APS: Star Wars 'A Decade or More Away'

Editor's Note: On April 23, the American Physical Society released the findings of a special study group on the science and technology of directed energy weapons such as those proposed in the Strategic Defense Initiative. The 424-page report concludes that the technology for these weapon systems would have to improve by factors of 100 to 1 million or more before they would perform acceptably. The following excerpts are taken from the executive summary and first chapter of the report. The American Physical Society (APS) convened this Study Group to evaluate the status of the science and technology of directed energy weapons (DEW). The evaluation focuses on a variety of lasers and energetic particle beam technologies for their potential applications to the defense against a ballistic missile attack.... The APS charged the Study Group to pro duce an unclassified report, which would provide the membership of the Society, other scientists and engineers, as well as a wider interested audience, with basic technological information about DEW. It is hoped that this report, detailing the current state of the art and the future potential of DEW for strategic defense purposes, will serve as a technical reference point for better-informed public discussions on issues relating to the Strategic Defense Initiative. Major Conclusions Although substantial progress has been made in many technologies of DEW over the last two decades, the Study Group finds significant gaps in the scientific and engineering understanding of many issues associated with the development of these technologies. Successful resolution of these issues is critical for the extrapolation to performance levels that would be required in an effective ballistic missile defense system. At present, there is insufficient information to decide whether the required extrapolations can or cannot be achieved. Most crucial elements required for a DEW system need improvements of several orders of magnitude. Be cause the elements are interrelated, the improvements must be achieved in a mutually consistent manner. We estimate that even in the best of circumstances, a decade or more of intensive research would be required to provide the technical knowledge needed for an informed decision about the potential effectiveness and survivability of directed energy weapon systems. In addition, the important issues of overall system integration and effectiveness depend critically upon information that, to our knowledge, does not yet exist. The following observations elaborate on the above finding. We estimate that all existing candidates for directed energy weapons (DEWs) require two or more orders of magnitude, (powers of 10) improvements in power output and beam quality before they may be seriously considered for application in ballistic missile defense systems. In addition, many supporting technologies such as space power, beam control and delivery, sensing, tracking, and discrimination need similar improvements over current performance levels before DEWs could be considered for use against ballistic missiles. Directed energy weapon candidates are currently in varied states of development. Among the many possibilities, infrared chemical lasers have been under study for the longest period and several high power laboratory models have been built. However, because of their long wavelengths and other technical features, these lasers are perceived to be less attractive candidates for BMD [ballistic missile defense] weapons even though they are closest to the required performance levels in a relative sense. Free electron lasers and excimer lasers are currently perceived as more attractive candidates for BMD missions; but few high power laboratory models have been operated, and the scaling required to reach relevant power levels is estimated to be greater than that for chemical lasers. Nuclear-explosion-pumped X-ray lasers, although the subject of much public discussion, are currently under study at the research level. In our opinion, their BMD potential is uncertain. Charged and neutral particle beam devices build on an existing base of accelerator technology but require considerable extrapolations beyond current performance levels. Supporting technologies are also in varied states of development. In many areas, re search is progressing at a rapid pace, for ex ample schemes for rapid steering of optical beams, and active systems for tracking to microradian class or better. Other critical technologies, such as the techniques for interactive discrimination, are being conceived and addressed. The same caution de scribed above for DEWs applies here, namely, proposed supporting technologies need to be systematically studied before their performance at parameter levels appropriate to BMD applications can be realistically evaluated. Like any defensive system, an effective DEW defensive system must be able to handie an evolving and unpredictable missile threat. In addition to retrofit and redesign of the missiles themselves, decoys and other effective penetration aids can be developed by the offense over the long times required to develop and deploy ballistic missile defenses. In contrast to the technical problems faced in developing DEWs capable of boost phase kill for defense systems, the options available to the offense, including direct at tacks on DEW platforms, may be less difficult and costly to develop and may require fewer orders-of-magnitude performance improvements. A successful BMD system must survive, but survival of high value space-based assets is problematic. Ground-based