AAWSAP DIRD, Laser Lightcraft Nanosatellites, November 2010

This Defense Intelligence Reference Document (DIA-08-1011-001), dated 1 November 2010, was prepared by the Defense Intelligence Agency's Defense Warning Office under the Advanced Aerospace Weapon System Applications program. It covers nanosatellite technologies, laser Lightcraft propulsion, a weapon mission selection study and a multi-megawatt laser study. The author recommends that the Department of Defense, working with NASA, bring laser Lightcraft propulsion research back to the United States and restart the Air Force X-50LR test flight program.

From the source:Release of 2026-09-18 Incident: 11/1/10, 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 examines laser-propelled “Lightcraft” as a possible low-cost method to launch very small satellites into low Earth orbit by using a remote high-energy laser to supply most of the propulsion energy rather than relying entirely on onboard energy sources. The report combines a survey of nanosatellite trends with a review of “Lightcraft” propulsion concepts, vehicle design, beam-control requirements, and mission studies, and argues that the most promising application is the launch of nano- or pico-satellites, especially Earth- and space-observing payloads of a few kilograms or less. It presents the concept as potentially much cheaper than conventional multistage rockets for very small payloads, while also noting significant practical constraints including strict beam-riding geometry, atmospheric losses, demanding pointing and adaptive-optics requirements, and heavy dependence on large ground-, sea-, or air-based laser infrastructure. Overall, the document presents laser “Lightcraft” as a technically plausible launch concept whose attractiveness depends on whether the supporting laser and beam-control system can be made reliable and economical at operational scale.

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Figure 30. Free-Electron Laser Electron Beam Phase-Space Evolution (courtesy of the Naval
Post-Graduate School FEL Lab).
In the quantum picture of how FELs operate, the "wiggling" electrons rad iate light and
that light then gets stored between the resonator mirrors. And additional light radiation
(that enters the resonator) in the presence of "stored light" results in stimulated
emission, which is the lasing process. The classical interpretation of this process is that
the electrons travel with the light radiation and exchange energy with it. Some
electrons gain energy while some lose energy to the light radiation. The electrons in
the beam will "bunch" within each optical wavelength, thus these bunched electrons will
radiate coherently to produce laser light. This mechanism is represented graphically in
Figure 29 and Figure 30.
The main appeal of free-electron lasers (FELs) is that they can be built for emission
frequencies ranging from the terahertz region, through t he infrared and visible
spectrum, up to X-rays. Also, a single device often allows wavelength tuning over a
large range and the output power can be scaled up very high. As in many spectral
regions, it is not easy to make resonator mirrors; many FELs work without such mirrors
and rely on amplified spontaneous emission. This can still be relatively efficient if t he
gain is high enough. One then actually has a superluminescent source. The big
disadvantage of FELs is t heir very large and expensive setup; they can only be used at
large facilities. The benefits of FE Ls are :
• Continuously wavelength tunable, i.e., they can produce different wavelengths
during operation.
• Desig nable to produce a range of wavelengths, from microwaves to X-rays.
• Scalable to very hig h beam power because they use a vacuum for t heir gain
medium - laser medium cannot be damaged.
• Not affected by heat problems t hat are common in other laser technologies .
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