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Technical Paper

Thermal Strategy for the Phoenix Robotic Arm Deployment

2009-07-12
2009-01-2438
The Mars Scout Phoenix Lander successfully landed in the Martian northern latitude on May 25, 2008. The Robotic Arm, which was designed to dig and to transfer soil samples to other Lander instruments, contained a number of actuators that had specific operational windows on the Martian surface due to the bearing lubricant. The deployment of the Robotic Arm was planned for Sol 2 (Mars days are referred to “Sols”). A few weeks before Mars landing, the Robotic Arm operations team learned that a strict flight rule had been imposed. It specified that the deployment shall be accomplished when the actuators were at or above −25°C since the deployment activity was qualified with the actuators at −40°C. Furthermore, the deployment plan identified a window of opportunity between 13:00 Local Solar Time (LST, equivalent to dividing the Sol into 24 equal Martian hours) and 15:30 LST.
Journal Article

Thermal Design Trade Study for the Mars Science Laboratory ChemCam Body Unit

2009-07-12
2009-01-2462
The Mars Science Laboratory will be the next Martian mobility system that is scheduled to launch in the fall of 2011. The ChemCam Instrument is a part of the MSL science payload suite. It is innovative for planetary exploration in using a technique referred to as laser breakdown spectroscopy to determine the chemical composition of samples from distances of up to about 9 meters away. ChemCam is led by a team at the Los Alamos National Laboratory and the Centre d'Etude Spatiale des Rayonnements in Toulouse, France. The portion of ChemCam that is located inside the Rover, the ChemCam Body Unit contains the imaging charged-coupled device (CCD) detectors. Late in the design cycle, the ChemCam team explored alternate thermal design architectures to provide CCD operational overlap with the Rover's remote sensing instruments. This operational synergy is necessary to enable planning for subsequent laser firings and geological context.
Technical Paper

Implications of the VBNC State of B. cepacia and S. maltophilia on Bioreduction and Microbial Monitoring of ISS Potable Waters

2005-07-11
2005-01-2933
Certain Eubacteria enter a viable but nonculturable (VBNC) state upon encountering unfavorable environmental conditions. VBNC cells do not divide on conventional media yet remain viable and in some cases retain virulence. Here, we describe the VBNC state of two opportunistic pathogens previously isolated from ISS potable waters, Burkholderia cepacia and Stenotrophomonas maltophilia. Artificially inoculated microcosms were exposed to the biocidal agents copper (CuSO4) and iodine (I2) in an attempt to induce nonculturablility. Viability was assessed via fluorescent microscopy (direct viable count assay coupled with BacLight™ staining) and metabolic activity was monitored by quantifying both intracellular ATP and transcribed rRNA (reverse transcriptase quantitative PCR). Culturablility was lost in both B. cepacia and S. maltophilia within two days of exposure to copper or high concentrations of iodine (6 or 8 ppm).
Technical Paper

Design and Flight Qualification of a Paraffin-Actuated Heat Switch for Mars Surface Applications

2002-07-15
2002-01-2275
The Mars Exploration Rover (MER) flight system uses mechanical, paraffin-actuated heat switches as part of its secondary battery thermal control system. This paper describes the design, flight qualification, and performance of the heat switch. Although based on previous designs by Starsys Research Corporation1,2, the MER mission requirements have necessitated new design features and an extensive qualification program. The design utilizes the work created by the expansion of a paraffin wax by bringing into contact two aluminum surfaces, thereby forming a heat conduction path. As the paraffin freezes and contracts, compression springs separate the surfaces to remove the conduction path. The flight qualification program involved extensive thermal performance, structural, and life testing.
Technical Paper

Fabrication of laterally coupled InGaAsSb-GaSb-AlGaAsSb DFB laser structures

2000-07-10
2000-01-2305
The development of tunable diode laser systems in the 2 - 5 μm spectral region will have numerous applications for trace gas detection. To date, the development of such systems has been hampered by the difficulties of epitaxial growth, and device processing in the case of the Sb-based materials system. One of the compounding factors in this materials system is the use of aluminum containing compounds in the laser diode cladding layers. This makes the regrowth steps used in traditional lasers very difficult. As an alternative approach we are developing laterally coupled antimonide based lasers structures that do not require the regrowth steps. In this paper, the materials growth, device processing and development of the necessary drive electronics for an antimony based tunable diode laser system are discussed.
Technical Paper

A Miniature Quadrupole Mass Spectrometer Array and GC For Space Flight: Astronaut EVA and Cabin-Air Monitoring

2000-07-10
2000-01-2300
A miniature quadrupole mass spectrometer array and gas chromatograph have been designed and built for NASA flight missions. Without the gas chromatograph the mass spectrometer is to be used for detection, by astronauts in EVA, of N2, O2, the hydrazines, and NH3 leaks in the hull of the International Space Station, and of adsorbed hydrazines on the astronauts’ suits. The fully-adapted astronaut system, with all software and visual readout, is called the Trace Gas Analyzer. When interfaced with the miniature gas chromatographic system, the mass spectrometer will be useful for a variety of NASA missions involving more complex gas mixtures. The missions include planetary exploration (to Venus, Europa, Titan, etc.), as well as cabin-air monitoring for long-duration human flight to the Moon, Mars, and beyond.
Technical Paper

