The 2,492nd Meeting of the Society

March 22, 2024 at 8:00 PM

Powell Auditorium at the Cosmos Club

The Emerging Directed Energy Weapons

Are they finally ready to provide real military capability?

Thomas J. Karr & James Tribes

Thomas J. Karr
Defense Science Board and the Air Force Scientific Advisory Board
Chief Scientist for Sensors and Directed Energy, The MITRE Corp
Principal Owner, Alamo Scientific LLC

James Tribes
Principal Director for Directed Energy
Office of the Director of Defense Research and Engineering for Modernization
US Department of Defense

Sponsored by PSW Science Member Edward Gadasu

About the Lecture

High power microwave sources first appeared prior to World War II. Lasers were invented in 1960. Both have the potential to become revolutionary military weapons. Despite major military investments by multiple nations over the last 60 years, their potential has not been realized. In the last several years both microwave and laser technology has improved considerably. This has resulted in the development, testing, and operational demonstration of numerous directed energy weapons. Directed energy weapons may be on the threshold of becoming used by multiple nations.

What are they? How do they work? What missions are they being developed for? What will be their benefits? How will they achieve useful military effects What is the United States developing? What are other countries developing? What are the major limitations? What are the key challenges that still need to be overcome before directed energy weapons become part of military arsenals?

This lecture by the two former Directors of Directed Energy Weapons for the U.S. Department of Defense will provide some answers to these questions.

Selected Reading & Media References
(1) “The New Laser Weapons,” Thomas Karr and James Tribes, Physics To-day 77 (1), 32-38 (1 January 2024);
(2) Department of Defense Directed Energy Weapons: Background and Issues for Congress, Congressional Research Service, 22 Aug 2023,
(3) Directed Energy Weapon Supply Chains: Securing the Path to the Future, NDIA/ETI, January 2024
(4) “All 11 US Super Carriers At ‘Grave Risk’, The EurAsian Times, 22 Nov 2023
(5) N. Bloembergen et al., Physics and Limitations of DEW for Missile Defense, Rev. Mod. Phys. 59, S1 (1987). A comprehensive reference on directed energy weapons still available as a downloadable PDF.
(6) “Missile Threat,” Missile Defense Project, CSIS,
(7) B. Manz, “High-power microwave systems—getting (much, much) closer to operational status,”, 24 Jan 2023
(8) T.H. Loftus et al., IEEE J. Sel. Top. Quant. Elec. 13, 487 (2007)
(9) G. D. Goodno, J.E. Rothenberg, Coherent Laser Beam Combining, A. Grignon, ed., Wiley (2013), p. 3
(10) M.D. Perry et al., “Laser containing a distributed gain medium,” US Patent 6,937,629 B2 (30 Aug 2005)
(11) W.F. Krupke, Prog. Quant. Elec. 36, 4 (2012)

About the Speaker

Thomas J. Karr
Thomas Karr is Special Government Employee for the Undersecretary of Defense for Research & Engineering (OUSD/R&E), the Defense Science Board, and the Air Force Scientific Advisory Board. He is also Chief Scientist for Sensors and Directed Energy at MITRE Corporation, and he is the owner of Alamo Scientific, LLC. Previously Tom was Principal Director for Directed Energy in the OUSD/R&E, Program Manager in the DARPA Office of Strategic Technology, Director of Innovative System Solutions at Raytheon Space & Airborne Systems, among numerous other positions in reseach and technology development.

Tom’s research interests include national economic and military security strategy; remote sensing of the Earth and space; commercial space industry development; relativistic quantum sensing and information; laser pulse interactions with matter; and electromagnetic propagation through air, water, plasma, and nano-structured matter.

At OUSD/R&E Tom managed all DoD directed energy research, development, test and engineering. At DARPA he led the development of autonomous precision navigation systems that do not require GPS and conceived and directed the development of synthetic aperture laser radar for high-resolution imaging of deep space objects. At Lawrence Livermore National Laboratory (LLNL) he led a re-design of US “national technical means” of intelligence collection, resulting in new US intel architectures; led the development and commissioning of the first system predicting SCUD missile impact points while in flight; and discovered fundamental properties of high power laser propagation through the atmosphere, confirming all predictions by experiment. Also at LLNL he discovered a new relativistic wave equation for interacting spin-½ particles, and applied this wave equation to quarks bound into pions, revealing additional internal structure in pions beyond the standard model of colored gluons. Tom also o-founded the first US commercial radar satellite company, RDL Space Corp. He is an author on 64 publications in scientific journals and inventor on three patents.

Among many honors and awards, he received the DARPA Meritorious Public Service Medal, is an Optica Fellow, a Fellow of the Military Sensing Symposium, and a Fellow of the Society of Photo-Optical Instrumentation Engineers (SPIE). He has also held visiting fellowships at the Center for Theoretical Studies at the University of Miami, as a Joliot-Curie Fellow of the Commissariat a l’Énergie Atomique de France and the Centre d’Etudes Nucléaires Université Pierre et Marie Curie in Paris, at the Center for Theoretical Physics at the Univeristy of Miami, and twice at the University of Maryland.

Tom earned an AB in Physics at Princeton University and a PhD in Physics at the University of Maryland.

James Tribes
James Tribes is Special Government Employee of the Office of the Under-Secretary for Defense for Research and Engineering (OUSD/RD) supporting directed energy weapons efforts, the Missile Defense Agency, and the Defense Science Board. Previously, he was Principal Physicist for Directed Energy for OUSD/RD and the Principal Director for Directed Energy for OUSD/RD. Before joining OUSD/RD Jim was with Lawrence Livermore National Laboratory for almost 40 years, where he served as a Group Leader, Division Leader for Medical Technology and Biophysics, Division Leader for Applied Physics, and Division Leader for Physics.

Jim has worked on a broad range of topics including x-ray lasers, laser fusion, nuclear weapons physics, nuclear weapons engineering, x-ray optics, x-ray imaging, space technology, detectors, biophysics, bio-detection, night vision, military special operations technology, medical technology, tomography, nuclear non-proliferation, intelligence analysis, quantum science, and conventional weapons technology.

Jim is an author on 62 scientific publications and an inventor on seven patents. Among other honors and awards he is a Fellow of the American Physical Society and served on advisory boards for both the Texas A&M Aerospace Department and the UC Berkeley Nuclear Engineering Department.

Jim earned a BS in Physics at Georgia Tech and a PhD in Physics at Yale.