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NASA NTRS1990

Fluorescence from excitation of CH4, CH3OH and CH3SH by extreme vacuum ultraviolet radiation

The photoabsorption and fluorescence cross sections of CH4, CH3OH, and CH3SH were measured in the wavelength regions of 52-106, 48-106, and 48-106 nm, respectively. The fluorescence spectra were dispersed to identify the emitting species. Emissions from the excited species of H(asterisk) and CH(asterisk) are commonly observed for all three molecules. Emission from the excited CH2(asterisk) is observed from CH4, OH(asterisk) from CH3OH and CS(asterisk) from CH3SH. The photoexcitation processes that may produce the observed emission bands are discussed.

Ma, Guang↗

NASA NTRS1972

Experimental Investigation of the Mechanical Behavior of a Filled Elastomer at Pressures Below 10 to the -6th Power Torr

The mechanical behavior of a filled elastomer was studied with emphasis on understanding the vacuum-material interactions occurring, and to develop analytical techniques for predicting the vacuum behavior. The test results indicate that two separate mechanisms are involved in the observed property changes: the first controls the time response to applied stress; the second determines the initial internal state of the materials as the result of stresses. It is concluded that the mechanical property changes are attributable to changes in the relaxation processes occurring in the material. These changes are brought about by outgassing of water. Recommendations for future investigations are included.

Gregory, G. L.↗

NASA NTRS1991

Thermoplastic coating of carbon fibers

Using a continuous powder coating process, more than 1500 meters of T 300/LaRC-TPI prepreg were produced. Two different types of heating sections in the coating line, namely electrical resistance and convection heating, were utilized. These prepregs were used to fabricate unidirectional composites. During composite fabrication the cure time of the consolidation was varied, and composites samples were produced with and without vacuum. Under these specimens, the effects of the different heating sections and of the variation of the consolidation parameters on mechanical properties and void content were investigated. The void fractions of the various composites were determined from density measurements, and the mechanical properties were measured by tensile testing, short beam shear testing and dynamic mechanical analysis.

Edie, D. D.↗

NASA NTRS1990

The Extended Duration Orbiter Regenerable CO2 Removal System

A new carbon dioxide scrubber system is undergoing development for extended duration orbiter (EDO) missions. The EDO requirements of missions up to 18 days and the capability for future missions up to 30 days necessitated the development and implementation of a regenerative CO2 removal process. This new system will reduce the launch weight and stowage volume as compared to the present method of CO2 removal, lithium hydroxide, which is stowed in canisters. The selected design, called the Regenerable CO2 Removal System (RCRS), uses a solid amine material to adsorb carbon dioxide and water vapor and periodically desorb these to space vacuum. The RCRS, which is located below the middeck floor, interfaces with the orbiter's cabin Atmospheric Revitalization System and is adjustable from four to seven crewmembers. The RCRS is designed to automatically cycle the beds from absorb to vacuum-desorb every 30 minutes. Also incorporated into the design are features such consumable recovery, external leak protection, trace contaminant control and automatic control logic operation.

Ouellette, Fred A.↗

NASA NTRS2011

Electrostatic Beneficiation of Lunar Regolith: Applications in In-Situ Resource Utilization

Upon returning to the moon, or further a field such as Mars, presents enormous challenges in sustaining life for extended periods of time far beyond the few days the astronauts experienced on the moon during the Apollo missions. A stay on Mars is envisioned to last several months, and it would be cost prohibitive to take all the requirements for such a stay from earth. Therefore, future exploration missions will be required to be self-sufficient and utilize the resources available at the mission site to sustain human occupation. Such an exercise is currently the focus of intense research at NASA under the In-situ Resource Utilization (ISRU) program. As well as oxygen and water necessary for human life, resources for providing building materials for habitats, radiation protection, and landing/launch pads are required. All these materials can be provided by the regolith present on the surface as it contains sufficient minerals and metals oxides to meet the requirements. However, before processing, it would be cost effective if the regolith could be enriched in the mineral(s) of interest. This can be achieved by electrostatic beneficiation in which tribocharged mineral particles are separated out and the feedstock enriched or depleted as required. The results of electrostatic beneficiation of lunar simulants and actual Apollo regolith, in lunar high vacuum are reported in which various degrees of efficient particle separation and mineral enrichment up to a few hundred percent were achieved.

