AAWSAP DIRD, Laser Lightcraft Nanosatellites, November 2010

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In order to launch a laser-propelled Lightcraft nanosat or picosat from the ground, sea,
or air, it will be necessary to control and steer the high-energy laser (HEL) beam, while
at the same time making real-time adjustments to account for platform motion, optical
train and atmospheric effects on beam propagation, so that the beam maintains high
quality, low-loss, precision contact with the Lightcraft from launch all the way up to
LEO. While the atmospheric effects on laser beam propagation were briefly discussed
in the Lightcraft Nanosatellite Configuration section of Chapter 2, a more in-depth
examination of this phenomenon can be found in Reference 32. In what follows, we
briefly discuss what a HEL beam control system is designed to do and what innovations
were recently developed by the various DoD directed energy weapons programs that
are just now being successfully tested and deployed.
A beam control system is designed to:tt
•
Acquire and precisely track a designated target.
•
Handles the HEL beam emitted from the laser:
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Aligns the HEL beam to the optical train's axis - from the laser resonator to the
beam director's exit aperture.
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Safely relays the HEL beam through the optical train with minimal loss of
energy and beam quality.
•
Expands the HEL beam and focuses it at the range of the target.
•
Places and maintains the HEL beam on the desired target's aimpoint.
•
Corrects for beam quality degradations in the optical train or the atmosphere (if
needed).
HEL weapons usually have high-power optical trains containing more than a dozen
mirrors. However, these systems need to be far more compact with minimal high­
power trains. As directed energy weapon applications begin to employ smaller HEL
systems, the size, weight and complexity of the accompanying beam control system
has come down as well. The typical HEL beam control system includes: ** 1) a gimbaled
beam director, 2) tracking and pointing functions, 3) adaptive optics, 4) acquisition
sensors, and 5) target illuminators. Solutions have been recently developed to drive
towards a smaller, lighter and simpler beam control system while considering the entire
end-to-end system architecture. Existing beam control solutions are robust but large
and complex. The technical strides achieved in the past 20 years in wavefront sensing,
aperture sharing elements, beam tracking and beam correcting provide new tools to
offer a simplified low mirror count beam control system while retaining the ruggedness
of function necessary for a laser weapon.
Figure 33 and Figure 34 show schematics of a notional inertially-stabilized
pointer/tracker mount and beam control system that was developed by NAVSEA's
DE&EWS Program.
ttD. Kiel, Directed Energy Systems Symposium Short Course, Naval Post-Graduate School, Monterey, CA, 2010.
**D. Kiel, Directed Energy Systems Symposium Short Course, Naval Post-Graduate School, Monterey, CA, 2010.
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