News 1998 Army Science and Technology Master Plan

C. Aerospace Propulsion and Power

1. Scope

Advanced propulsion and power technologies provide the muscle for Army land combat systems. Toward that end, the Army aerospace propulsion and power technology area includes aircraft propulsion systems and components that are more compact, lighter weight, higher horsepower, more fuel efficient, and lower cost than those currently available. It also includes compact, lighter weight, lower cost, and longer duration aircraft and space vehicle power generation and transmission systems and their components, including primary power transmission for rotorcraft. In addition, it includes associated advanced fuels and lubricants.

Aerospace propulsion and power excludes efforts directed toward generic materials, which are included in Section IV–P, "Materials, Processes, and Structures." It also excludes moderate– to large–scale manufacturing process development, which is included in Section IV–T, "Manufacturing Science and Technology." While there is similarity between gas turbines used for rotorcraft propulsion and those used on missiles, missile propulsion encompasses more than just the gas turbine field. Due to the larger amount of commonality between missile and conventional weapon propulsion systems, missile propulsion is discussed in Section IV–I, "Conventional Weapons."

2. Rationale

Army aerospace propulsion and power technology programs are key enabling elements of the AMP, feeding directly into (1) upgrading existing systems, (2) conducting development, and (3) supporting advanced concepts, as discussed in Section III–D. In addition to their contributions to the battle laboratory warfighting capability, these technologies will enable Army XXI to project the force, to protect the force, and to sustain the force. Longer term elements of the aerospace propulsion and power technology program form the required foundation for large reductions in fuel dependence, which are key to AAN planning.

Army aerospace propulsion and power technology is developed in close coordination with the Air Force, Navy, Defense Advanced Research Projects Agency (DARPA), NASA, and industry, thus inherently promoting dual–use technologies and processes. Despite budgetary constraints, the joint Army, Air Force, and Navy programs, leveraging of NASA resources, and substantial use of cooperative agreements with industry have achieved significant progress. As a result, both the civilian industry and the military industrial base are strengthened and development is faster, more efficient, and less costly. In–house Army laboratory expertise is needed to ensure that those technologies unique to Army applications are addressed and to perform the high–risk, longer term technical investigations, research, and development that ensure attainment of Army objectives and ensure that the Army continues to be a smart buyer. The overall cost to the taxpayer for joint ventures beneficial to both military and civilian applications is therefore minimized.

3. Technology Subareas

a. Rotorcraft Propulsion

Goals and Timeframes

Under the integrated high performance turbine engine technology (IHPTET) program, the Army, Air Force, Navy, NASA, DARPA, and industry are working together to reduce specific fuel consumption of gas turbines by 40 percent, to increase the power–to–weight ratio by 120 percent, and to reduce production and maintenance costs by 35 percent for future engines (compared with current capability) by FY03, STO IV.C.01. While this is an integrated effort of many organizations, the requirements of small turbo– machines dictate that the Army emphasize component technology development that is unique to Army turboshaft engines.

This enhanced propulsion capability will significantly improve Army rotorcraft range and payload characteristics starting in the year 2000. (IHPTET technology will also be applicable for ground vehicles.) An advanced concepts (or IHPTET IV) activity has begun with the goal of defining the path for gas turbine propulsion technologies and challenges beyond IHPTET Phase III.

Major Technical Challenges

Challenge—Attainment of Phase III joint turbine advanced gas generator (JTAGG) goals requires a very high compressor pressure ratio and high rotational speed. Using current practices, a robust, high–pressure ratio compression system would require multiple stages, adding complexity and weight. In addition, the stresses resulting from the combination of compressor exit temperature and rotational speed goals exceed the capabilities of current material.

Approach—Apply evolving compressor design tools and materials to design, fabricate, and test axial and centrifugal compressor stages to provide a validated methodology for attaining the JTAGG III compression system goals in two stages. Develop an active compressor stability control system to expand the usable compression system operating range.

