Experimental and Numerical Studies of Laser Sustained Gas Plasmas
Abstract
Laser propulsion is the production of high specific impulse rocket thrust using a high power laser as a remote energy source. Specific impulses in excess of 1000 seconds are achievable because propellant temperatures are very high and low molecular weight gases can be used. This report focuses on the energy conversion mechanisms of laser-sustained plasmas in pure flowing argon and argon/helium mixtures. Experiments at very high argon mass flux (55 kg/m2s) and pressure as high as 2.5 atmospheres have been performed. The results indicate that nearly all the laser power can be absorbed (>97%), and efficiencies approaching 50% can be obtained. Experiments with mixtures of argon and helium indicate that the high specific heat and thermal conductivity of the helium tends to allow for more of he absorbed energy to be retained rather than reradiated to the chamber walls. This despite the fact that the very high ionization energy of helium limits the global absorption to values below that for pure argon plasmas. Fundamental research concerning laser sustained plasmas such as the independent experimental determinations of electron number density and electron number density and electron temperature is required. This will allow the evaluation of the local thermal equilibrium which is needed in order to better interpret the spectroscopic and numerical results. Also required is the more accurate determination of downstream plasma exhaust gas temperature via Rayleigh scattering thermometry. This technique is impervious to plasma and laser irradiation interferences and to gas heat loss to the chamber walls, thus thermal efficiency calculations will be much more accurate than in the past.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1989
- Accession Number
- ADA208129
Entities
People
- Ayhan Mertogul
- Herman Krier
- Jyoti Mazumder
- Scott Schwartz
- Xiangli Chen
Organizations
- University of Illinois Urbana–Champaign