Self-Sterilizing Properties of Martian Soil: Possible Nature & Implications

2000-07-10
2000-01-2343
As a result of the Viking missions in 1970s, the presence of a strong oxidant in Martian soil was suggested. Here we present a testable, by near-term missions, hypothesis that iron(VI) contributes to that oxidizing pool. Ferrate(VI) salts were studied for their spectral and oxidative properties and biological activities. Ferrate(VI) has distinctive spectroscopic features making it available for detection by remote sensing reflectance spectra and contact measurements via Mössbauer spectroscopy. The relevant miniaturized instrumentation has been developed or is underway, while XANES spectroscopy is shown to be a method of choice for the returned samples. Ferrate(VI) is capable of splitting water to yield oxygen, and oxidizing organic carbon to CO2. Organic oxidation was strongly abated after pre-heating ferrate, similar to the observations with Mars soil samples.
Technical Paper

Lifetimes of AMTEC Electrodes: Rhodium-Tungsten and Titanium Nitride

1999-08-02
1999-01-2704
The lifetime of an AMTEC electrode is predicted from the rate of grain growth in the electrode. The rate of growth depends on several physical characteristics of each material, including the rate of diffusion of the material on itself. Grain growth rates for rhodium-tungsten and titanium nitride electrodes have been determined, and have been used to predict operating lifetimes of AMTEC electrodes. For lifetimes of 10 years or more, RhxW electrodes may be used at any operating temperature supportable by the electrolyte. TiN electrodes may be used in AMTEC cells only at operating temperatures under 1150 K.
Technical Paper

Slow Reversible and Quasi-Reversible Performance Changes in AMTEC Electrodes and Electrolytes

1999-08-02
1999-01-2705
This paper reports several slow reversible and quasi-reversible processes which occur in the porous electrode/solid electrolyte combination at AMTEC operating temperatures. These processes help to elucidate the evolution of the electrode and electrolyte characteristics with time. They also demonstrate that the atomic constituents of the electrode/electrolyte engage in significant dynamic motion. We report the stability of the sodium beta“-alumina phase in low pressure sodium vapor at 1173K up to 3000 hours, and the decomposition of the sodium meta-aluminate (NaAlO2) phase present at about 1% in the BASE ceramic, which gives rise to transient local increases in the solid electrolyte resistivity due to local micro-cracking. We also report slow apparent morphological changes, possibly surface or grain boundary reconstruction, in TiN and RhW electrodes driven by changes in the local sodium activity.
Technical Paper

Model for Grain Growth in AMTEC Electrodes

1999-08-02
1999-01-2703
The power produced by an AMTEC is dependent on the porosity of the electrode layers deposited on the surface of the BASE tubes. The elevated temperatures at which these power generators operate result in a slow growth or coalescence of the grains that comprise the electrode layers thereby reducing porosity and effective surface area. The lifetime of AMTEC electrodes is therefore related to the rate of grain growth of the electrode material. A preliminary model has been developed to determine the rate of grain growth over the operational lifetime of an AMTEC. This model examines the conditions for continuous growth as a function of the relative sizes, boundary and activation energies and mobilities of the grains. An assumption of strain-free growth has been made in determining the factors for normal growth. Experimental measurements for titanium nitride alloy electrodes are compared with this model. Predictions are made for performance lifetimes out to 10 years.
Technical Paper

Validation of the SCARLET Advanced Array on DS1

1999-08-02
1999-01-2630
In October, 1998, the first of the NASA New Millennium Spacecraft, DS1, was successfully launched into space. The objectives for this spacecraft are to test advanced technologies that can reduce the cost or risk of future missions. One of these technologies is the Solar Concentrator Array with Refractive Linear Element Technology (SCARLET). Although part of the advanced technology validation study, the array is also the spacecraft power source. Funded by BMDO, the SCARLET™ concentrator solar array is the first spaceflight application of a refractive lens concentrator. As part of the DS1 validation process, the amount of array diagnostics is very extensive. The data obtained includes temperature measurements at numerous locations on the 2-wing solar array. For each individual panel, a 5-cell module in one of the circuit strings is wired so that a complete I-V curve can be obtained. This data is used to verify sun pointing accuracy and array output performance.
Technical Paper

Mars Rover 2003 Battery Charger

1999-08-02
1999-01-2447
The Jet Propulsion Laboratory Mars Exploration Program Office is currently planning a series of exciting missions to the Red Planet. During each launch opportunity, the missions to Mars will include a Rover mission. During the earlier Rover missions to Mars such as the Mars Pathfinder mission carrying the Sojourner Rover in 1997, the main rover power source was a solar array. The power subsystem of the Sojourner Rover included a solar panel for power during the day, a non-rechargeable lithium battery for power during the night, and a power electronics board for power conditioning and distribution. Starting with the year 2003 the rover missions to Mars will incorporate a rechargeable energy storage device rather than a non-rechargeable power source. Included in the power electronics board, will be a battery controller/charger. The battery controller/charger will be able to monitor and control three parallel 4-cell battery strings.
Technical Paper

Noise Environment Reduction Foam Spheres in Space

1989-09-01
892373
The advent of lightweight fairings for new spacecraft and the increased thrust of new launch vehicles have intensified the need for better techniques for predicting and for reducing the low frequency noise environment of spacecraft at lift-off. This paper presents a VAPEPS (VibroAcoustic Payload Environment Prediction System) parametrical analysis of the noise reduction of spacecraft fairings and explores a novel technique for increasing the low frequency noise reduction of lightweight fairings by approximately 10 dB.
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