Physical Processes in an MPD Arc First Semiannual Report

Short pulse probing of interior physical characteristics of MPD arc - electric impedance of accelerato

Integrated propulsion for near-Earth space missions. Volume 1: Executive summary

Tradeoffs between electric propulsion system mass ratio and transfer time from LEO to GEO were conducted parametrically for various thruster efficiency, specific impulse, and other propulsion parameters. A computer model was developed for performing orbit transfer calculations which included the effects of aerodynamic drag, radiation degradation, and occultation. The tradeoff results showed that thruster technology areas for integrated propulsion should be directed towards improving primary thruster efficiency in the range from 1500 to 2500 seconds, and be continued towards reducing specific mass. Comparison of auxiliary propulsion systems showed large total propellant mass savings with integrated electric auxiliary propulsion. Stationkeeping is the most demanding on orbit propulsion requirement. At area densities above 0.5 sq m/kg, East-West stationkeeping requirements from solar pressure exceed North-South stationkeeping requirements from gravitational forces. A solar array pointing strategy was developed to minimize the effects of atmospheric drag at low altitude, enabling electric propulsion to initiate orbit transfer at Shuttle's maximum cargo carrying altitude. Gravity gradient torques are used during ascent to sustain the spacecraft roll motion required for optimum solar array illumination. A near optimum cover glass thickness of 6 mils was established for LEO to GEO transfer

Integrated propulsion for near-Earth space missions. Volume 2: Technical

The calculation approach is described for parametric analysis of candidate electric propulsion systems employed in LEO to GEO missions. Occultation relations, atmospheric density effects, and natural radiation effects are presented. A solar cell cover glass tradeoff is performed to determine optimum glass thickness. Solar array and spacecraft pointing strategies are described for low altitude flight and for optimum array illumination during ascent. Mass ratio tradeoffs versus transfer time provide direction for thruster technology improvements. Integrated electric propulsion analysis is performed for orbit boosting, inclination change, attitude control, stationkeeping, repositioning, and disposal functions as well as power sharing with payload on orbit. Comparison with chemical auxiliary propulsion is made to quantify the advantages of integrated propulsion in terms of weight savings and concomittant launch cost savings

The use of a coaxial gun for plasma propulsion Final report

Plasma propulsion by coaxial gu

Instability heating of the HDZP

We present a model of dense Z-Pinch heating. For pinches of sufficiently small diameter and high current, direct ion heating by m=0 instabilities becomes the principal channel for power input. This process is particularly important in the present generation of dense micro-pinches (e.g., HDZP-II) where instability growth times are much smaller than current risetimes, and a typical pinch diameter is several orders smaller than that of the chamber. Under these conditions, m=0 formation is not disruptive: the large E{sub z} field reconnects the instability cusps externally, after which the ingested magnetic flux decays into turbulent kinetic energy of the plasma. The continuous process is analogous to boiling of a heated fluid. A simple analysis shows that an equivalent resistance R{sub t} = {ell}/4{radical}Nm{sub i}({mu}{sub 0}/{pi}){sup 3/2}I/r appears in the driving circuit, where I is the pinch current, N is the line density, {ell} is the pinch length, m{sub i} is the ion mass, and r is the pinch radius. A corresponding heating term has been added to the ion energy equation in a 0-D, self-similar simulation, which had been written previously to estimate fusion yields and radial expansion of D{sub 2} fiber pinches. The simulation results agree well with the experimental results from HDZP-II, where the assumption of only joule heating produced gross disagreement. Turbulent ion heating should be the dominant process in any simple pinch carrying meg-ampere current and having submillimeter radius