2003-2004 Assessment of the Army Research Laboratory (2005)

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6 Vehicle Technology Directorate INTRODUCTION 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 respectively characterize the funding profile and the staffing profile for VTD. The assessment detailed below reflects visits by the Panel on Air and Ground Vehicle Technology to the VTD sites at NASA Glenn (in May 2003) and NASA Langley (in May 2004), as well as the July 2004 meeting of the ARL Technical Assessment Board. ACCOMPLISHMENTS AND OPPORTUNITIES Most Significant Advances Two major VTD programs continued to advance during the past 2 years: the Active Stall Control Engine Demonstration (ASCED) program and the Survivable, Affordable, Reparable Airframe Program (SARAP). The ASCED program is intended to support helicopter operation in areas where airborne particu- lates might be encountered (e.g., over unimproved runways, in desert regions, or in combat zones). While operating in such conditions, helicopters will experience erosion of compressor blades and deposition of particulates on hot section components, even with sand separators and screens in place and 31 

32 2003–2004 ASSESSMENT OF THE ARMY RESEARCH LABORATORY operational. Both types of problem cause engine deterioration that degrades performance (efficiency) and surge margin. The loss of engine performance is undesirable because it reduces the load-carrying capacity of the machine. The loss of surge margin increases the risk that the helicopter will experience a stall/surge event and an associated and dangerous loss of a significant fraction of engine power. Research by the VTD staff has demonstrated that it is possible to detect the onset of rotating stall/surge for a combined axial/centrifugal compressor machine, and that information on such precursor signatures can be transmitted to the engine controller so that it can recognize the impending difficulty and take corrective action. The Panel and the Board are pleased with the progress in facility enhancements, engine modifica- tions, and experimental demonstrations in the ASCED program. The Panel has concerns, however, that the erosion-damaged engine used in the demonstration is not representative of other new engine re- sponses (see the section “Opportunities and Challenges,” below). The Survivable, Affordable, Reparable Airframe Program is intended to meet an important Army need—the design of helicopter fuselages and airframes so that they can better withstand battle damage. Some very good engineering and scientific research is being conducted under this rubric. It builds on accomplishments (noted in previous assessments by the Board) in composite fabrication and in crack growth in composite materials and addresses the broader, directly relevant application of allowing helicopters to withstand and inhibit the development and propagation of cracks resulting from the impact of enemy fire. The overall quality of technical presentations of the VTD researchers in the ASCED program, in the SARAP, and generally, continues to improve and represents increasingly higher caliber each year. In addition, the Panel was pleased to note an increasing awareness within ARL that this directorate is an intellectual resource whose quality and application are continually improving. One specific highlighting of this high competency is the VTD’s strong interaction with its industry partners (e.g., Bell Helicopter, Boeing, and Sikorsky) in areas such as the SARAP and active rotor design. Opportunities and Challenges Mission, Organization, Funding, and Staffing of the Directorate At the top of a list of current opportunities and challenges for the VTD is that the quality of the research produced by the VTD as a stand-alone entity within ARL could in the future be in doubt because of significant changes affecting VTD’s current mission, organization, funding, and staffing. This concern about the future of quality research is due in part to changes made by the directorate’s long-standing partner, NASA, which had set the pace for new technologies with vehicles such as the XV-15 tilt rotor, which led to the V-22. Now the NASA Glenn Research Center no longer has a rotorcraft mission and is moving away from turbomachinery, and NASA Langley is mothballing or closing structural and wind tunnel test facilities. Thus, the Army has assumed a stronger role in defining future technical objectives, and both the Army and industry are very influential in setting technology goals for future manned and unmanned vehicles. It is also the case that the Army is changing its focus in ways that spark concern among the VTD leadership about the directorate’s future relationship with the Research, Development and Engineering Command (RDECOM), as well as with an evolving NASA. Factors that relate to concern regarding VTD’s funding situation include the following: the funding of research projects largely as procurements (e.g., ASCED and Active Twist Rotor), one-time funding decisions (e.g., reducing a basic research account fund at a university to satisfy a Department of the Army requirement), and consistent deficiencies in salary accounts. The ARL leadership has addressed 