Challenge—The future generation combustion system must accept inlet air at very high temperatures and pressures, accomplish nearly stoichiometric combustion in a small volume with low emissions, and deliver products of combustion to the turbine with an acceptable temperature uniformity. This is to be accomplished in a robust, affordable, lightweight compact combustor with improved operability over a very wide operating range.

Approach—Develop advanced technologies, including three–dimensional (3D) steady and unsteady computational codes, new materials and fabrication techniques, total thermal management, and novel combustion stabilization techniques to enable accomplishment of JTAGG III combustion system goals for turboshaft engines.

Challenge—Critical to the attainment of Phase III JTAGG will be the development of high work, lightweight turbine systems that operate at significantly increased turbine inlet temperatures. High performance must be delivered with minimal or no cooling in a temperature environment more severe than in current turbines. What cooling air is available for use will also be at higher temperature.

Approach—Apply high strength, high temperature, low–density materials that allow operation in a high temperature environment with minimal or no cooling. Materials under consideration include monolithic ceramic or intermetallic composites for the turbine vanes and blades. Enhance analysis tools to include 3D steady and unsteady computational codes to provide a better understanding of the aerodynamic and heat transfer mechanism in extremely complex airfoils. Configure turbine disks with a dual alloy or dual microstructure to tailor material characteristics with bore and rim mechanical requirements. Develop innovative techniques to attach blades made of nontraditional materials to disks in the high rotational stress, high temperature environment of Phase III JTAGG turbines.

Challenge—Gas turbine engine mechanical components of Phase III JTAGG engines and beyond must support the mechanical, thermal, and rotational loads imposed by the extremely high operating temperatures, pressures, and speeds required by the thermodynamic cycle. Bearing, seal, lubricant, and material requirements all simultaneously exceed existing system capabilities significantly. Failure to meet technology goals for mechanical components would prohibit attainment of IHPTET Phase III and advanced concepts goals.

Approach—Of all the phase III IHPTET goals, those for mechanical systems are the most universally applicable across engine types. For this reason, the Army will continue to leverage the overall government–industry IHPTET mechanical components research team’s attention to turboshaft engine needs. Extend successes in basic research to investigate development of higher temperature lubricants and advanced bearing materials. Army, Air Force, Navy, NASA, and industry magnetic bearing developments will be extended to higher temperatures. Magnetic bearing systems enable reduced parasitic losses, minimization/control of tip clearances, active health monitoring for increased performance, reliability, and maintainability. Investigate materials and design innovations for application to shaft designs with high bending stiffness and high–strength capability in a small diameter.

b. Rotorcraft Drives

Goals and Timeframes

Through integration of the technological development activities of the Army, Navy, NASA, DARPA, industry, and academia, a 25 percent increase in shaft horsepower–to–weight, a 10 decibel reduction in transmission–generated noise, a 2X baseline mean time between replacements (MTBR) and a 10 percent reduction in production cost will be demonstrated for rotorcraft drives in FY00, STO III.D.03. Goals for 2010 and beyond will extend the power–to–weight ratio goal to 40 percent while reducing noise 15 dB from baseline, holding MTBR steady and reducing production cost 30 percent.

Major Technical Challenges

Challenge—The goals established for the Advanced Rotorcraft Transmission (ART) II, STO III.D.03, present conflicting technical challenges. Standard approaches to noise reduction and life extension would yield weight increases. The challenges, therefore, involve developing analytical tools that would enable the design of components with high strength and low noise, allow the application of advanced lightweight materials with higher strength and increased pitting, scoring and corrosion resistance, system designs with nearly equal load sharing, and minimized lubrication. These components must then be shown to maintain their performance improvement when integrated into a complete drive system. Future systems will incorporate lightweight electric power generation, transmission and drives.

