AAWSAP DIRD, Laser Lightcraft Nanosatellites, November 2010

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Chapter 4: Summary of Multi-Megawatt Laser Study for
Lightcraft Propulsion Applications
SUMMARY OF LASER STUDY PERFORMED BY TEXTRON SYSTEMS
In 2002, V. Hasson (TEXTRON Systems Corporation) conducted a study of candidate
multi-megawatt laser systems for laser Lightcraft propulsion [29].
Candidate high-power/high-energy lasers identified in the study:
• Carbon Dioxide (CO2) Laser: technical issues include large wavelength and
atmospheric absorption of the laser beam.
• Carbon Monoxide (CO) Laser: technical issues include large wavelength,
atmospheric absorption of the laser beam, and toxicity of the lasing fuel (CO
gas).
• Hydrogen Fluoride (HF) or Deuterium Fluoride (DF) Laser: technical issues include
atmospheric absorption of the laser beam, corrosive lasing fuel chemicals, pulse
energy, running cost, and beam quality.
• Chemical Oxygen-Iodine Laser (COIL): technical issues include fuel chemicals,
pulse energy, and running costs.
• Bulk Slab Solid-State Laser (BSSSL): technical issues include cost, average
power, and run duration.
The first four gas dynamic and chemical laser candidates have already demonstrated
megawatt-class average beam output power. The study then reviewed the
development, testing and operational legacy of the first candidate laser technology,
which included a review of the various system architectures that use other gas mixtures
combined with CO2. The study recommended a new design for a 10 MW (beam output
power) electron gun-driven CO2/gas mixture laser because this technology does not
require additional R&D and can be implemented now. The other gases selected for the
lasing fuel are N2 and H2, which, in combination with CO2, offer superior performance
over systems using helium.
However, very recent technologically disruptive innovations led to the 10-fold increase
in the beam output power of bulk slab SSLs and their newly emergent solid-state
cousin, called high-power fiber lasers, which has made these devices more competitive
with high-power chemical and gas dynamic lasers on the basis of average beam power,
peak beam power, electrical wall plug and optical efficiencies, cost, complexity, mass,
and size. Free-electron lasers are another class of laser technology that was not
reviewed by Hasson, but recent technological innovations are accelerating their
development to the point where their present average beam output power of 20 kW will
be increased to 100 kW or higher within the next 12 to 24 months following the
publication of this report. The output beams of several of these laser devices can be
optically combined to produce a single beam with megawatt-class average output
power. It is for this reason that we will summarize their technology in Summary of
Emergent High-Power Solid-State and Free-Electron Laser Technologies section.
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