VEHICLE TECHNOLOGY DIRECTORATE 33 VTD’s funding for full-time staff positions, but on a basis that apparently allows VTD to operate with a decreasing research staff and significant reductions in overhead resources. It is also not yet clear how the stabilization of NASA’s new full-cost accounting system will affect VTD’s budgetary situation. In any event, current salary and overhead inflation trends, combined with a flat or reduced mission scope, will challenge VTD’s ability to maintain a quality research staff. Discussions between the Panel and the VTD leadership during the visits to the NASA Glenn site (2003) and the NASA Langley site (2004) suggested that the VTD leadership is quite concerned about the future of the directorate. The VTD Director believes that the VTD’s core competency is in rotor/ structural dynamics and that its efforts in structural integrity would be dropped if the VTD continues to be financially pressed. In view of the anticipated retirements of both the VTD Director and Deputy Director, now may be an appropriate time for ARL to consider in careful detail the future of VTD. This directorate is a valuable intellectual and technical resource. It may be possible that this resource might better serve its Army clientele and continue its important technical work if its NASA Glenn and NASA Langley components were (organizationally) moved, either together or separately, into other parts of ARL. For example, some of the structural work done at NASA Langley would seem to couple naturally with the mechanics and structures work done by the Weapons and Materials Research Directorate (WMRD). This might, for example, foster synergy in preventing battle damage to helicopters and to land vehicles. The Directorate’s Institutional Knowledge An opportunity and challenge related to those described above is occasioned by changes in senior staff, including both retirements and changes in division leadership (in addition to the changes in VTD’s top management, as noted). Several senior researchers have recently retired. In the past 2 years, three new division leaders have been appointed, and many of the researchers have been replaced, generally by less-experienced personnel. This replacement of senior, experienced personnel has led to a continuing problem with the maintenance of institutional knowledge. (A related problem, which is hard to charac- terize, is that some individual research programs terminated when senior investigators left or retired, thereby raising questions about whether research priorities are established by the competencies or interests of available personnel.) Keeping test procedures and test results alive and repeatable or retriev- able has been a long-standing concern. In many areas the technological value of tests is maintained in derived numbers that are published and stored in databases and handbooks. Similar to test procedures in materials testing, many of the procedures are documented in American Society for Testing and Materi- als (ASTM) Test Method Handbooks. Thus, the VTD’s leadership anticipates severe data maintenance problems in testing areas such as wind tunnels and crashworthiness. The VTD leadership feels that it is only possible to publish derived information: the “system” no longer gives credit to VTD (or ARL) engineers for producing elaborate laboratory reports, as ARL (and the National Advisory Committee for Aeronautics [NACA] and then NASA) still did in the 1960s. For example, in a Comanche helicopter tail buffet test conducted by VTD several years ago, VTD actually published the entire time-load history data on digital media. The original data for the Active Twist Rotor also still exist only in (internal, unpublished) digital form, which clearly limits their usefulness. The perceived future usefulness of such experimental data decreases if and when the derived data are first published. It decreases again when a second-generation test is performed, and it probably becomes useless when a full-scale aircraft flies successfully. However, there is a problem because, absent a means and a reward for publishing such experimental data, whole disks of old (unpublished) data lose whatever value they might still have when research staff retire. 

