AAWSAP DIRD, Laser Lightcraft Nanosatellites, November 2010

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UNCLASSIFIED/;'POR: OPPICIAE USE 014Lf
An outline of the conceptual design features of the proposed 10 MW electron gun-driven
CO2/gas mixture laser is [29]:
• Scalability of total beam output power, beam combining concept.
• Power oscillator or master oscillator-power amplifier (MOPA) design.
• Unstable optical resonator cavity with grating and rotating mirrors beam-combine
techniques.
• Flow and gas handling system with blow down and exhaust to the atmosphere.
• Acoustics suppression with expansion horn downstream and anode muffler.
In this concept there are four separate laser transmitters each generating 2.5 MW
output beams that are combined into a single 10 MW output beam. The oscillator
parameters for each beam transmitter are [29]:
• Energy loading, Ep: Ep = 300 J (higher loadings at reduced gas temperature);
gain volume= 0.27 m3 (x 4 lasers); A to K = 0.3 m; gain length = 3 m.
• Specific laser output = 65 J/1.
• Estimated extraction efficiency = 20%.
• Pulse repetition rate: 125 Hz@ 20µs.
• Laser power, P = 2.5 MW/beam x 4 beams = 10 MW.
• Laser energy per pulse = 18 kJ/beam x 4 beams = 72 kJ.
• Output wavelengths: 10.6 µm, 10.2 µm, 9.6 µm, and 9.3 µm (mixed).
• Gas mixture ratio (for N2:CO2:H2): 3:1:0.08.
• Gas pressure = 1.013 x 105 Pa (or 1 atmosphere).
• Flash factor = 1.3.
The optical resonator cavity and optical components specifications are [29]:
• Resonator type: confocal unstable with rotating mirrors beam combining.
• Magnification, M = 4.
• Cavity length, L = 36.5 m.
• Equivalent Fresnel number = 3.4.
• Cavity end mirrors radius of curvature: RMirrorl = 97.3 m (concave), RMirror2 = 24.3
m (convex).
• Gain cell: volume = 0.3 x 0.3 x 3.0 m3, length = 3 m.
• Beam combine mirrors: 75 x 75 cm2 flat (30 x 30 cm2 apertures) @ "' = 10.59
µm.
• Low pressure hot cell: 0.3 to 0.5 GHz suppression near line center.
• Output scraper mirror: D = 0.075 m (taped).
See Figure 16 and Figure 17 for schematics of the power oscillator optics and the MOPA.
The laser operation requirements for the gas flow system are (see Figure 18) [29]:
• Flow System: blow down.
• Gain Section
•
Cross-section, A = 0.3 m x 3.0 m = 0.9 m2.
•
Volume, V = 0.3 m x 0.3 m x 3.0 m = 0.27 m3•
•
Flow speed, u = 50 m/sec (@ 125 Hz & flash factor= 1.3).
•
Dynamic pressure, ~P = 2000 Pa (or 0.02 atmospheres).
•
Mass flow rate, Q = 60 kg/sec per module (45 m3/sec std).
•
Run time, t = 300 seconds
UNCLASSIFIED'I i'FAA: 061i1Clali.k W&& 8PtLY
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