Another look back at gas lasers

May 4, 2015
Jeff Hecht's article "Gas lasers: Durable survivors evolve new forms" in the March 2015 issue of Laser Focus World provided many fond memories of our early days in the new field of lasers and an excellent perspective on how the gas laser has subsequently evolved.

Jeff Hecht's article "Gas lasers: Durable survivors evolve new forms" in the March 2015 issue of Laser Focus World provided many fond memories of our early days in the new field of lasers and an excellent perspective on how the gas laser has subsequently evolved. Of course, if one overturns this many historical rocks, it is to be expected that a few nits are to be found by the readers. There are two familiar to me that I believe are worth mentioning.

The first is minor, but I have always been proud of our "white light" gas laser, which we demonstrated in those early days.1 That brief note reports our lasing an optimized argon-krypton gas mixture to obtain a radiatively balanced primary color mixture to give a white-light beam output. Interestingly, a few years ago, when assisting Lockheed Martin Aculight with its RELI fiber laser program, it occurred to me that the concept of their spatial beam-combined (SBC) laser is very similar to that of our 45-year-old white light (WL) laser—namely for multiple wavelength laser outputs to all exit in a single beam from the laser system!

The closure of the NASA Electronics Research Center (Cambridge, MA) unfortunately curtailed further work on this WL laser; also, NASA lost our patent application. Thus, very little more was heard about it, but I would have enjoyed seeing recognition of this novel gas laser in Jeff's article.

My second item deals with Jeff's comments about the demise of the last megawatt-class gas laser weapon system, the COIL-based Airborne Laser (ABL) system. He states, as do many others, that the chemical oxygen-iodine laser had run years behind schedule, billions of dollars over budget, and the Pentagon pulled its budget since it lacked the range to shoot down boost-phase missiles. Having led the small group of experts at Lockheed (no Martin yet in 2002!) that designed the innovative beam control and fire control systems that was chiefly responsible for the target range achieved by the ABL system, I am compelled to comment! Unfortunately, much of ABL's design and performance information is restricted to U.S. Government employees only, so I must carefully limit my comments. But there is much open literature information available on Team ABL's (Boeing, TRW/Northrop Grumman, and Lockheed Martin) YAL-1 websites. Another information site, full of links to other ABL data, is the Wiki ABL website: http://en.wikipedia.org/wiki/Boeing_YAL-1.

First, it must be stated that the ABL program was to provide a remotely located, speed-of-light deterrent means that our country didn't have then-an ability to kill boosting short-range-capability Theater Ballistic Missiles (TMDs) like the Scud then believed to have struck the billet in Dhahran, Saudi Arabia, that had recently killed 27 GIs. The program was to start with a short-target-range, so-called PDRR system, which would be followed by a full-target-range, so-called EMD system. The first would demonstrate that the risks associated with this complex system were solved-a boost-phase missile could be killed (albeit at modest range) and the government could then proceed with a second, upgraded system, which would wring out any remaining engineering and manufacture risks associated with then producing a number of fully operational weapon-grade systems.

Indeed, as Jeff indicated, ABL could not meet its ambitious schedule. There are too many reasons to discuss here, but it started with the loss of Lockheed's ITEK optics technology subcontractor, followed by the loss of our optical coaters who went to commercial "dot-com-bubble" work, and generally our finding that the prior large optical technology infrastructure support system had deteriorated and had to be rebuilt. Such a stretch of schedule of course was responsible for a commensurate stretch of spending as Jeff stated. But finally, as announced by MDA on Feb. 11, 2010, the program demonstrated a remote kill of a fast-moving, slender boosting missile.2 But was it at a military significant range? No, it was by the PDRR and, hence, it was not configured to do so. But its risk reduction demonstration quieted those many naysayers who said the MW-class beam propagation through the atmosphere was impossible and that we could never hold our focused beam on such a small, remote, and fast-moving target for sufficient time to cause its destruction. And the demonstration indicated that a more powerful EMD-like system with enhanced laser power would likely demonstrate a military range capability.

But as long-duration programs frequently do, the world changes as they proceed. Other laser weapon systems, almost exclusively using our ABL Beam/Fire Control design, seemed to show that smaller tactical systems were in the offing. Other missile-based counter-boost phase missile concepts were also progressing. And the military was becoming less tolerant of the logistics trail of a MW-class chemical laser like COIL, especially when newer developments in the electrical laser arena appeared near-term. So it was that although ABL demonstrated what its PDRR was meant to do, the move to the full-target-range-capable EMD was not made. As an MDA executive later explained to our audience at a Lockheed Martin all-hands meeting, although our beam control system design worked fine and would likely be retained for the next-generation airborne laser weapon system, the chemical laser would not since it could not meet evolving military requirements.

REFERENCES

1. E. T. Leonard, M. A. Yaffee, and K. W. Billman, Appl. Opt., 9, 5, 1209 (May 1970).

2. See http://www.mda.mil/news/10news0002.html.

Ken Billmanis the owner and manager of Ken Billman Energy & Photon Systems; (650) 215-8739.

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