Trigwell, Steve↗

NASA NTRS2011

First Results from ARTEMIS, a New Two-Spacecraft Lunar Mission: Counter-Streaming Plasma Populations in the Lunar Wake

We present observations from the first passage through the lunar plasma wake by one of two spacecraft comprising ARTEMIS (Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon's Interaction with the Sun), a new lunar mission that re-tasks two of five probes from the THEMIS magnetospheric mission. On Feb 13, 2010, ARTEMIS probe P1 passed through the wake at 3.5 lunar radii downstream from the Moon, in a region between those explored by Wind and the Lunar Prospector, Kaguya, Chandrayaan, and Chang'E missions. ARTEMIS observed interpenetrating proton, alpha particle, and electron populations refilling the wake along magnetic field lines from both flanks. The characteristics of these distributions match expectations from self-similar models of plasma expansion into vacuum, with an asymmetric character likely driven by a combination of a tilted interplanetary magnetic field and an anisotropic incident solar wind electron population. On this flyby, ARTEMIS provided unprecedented measurements of the interpenetrating beams of both electrons and ions naturally produced by the filtration and acceleration effects of electric fields set up during the refilling process. ARTEMIS also measured electrostatic oscillations closely correlated with counter-streaming electron beams in the wake, as previously hypothesized but never before directly measured. These observations demonstrate the capability of the comprehensively instrumented ARTEMIS spacecraft and the potential for new lunar science from this unique two spacecraft constellation.

Halekas, J. S.↗

NASA NTRS2014

First Results from ARTEMIS, A New Two-Spacecraft Lunar Mission: Counter-Streaming Plasma Populations in the Lunar Wake

We present observations from the first passage through the lunar plasma wake by one of two spacecraft comprising ARTEMIS (Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon's Interaction with the Sun), a new lunar mission that re-tasks two of five probes from the THEMIS magnetospheric mission. On Feb 13, 2010, ARTEMIS probe P1 passed through the wake at approximately 3.5 lunar radii downstream from the Moon, in a region between those explored by Wind and the Lunar Prospector, Kaguya, Chandrayaan, and Chang'E missions. ARTEMIS observed interpenetrating proton, alpha particle, and electron populations refilling the wake along magnetic field lines from both flanks. The characteristics of these distributions match expectations from self-similar models of plasma expansion into vacuum, with an asymmetric character likely driven by a combination of a tilted interplanetary magnetic field and an anisotropic incident solar wind electron population. On this flyby, ARTEMIS provided unprecedented measurements of the interpenetrating beams of both electrons and ions naturally produced by the filtration and acceleration effects of electric fields set up during the refilling process. ARTEMIS also measured electrostatic oscillations closely correlated with counter-streaming electron beams in the wake, as previously hypothesized but never before directly measured. These observations demonstrate the capability of the comprehensively instrumented ARTEMIS spacecraft and the potential for new lunar science from this unique two spacecraft constellation.

Plasma↗

NASA NTRS2016

Wavefront-Error Performance Characterization for the James Webb Space Telescope (JWST) Integrated Science Instrument Module (ISIM) Science Instruments

The science instruments (SIs) comprising the James Webb Space Telescope (JWST) Integrated Science Instrument Module (ISIM) were tested in three cryogenic-vacuum test campaigns in the NASA Goddard Space Flight Center (GSFC)'s Space Environment Simulator (SES). In this paper, we describe the results of optical wavefront-error performance characterization of the SIs. The wavefront error is determined using image-based wavefront sensing (also known as phase retrieval), and the primary data used by this process are focus sweeps, a series of images recorded by the instrument under test in its as-used configuration, in which the focal plane is systematically changed from one image to the next. High-precision determination of the wavefront error also requires several sources of secondary data, including 1) spectrum, apodization, and wavefront-error characterization of the optical ground-support equipment (OGSE) illumination module, called the OTE Simulator (OSIM), 2) plate scale measurements made using a Pseudo-Nonredundant Mask (PNRM), and 3) pupil geometry predictions as a function of SI and field point, which are complicated because of a tricontagon-shaped outer perimeter and small holes that appear in the exit pupil due to the way that different light sources are injected into the optical path by the OGSE. One set of wavefront-error tests, for the coronagraphic channel of the Near-Infrared Camera (NIRCam) Longwave instruments, was performed using data from transverse translation diversity sweeps instead of focus sweeps, in which a sub-aperture is translated andor rotated across the exit pupil of the system.Several optical-performance requirements that were verified during this ISIM-level testing are levied on the uncertainties of various wavefront-error-related quantities rather than on the wavefront errors themselves. This paper also describes the methodology, based on Monte Carlo simulations of the wavefront-sensing analysis of focus-sweep data, used to establish the uncertainties of the wavefront error maps.

