0191-9067/85 $3.00 + .00 Copyright ® 1985 SUN SAT Energy Council ADVANCED SCHEME OF CO2 LASER FOR SPACE PROPULSION KAZUO MAENO Muroran Institute of Technology 27-1 Mizumoto, Muroran Hokkaido, 050 Japan Abstract — An improved scheme of CO2 mixing laser with glow discharge is investigated for the purpose of laser propulsion experiments utilizing a solar cell array on the space station. The analyzed characteristics of this CO2 mixing laser show favorable results without catalyst He, which corresponds to the distributions of measured small signal gain coefficient in our fundamental experiments. While employing this improved scheme of CO2 laser, the specific features of space laser propulsion experiment in the 1990s are studied. INTRODUCTION Recent developments in the investigation of high power lasers make it possible to consider a scheme of laser propulsion, which has the favorable specific impulse range of 500-2000 sec for orbital transfer of subsatellite (1,2). Typical laser candidates and their characteristics attainable today for laser propulsion are indicated in Table 1. Considering the features in this table, it may be remarked that CO2 electric discharge laser (EDL of high speed subsonic, or supersonic) is the most suitable for the experiments of laser propulsion in the 1990s. This paper concerns the scheme of supersonic or high speed subsonic CO2 EDL with gasdynamic mixing that seems to give more improved performance (3,4) than conventional premixed CO2 EDLs. SUPERSONIC CO2 MIXING EDL The concept of supersonic CO2 mixing laser, in which the laser energy is supplied by DC glow discharge in supersonic N2 flow, has the merits of high mass flow rate with supersonic velocity (high power) and low translational temperature (high efficiency) by adiabatic expansion. It shows the favorable practicability in 10.6 gm radiation for space energy transmission. Figure 1 indicates a tentative nozzle arrangement of supersonic CO2 mixing EDL investigated in preliminary research at our institute. In this concept of CO2 mixing EDL, N2 in the plenum chamber is guided into supersonic conical nozzles with adiabatic expansion. Then it is vibrationally excited by radial glow discharge to mix with separately expanded CO2 through the inner conical nozzles at the exit of screen nozzle (12 coaxial arrays). Utilizing this experimental setup, the small signal gain coefficient was measured. A numerical analysis was also conducted to estimate the performance of this laser scheme. The flow in the laser device is partitioned into several sections of the separated supersonic nozzle expansions of N2 and CO2, glow discharge section in
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