From the abstract of the report:
“Laser propulsion is the production of high specific impulse rocket thrust using a high-energy laser as a remote power source. Specific impulses in excess of 1000 sec are achievable because propellant temperatures are very high and low molecular weight gases can be used. This report highlights the research status of the fourth year of AFOSR sponsored work for converting the laser energy, and reports the results of ongoing experiments using laser sustained plasmas as the conversion mechanism. Major new findings from our spectroscopic techniques to diagnose the laser-sustained plasmas are also reported. The results indicate that it is possible to absorb almost all of the laser energy in the plasma, but that more effective ways are required to assure that the thermal energy of the gases flowing around and through the plasma(s) can approach efficiencies exceeding 50 percent.”
The below document was obtained from the Defense Technical Information Center (DTIC) through FOIA Case 2019-3.
Laser-Sustained Plasmas for Application to Rocket Propulsion, April 1987 [149 Pages, 10MB]