROM estimates on its collective judgment, which, in turn, was based on the members’ extensive experience and expertise in aerospace propulsion. By definition, these estimates are rough; however, the committee believes each is reasonably within the correct order of magnitude. In its recent budget requests, the Air Force did not project changing its investment in propulsion S&T in future years much from its current level. The committee believes this investment needs to be increased if technical gaps are to be filled. KEY RECOMMENDATIONS The committee’s key recommendations are listed below. Supporting discussion for the recommendations is provided in Chapters 2-7 of the report, and the recommendation numbers here in the Executive Summary correspond to their numbers there. Military Propulsion Recommendation 2-1. DoD should develop strategy documents containing clear guidance on future required capabilities in all system development areas and should pursue funding to achieve those capabilities.

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A Review of United States Air Force and Department of Defense Aerospace Propulsion Needs Air-Breathing Propulsion Recommendation 3-1. To accelerate the development of new engine technologies, the Air Force gas turbine S&T funding should be increased significantly, from approximately $100 million annually to a level that reflects buying power at the time when the F-15 and F-16 engines were being developed. Top priority should be given to overcoming the technology barriers that will have the largest impact on future weapons systems: Compressor discharge temperature limits, Turbine inlet temperature limits, High-temperature, high-heat-sink fuels for thermal management, Lightweight structures, and Signature control. Some of these barriers apply as well to ramjet/scramjet systems. Recommendation 3-2. The Air Force and DoD should execute a total system engineering process starting with a preliminary design to establish project feasibility when undertaking any new propulsion development program. Recommendation 3-3. DoD should restore gas turbine S&T funding under the Versatile, Affordable, Advanced Turbine Engine (VAATE) program to the original planned level. VAATE should address the primary risk areas necessary to advance jet engine technology, which include a robust engine demonstrator program and key producibility challenges. Recommendation 3-4. DoD should sustain the current funding for the Component Improvement Program to ensure solutions to operational problems and safety issues and the development of future upgrades. Recommendation 3-5. DoD should reinstate an engine model derivative program (EMDP) to speed the transitioning of technology to the legacy fleet to improve safety, reliability, and affordable readiness for DoD. An earlier EMDP demonstrated its utility and value for the current fleet of engines, most of which were developed spirally through this program or similar programs in the commercial sector.

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A Review of United States Air Force and Department of Defense Aerospace Propulsion Needs Recommendation 3-6a. The Army should consider combining its Affordable Advanced Turbine Engine (AATE) demonstration program and its unfunded Improved Turbine Engine Program, also targeted at 3,000 shaft horsepower (SHP). Recommendation 3-6b. The Army should ensure that the size of the Future Affordable Turbine Engine (FATE) program, which remains undecided, is suitable for the demonstration of a 10,000-SHP class small gas turbine. The FATE demonstration could then form the basis for a new engine for a future heavy-lift helicopter mission or the Joint Unmanned Combat Air System mission. Recommendation 3-6c. In addition to developing two new small gas turbines, DoD should carefully investigate innovative ways to integrate advanced engines and advanced vehicle propulsion systems. Examples here include novel inlets, exhausts, IR suppression systems, particle separators, integrated flight/engine controls, and systems to manage component health. Recommendation 3-7. Given the criticality of the high Mach number cruise missile, DoD should support the success of these system demonstrations by funding programs to ensure the availability of high-temperature materials. Recommendation 3-8. DoD should develop a strategy to exploit the synergies between the hypersonics programs in each of the Services for the benefit of DoD, in the form of a common technology and cost savings. There are alternative solutions for both time-critical, hardened targets and flexible space warfare, and these should also be studied and compared with the scramjet solution. Recommendation 3-9. DoD should invest in several critical technologies that will impact all types and classes of propulsion systems: high-temperature materials, including high-temperature blade/vane materials and coatings; high-temperature and high-heat-sink fuels; lightweight structures; and accurate analytical modeling. Recommendation 3-10. DoD should continue to invest enough in emerging propulsion technologies to preclude technological surprise. These