34 2003–2004 ASSESSMENT OF THE ARMY RESEARCH LABORATORY Mentoring Within the Directorate Another opportunity and challenge appears to be that of senior investigators providing positive opportunities for growth to younger and newer colleagues. Several senior investigators, in several areas, showed great awareness of and sensitivity to work being done in their respective research communities. On the other hand, some investigators, especially younger ones, may not be adequately aware of previous and recent work in the areas in which they are working and presenting. Helping to develop such awareness is an important part of the mentoring process. Computational Modeling in the Directorate One particularly important aspect of mentoring—and, indeed, of general scientific style—is the realm of computational modeling. While the computational work done at the NASA Langley site continues to improve, for example, there is still ample room for further improvements in both standards and style. Questions that should be addressed include these: Are the right computer tools being exer- cised? Why are general research results presented for particular numerical values of variables? Why are they not done in terms of dimensionless variables that obviate the need to repeat calculations for each individual configuration or case? Is enough attention being paid to finite elements method/finite ele- ments analysis (FEM/FEA) mesh refinement—especially when considering cases in which scale is clearly quite important? A strongly related concern here is the increasing dependence on FEM/FEA as a replacement for the experimental, experiential verification of analytical models. The Panel was informed of the following by VTD leadership: “The new generation of VTD technical leaders leans much harder on the researchers to develop advanced analytical methods of solving key problems and/or reducing the amount of ever- costlier experimentation. ASCED is a great example of full-level computation, and we can show similar progress in structures and aeromechanics.” This is a dangerous trend on its own terms, although it may be unavoidable in certain circumstances and in view of future budget limits and uncertainties. The VTD leadership recognizes that there are limits to this approach; they pointed out that “the total validation of the dynamics of complete rotor systems still has significant weaknesses in the correct implementation of the entire physics package.” Clearly, when coupled with computational practices that are less than perfect, the dangers are exacerbated still further. This is an opportune time to remind the VTD of the Army Research Laboratory Technical Assessment Board’s recommendation in the previous biennial report that ARL should consider a systematic initiative to improve computational modeling across ARL.1 As noted then, changes in computational style will become effective only when they are em- braced by senior scientists and management, and when consistent and suitable mentoring of the younger scientists is implemented. In this context, a variety of large-scale computational tools currently exist both within government laboratories and on the commercial market. As part of a computing initiative, VTD might assign to some of its capable young researchers the job of systemically identifying, securing, and coming to fully understand through comparative applications many of these large-scale computational tools for specific applications essential to ARL and pertinent to VTD. This effort would supplant trying to find new 1National Research Council. 2003. 2001-2002 Assessment of the Army Research Laboratory. Washington, D.C.: The Na- tional Academies Press, pp. 32-33. 

VEHICLE TECHNOLOGY DIRECTORATE 35 problems to do and trying to develop new computational tools. If VTD’s computational experts are fully abreast of computational techniques for application to the class of materials and structures that is VTD’s focus, they could become a valuable resource to the rest of ARL. Finally, as another form of challenge, many of the managerial presentations to the Panel did not describe a clear vision and connection to the directorate’s mission. In addition, many of the individual research presentations did not fully explain how the research undertaken contributed to meeting the Army’s needs. The Panel has repeatedly asked for simple opening statements and/or slides that would delineate a project’s goals in the context of the Army needs, but this was not regularly included as a standard presentation item. CONTRIBUTIONS TO ARMY NEEDS AND THE BROADER COMMUNITY Contributions to Army Needs Potential Contributions of Two Major Programs The ASCED program and the SARAP seem to be successfully and vigorously aimed at meeting future Army needs. Both would obviously have immediate application in environments such as those found in Afghanistan and Iraq. Good progress is being made on both programs, although further efforts, including the ones discussed below, are required before transition can occur. The Panel and the Board are pleased with the progress in facility enhancements, engine modifica- tions, and experimental demonstrations—although there are concerns that responses of the erosion- damaged engine used in the demonstration are not representative of responses of other, new engines. In addition, the strong interaction with industry partners (e.g., Bell Helicopter, Boeing, and Sikorsky) was also noted quite favorably by the Panel. However, there are some concerns about further developments that are planned for the computer code, TURBO, that did not predict the experimentally observed compressor operation range extension