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Board on Army Science and Technology Review of the Army’s Assessment Methodology for Combat Vehicle Vulnerability to Anti-Armor Weapons

“During the combat-loaded, live-fire testing of the Bradley Fighting Vehicle System (BFVs) in 1986, differences of viewpoint arose among the Office of the Secretary of the Army, the Office of the Secretary of Defense, and the Congress regarding the role and conduct of live-ammunition firings and the interpretation of results in assessing the vulnerability of armored vehicles. To resolve these differences, the National Research Council’s Board on Army Science and Technology was requested by Walter W.Hollis, Deputy Under Secretary of the Army (Operations Research), to examine and make recommendations concerning the Army’s assessment of vulnerability of armored vehicles against anti-armor weapons. Accordingly, a Committee on the Review of Army Vulnerability Assessment Methods was formed to conduct the necessary studies” (NRC, 1989). The committee was tasked to conduct a review independently of the Army’s in-house laboratories and contractors to (1) address issues that will help the Army define the objectives of its vulnerability assessment program, (2) define and analyze alternative ways to balance computation and live fire testing in reaching conclusions about vehicle vulnerability, (3) identify technical deficiencies where they exist, and (4) suggest alternatives for improvement as appropriate. The conclusions reached by the committee are given below (NRC, 1989).

1.

A clear distinction must be made between (a) live firings conducted against fully combat-loaded vehicles, and (b) live firings conducted against vehicle components, subsystems, and prototypes during the course of engineering design and development. The latter tests are intended to provide engineering information at minimum cost and expenditure of resources. Combat-loaded, live-fire tests are for a different purpose, namely, to provide an independent check on the general success of the design and development process with regard to the vulnerability of the vehicle to enemy fire with threat weapons likely to be encountered on the battlefield.

2.

The preparation of a ROC (Required Operational Capability) precedes the initiation of design and development of a new combat vehicle. All too often, the ROC underestimates the importance of emerging armor/anti-armor technologies. The result is that by the time the vehicle is ready to



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typesetting files. Page breaks are true to the original; line lengths, word breaks, heading styles, and other typesetting-specific formatting, however, cannot be retained, About this PDF file: This new digital representation of the original work has been recomposed from XML files created from the original paper book, not from the original Board on Army Science and Technology and some typographic errors may have been accidentally inserted. Please use the print version of this publication as the authoritative version for attribution. Review of the Army’s Assessment Methodology for Combat Vehicle Vulnerability to Anti-Armor Weapons C “During the combat-loaded, live-fire testing of the Bradley Fighting Vehicle System (BFVs) in 1986, differences of viewpoint arose among the Office of the Secretary of the Army, the Office of the Secretary of Defense, and the Congress regarding the role and conduct of live-ammunition firings and the interpretation of results in assessing the vulnerability of armored vehicles. To resolve these differences, the National Research Council’s Board on Army Science and Technology was requested by Walter W.Hollis, Deputy Under Secretary of the Army (Operations Research), to examine and make recommendations concerning the Army’s assessment of vulnerability of armored vehicles against anti-armor weapons. Accordingly, a Committee on the Review of Army Vulnerability Assessment Methods was formed to conduct the necessary studies” (NRC, 1989). The committee was tasked to conduct a review independently of the Army’s in- house laboratories and contractors to (1) address issues that will help the Army define the objectives of its vulnerability assessment program, (2) define and analyze alternative ways to balance computation and live fire testing in reaching conclusions about vehicle vulnerability, (3) identify technical deficiencies where they exist, and (4) suggest alternatives for improvement as appropriate. The conclusions reached by the committee are given below (NRC, 1989). 1. A clear distinction must be made between (a) live firings conducted against fully combat- loaded vehicles, and (b) live firings conducted against vehicle components, subsystems, and prototypes during the course of engineering design and development. The latter tests are intended to provide engineering information at minimum cost and expenditure of resources. Combat-loaded, live-fire tests are for a different purpose, namely, to provide an independent check on the general success of the design and development process with regard to the vulnerability of the vehicle to enemy fire with threat weapons likely to be encountered on the battlefield. 2. The preparation of a ROC (Required Operational Capability) precedes the initiation of design and development of a new combat vehicle. All too often, the ROC underestimates the importance of emerging armor/anti-armor technologies. The result is that by the time the vehicle is ready to 78