wavefront error↗

NASA NTRS2017

Long-Term Cryogenic Propellant Storage on Mars with Hercules Propellant Storage Facility

This report details the process and results of roughly sizing the steady state, zero boil-off thermal and power parameters of the Hercules Propellant Storage Facility. For power analysis, isothermal and isobaric common bulkhead tank scenarios are considered. An estimated minimum power requirement of 8.3 kW for the Reverse Turbo-Brayton Cryocooler is calculated. Heat rejection concerns in soft vacuum Mars atmosphere are noted and potential solutions are proposed. Choice of coolant for liquid propellant conditioning and issues with current proposed cryocooler cycle are addressed; recommendations are made, e.g. adding a Joule-Thomson expansion valve after the Reverse Turbo-Brayton turbine in order to have two-phase, isothermal heat exchange through the Broad Area Cooling system. Issues with cross-country transfer lines from propellant storage to flight vehicle are briefly discussed: traditional vacuum jacketed lines are implausible, and Mars insulation needs to be developed.

Propellant Storage↗

NASA NTRS2019

High Temperature Vaporization into Different Environments

Materials in extreme environments are often negatively affected by the process of vaporization. The maximum vaporization rate is determined by calculating a flux from the equilibrium vapor pressure(s) of each component. However, this maximum vaporization flux is decreased by the vaporization coefficient and the atmosphere above the material. This paper discusses each of these factors for common oxides, using SiO2 as an example. Vaporization into a vacuum is an ideal starting point, as the basic mechanisms for vaporization have been derived from these studies. Imposing an over-pressure of a static gas changes the vaporization rates from both a thermodynamic and kinetic aspect. Finally, a flowing gas is the most common situation encountered in many extreme environments. Laminar and turbulent flow effects are be treated with both analytical transport expressions and computational fluid dynamics (CFD). The example of a vaporizing SiO2 coupon in a laboratory furnace is examined with both the analytical expressions and with CFD.

Jacobson, Nathan↗

NASA NTRS2012

Method to Remove Particulate Matter from Dusty Gases at Low Pressures

Future human exploration of Mars will rely on local Martian resources to reduce the mass, cost, and risk of space exploration launched from Earth. NASA's In Situ Resource Utilization (ISRU) Project seeks to produce mission consumables from local Martian resources, such as atmospheric gas. The Martian atmosphere, however, contains dust particles in the 2-to-10 -micrometer range. These dust particles must be removed before the Martian atmospheric gas can be processed. The low pressure of the Martian atmosphere, at 5 to 10 mbars, prevents the development of large voltages required for a standard electrostatic precipitator. If the voltage is increased too much, the corona transitions into a glow/streamer discharge unsuitable for the operation of a precipitator. If the voltage is not large enough, the dust particles are not sufficiently charged and the field is not strong enough to drive the particles to the collector. A method using electrostatic fields has been developed to collect dust from gaseous environments at low pressures, specifically carbon dioxide at pressures around 5 to 10 mbars. This method, commonly known as electrostatic precipitation, is a mature technology in air at one atmosphere. In this case, the high voltages required for the method to work can easily be achieved. However, in carbon dioxide at low pressures, such as those found on Mars, large voltages are not possible. The innovation reported here consists of two concentric cylindrical electrodes set at specific potential difference that generate an electric field that produces a corona capable of imparting an electrostatic charge to the incoming dust particles. The strength of the field is carefully balanced so as to produce a stable charging corona at 5 to 10 mbars, and is also capable of imparting a force to the particles that drives them to the collecting electrode. There are only two possible ways that dust can be removed from Martian atmospheric gas intakes: with this electrostatic precipitator design, and with the use of filters. However, filters require upstream compression of the gas to be treated because the atmospheric pressure on Mars is too close to vacuum to use a vacuum pump downstream to the filter to draw the gas through the filter. The electrostatic precipitator is the best and more efficient solution for this environment. No other precipitator designs have been developed for the environment of Mars due to the challenges of the low atmospheric pressure. Dust particles are charged using corona generation around the high-voltage discharge electrode, which ionizes gas molecules. Since the atmospheric gas intakes for the ISRU processing chambers will likely be cylindrical, cylindrical precipitator geometry was chosen. The electrostatic precipitator design presented here removes simulated Martian dust particles in the required range in a simulated Martian atmospheric environment. The current-voltage (I-V) characteristic curves taken for the nine precipitator configurations at 9 mbars of pressure showed that a cylindrical collecting electrode 7.0 cm in diameter with a concentric positive high voltage electrode 100 m thick provides the best range of voltage and charging corona current. This precipitator design is effective for the size of the dust particles expected in the Martian atmosphere. Mass determination, as well as microscopic images and particle size distributions of dust collected on a silicon wafer placed directly below the precipitator with the field on and off, showed excellent initial results.

