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Thermal characterization was performed on a vapor compression heat pump using a novel, hybrid two phase loop design. Previous work on this technology has demonstrated its ability to provide passive phase separation and flow control based on capillary action. This provides high quality vapor to the compressor without relying on gravity-based phase separation or other active devices. This paper describes the subsequent work done to characterize evaporator performance under various startup scenarios, tilt angles, and heat loads. The use of a thermal expansion valve as a method to regulate operation was investigated. The effect of past history of use on startup behavior was also studied. Testing under various tilt angles showed evaporator performance to be affected by both adverse and favorable tilts for the given compressor. And depending on the distribution of liquid in the system upon startup, markedly different performance can result for the same system settings and heat loads.

Phoenix is NASA's first Mars Scouts Mission that will place a soft-lander on the Martian surface at a high northern latitude. Much of the Mars surface environmental flight data from landed missions pertains to the near-equatorial regions. However, orbital observations have yielded very useful data about the surface environment. These data along with a simple, but highly effective one-dimensional atmospheric model was used to develop the Phoenix surface thermal environment. As candidate landing sites were identified, parametric studies including statistical variations were conducted to prescribe minimum nighttime and maximum daytime temperature design Sols (a Martian day). Atmospheric effects such as clouds and ice were considered. Finally, recent candidate landing site imaging conducted by the Mars Reconnaissance Orbiter revealed that the prime site contained a much higher rock density than first thought.

Work is underway to deliver an instrument for analysis of the atmosphere aboard the International Space Station. The Vehicle Cabin Atmosphere Monitor (VCAM) is based on a low-mass, low-power miniature preconcentrator gas chromatograph/mass spectrometer (PCGC/MS) capable of providing sub-ppm measurements of volatile constituents in a space vehicle or outpost. VCAM is designed to operate autonomously, maintenance-free, once per day, with its own carrier and calibration gas supplies sufficient for a one-year lifetime. VCAM performance is sufficient to detect and identify 90% of the target compounds specified at their 180-day Spacecraft Maximum Allowable Concentration (SMAC) levels. The flight units will be delivered in mid-2008 and be operated in the ISS EXPRESS rack.

The Orbiting Carbon Observatory (OCO) instrument is scheduled for launch onboard an Orbital Sciences Corporation LEOStar-2 architecture spacecraft in December 2008. The instrument will collect data to identify CO2 sources and sinks and quantify their seasonal variability. OCO observations will permit the collection of spatially resolved, high resolution spectroscopic observations of CO2 and O2 absorption in reflected sunlight over both continents and oceans. OCO has three bore-sighted, high resolution, grating spectrometers which share a common telescope with similar optics and electronics. A 0.765 μm channel will be used for O2 observations, while the weak and strong CO2 bands will be observed with 1.61 μm and 2.06 μm channels, respectively. The OCO spacecraft circular polar orbit will be sun-synchronous with an inclination of 98.2 degrees, mean altitude of 705 km and 98.9 minute orbit period.

A Small Loop Heat Pipe (SLHP) featuring a wick of only 1.27 cm (0.5 inches) in diameter has been designed for use in spacecraft thermal control. It has several features to accommodate a wide range of environmental conditions in both operating and non-operating states. These include flexible transport lines to facilitate hardware integration, a radiator capable of sustaining over 100 freeze-thaw cycles using ammonia as a working fluid and a structural integrity to sustain acceleration loads up to 30 g. The small LHP has a maximum heat transport capacity of 120 Watts with thermal conductance ranging from 17 to 21 W/°C. The design incorporates heaters on the compensation chamber to modulate the heat transport from full-on to full-stop conditions. A set of start up heaters are attached to the evaporator body using a specially designed fin to assist the LHP in starting up when it is connected to a large thermal mass.

The Trace Gas Analyzer (TGA, Figure 1) is a self-contained, battery-powered mass spectrometer that is designed for use by astronauts during extravehicular activities (EVA) on the International Space Station (ISS). The TGA contains a miniature quadrupole mass spectrometer array (QMSA) that determines the partial pressures of ammonia, hydrazines, nitrogen, and oxygen. The QMSA ionizes the ambient gas mixture and analyzes the component species according to their charge-to-mass ratio. The QMSA and its electronics were designed, developed, and tested by the Jet Propulsion Laboratory (1,2). Oceaneering Space Systems supported JPL in QMSA detector development by performing 3D computer for optimal volumetric integration, and by performing stress and thermal analyses to parameterize environmental performance.

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.

A paraffin-actuated heat switch has been developed for thermal control of the batteries used on the 2003 Mars Exploration Rovers. The heat switch is used to reject heat from the rover battery to a radiator. This paper describes the development test program designed, in part, to measure the thermal conductance of the heat switch in an 8 Torr CO2 environment over the expected operating temperature range of the battery. The switch has a closed conductance of about 0.6 W/°C and an open conductance of 0.019 W/°C. The test program also included measuring the battery temperature profile over a hot case and a cold case Mars diurnal cycle. The test results confirm that the battery will remain well within the upper and lower allowable flight temperatures in both cases.

Phoenix, NASA's first Mars Scouts mission, will be launched in 2007 and will soft-land inside the Martian Arctic Circle, between north 65° and 72° North latitude, in 2008 to study the water history and to search for habitable zones. Similar to the IDD (Instrument Deployment Device) on the Mars Exploration Rovers (MER), Phoenix has a Robotic Arm (RA) which is equipped with a scoop to dig into the icy soil and to deliver the soil samples to instruments for scientific observations and measurements. As with MER, the actuators and the bearings of the Phoenix RA in a non-operating condition can survive the cold Martian night without any electrical power or any thermal insulation. The RA actuators have a minimum operating allowable flight temperature (AFT) limit of -55°C, so, warm-up heaters are required to bring the temperatures of all the RA actuators above the operating AFT limit prior to early morning operation.

Early development of concepts for space structures up to 1000 meters in size was initiated in the early 1960's and carried through the 1970's. The enabling technologies were self-deployables, on-orbit assembly, and on-orbit manufacturing. Because of the lack of interest due to the astronomical cost associated with advancing the on-orbit assembly and manufacturing technologies, only self-deployable concepts were subsequently pursued. However, for over 50 years, potential users of deployable antennas for radar, radiometers, planar arrays, VLBF and others, are still interested and constantly revising the requirements for larger and higher precision structures. This trend persists today. An excellent example of this trend is the current DARPA/SPO ISAT Program that applies self-deployable structures technology to a 300 meter long active planar array radar antenna. This ongoing program has created a rare opportunity for innovative advancement of state-of-the-art concepts.

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.

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.

The overall goal of this program was the development of a 10 m. diameter, self-deployable antenna based on an open-celled rigid polyurethane foam system. Advantages of such a system relative to current inflatable or self-deploying systems include high volumetric efficiency of packing, high restoring force, low (or no) outgassing, low thermal conductivity, high dynamic damping, mechanical isotropy, infinite shelf life, and easy fabrication with methods amenable to construction of large structures (i.e., spraying). As part of a NASA Phase II SBIR, Adherent Technologies and its research partners, Temeku Technologies, and NASA JPL/Caltech, conducted activities in foam formulation, interdisciplinary analysis, and RF testing to assess the viability of using open cell polyurethane foams for self-deploying antenna applications.