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REVIEW OF ARMY’S ASSESSMENT METHODOLOGY FOR VULNERABILITY 79 be fielded, the threat environment is more severe and perhaps even different in nature than typesetting files. Page breaks are true to the original; line lengths, word breaks, heading styles, and other typesetting-specific formatting, however, cannot be retained, About this PDF file: This new digital representation of the original work has been recomposed from XML files created from the original paper book, not from the original that called for in the ROC. It is recommended that, as part of the design process, future designs allow for enhancement of ballistic protection during the vehicle’s lifetime. 3. It is important that vulnerability assessments of combat vehicles be as dependable as possible. and some typographic errors may have been accidentally inserted. Please use the print version of this publication as the authoritative version for attribution. Not only are they important in defining the hazards to crew and vehicle, they are essential in assessing vehicle survivability on the battlefield, as well as for many other important Army planning purposes. A complete description of the vulnerability of a vehicle is, however, a complex task. For each attacking weapon and warhead combination, the damage due to attack from all directions and at all ranges must be taken into account. To arrive at vulnerability assessments, therefore, the only recourse is to make use of mathematical models capable of being executed on a high-speed computer, so that the damage due to large numbers of attacks can be assembled. Such models must be supported by an adequate base of data obtained experimentally by firings against armor samples, components, and subsystems. 4. Vulnerability models designed to at least two levels of comprehensiveness are required. For preliminary design purposes, a model is needed which provides relatively rapid estimates at an accuracy level sufficient to compare the relative advantages of competing concepts. At the opposite end of the spectrum, a more detailed model is needed for assessing the vulnerability of a design with best achievable accuracy. The committee has concluded that suitable models for addressing these needs are not currently available and further development is needed. 5. The committee has reviewed the current BRL approach to more accurate model building. It is, in essence, based on the belief that better accuracy will result from models of increasing detail, i.e., models that incorporate the vehicle exterior and interior geometry in relatively minute detail and that trace behind-armor damage virtually fragment by fragment. It is the committee’s opinion that such an approach is not justified because of the inability to forecast with precision the characteristics and performance of ever-evolving threat weapons, and because of the inherently stochastic nature of penetration and behind-armor damage mechanisms. The trend toward increasingly detailed models is not a productive direction and the committee suggests that BRL reconsider its current direction for model design. A lesser degree of detail, using an approach based on a more generic assessment of the vulnerability of major components, would still provide valid vulnerability estimates with reduced data requirements and shorter computational times. 6. BRL is the Army’s principal laboratory responsible for armor/anti-armor technology. Based on a review of the BRL data, encompassing unclassified as well as classified data, but not including sensitive compartmented information, it is evident that there is a significant lack of experimental information, particularly concerning the more sophisticated armor designs and anti-armor weapons represented representative of modern practice. A principal reason appears to be that in recent years the experimental work has tended to be conducted on an ad hoc basis for different development programs. The experimental research program that has been instituted to establish an integrated data base for use as a reference source for future designs and as a guide for formulating further research efforts has been neither coordinated nor comprehensive. The inadequacy of this experimental program is the largest single deficiency contributing to uncertainty in our current vulnerability estimates. 7. One purpose of this study is to better define the role of live-fire tests against fully combat- loaded prototype vehicles. It is important, therefore, to carefully delineate what functions these tests fulfill and, equally important, what they do not add to the process of vulnerability assessment. Specifically, combat-loaded, live-fire tests do not contribute significantly to the assessment of vulnerability in a form needed to support subsequent survivability assessments and for other necessary Army uses. The quantity of data gathered by such tests is too limited in scope and depth to be statistically significant. 8. Combat-loaded, live-fire tests will accomplish the following, provided the test series consists of randomly selected firings with shotlines selected by the procedure outlined in Chapter 5 or its equivalent: • During the interval between the start of the development and design process and the live- fire tests, the threat environment on the battlefield may have changed appreciably. Since the combat-loaded, live-fire tests are to be conducted with weapons constituting updated threat weapons, they provide some assessment of the vehicle performance with regard to vulnerability to weapons not incorporated in the ROC document. • The tests are conducted in an environment of high visibility within the Department of Defense,

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80 APPENDIX C Congress, and, save for the limitations of classified data, the public at large. Knowing typesetting files. Page breaks are true to the original; line lengths, word breaks, heading styles, and other typesetting-specific formatting, however, cannot be retained, About this PDF file: This new digital representation of the original work has been recomposed from XML files created from the original paper book, not from the original that the test results will be carefully observed during the approval process leading to large-scale production, the program manager and his staff will be motivated to ensure that adequate weight is given to vulnerability considerations throughout the design process. and some typographic errors may have been accidentally inserted. Please use the print version of this publication as the authoritative version for attribution. • The tests may uncover vulnerabilities that have not been anticipated and that represent design deficiencies. Experience to date has in fact shown that valuable information of this kind has emerged from combat-loaded tests. • The results of combat-loaded, live-fire tests should not by themselves be construed as a basis for approval or disapproval of the transition to full-scale production. Many additional factors must be taken into account in arriving at this decision. 9. Combat-loaded, live-fire tests do not provide information of significant value for validating vulnerability models, although they may disclose vulnerabilities which have been overlooked in model formulations. The committee recommends that such tests should not be conducted with this purpose in mind. 10. Experience to date with combat-loaded, live-fire tests has indicated that they do produce positive findings helpful in reducing vehicle vulnerability. Many of the findings, however, could have been anticipated by more careful engineering testing conducted earlier and with substantially lower expenditure of resources. 11. To improve future design practices, and particularly to help less experienced designers without extensive “corporate” experience, the committee recommends preparation of a manual of good design practices for combat vehicles to reduce the vulnerability to penetrating rounds. Reflecting a compilation of sound design rules, as well as practices to be avoided, such a manual will help to prevent future mistakes that might result in increased vulnerability. Reference • National Research Council (NRC), Committee on a Review of Army Vulnerability Assessment Methods, 1989. Armored Combat Vehicle Vulnerability to Anti-Armor Weapons, A Review of the Army’s Assessment Methodology, Board on Army Science and Technology, Commission on Engineering and Technical Systems, Washington, D.C.: National Academy Press.