Calle, Carlos↗

NASA NTRS1974

Thermal rearrangements in polypentenamer and polyoctenamer

Experiments were conducted to show that polypentenamer and polyoctenamer, in common with 1,4-polybutadiene, undergo anaerobic thermal cis-trans isomerization at temperatures as low as 200 degrees C. Their activation energies for isomerization are comparable to that of polybutadiene. The relative rate constants are found to decrease in the order: polybutadiene, polypentenamer, polyoctenamer. When heated in a vacuum at 200 to 270 degrees C, polypentenamer exhibits a loss of double bonds. This disappearance of unsaturation has no counterpart in polybutadiene or polyoctenamer. In polypentenamer, a mechanism for a thermally-induced ring closure that is different from the one shown for the cyclization-depolymerization of various unsaturated polymers is evident. The cyclization-depolymerization process does cause a loss of double bonds in polybutadiene and polyoctenamer at temperatures greater than or equal to 275 degrees C.

Golub, M. A.↗

NASA NTRS1993

Combined space environment on spacecraft engineering materials

Spacecraft structures and surface materials exposed to the space environment for extended periods, up to thirty years, have increased potential for damage from long term exposure to the combined space environment including solar ultraviolet radiation, electrons, and protons and orbiting space debris. The space environment in which the Space Station Freedom and other space platforms will orbit is truly a hostile environment. For example, the currently estimated integral fluence for electrons above 1 Mev at 2000 nautical miles is above 2 x 10(exp 10) electrons/cm(sup 2)/day and the proton integral fluence is above 1 x 10(exp 9) protons/cm(sup 2)/day. At the 200 - 400 nautical miles, which is more representative of the altitude which will provide the environment for the Space Station, each of these fluences will be proportionately less; however, the data indicates that the radiation environment will obviously have an effect on structural materials exposed to the environment for long durations. The effects of ultraviolet radiation, particularly in the vacuum ultraviolet (less than 200 nm wavelength) is more difficult to characterize at this time. Very little data is available in the literature which can be used for determining the life cycle of a material placed in space for extended durations of time. In order to obtain critical data for planning and designing of spacecraft systems, use of a small vacuum system at the Environmental Effects Facility at MSFC, which can be used for these purposes was used. A special effort was made to build up this capability during the course of this research effort and perform a variety of experiments on materials proposed for the Space Station. A description of the apparatus and the procedure devised to process potential spacecraft materials is included.

Workman, Gary L.↗

NASA NTRS2009

NPP Clouds and the Earth's Radiant Energy System (CERES) Predicted Sensor Performance Calibration and Preliminary Data Product Performance