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A Review of United States Air Force and Department of Defense Aerospace Propulsion Needs technologies have the potential to provide niche propulsion capabilities (e.g., for unmanned aircraft systems), future revolutionary alternatives, and improvements to gas turbine engines and conventional rockets. Current DoD funding levels for emerging propulsion technologies should be maintained or increased, and a high-level advisory body should periodically review the effort to ensure quality. Rocket Propulsion for Access to Space Recommendation 4-1. The Air Force should place a high priority on developing an integrated total system engineering process using quantitative life-cycle mission success as the selection criterion for near-term, highly leveraged engineering technology funded by the Air Force. This process is crucial to defining justifiable total system architectures, rocket propulsion systems requirements, and critical technologies for military space transportation to support the Air Force Space Command’s Strategic Master Plan FY06 and Beyond. Recommendation 4-2. DoD should begin work relatively slowly, investing about $5 million per year, in the committee’s judgment, on technology development for an advanced-cycle booster engine that could provide the basis for a new far-term access-to-space vehicle. Recommendation 4-3. DoD should place a high priority on development of a new medium-thrust (50,000-80,000 lb) upper-stage LOx/H2 engine to assure the nation’s strategic access to space. The cost of developing such an engine through its initial operational capability (IOC) is estimated by the committee at $150 million to $250 million, providing the design does not try to push new technologies to their limits. Recommendation 4-5. In September 2005, the Defense Advanced Research Projects Agency (DARPA) downselected to just one company for Phase 2B. DARPA should continue to fund and monitor this company to completion of the Force Application and Launch from the Continental United States (FALCON) program objectives. The Air Force should evaluate the propulsion technologies to be demonstrated for the air-launched FALCON vehicle and include them in total system studies of options for operationally responsive spacelift (ORS) vehicles.

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A Review of United States Air Force and Department of Defense Aerospace Propulsion Needs Recommendation 4-6. The Air Force and DoD should sponsor a detailed system engineering study to fully understand the transformational potential of cost-effective, operationally responsive launch of small, micro-, and nanosatellites (particularly for large-number satellite arrays) utilizing air-based vertical launch concepts. The propulsion technologies that are needed to take full advantage of such launch platforms should be identified and developed. Recommendation 4-8. The Air Force should develop in-house test beds for liquid, solid, and hybrid rocket motors. Because limited funding seems to be at least part of the reason this is not being done, the Air Force should seek to increase the funding for both liquid and solid rocket test beds at the Air Force Research Laboratory (AFRL). Recommendation 4-12. DoD and the Air Force should fund a program to explore various approaches to creating storable oxidizers that would significantly enhance rocket performance with different storable fuels. This program should utilize a consortium of academic, industry, and government laboratories to pursue highly innovative concepts for achieving this breakthrough. Recommendation 4-15. The Air Force and DoD should devote more of their annual S&T rocket propulsion budget resources over the next few years to rocket propulsion; to technologies that would enable the successful introduction of mission-based ORS; and to other flexible, small-satellite launch capabilities in the medium term. The committee’s estimate of the additional focused investments is $50 million to $75 million annually. Rocket Propulsion for In-Space Operations and Missiles Recommendation 5-1. DoD should support extensive basic research and technology projects for various in-space propulsion thruster concepts and for in-space electric power generation and energy storage. This fundamental long-range support need not be tied to any specific mission or platform requirement. The current range of technical opportunities is so great that progress will be directly proportional to annual resource allocations over the next 10 years. The committee estimates that at least $20 million should be considered as a yearly allocation in these areas.

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A Review of United States Air Force and Department of Defense Aerospace Propulsion Needs Recommendation 5-2. DoD should fund total architectures and operations studies for various future DoD/Air Force missions to determine the advantages of on-orbit refueling capability. Future funded technology work should complete the validation of full operational design criteria for the transfer of hydrazine. Those basic design criteria should be expected to be applicable to other storable low-vapor-pressure fuels like monomethylhydrazine (MMH). A subsequent program should be instituted to extend the technologies to storable oxidizers such as mixed oxides of nitrogen (MON) and, finally, to liquid oxygen (LOx). The committee believes a funding level of $10 million per year, in addition to that discussed in Recommendation 5-1, over the next 10 years would permit finalizing an IOC module for N2H4 and pursuing subsequent technology demonstrations with MON and LOx. Recommendation 5-3. The Air Force and DoD should establish an explicit plan with appropriate funding to develop really capable in-house test beds for developing the technology for motors using solid propellants and engines using liquid propellants and for validating design criteria. Recommendation 5-4. DoD should ensure that the development of advanced tactical missiles, responsive global-reach missiles, and antiballistic missiles (ABMs) satisfies four key requirements: effective energy/trajectory management, higher-energy-density performance, minimum smoke exhaust, and insensitive propellants. The S&T part of the DoD/Air Force strategic plan for missiles should focus on the technologies and design criteria necessary to meet these goals. The committee’s estimate of annual funding that would be required to make reasonable progress in establishing advanced capabilities in these areas is $20 million to $30 million. Cross-cutting Technologies Recommendation 6-1. The Air Force should initiate a 5- to 7-year comprehensive program of fundamental fuels research. The goal of this program should be to study properties of smart fuel additives; surrogate fuels; synthetic fuel process technologies; synthetic fuels produced from feedstocks such as coal, oil shale, and biomass; and synthetic-conventional fuel blends. Systematic molecular and chemical kinetics modeling studies should be performed to establish a fundamental database of fuel and combustion properties.

