There is a growing interest in the use of micro and nanosatellites within the aerospace community. Constellations of small satellites may eventually replace much larger, single function spacecraft as a cheaper, more flexible alternative. Micro-technologies will be required to enable small satellite missions including efficient, low-cost propulsion systems for maneuvering. A MEMS fabricated propulsion system has been developed for maneuvers on an upcoming University nanosatellite mission. The Free Molecule Micro-Resistojet (FMMR) is an electrothermal propulsion system designed for on-orbit maneuvers of nanosatellites, which are defined as spacecraft with an initial mass less than 10 kg. The FMMR has been tested using a torsion force balance to assess its performance using a variety of propellants including helium, argon, nitrogen and carbon dioxide. The experimental performance results compare favorably with results obtained from gas kinetic theory, which were used in the design phase to estimate the thruster's performance. The measured performance of the FMMR in this study has proven to be adequate to perform attitude control maneuvers for the University nanosatellite mission.

Gas and ion transport in the capillary-skimmer subatmospheric interface of a mass spectrometer, which is typically utilized to separate unevaporated micro-droplets from ions, was studied numerically using a two-step approach spanning multiple gas dynamic regimes. The gas flow in the heated capillary and in the interface

Coherent Rayleigh-Brillouin scattering (CRBS) line shapes generated from all narrow-band pump experiment, Direct Simulation Monte-Carlo (DSMC) approach, and published kinetic line shape models are presented for argon, molecular nitrogen, and methane at 300 & 500 K and 1 atm. The kinetic line shape models require uncertain gas properties, such as bulk viscosity, and assume linearization of the kinetic equations from low intensities (<1 x 10¹⁵ W/m²) operating in the perturbative regime. DSMC, a statistical approach to the Boltzmann equation, requires only basic gas parameters available in literature and simulates the forcing function from first principles without assumptions on laser intensity. The narrow band experiments show similar results to broadband experiments and validate the use of DSMC for the prediction of CRBS line shapes.

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 93524-7048 AFRL-PR-ED-JA-2005-293 DISTRIBUTION / AVAILABILITY STATEMENTApproved for public release; distribution unlimited. AFRL-ERS-PAS-2005-200. SUPPLEMENTARY NOTES©2006 American Institute of Physics, published in Physics of Fluids 18, 093601 (2006) 14. ABSTRACT Gas flows through orifices and short tubes have been extensively studied from the 1960s through the 1980s for both fundamental and practical reasons. These flows are a basic and often important element of various modern gas driven instruments. Recent advances in micro-and nanoscale technologies have paved the way for a g generation of miniaturized devices in various application areas, from clinical analyses to biochemical detection to aerospace propulsion. The latter is the main area of interest of this study, where rarefied gas flow into a vacuum through short tubes with thickness-to-diameter ratios varying from 0.015 to 1.2 is investigated both experimentally and numerically with kinetic and continuum approaches. Helium and nitrogen gases are used in the range of Reynolds numbers from 0.02 to 770 (based on the tube diameter), corresponding to Knudsen numbers from 40 down to about 0.001. Propulsion properties of relatively thin and thick tubes are examined. Good agreement between experimental and numerical results is observed for mass flow rate and momentum flux, the latter being corrected for the experimental facility background pressure. For thick-to-thin tube ratios of mass flow and momentum flux versus pressure, aminimum is observed at a Knudsen number of about 0.5. A short tube propulsion efficiency is shown to be much higher than that of a thin orifice. The effect of surface specularity on a thicker tube specific impulse was found to be relatively small. Measurements and computations of mass flow and momentum flux through short tubes in rarefied gases Gas flows through orifices and short tubes have been extensively studied from the 196...

