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The purpose of this publication is to describe the characteristics of the millipound pulsed plasma propulsion system as an aid to potential spacecraft designers and users of electric propulsion. It contains performance and interface data, design constraints, and various other considerations applicable to the implementation of the pulsed plasma propulsion system. (Author)

The objective of this program is to identify, validate and assess advantages to the Air Force of using high performance pulsed plasma electric propulsion technology for satellite stationkeeping, attitude control, drag make-up, and solar pressure compensation and to develop pulsed plasma propulsion system/spacecraft integration and design criteria.

The objective of this program is to assess the feasibility of the beamed energy propulsion concept for Air Force missions. The work is divided into three major tasks: (1) system studies; (2) theoretical analyses of the coupling mechanisms between the beamed energy and propellant working fluid and (3) preparation of a test plan for the experimental investigation of the coupling processes for various laser/propellant combinations. The results of the study indicate that beamed energy propulsion is technically feasible. No fundamental obstacles have been identified. However considerable technical development is needed in many areas before the concept can be operationally implemented. Three promising applications have been identified. The laser powered tug can be cost effective compared to an advanced cryogenic tug. Apsidal rotation correction and drag make-up are two other missions where significant advantages may be realized for the laser powered concept. Extensive hardware development is required. Critical areas include the lasers, thrusters, thruster reaction chamber windows and the collection and coupling subsystems., See also Volume 3, AD-C008 938.

The objective of this program is to assess the feasibility of the beamed energy propulsion concept for Air Force missions. The results of the study indicate that beamed energy propulsion is technically feasible. No fundamental obstacles have been identified. However considerable technical development is needed in many areas before the concept can be operationally implemented. In order to minimize the required collector area, laser concepts are preferred over microwaves. If space based laser transmitter concepts are to be cost effective they will require the availability of megawatt level space nuclear or solar power stations. In view of the large total energy required for each mission, ground based transmitters will be most cost effective when they are operated closed cycle from central station electric power. Laser transmitting ranges greater than several hundred nautical miles will result in excessive collector sizes. Therefore, ground based transmitters applications will be restricted to orbital functions which can be performed at low orbital altitudes. Three promising applications have been identified. The laser powered tug can be cost effective compared to an advanced cryogenic tug. Apsidal rotation correction and drag make-up are two other missions where significant advantages may be realized for the laser powered concept., See also Volume 2, AD-A035 061.

A three-year program to develop and advance Electrofluid Dynamic (EFD) Power Generation technology is described. A range of axisymetric EFD channel sizes from 1/12 inch operating with inlet pressures of 700 psig to the 1/48 inch channel designed to operate with 3000 psig were experimentally studied. Failure of gas-breakdown scaling laws prevented the designed 70 watts from being achieved with the small sizes at high pressure. Experimental work on the high voltage breakdown of high pressure gases including air, Hydrogen, SF6, Argon, Nitrogen CO2, and mixtures using various Freons shows a degradation of anticipated strength at about 10 to the 8th power V/M. Theoretical analyses and experimental measurements have been made on the droplet size and density in EFD generators using humid air for EFD channel sizes from 1/4 inch to 1/48 inch. Analyses also include nucleation and growth of Mercury and steam. A preliminary design study of the short duration airborne 6 MW conversion system and a long duration 1 KW and 100 KW ground based system using EFD is included. (Author)

This report describes the work that has been performed during the first year of a three year Study on Electrofluid Dynamic Power Generation Program. The major goal is to improve the measured performance capabilities of EFD energy conversion devices to the point where their feasibility for specific Air Force missions has been demonstrated and their overall system design implications can be factored into quantitative assessments of total EFD generating systems.

The report describes a program to develop high performance colloid thruster systems. An electrostatically vectorable high thrust-density colloid source was developed and endurance tested for periods up to 2000 hours. The investigation of pulsed colloid thruster technology resulted in a demonstration of a feasible concept. Also, a breadboard high voltage supply for a pulsed thruster was built and demonstrated as well as a high voltage isolation valve to electrically decouple the propellant storage system from an individual thruster., Prior to Jul 1971, this work was sponsored and directed by the Air Force Aero Propulsion Lab.

Efforts were continued on a study program to improve the efficiency of thermionic converters which have nonplanar geometries. Specifically, the investigation concerns the production of nonplanar cathodes having more uniform work functions and surface characteristics than are obtained with standard cathode fabrication techniques. A thermionic emission electron microscope for observing work function uniformity was constructed. Arc cast, single crystal, and vapor deposited molybdenum cathodes were examined with the microscope. Active spots due to electropolishing were observed on the (110) face of the single crystal. A vapor deposited cathode was found to have areas of uniform work function. A brief summary is given of the over-all course of the first year of the program and its most significant achievements.

Chemical vapor deposition techniques are being studied as a possible means of producing nonplanar thermionic cathodes having a high degree of uniformity of work function. Vapor deposited molybdenum coatings have been produced by chemical reduction of molybdenum hexafluoride pyrolysis of molybdenum hexacarbonyl and pyrolysis of molybdenum pentachloride. Plating conditions were varied for each process to determine the effect of plating conditions on the preferred orientations of crystallographic planes parallel to the plating surfaces. Both (100) and (111) preferred orientations have been found for the hexafluoride reductions. The pentachloride samples have strong (100) orientations. The hexacarbonyl samples apparently are not pure molybdenum and do not have the expected molybdenum diffraction pattern.

This research program is intended to extend the state of the art in heavy particle electrostatic propulsion. The work performed in the first half of the program is described particularly as it relates to the average charge/mass ratios obtained, charged particle beam currents, beam neutralization and post acceleration with 100 KV.

Progress towards the development of practical colloid thrusters for space application is described. 100 hour life tests with neutralized and unneutralized beams have been performed for thrusts in excess of 100 micropounds. Specific impulses in excess of 1000 seconds have been achieved at a cost in reduction of mass efficiency to 62%. A mass efficiency of 77% was obtained at 643 seconds specific impulse. Several newer thruster concepts and problems associated with beam diagnostics are discussed. Specific areas covered include thrust vectoring, high voltage colloid beams, propellant stability, investigation of new propellants and refinements in time of flight techniques for colloid beam analysis. The report concludes with a resume of the present status of colloid research and recommendations for the future direction of related research. (Author)