assets of DEW systems are also subject to threats. Architectures which address the responsive threat are still in their infancy. As an overall BMD system employing directed energy weapons becomes more complex, the currently unresolved issues of computability, testability, and predictability become increasingly critical…. Perspective Group notes that predicting the course of technological progress can be particularly difficult. Very optimistic predictions are of-ten made for technologies or schemes which are at very early stages of development. Whenever orders of magnitude of improvement are necessary in operating parameters, it is likely that many new discoveries and inventions will have to be made. The discrepancy between the present state of the art of DEW and the ultimate requirements is so large that major gaps in technical understanding must be closed before engineering technology verification could become productive. Forcing immature technology to this verification phase can have two undesirable consequences. First, it tends to freeze technology at levels inadequate for its ultimate goals. And second, it tends to absorb resources which could otherwise be used for research on more promising ideas. Past experience with the progression from theoretical concept, via proof of principle, understanding of details, technical development, engineering, to eventual deployment in a very large system, shows that technology typically is frozen several years before deployment, and basic science more than a decade before that. Because of the extensive development needed in many technological areas important to the systems, we judge that the deployment of a substantial DEW component in a BMD system cannot be foreseen before the year 2000. The offense can use the long development test, and deployment time to respond with similar, or dissimilar, technological developments. The Group did not review classified intelligence information about the likely technological responses from the Soviet Union, but rather relied primarily on general scientific and engineering principles in considering potential countermeasures. The un certainty about the responsive threat, in turn, may raise the requirements for lethality and will make survivability more uncertain. A deployed DEW defensive system may have to face the threat of DEW on the offensive side, in addition to all other conventional threats. If a DEW system is capable of disabling a ballistic missile in the boost or post-boost phase, it is likely that is also meets the lethality requirements against a space platform. Because achieving the ultimate goal of population defense appears so difficult from a technological point of view, many people have advocated more limited missions for DEWs, including antisatellite (ASAT) weapons and target discrimination. DEW requirements can be considerably lower for these reduced objectives. The role of DEW could be minor, if not negligible, in case only hard-point defense of land-based silos is contemplated. Limitations in Scope The sheer size of the technological development of DEW, let alone deployment, is such that it raises questions about manpower and economic cost. Engineering manpower requirements are likely to be high. The Group believes that these are very important issues, and should be studied because of their possible impact on civilian economy, inter national competitiveness, armed services, and technical manpower. The Group notes the existence of these issues but does not address them and it refrains from conclusions in this respect. Another important issue which has not been dealt with in detail is launch costs. Deployment of any BMD system with extensive space-based components will require that the cost of placing mass in orbit be significantly reduced. We have not evaluated the prospects for success in this endeavor. However, it is worth noting that such major cost reductions would also pro duce major changes in the nature and capabilities of the offensive threat. Finally, this study does not deal with the very important issue of cost effectiveness of directed energy weapons in their use in ballistic missile defense.... From Report to the APS of the Study Group on Science and Technology of Directed Energy Weapons. Copies are available from APS, 2000 Florida Ave., N. W, Washington, DC 20009. The cost is $50 for members, and $200 for non-members. It also is scheduled to be published in July or August in Reviews of Modern Physics. The cost for a reprint will be $20. THE APS Study Group Consisted of: Nico Bloembergen (co-chairman), Harvard University C.K.N. Patel (co-chairman), AT&T Bell Laboratories Petras Avlzonls, Air Force Weapons Laboratory, Kirtland A.FB. Robert Clam, Sandia National Laboratories Abraham Hertzberg, Aerospace & Energetics Research Program, University of Washington Lt. Col. Thomas H. Johnson, U.S. Military Academy, West Point Thomas Marshall, Columbia University Bruce Miller, Sandia National Laboratories Walter Morrow, Lincoln Laboratories, Massachusetts Institute of Technology Edwin Salpeter, Newman Laboratory for Nuclear Studies, Cornell University Andrew Sassier, Lawrence Berkeley Laboratory Jeremiah Sullivan, Physics Department, University of Illinois James C. Wyant, Wyko Corp. Amnon Yariv, Department of Applied Physics, California Institute of Technology Richard N. Zare, Department of Chemistry, Stanford University AJ. Glass (principal consultant), KMS Fusion, Inc. L. Charles Hebel (executive officer), Palo AltO Research Center.

APS: Star Wars 'A Decade or More Away'

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