Broadband coherent Rayleigh-Brillouin scattering (CRBS) was used to measure translational gas temperatures for nitrogen, argon, and methane at the ambient pressure of 0.8 atm. Temperatures derived from spectral analysis were compared with experimentally-measured temperatures, with a maximum 5.2% difference for all gases at all temperatures; and with nitrogen, argon, and methane exhibiting average differences over the temperature range tested of 0.8%, 1.4% and -0.5%, respectively. These values are consistent with the 2% estimated, experimental error of the experiment. Improving upon the efficiency of previous line shape acquisition methods, CRBS data were spectrally de-convolved using a cost effective, purpose-designed, Fabry-Perot etalon spectrometer. The resulting line shapes were compared to models obtained from approximations to the 1D Boltzmann equation. Although this study employed broadband CRBS for explicit gas temperature measurement, similar line shape acquisition techniques could be used with broadband coherent Rayleigh scattering (CRS) to experimentally-measure gas temperatures, pressures and other transport properties in both the kinetic (CRBS) and rarefied (CRS) regimes.

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. Edwards AFB CA 93524-7048A conical surface roughness model applicable to particle simulations has been developed. The model has been experimentally validated for channel flows using helium and nitrogen gases at Reynolds numbers from 0.01 to 10 based on inlet conditions. To efficiently simulate gas-surface interaction, molecular collisions with the actual rough surface are simulated by collisions with a randomly positioned conical hole having a fixed opening angle. This model requires only one surface parameter, average surface roughness angle. This model has also been linked to the Cercignani-Lampis scattering kernel as a required reference for use in deterministic kinetic solvers. Experiments were conducted on transitional flows through a 150μm tall, 1cm wide, 1.5cm long microchannel where the mean free path is on the order of the roughness size. The channel walls were made of silicon with: (i) polished smooth surfaces, (ii) regular triangular roughness, and (iii) regular square roughness with characteristic roughness scales of <1μm, 11μm, and 29μm respectively. For the triangular roughness, mass flow reductions ranged from 6% at the higher stagnation pressures tested to 25% at the lower stagnation pressures tested when compared to the smooth channel. 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES 19a. NAME OF RESPONSIBLE PERSON Dr. Ingrid Wysong a. REPORT Unclassified b. ABSTRACT Unclassified c. THIS PAGE Unclassified SAR 10 19b. TELEPHONE NUMBER (include area code) N/A Standard Form 298 (Rev. 8-98)A conical surface roughness model applicable to particle simulations has been developed. The model has been experimentally validated for channel flows using helium and nitrogen gases at Reynolds numbers from 0.01 to 10 based on inlet conditions. To efficiently simulate gas-surface interaction, molecular collisions with the actual rough surface are simulated by collisions with a randomly positioned conical hole having a fixed opening angle. This model requires only one surface parameter, average surface roughness angle. This model has also been linked to the Cercignani-La...

Energy deposition from high intensity pulsed optical lattices to a neutral gas was experimentally recorded for molecular nitrogen at 300/500 K and methane at 300 K. The magnitude of acoustic waves generated by the interaction was experimentally measured and simulated using the direct simulation Monte-Carlo method. The relationship between the lattice velocity and the measured acoustic wave magnitude was compared to numerical simulation which both exhibited dependence on lattice velocity, indicating that the detected pressure wave was the result of gas heating from the optical lattice and not from other forms of laser energy deposition.

Molecular nitrogen at 0.8 atm and 300/500 K and methane at 0.8 atm and 300 K were subjected to optical lattices formed by narrowband, 532 nm, laser pulses with intensities on the optical axis near, but below, the gas ionization limit. A third pulse was introduced to experimentally probe the response, as a function of the lattice velocity, of the gas to the deep monochromatic potential wells formed by the lasers. Coherent Rayleigh-Brillouin scattering (CRBS) line shapes were recorded and compared to numerically predicted magnitudes of the density perturbations induced in the gas. Both experimental results and those from direct simulation Monte-Carlo simulations show deviation from previously published low intensity CRBS line shape models. The deviation indicates a similar trend, as a function of lattice velocity, as that relating to previously published energy and momentum transfer calculations for high intensity lattices. Furthermore, the deviation indicates a maximum intensity at which current CRBS theory is valid.