Chapter IV. Technology Development
Army Science and Technology Master Plan (ASTMP 1997)


C. Aerospace Propulsion and Power

1. Scope

Advanced propulsion and power technologies provide the muscle for Army land combat systems. Toward this end, the Army aerospace propulsion and power technology area focuses on technologies that will result in aircraft and missile propulsion systems and components, including prime power transmission, that are more compact, lighter weight, higher horse power, more fuel efficient, and lower cost than those currently available. It also focuses on compact, lighter weight, lower cost, and longer duration aircraft and space vehicle power generation systems and their components. In addition, it includes associated fuels and lubricants. It excludes efforts directed toward generic materials, which are included in Materials, Processes and Structures, and moderate- to large-scale manufacturing process development, which is included in Manufacturing Science and Technology. Missile propulsion is discussed in Section I, Conventional Weapons.

2. Rationale

Aerospace propulsion and power technology will provide mobility for next generation Army aircraft and missiles and upgrades to current systems. These systems, coupled with modern doctrine, tactics, and training, will provide our soldiers the capabilities needed to execute precision strikes, to dominate maneuver battles, and to project and sustain combat power.

Army aerospace propulsion and power technology is developed jointly and in close coordination with the other military services, the National Aeronautics and Space Administration (NASA), and industry, thus inherently promoting dual use technologies and processes. As a result, both 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 pertinent to Army requirements are addressed, and to enable the Army to be a smart buyer and to perform the high risk technical investigations, research, and development that ensure attainment of Army requirements. The overall cost to the taxpayer for joint ventures having both military and civilian applications is therefore minimized.

3. Technology Subareas

a. Rotorcraft Propulsion

Goals and Time Frames

In the gas turbine area, under the Integrated High Performance Turbine Engine Technology (IHPTET) program, the Army, other Services, National Aeronautics and Space Administration (NASA), Defense Advanced Research Projects Agency (DARPA), and industry are working together to reduce specific fuel consumption by 40 percent and to increase the power-to-weight ratio by 120 percent of future (compared with current) engines by FY03. This enhanced propulsion capability will significantly improve Army rotorcraft range and payload characteristics starting in the year 2000 and beyond. IHPTET technology will also be applicable for ground vehicles. An "Advanced Concepts (or IHPTET IV)" activity has also begun with the goal of defining the path for gas turbine propulsion technologies and challenges beyond IHPTET Phase III.

b. Progress and Plans

Gas Turbine Engine Technology

Typically, turbine rotors use the "fir-tree" method for the blade/disk attachment. However, by employing an integrally bonded blade /disk rotor, the disk material in the "dead" rim can be eliminated, significantly reducing disk weight. Under the Low Inertia Turbine Program, AlliedSignal has fabricated an integrally bonded rotor consistent with the JTAGG II /IHPTET Phase II goals (STO IV.C.1). Design bond strength requirements have been success fully demonstrated in an 1100 F-spin test. Minor modifications have been made to improve the bonding process, and another rotor will be fabricated and spin pit tested in 1Q FY97. This is the attachment configuration for the JTAGG II HPT which, upon successful completion, will reduce the risk of incorporating this technology into the gas generator.

Rotorcraft Drive Technology

Spiral-bevel gears (SBGs) are used extensively in rotorcraft applications to transfer power and motion through nonparallel shafts. While SBGs have had considerable success in these applications, they are a major source of vibration in gearboxes, and thus a main source of cabin noise. An analytically based optimal design tool was developed which modifies the gear tooth profile to minimize SBG noise and vibration. Advanced design spiral-bevel gears were tested, including configurations with increased fillet radius to reduce tooth bending stress, modified tooth geometry to reduce noise, and provisions to reduce premature contact and eliminate wear problems. In FY96, an optimum design was fabricated and tested. The test demonstrated more than a 50 percent decrease in gearbox vibration and over 10dB in noise reduction.

Major Technical Challenges

In order to reduce fuel consumption, turbine engine thermodynamic efficiency must be in creased. Meeting IHPTET goals will require cycle temperatures near or equal to stoichiometric combustion conditions. If the engine power-to-weight ratio is to be increased, materials must be found that can survive substantially higher operating temperatures, approaching 1900C (3500F) in the combustor and turbine, and withstand a 280C (500F) increase over present levels in the compressor while retaining required mechanical strength. In addition, methodologies must be developed and validated for the design of more highly loaded aerodynamic components, allowing lower parts counts. And drive train research must be performed to lower weight, volume, noise, and durability barriers. Specific technical challenges are highlighted below.

(1) Gas turbine engine technology

(2) Rotorcraft drive technology

c. Fuels and Lubricants

Goals and Time Frames

In the fuels and lubricants sub-subarea, the Army's major thrust is in the development and demonstration of new analytical technologies by 1997 for rapid assessment of petroleum quality using spectroscopic and chromatographic methods. The technology being developed will be incorporated into the Army's new Petroleum Quality Analysis system.

Major Technical Challenges

The new analytical methods will enable a significant reduction 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, correlating testing results, and developing expert systems.

4. Roadmap of Technology Objectives

The roadmap of technology objectives for Aerospace Propulsion and Power is shown in Table IV-C-1, below.

Table IV-C-1. Technical Objectives for Aerospace Propulsion and Power

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