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This Defense Intelligence Reference Document from the Defense Intelligence Agency, dated 1 November 2010, was produced under the Advanced Aerospace Weapon System Applications (AAWSA) Program. It describes nanosatellite technologies and proposes launching nanosats into orbit with laser Lightcraft propulsion. It also covers a weapon mission selection study and multi-megawatt laser options. The author recommends that the Department of Defense and NASA bring Lightcraft R&D back to the United States and restart the X-50LR flight demonstration program.
“The Advance”13 pages
UNCLASSIFIED/ ,era~ 8FFHiil.«1k 1!181! ··•kY deemed possible with emerging MEMS technologies being developed under the National Nanotechnology Initiative for both chemical and FEEP thrusters (see Chapter 2 for details). It was also found that the currently configured composite structure for the Lightcraft forebody must be reduced from 2-ply to 3-ply (with the same ply-thickness) to meet Lightcraft airframe mass requirements. Another important finding in the study was the significant influence of the ground-based laser wavelength (A) on Lightcraft performance. Figure 8 illustrates the adverse beam propagation geometry associated with ETO laser propulsion by means of ground-based lasers. It is seen that beam propagation distances through the Earth's atmosphere are short during initial flight phases when the path length traveled by laser energy to the Lightcraft is least. But during latter flight phases (when the vehicle itself is above the sensible atmosphere) the beam propagation path within the atmosphere is much longer, and power losses due to atmospheric attenuation become ever greater with increasing range. And since power losses due to laser beam spreading - even in vacuo - also increase with increasing distance from the laser, power losses are greatest at the end of laser propulsion (when vehicle distance from the laser is greatest). For a ground-based laser with given aperture diameter, adaptive optics, atmospheric conditions, and radiated power, the laser power collected by the Lightcraft was found to be extremely sensitive to laser wavelength. Here, A determined the amount of radiated laser power lost through "thermal blooming," turbulence, and "extinction" during beam passage through the Earth's atmosphere in addition to the power lost from "diffraction" (beam spreading at longer ranges) during propagation through the vacuum of space. And since each loss mechanism was a function of A, Froning and Davis considered each loss mechanism in their estimation of lost power for the six different laser wavelengths associated with the six different ground-based laser candidates that were evaluated in the study. Shown in Figure 10 (without dimensions) is the fraction of radiated laser power collected by the Lightcraft at maximum laser propulsion range (when necessary "cut- off" velocity for orbital flight is achieved) for the spectrum of wavelengths investigated. It is seen that a significant fraction of laser-radiated power is lost, even if there were no atmospheric transmission losses at all. And additional losses associated with beam propagation through the atmosphere are seen to result in power losses on the order of 75% to 99%. Figure 11 shows that significantly more power would be available at the end of laser airbreathing flight than at the end of laser rocket flight. This might benefit surface-to-air Lightcraft missions that would mainly entail airbreathing flight. 21 UNCLASSIFIED//FlilA. lilFFllil Ck Wli&i a,1k>/
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Report, from the dia collection. The PDF is mirrored here; the original link is above. 77 pages are in the text index: search them above, or from the library's search.