Arcjet Diagnostics for Measuring Velocity, Density and Temperature
Abstract
New diagnostic techniques to measure the fundamental plasma properties of an arcjet are being developed collaboratively between the Air Force Phillips Laboratory and the University of Southern California. These diagnostics are for measuring each of the principal parameters defining the plasma state within an arcjet: velocity, temperature, and density. Velocity measurements are being obtained from a new technique we have named Current Modulation Velocimetry (CMV). A current spike applied to the arcjet input current generates an optical emission event that is observed to travel downstream with the propellant flow. Observing this event at two axial locations, a fixed distance apart, provides an average bulk velocity of the gas flowing out of the arcjet nozzle. Species density measurements are to be obtained using Pulsed Electron Beam Fluorescence. A pulsed beam of focused electrons bombard a gas sample causing the resulting emitted fluorescence to be proportional to the local species density. Proper calibration with known samples can then provide absolute density values. Emission spectroscopy is employed to measure propellant excitation, rotational and vibrational temperatures inside the arcjet nozzle. Small (0.020") holes have been drilled through the arcjet nozzle to provide internal optical access. Velocity and density measurements are being conducted on the standard NASA Lewis 1kW arcjet while spectroscopic measurements are being taken on a 30kW class arcjet.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1994
- Accession Number
- ADA436570
Entities
People
- Daniel A. Erwin
- Frederick M. Lutfy
- Jeffrey A. Pobst
- John H. Schilling
- Ronald A. Spores
- William A. Hargus , Jr.