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A Review of United States Air Force and Department of Defense Aerospace Propulsion Needs Recommendation 6-2. The Air Force should fund manufacturing technology (ManTech) at a level sufficient to enable future advances in materials for propulsion technology. Strategies, Issues, and Funding Trends Recommendation 7-1. Engine test capabilities at the Oklahoma City Air Logistics Center (OC-ALC) should allow for engineering changes of existing hardware to be accomplished by the cognizant engineering authorities and, after configuration control board approval, for demonstrating the approved technology-enhanced hardware or accessory on the government test stand at OC-ALC. This would shorten the cycle time for introducing minor engineering improvements into the current legacy fleet of engines and reduce the overall costs to accomplish the qualification. Additionally, it would provide a test bed on which to qualify non-original-equipment-manufacturer (non-OEM) repaired or reengineered parts, new sources of repair, or non-OEM suppliers of parts. Recommendation 7-2. DoD should change the way it manages, contracts for, and buys fuel for the existing fleet. Three years after a system enters into service, budgets for repairs, component improvement, and overall fuel cost should be transferred to the base that maintains the propulsion system. In addition, testing to qualify engine repairs and component improvements should be conducted at the facilities responsible for maintaining the engine. Recommendation 7-3. The Air Force and DoD should apply spiral development to all weapons systems that are in service longer than it takes to develop a new generation of technology. Recommendation 7-4. DoD should adopt commercial best practices to reduce costs and exploit the technical expertise of its research laboratories to enhance the integration process in its product centers and depots. Recommendation 7-5. DoD and major propulsion contractors should define the process changes needed to produce 1- to 2-year technology demonstrations. Decreasing the interval between demonstrations of technology in major propulsion systems will increase the rate of technology development.

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A Review of United States Air Force and Department of Defense Aerospace Propulsion Needs Recommendation 7-6. To reduce the cost of fuel burn and of sustaining the portion of the existing fleet that will be in service in 2020, DoD should develop innovative contracting methods to facilitate the incorporation of evolving technologies into existing engines. Recommendation 7-7. AFRL should maintain a core competency in propulsion technologies by strengthening its unique infrastructure to meet future warfighter needs. Recommendation 7-9. DoD should restore 6.2 and 6.3 technology development funding to levels that give buying power equal to the level that prevailed when the United States held an undisputed lead in engine technology—i.e., the time when the F100 and F110 engines were being developed. DoD should aggressively pursue strategies to reduce sustainment and other recurring costs. It should increase 6.1 funding commensurately. Recommendation 7-10. The Director, Defense Research and Engineering (DDR&E) should undertake a focused effort on cataloging and making accessible the findings of past technology programs, perhaps even combining the VAATE, the Integrated High-Payoff Rocket Propulsion Technology, and the Integrated High-Performance Turbine Engine Technology databases at the lower taxonomy levels to enhance technology cross-fertilization. DDR&E should also establish a feedback process and facilitate a cross-cutting flow of S&T during the development, acquisition, and sustainment phases. PRIORITIZATION OF COMMITTEE RECOMMENDATIONS Table ES-1 shows the committee’s prioritization, based on its members’ collective judgment, of all recommendations contained in the report.

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A Review of United States Air Force and Department of Defense Aerospace Propulsion Needs TABLE ES-1 Prioritization of Recommendations Near Terma Medium Termb Far Termc 2-1 (H) 3-9 (H) 3-6b (M) 3-1 (H) 4-2 (M) 3-9 (H) 3-2 (H) 4-4 (M) 3-10 (M) 3-3 (H) 4-7 (M) 4-5 (M) 3-4 (H) 4-8 (H) 4-6 (H) 3-5 (H) 4-10 (H) 4-8 (H) 3-6a (H) 4-11 (M) 4-12 (H) 3-6c (M) 4-12 (H) 5-1 (H) 3-7 (H) 4-14 (H) 5-2 (M) 3-8 (H) 4-15 (H) 7-4 (H) 3-9 (H) 5-1 (H) 7-7 (H) 4-1 (H) 5-2 (M) 7-8 (H) 4-3 (H) 5-3 (H) 7-9 (H) 4-4 (M) 5-5 (M) 7-11 (H) 4-6 (H) 5-6 (M)   4-9 (H) 5-7 (H)   4-10 H) 7-4 (H)   4-12 (H) 7-5 (H)   4-13 (H) 7-7 (H)   4-14 (H) 7-8 (H)   5-1 (H) 7-9 (H)   5-4 (M) 7-11 (H)   5-7 (H) 7-12 (H)   6-1 (H)     6-2 (H)     7-1 (H)     7-2 (M)     7-3 (H)     7-4 (H)     7-5 (H)     7-6 (H)     7-7 (H)     7-8 (H)     7-9 (H)     7-10 (M)     7-11 (H)     7-12 (H)     NOTE: H, high priority; M, medium priority. Some recommendations are applicable across all terms. aLess than 2 years. b2-5 years. cMore than 5 years.