with control. At best, a T700 case will be set up to initiate unsteady flow solution. The Panel and the Board are therefore concerned that the simulations will not make a meaningful contribution to the overall effort, and they recommend that the computational program goals be reexamined to identify how to address this issue. Within SARAP, some good engineering and scientific research is being done on the debonding of composite skin/stringer configurations. The Board suggests that several further improvements be con- sidered in order to improve the modeling of debonding. Convergence should be studied in the quantities of interest; it is possible that the results converge in one quantity of interest, but not in others. As an alternative, an iterative multigrid-type or composite-grid-type approach should be explored by which a fully shell model is computed to obtain a lower frequency response of the hybrid shell-three-dimen- sional model within the framework of the multigrid-type methods. It may be worthwhile to consider extracting stress intensity factors based on the information away from the crack tip (such as the J- integral). In this case, considerable mesh refinement is not required at the crack tip. These suggestions address both computation and the relevant physics. Unfortunately, the related work on polymer composites caused great concern in the Panel because of its styles of computational modeling, as noted earlier. Similarly, the Panel is very concerned that two new, young, and bright researchers are working on problems that could be categorized as “long ago solved.” The Panel finds it difficult to accept the rationale provided—that the work is needed to develop design tools—because current commercial codes can probably address the design issues. The Panel 

36 2003–2004 ASSESSMENT OF THE ARMY RESEARCH LABORATORY questions whether the senior researchers and managers have chosen wisely in assigning these projects and whether the young researchers have done an adequate job of reviewing the relevant literature and prior art. The Panel has further technical concerns about some different aspects of the modeling of the strength of damaged composite panels and structures. The Panel and the Board suggest an examination of the following questions: Is a higher-order continuum (i.e., coupled-stress analysis) needed for such work? What does the program FLASH really do? Are adhesives such as Nomex, which was used for bonding, still used in industry (e.g., by Bell Helicopter)? What is the real value of so-called selectively reinforced, multifunctional structures? Is the potential value of the alternative being pressed (in the choice between metals versus polymeric) being oversold? Notwithstanding the aforementioned concerns, both the ASCED program and SARAP are impor- tant efforts that are making substantial progress and give every indication that they will meet future Army needs. Example Projects That Demonstrate Transition The Vehicle Technology Directorate works to transfer or transition technology by disseminating knowledge and understanding about both technical information and products to engineering centers, industry, and academia. VTD works closely with the Research, Development, and Engineering Centers (RDECs) and their customers through Technology Planning Annexes (TPAs) and Cooperative Research and Development Agreements (CRADAs). From FY 2001 to the present, VTD has had eight TPAs with the Aviation and Missile RDEC (AMRDEC), the Tank-Automotive RDEC (TARDEC), and the Natick Soldier Center, some of which were renewed. VTD also established five CRADAs with industry and academia partners at Bell Helicopter, Boeing, Sikorsky, Rolands, and Polytechnico di Milano. In addi- tion, VTD disseminates technology through various forums to organizations such as the National Rotor- craft Technology Consortium, the American Helicopter Society, and the Joint Aircraft Survivability Program Office. Such dissemination activity suggests that VTD is the aviation technology authority (with current focus on helicopters) in basic and applied research and therefore is continually sought to provide expertise in aviation technologies for the engineering centers, industry, and academia. It is the Board’s understanding that VTD receives customer funding from other DOD organizations and industry. Most important is VTD’s well-established relationship with the National Aeronautics and Space Administration through an overarching Memorandum of Agreement and local Center Operating Agreements at the NASA Langley and NASA Glenn Research Centers. Although no money actually changes hands, these agreements have had a synergistic effect in the past, allowing both the Department of Defense and NASA to leverage dual-use technology. The Panel is also directly aware of two projects that are in various stages of transitioning into meeting daily Army needs. One of these is the work on the development of high-temperature ceramic composite combustor liners to replace their metallic counterparts in gas turbine engines. The ceramic liners weigh less than one-third of their metallic counterparts. In addition, since these ceramics can sustain higher temperatures than metals can, less energy is wasted on cooling the combustor linings. The second VTD project that shows transitional promise is one that the Panel did not formally review, namely, the Icing Research Tunnel, which is used to evaluate the effects of icing on full-size aircraft components or on models of aircraft. The facility can simulate real-time flying conditions and is in such high demand that it must be reserved more than a year ahead of its planned use. 