Approach—Validate the performance of advanced gear materials in cooperation with industry and academia by performing rig tests to compare the performance of new materials with benchmarked performance levels of standard gear materials. Fabricate components using newly developed design codes and validate predicted performance improvements on rig tests. Validate system health and usage monitoring tools and noise reduction and prediction codes using system–level tests. Analytical tools are derived from academia and government laboratories; hardware designs are developed with industry, and validation experiments are conducted by industry, academia, or in government laboratories. The totally integrated program focuses resources on the common goals of the government and industry.

c. Fuels and Lubricants

Goals and Timeframes

In fuels and lubricants, the Army’s major thrust is in the development and demonstration of new analytical technologies for rapid assessment of both petroleum quality and type, using spectroscopic and chromatographic methods. The technology being developed is to be incorporated into the Army’s new petroleum quality analysis (PQA) system.

Major Technical Challenges

The new analytical methods will enable significant reductions in the operational requirements for petroleum testing in the field (i.e., 50 percent less manpower, 70 percent reduced testing time, and 60 percent less test hardware). The technical challenges encompass compressing the testing time, developing improved detection systems, reducing the size of the associated components, correlating test results, and developing expert systems for applying corrective measures.

4. Roadmap of Technology Objectives

The roadmap of technology objectives for Aerospace Propulsion and Power is shown in Table IV–2.

5. Linkages to Future Operational Capabilities

The influence of this technology area on TRADOC FOCs is summarized in Table IV–3.

Table IV–2.  Technical Objectives for Aerospace Propulsion and Power

Technology Subarea

Near Term FY98–99

Mid Term FY00–04

Far Term FY05–13

Rotorcraft Propulsion High–efficiency, high–pressure ratio, dual–alloy centrifugal impellers

Characterization of start up process of nontraditional compression system

Nonintrusive ignition

Turbines with high cooling effectiveness airfoils bonded to pondered metal disk

Flight weight magnetic bearing control

Nonmetallics for combustor and turbine applications

3.5 million diameter in millimeters x rotational speed ceramic steel roller bearings

Higher temperature inter–/nonmetallics for turbines and combustors

Stability enhancement/active surge control concept demonstration

Alternate compression system demonstration

Metal matrix composites for compression systems application

Wide operating range, low pattern factor combustion system

1000_ Fahrenheit (F) magnetic bearing

Nontraditional seals

High stiffness/strength shaft

Unconventional compression, combustion, power producing systems, and arrangements

Smart engine concepts demonstration

Improved aerodynamic performance small components

Shrouded rotating components

Alternate concepts for waste energy recovery

Advanced lightweight, high temperature materials

Supercritical fuel injector

Rotorcraft Drives Hardened/ground face gears manufactured and rig tested

Seeded fault diagnostic/prognostic spiral bevel gear tests

Hardened/ground face gears life and reliability data documentation

High–speed gearing thermal behavior validation test

Efficient electric components rig test

High temperature, lightweight lube system

Low noise, lightweight planetary gear system

Nonferrous, hybrid gear, and shaft systems

Electric power transmission feasibility demonstration

Fuels and Lubricants Develop field supportable, fast fuel quality analyzer    


Table IV–3.  Aerospace Propulsion and Power Linkages to Future Operational Capabilities

Technology Subarea

Integrated and Branch/Functional Unique Future Operational Capabilities

Rotorcraft Propulsion TR 97–022 Mobility—Combat Mounted
TR 97–035 Power Source and Accessories
TR 97–036 Nonprimary Power Sources Combat Vehicles/Support Systems
TR 97–037 Combat Vehicle Propulsion
Rotorcraft Drives TR 97–022 Mobility—Combat Mounted
TR 97–035 Power Source and Accessories
TR 97–036 Nonprimary Power Sources Combat Vehicles/Support Systems
TR 97–037 Combat Vehicle Propulsion
Fuels and Lubricants TR 97–029 Sustainment
TR 97–030 Sustainment Maintenance
TR 97–037 Combat Vehicle Propulsion

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