Experimental and Computational Investigation of a RF Plasma Micro-Thruster

A prototype RF plasma micro-thruster has been investigated numerically and experimentally. The experimental results were obtained on a thrust stand capable of micro-Newton resolution. Thrust and mass flow (hence specific impulse) were measured for an argon propellant at mass flows ranging from 0.4 to 5.5 mg/s. An increase over the cold gas thrust of up to 20% was observed for a discharge frequency of 100 MHz and an input power of 77 W. Propulsive efficiency was seen to increase both experimentally and numerically for increasing mass flow and decreasing discharge frequency

Experimental and Computational Study of Area and Perimeter Contributions to Radiometer Forces

The relative contribution to the radiometric force of the area and perimeter of the vane is studied experimentally and numerically. Experimentally, a circular vane, a low-aspect rectangular vane, and a high-aspect rectangular vane were all tested on a force balance, with nano-Newton resolution, placed in a stagnant gas. The computational results were obtained through 2-D simulations using the direct simulation Monte Carlo method, as well as a discrete ordinate solution of the ES model kinetic equation. Gas pressure was varied from 0.006 to 6 Pa, which was a broad enough range to observe the characteristic peak force production of a radiometer in the transition regime, where the peak occurs at Kn ~ 0.1. It was found that the area of a radiometer vane is responsible for a significant amount ofthe total force production through a wide range of operating pressures. It is only at the highest background pressures, well after force production has peaked, that the vane perimeter appears to dominate the operation of the radiometer

Resonant Laser Manipulation of an Atomic Beam

Abstract. Theories for laser-atom interactions have been under development since the advent of laser technology. The theories have yet to be adequately integrated into kinetic flow solvers. Realizing this integration would greatly enhance the scaling of laser-species interactions beyond the realm of ultra-cold atomic physics. A representative numerical investigation was conducted using a custom collisionless gas particle trajectory code, demonstrating this goal in the present study. The investigation covered neutral atomic beam steering and collimation using near-resonant laser fields. In addition to the numerical investigation, a validating experiment was conducted. The experimental results showed good agreement with the numerical simulations when experimental parameters, such as finite laser line width, were taken into account. These simulations showed trends and some limitations associated with the use of a continuouswave Gaussian laser fields for the steering and collimation of a geometrically skimmed cesium atomic beam using the photon scattering force and the near-resonant induced dipole gradient force. These simulations indicate possible integration of the resonant laser-atom interaction with other rarefied and collisional solvers for similar species such as alkali metals

Nozzle Plume Impingement on Spacecraft Surfaces: Effects of Surface Roughness

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY) SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S) Air Force Research Laboratory (AFMC) AFRL/PRS SPONSOR/MONITOR'S Pollux Drive NUMBER(S) Edwards AFB CA 93524-70448 AFRL-PR-ED-JA-2005-306 DISTRIBUTION / AVAILABILITY STATEMENT Approved for public release; distribution unlimited (PA no. AFRL-ERS-PAS-2005-219). SUPPLEMENTARY NOTES Published in Journal of Spacecraft and Rockets, AIAA-2005-5065. ABSTRACT An experimental and numerical effort was undertaken to assess the effects of a cold gas (T 0 -300 K) nozzle plume impinging on simulated spacecraft surfaces. The nozzle flow impingement is investigated experimentally using a nano-Newton resolution force balance and numerically using the Direct Simulation Monte Carlo (DSMC) numerical technique. The Reynolds number range investigated in this study is from approximately 2 to 350 using nitrogen propellant. The thrust produced by the nozzle was first assessed on a force balance to provide a baseline case. Subsequently, aluminum plates were attached to the same force balance parallel to the plume flow to simulate spacecraft surfaces in proximity to the thruster. Three plates were used in this study, an electropolished plate with smooth surface, and two rough surface plates with equally spaced rectangular and triangular grooves. A 15% degradation in thrust was observed both experimentally and numerically for the plate relative to the free plume expansion case. The effect of surface roughness on thrust was found to be small due to molecules backscattered from the plate to the nozzle plenum wall. Additionally, the influence of surface roughness in the diverging part of the nozzle on thrust was examined numerically and found to be significant at Reynolds numbers less than 10. Abstract An experimental and numerical effort was undertaken to assess the effects of a cold gas (T 0 =300 K) nozzle plume impinging on a simulated spacecraft surface. The nozzle flow impingement is investigated experimentally using a nano-Newton resolution force balance and numerically using the Direct Simulation Monte Carlo (DSMC) numerical technique. The Reynolds number range investigated in this study is from approximately 2 to 600 using nitrogen propellant. The thrust produced by the nozzle was first assessed on a force balance to provide a baseline case. Subsequently, aluminum plates were attached to the same force balance parallel to the plume flow. Three plates were used in this study, an electropolished plate with smooth surface, and two rough surface plates with equally spaced rectangular and triangular grooves. A 15% degradation in thrust was observed both experimentally and numerically for the plate relative to the free plume expansion case. The effect of surface roughness on thrust was found to be small due to molecules back scattered from the plate to the plenum wall. Additionally, the influence of surface rougness in the diverging part of the nozzle on nozzle thrust was examined numerically, and found to be significant at Reynolds numbers on the order or less than 10

Review of the EP activities of US academia

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76897/1/AIAA-2001-3227-398.pd

Plume Impingement Analysis for the European Service Module Propulsion System

Plume impingement analyses were performed for the European Service Module (ESM) propulsion system Orbital Maneuvering System engine (OMS-E), auxiliary engines, and reaction control system (RCS) engines. The heat flux from plume impingement on the solar arrays and other surfaces are evaluated. This information is used to provide inputs for the ESM thermal analyses and help determine the optimal configuration for the RCS engines