Continuation of the Earth Radiation Budget (ERB) Climate Data Record (CDR) has been identified as critical in the 2007 NRC Decadal Survey, the Global Climate Observing System WCRP report, and in an assessment titled Impacts of NPOESS Nunn-McCurdy Certification on Joint NASA-NOAA Climate Goals. In response, NASA, NOAA and NPOESS agreed in early 2008 to fly the final existing CERES Flight Model (FM-5) on the NPP spacecraft for launch in 2010. Future opportunities for ERB CDR continuity consist of procuring an additional CERES Sensor with modest performance upgrades for flight on the NPOESS C1 spacecraft in 2013, followed by a new CERES follow-on sensor for flight in 2018 on the NPOESS C3 spacecraft. While science goals remain unchanged for the long-term ERB Climate Data Record, it is now understood that the task of achieving these goals is more difficult for two reasons. The first is an increased understanding of the dynamics of the Earth/atmosphere system which demonstrates that rigorous separation of natural variability from anthropogenic change on decadal time scales requires higher accuracy and stability than originally envisioned. Secondly, future implementation scenarios involve less redundancy in flight hardware (1 vs. 2 orbits and operational sensors) resulting in higher risk of loss of continuity and reduced number of independent observations to characterize performance of individual sensors. Although EOS CERES CDR's realize a factor of 2 to 4 improvement in accuracy and stability over previous ERBE CDR's, future sensors will require an additional factor of 2 improvement to answer rigorously the science questions moving forward. Modest investments, defined through the CERES Science Team s 30-year operational history of the EOS CERES sensors, in onboard calibration hardware and pre-flight calibration and test program will ensure meeting these goals while reducing costs in re-processing scientific datasets. The CERES FM-5 pre-flight radiometric characterization program benefited from the 30-year operational experience of the CERES EOS sensors, as well as a stronger emphasis of radiometric characterization in the Statement of Work with the sensor provider. Improvements to the pre-flight program included increased spectral, spatial, and temporal sampling under vacuum conditions as well as additional tests to characterize the primary and transfer standards in the calibration facility. Future work will include collaboration with NIST to further enhance the understanding of the radiometric performance of this equipment prior to flight. The current effort summarizes these improvements to the CERES FM-5 pre-flight sensor characterization program, as well as modifications to inflight calibration procedures and operational tasking. In addition, an estimate of the impacts to the system level accuracy and traceability is presented.

Priestly, Kory↗

NASA NTRSDate not supplied

Thermal Design Challenges Posed by the Four Bed CO2 Scrubber COTS Air-Save Pump

The Four Bed Carbon Dioxide (4BCO2) scrubber Air-Save Pump (ASP) operates as part of the adsorbent bed regeneration cycle. The ASP removes residual air from the bed for return to the cabin prior to heat and vacuum exposure which drives out the CO2 regenerating the bed. 4BCO2 employs a Commercial Off-the-Shelf (COTS) scroll type air pump, repackaged in an acoustically insulated enclosure to reduce noise and mounted to a cold plate. The International Space Station (ISS) Low Temperature Loop (LTL) flow (operating between 38°F and 50°F) first cools the process air, and then flows through the cold plate, cooling the pump. This results in competing ASP thermal design goals: (1) to keep the pump and motor sufficiently cool and (2) to avoid forming condensation due to over-cooling. Surfaces below 60°F typically warrant careful consideration of condensation. A test-calibrated thermal model demonstrates such a balanced design is feasible with temperatures above 60°F. A separate, coupled fluid model predicts the potential for condensation formation, allowing risk assessment of flying with the unmodified design.

Daniel P Popok↗

NASA NTRSDate not supplied

Characterization of Volatiles from Simulated Lunar Highland Melts Under Vacuum

As part of the Artemis program that returns humans to the Moon for sustained presence, the in-situ resource utilization (ISRU) pilot plant is developing hardware to test systems in relevant lunar environments. As this evolves, the ever-growing field of interest requires in-depth understanding of the environment for operations. Lunar regolith contains compounds that can be harvested as resources such as fuel, or life support and construction feedstocks. Therefore, this necessitates an understanding of its constituents and processed by-products under some of the extreme conditions imposed for resource extraction.

Oxygen Extraction↗

NASA NTRSDate not supplied

Characterization of Volatiles from Simulated Lunar Highland Melts Under Vacuum

Oxygen Extraction↗

NASA NTRS1991

Materials processing in low gravity

Several NASA facilities are available for low gravity experimentation: the Drop Facilities at NASA Marshall and the KC-135 at NASA Johnson. The use of these facilities allows for a rather inexpensive method of determining whether or not particular experiments will be worthwhile candidates for space experiments. Equipment currently available include various furnaces for the Drop Tube, the Drop Tower, and the KC-135. The furnaces for the Drop Tube include both an electron beam and electromagnetic levitation furnace. A vacuum furnace is used for the Drop Tower. Several furnaces used in performing KC-135 solidification experiments include the Automated Directional Solidification Furnace, the Isothermal Casting Furnace, the Rapid Melt/Rapid Quench and the Polymer/Video Furnaces.

Workman, Gary L.↗