2005-2006 Assessment of the Army Research Laboratory (2007)

The Vehicle Technology Directorate (VTD) was reviewed by the Panel on Air and Ground Vehicle Technology. The directorate has four divisions that are reviewed by the Panel: Loads and Dynamics, Structural Mechanics, Engine Components, and Engine and Transmission Systems. The first two of these divisions are located at the National Aeronautics and Space Administration (NASA) Langley Research Center in Virginia, and the other two are located at the NASA Glenn Research Center in Ohio.

Tables A.1 and A.2 in Appendix A show the funding profile and the staffing profile for the VTD.

The assessment detailed below reflects visits by the Panel on Air and Ground Vehicle Technology to the VTD sites at NASA-Glenn (September 12-14, 2005) and NASA-Langley (May 23-25, 2006), as well as the December 2005 meeting of the ARL Technical Assessment Board.

There were three significant events that represented significant changes and potential impact on the VTD mission. The first of these was the selection of the directorate to be relocated to Aberdeen Proving Ground, Maryland, as part of the 2005 Base Realignment and Closure (BRAC) action. The second event was the retirement of the longtime Director of the VTD and the appointment of a replacement. The third was the announcement by NASA of its intent to restructure its aeronautics program and to focus more on space activities and on base technology in the aeronautics area. These moves indicate that the NASA aeronautics program will be operating with further budget reductions.

The BRAC announcement provided the VTD with the opportunity to conduct an introspective review of its activities and to conduct an ongoing strategic planning exercise to seek the best approach to addressing its mission and how it may best be accomplished without the four divisions being collocated in their entirety with NASA at the two NASA centers.

The retirement of the VTD Director and the appointment of a new Director appeared to the Board to have had no discernible negative functional effect on the operation of the directorate and the technical content of its activities. This level of leadership change, combined with the strategic planning, represent significant events that need to be carefully managed by ARL management to shape the VTD and maintain its valuable contribution to the Army mission. The Board’s assessment is that the ARL and VTD leadership are moving forward with positive responses to these events.

The announced change in focus of the NASA aeronautics program and its effect on the VTD mission have yet to be fully assessed. The most significant effect may relate to NASA’s potential actions with respect to wind tunnel operations. The VTD has been dependent on certain NASA wind tunnels for research, methods validation, and proof-of-concept testing. NASA currently has its operation of these facilities under cost-benefit review. The change from collocation with the NASA researchers should have a lesser negative impact on the important analytical methods development and applications work done by VTD, because these efforts will be reinforced by NASA’s focus on base technology.

Significant accomplishments during this assessment period were the demonstration in full-engine tests of the Active Stall Control Engine Demonstration (ASCED) concepts, the continued development and validation of both aerodynamic and structural analytical tools, and the application of these to Army vehicles. The Board also notes that the VTD is examining approaches to enhance the directorate’s ability to recognize evolving Army needs and to facilitate the transition of technology to the user.

The ASCED addresses the issues of helicopter engine performance deterioration and loss of operating stability, caused from operation in areas in which there are high concentrations of airborne particulates. Engines operating in these conditions experience erosion of compressor blades and deposition of material on the turbine components, resulting in significant losses of aerodynamic capability and a shift of the acceleration characteristics of the engine. The ASCED program used a comprehensive approach that included modeling of the aerodynamic characteristics of the components, the engine, and its control system; component tests to establish baseline characteristics of the components and the engine; and detailed exploratory investigations into several techniques to modify and enhance the stability of the components and the overall engine system. The activities leading up to the full-engine tests with the selected enhancement features were reviewed in the meeting at NASA-Glenn in 2005. The full-engine test to demonstrate the capabilities of the selected stability enhancement devices was reviewed in the 2006 meeting at NASA-Langley.

The program was viewed as having a high degree of relevance to the Army mission and to the broader helicopter community. The results of the initial analytical modeling and component testing were assessed by the Board as good work that followed sound engineering practices and produced good results. The Board was somewhat concerned that some of the analytical modeling work on the overall engine system had been delayed owing to the relocation of one of the university researchers involved in this work, but it was reported that this effort is being reinstated successfully.

The results of the engine tests with the stability enhancing configuration were very encouraging and were considered to represent considerable success for the program. However, there were several findings relating to improvements in the stability margins of the engine when the incorporated devices were in their passive mode. While this does not detract from the improvements demonstrated and attributed to the incorporated technologies, the Board recommends that the program be expanded to fully understand

the implications of all of the characteristics observed. The Board also recommends that the results be presented in an industry workshop so that the results may be quickly assimilated by the engine and operating community and these features incorporated as appropriate.

The directorate’s efforts to adapt and use analytical tools, addressing aerodynamic characteristics, and the resulting dynamic interaction of helicopter structures are considered by the Board to be sound engineering work on the basis of individual programs but of more value when viewed as part of the total analytical capability of VTD. This value is further enhanced when the analytical capability is placed in the context of an integrated package of analysis, model testing, and full-scale component and vehicle testing.

