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This Defense Intelligence Reference Document was prepared by the Defense Intelligence Agency's Defense Warning Office and dated 31 March 2010. It was produced under the Advanced Aerospace Weapon System Applications Program. It reviews chemical, solid-state, fiber, ultra-short pulse and free-electron lasers, as well as beam control, atmospheric propagation, DoD laser history and how spacecraft could be damaged by lasers. It projects that electrically powered lasers could enable MW-class weapons and spacecraft laser weapons within 20 years. It ends with shielding recommendations for spacecraft.
From the source:Release of 2026-09-18 Incident: 3/31/10, Las Vegas, Nevada. Released with redactions. This document is a Defense Intelligence Reference Document (DIRD), a technical reference format used by the Defense Intelligence Agency (DIA) to capture baseline knowledge on a specific topic for later analytic use. DIRDs are best understood as reference and synthesis products rather than as original research. It is one of 38 DIRDs produced under the Advanced Aerospace Weapon System Applications Program (AAWSAP) between 2009 and 2011. Because AAWSAP’s scope permitted a broad range of supporting topics, not every DIRD in the series directly concerns aerospace systems or future threat assessment. The following summary reflects the DIRD’s scope and framing at the time of writing and should not be read as implying current validation of the concepts discussed. This DIRD surveys the development of high-energy laser weapons and notes that, although lasers had already become important military tools for ranging, guidance, and other lower-power uses, true weapon-class systems remained limited by power generation, beam control, atmospheric propagation, and logistics. The report reviews major laser types along with the optical, tracking, and thermal-management systems needed to make them militarily useful. It argues that high-energy lasers can offer important advantages over kinetic weapons in speed, precision, and low collateral damage, especially against softer or fast-moving targets, while also emphasizing that practical deployment has long been hindered by hazardous chemical fuels, thermal blooming in the atmosphere, power-supply constraints for mobile systems, and waste-heat removal.
UNCLASSIFIED/ fFOA. OFFICIAL WSE er•tv The lower atmosphere is a difficult medium through which to propagate a laser beam. The molecules which make up the atmosphere and the aerosols which are suspended in it can scatter and absorb light, reducing the number of photons which arrive at the target. These effects are collectively referred to as "atmospheric extinction." Atmospheric ducting can bend the laser beam (this causes mirages), and atmospheric turbulence or thermal blooming (explained later) can enlarge the spot. These effects combine to reduce the beam's irradiance (measured in watts/cm 2) on the target and its effectiveness. Some are almost independent of wavelength while others can vary dramatically with small changes in wavelength. As a result, the wavelength for a laser weapon which operates in the lower atmosphere must be carefully chosen. Scattering occurs when photons strike molecules or aerosols in the atmosphere and are reflected away from the target direction. This effect is commonly observed in haze or fog but always exists, even in the clearest of skies. For example, as much as 50 to 75 percent of a laser beam's energy can be lost over a 10 km lower atmosphere path on a fairly clear day. Within reasonable limits, this reduction in photons reaching the target can be accommodated by increasing the laser power or reducing the range to the target. The losses due to scattering vary quite slowly with changes in wavelength; longer (infrared) wavelengths are less affected than shorter (visible) as can be seen from the green curve in Figure 12. Absorption occurs when molecules or aerosols in the atmosphere absorb some of the photons. This phenomenon, caused by resonant interaction, is very strongly dependent on wavelength and can vary by orders of magnitude with wavelength changes of a fraction of a micron (red curve in Figure 12). Extinction (the sum of absorption and scattering) is shown by the yellow curve in Figure 12 and for a low-power laser, there is no apparent difference as both effects simply reduce the number of photons which strike the target. However, if enough energy is absorbed in the laser beam's path (when using a high-power laser), it heats slightly which causes a distortion and defocusing of the laser beam. This effect is called thermal blooming and can be a significant limit on the performance of a lower atmosphere based MW-class laser system. It was a key reason (beyond the desire to eliminate chemicals) why the Navy abandoned development of DF chemical laser weapons for self-defense where thermal blooming is at its worst. One can see from Figure 12 that wavelengths around 1 μm, 1.2 μm, 1.6 μm and 2.2 μm offer the lowest absorption windows. Unfortunately, no MW-class lasers existed at those wavelengths and no candidates were apparent. For this reason, the Navy began the development of FEL technology which can be tuned to any desired optical or infrared wavelength. UNCLASSIFIED/ fFOA QFFl€1AL WSE 8NLY 15
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Official release, from the pursue collection. The PDF is mirrored here; the original link is above. 31 pages are in the text index: search them above, or from the library's search.