VEHICLE TECHNOLOGY DIRECTORATE 37 Support to the Troops in Iraq and Afghanistan VTD has not been directly connected to any current projects in either the Iraq or Afghanistan theaters, but it does consult for Fort Eustis, Virginia, which provides the first line of fleet support in aviation. Moreover, the ASCED program clearly is aimed at a serious problem endemic to those theaters, so VTD’s continuing good efforts on that program will produce practical, useful results at some point. Contributions to the Broader Community By and large, VTD has continued to reach out to the broader professional community. Most notably, researchers continue to present papers at appropriate conferences and to publish significant numbers of papers in proceedings of meetings and in the major journals in the VTD disciplines. From January 2001 through July 2004, VTD staff contributed 169 papers to presentations and proceedings, 95 refereed journal articles, 67 technical reports, and 21 patents. VTD research staff members are active participants in a variety of professional societies (e.g., the American Helicopter Society [AHS] and the American Institute of Aeronautics and Astronautics [AIAA]). Several hold offices on committees and boards within these societies, organize conferences, and otherwise actively participate. The VTD leadership and staff also actively participate in a variety of outreach activities (e.g., to Historically Black Colleges and Universities) and conduct a variety of events with nearby kindergarten through 12th-grade schools. Many of the VTD staff have been recognized by their professional communities by being invited to present papers and lectures and having earned “Best Paper” awards. Other honors include earning prizes and recognition from societies (e.g., appointment as associate fellows and fellows of AIAA and AHS), as well as earning promotions and awards from NASA and from ARL. RELEVANCE OF CROSSCUTTING ISSUES TO THIS DIRECTORATE Some groups within VTD have performed computational modeling in styles and to standards consistent with the best professional practices. However, there continue to be substantial instances in which researchers and investigators have not properly considered the following: • Verification (i.e., that a computer program does what it was intended to do); • Validation (i.e., that the computer program produces results that are valid in and relevant to the domain in which it was intended to operate); • Use of a variety of standard operating practices for doing calculations and presenting results (e.g., the use of appropriate dimensionless variables); and • The consequences of the widespread replacement of experiments by computational modeling (e.g., see the discussion on computational modeling above). There were no issues raised during the VTD reviews that directly concerned information security. However, as indicated above, concerns were raised about the maintenance of data and of institutional knowledge. VTD works closely with other directorates in ARL, mostly with the Weapons and Materials Re- search Directorate in structures technology and with the Survivability and Lethality Analysis Director- ate (SLAD) concerning aircraft survivability. There is technical expertise within VTD that could be 

38 2003–2004 ASSESSMENT OF THE ARMY RESEARCH LABORATORY applied in support of other missions of other ARL directorates (e.g., fostering synergy with WMRD in preventing battle damage to helicopters and to land vehicles). The SARAP effort, for example, could be of interest to WMRD and might benefit from interaction with WMRD staff. However, the Panel is not aware of any active interdirectorate activities relating to this program. Given the division of VTD between two disparate geographical sites (NASA Glenn and NASA Langley) and different mission flavors (turbomachinery and rotorcraft engines at NASA Glenn, and crashworthiness and rotorcraft blades at NASA Langley), it may be useful to consider opportunities for connectivity between VTD-Glenn and VTD-Langley, and with the Army Research Office (ARO), as being a form of interdirectorate activity. Such connectivity and interaction were reflected in some innovative work on ceramic thermal and environmental barrier coatings and crack propagation, and on scales and available tools. Because of the importance of the enabling high-temperature material technology, the connectivity issue for the thermal and environmental barrier coatings efforts at VTD-Glenn has been well addressed through extensive collaborative research for expanding coating applicability and promoting technology transfer. Research and development of coating technologies have been integrated through various gov- ernment, university, and industry programs, including an Army CTA Propulsion and Energy program aimed at developing durable ceramic environmental barrier coatings for Si3N4 engine components. Several university research programs have focused on fundamental aspects of the coating behavior, including among them Princeton and Pennsylvania State Universities. Strong government-industry partnerships have facilitated the development and commercialization of the thermal and environmental barrier coating technologies, with General Electric Aircraft Engines (GEAE) and Pratt & Whitney both being involved in processing and evaluation of coating systems. Combustor rig tests of low-conductivity thermal barrier coating on hardware components by GEAE were successfully completed and demon- strated in a NASA Ultra Efficient Engine Technology diagnostics test on a deflector and in a DOD Integrated High Performance Turbine Engine Technology test on a combustor liner. The coating sys- tems are currently being evaluated by GEAE for potential use in production engines. Pratt & Whitney has been involved in electron beam-physical vapor deposited (EB-PVD) process- ing optimization, burner rig testing, and erosion evaluation of several low-conductivity turbine airfoil systems. The advanced turbine airfoil low-conductivity coating systems are also being considered for further development for future pulse detonation engine-based, constant volume combustion cycle tur- bine hybrid engines. VTD conducted a Technical Interchange Meeting at VTD-Langley to address a concern that had been previously expressed by the Panel about connectivity between Langley and Glenn on fracture mechanics (crack propagation) research. At the Technical Interchange Meeting, it was concluded that fracture mechanics research at the two sites is significantly different, each having its own specialties and unique thrusts. However, the VTD researchers did agree to conduct yearly coordination meetings in order to update research, exchange publications, and review the potential for collaboration.