The Rotorcraft Wake Modeling Using p-VTM (Particle Vorticity Transport Model) work has demonstrated significant achievements. The Board is supportive of the program but suggests that the researcher more actively investigate other research in the field to avoid duplication of effort and to accelerate the reduction to practice of this tool. The Board also supports the effort to minimize computer time through the use of multigrid approaches to providing high resolution for computational fluid dynamics (CFD) methods, and again recommends that the researcher stay abreast of other similar work in the field. The application of the analytical tools to specific applications and configurations is considered a significant part of VTD’s mission, and the efforts briefed on the UH-60 helicopter, the Coaxial Rotor concept, and others are assessed to be good, sound work.

VTD’s eventual movement from the NASA centers will necessitate a significant movement of personnel and a change in the relationship with the NASA personnel and facilities. ARL and VTD management is taking advantage of this opportunity to conduct a focused strategic planning activity without excessive reliance on past practices and approaches and to draw closer to other components of the ARL system. The Board looks forward to the results of this ongoing planning activity.

The VTD has evolved an approach in all four divisions that has been successfully demonstrated. It is characterized by a combination of applying analytical tools, using experimental methods in controlled tests, and applying these to real full-scale vehicles and components. This approach has included a mix of Army, NASA, academic, and industrial researchers.

The Board notes that the CFD work being conducted is of significant value to understanding issues encountered in the design, operations, and system evaluation phases of a program. The same type of value is assessed as being contributed by the work on material characterization, fracture mechanics, and damage assessment. It is noted that the work on Fracture Toughness/Fatigue Resistance of Composites with Embedded Sensors has potential application to future development and operational systems.

The methodology used by the divisions at the NASA-Glenn Center also includes a mix of both analytical and experimental activities. An example of this was noted in the discussion above of the ASCED program. This division appears to be spread very thin when the staff level is compared with the number of programs currently underway, but this is partly explained by the participation of Army researchers in NASA programs of interest to the Army.

The Board views VTD’s programs in general as making contributions to Army needs with a wide range of near-term and far-term activities. Examples of programs that have the potential of direct contribution to near-term needs include the ASCED, which addresses engine deterioration issues currently being encountered in deployed aircraft. Also in this category are the Terahertz (THz) Nondestructive Evaluation (NDE) for Aging Aircraft Corrosion and Damage and the Application of Thermal NDE for Advanced Structures programs. These programs provide the operator with techniques for inspecting critical structures and determining the readiness of equipment. This capability also holds the potential for extending equipment deployment and decreasing the load on critical depot assets.

Programs such as the Active Twist Rotor, Tiltrotor Aeroelasticity, Multigrid Methods for High-Resolution CFD, and some of the advanced turbine material characterization programs are more long term in nature, since they are in the methods validation phase and, while a portion of these programs may find near-term applications, their full value will be realized in solving future problems and configuring new systems.

The latest review included considerable attention to the contributions that the VTD makes to industry and how this value is realized. The Board identifies three contributing factors:

1. The capable people who have experience and a balance of analytical, experimental, and applied backgrounds (i.e., dedicated personnel experienced in rotorcraft propulsion and structures with a good balance of analytical and experimental knowledge);

2. Analytical capability that is focused on Army issues (focused on the adaptation, validation, and application of codes to actual aircraft, experimental vehicles, and tests); and

3. Facility interface capability that goes beyond conducting a test in response to an external request and includes interactively designing the test and test vehicle, as well as real-time guidance of activities (i.e., access to relevant facilities to define the test configurations and procedures and to participate in a management role in the conduct of experimental work).

Examples noted by the Board that can be categorized as contributing to the broader community include the program on Nonlinear Airframe Dynamics that industry may use to address the continuing problem of preventing tail wag in rotorcraft. The Coaxial Rotor Modeling effort, while in its early stage of development, was noted as being important to the Joint Heavy Lift work currently underway. In the Engine and Transmission Systems area, selective parts of the work are considered to have direct and immediate application to existing systems, and they are making a significant contribution to the design database. Much of the high-temperature material work being done by VTD personnel at the NASA-Glenn Center is considered by the Board to be unique and important, and this important work is not being pursued in industry or academia.

The Board notes that the VTD is exploring new avenues of crosscutting work as part of its strategic planning in response to the BRAC action. There are excellent examples of information transfer and

cooperation between the VTD, industry, and academia, and there are other cases in which the work may be categorized as introspective and insular. Specifically, it is noted that several researchers did not seem to be aware of work in their fields that was underway at other research institutes and in industry. The VTD is staffed with capable people, who, in some cases, would benefit from broader exposure to others working in their fields or in similar fields.

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