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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.

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.

Polymers are one of the major constituents in electrical components. A study investigating pre-combustion off-gassing and particle release by polymeric materials over a range of temperatures can provide an understanding of thermal degradation prior to failure which may result in a fire hazard. In this work, we report simultaneous measurements of pre-combustion vapor and particle release by heated polymeric materials. The polymer materials considered for the current study are silicone and Kapton. The polymer samples were heated over the range 20 to 400°C. Response to vapor releases were recorded using the JPL Electronic Nose (ENose) and Industrial Scientific's ITX gas monitor configured to detect hydrogen chloride (HCl), carbon monoxide (CO) and hydrogen cyanide (HCN). Particle release was monitored using a TSI P-TRAK particle counter.

The Third Generation ENose is an air quality monitor designed to operate in the environment of the US Lab on the International Space Station. It detects a selected group of analytes at target concentrations in the ppm regime at an environmental temperature range of 18 - 30 °C, relative humidity from 25 - 75% and pressure from 530 to 760 torr. The abilities of the device to detect ten analytes, to reject confounders as “unknown” and to deconvolute mixtures of two analytes under varying environmental conditions has been tested extensively in the laboratory. Results of ground testing showed an overall success rate for detection, identification and quantification of analytes of 87% under nominal temperature and humidity conditions and 83% over all conditions.

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.

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.

An array-based sensing system based on polymer-carbon composite conductometric sensors is under development at JPL for use as an environmental monitor in the International Space Station. Sulfur dioxide has been added to the analyte set for this phase of development. Using molecular modeling techniques, the interaction energy between SO2 and polymer functional groups has been calculated, and polymers selected as potential SO2 sensors. Experiment has validated the model and two selected polymers have been shown to be promising materials for SO2 detection.

An array-based sensing system based on 32 polymer/carbon composite conductometric sensors is under development at JPL. Until the present phase of development, the analyte set has focused on organic compounds (common solvents) and a few selected inorganic compounds, notably ammonia and hydrazine. The present phase of JPL ENose development has added two inorganics to the analyte set: mercury and sulfur dioxide. Through models of sensor-analyte response developed under this program coupled with a literature survey, approaches to including these analytes in the ENose target set have been determined.

In January 2004, two Mars Exploration Rovers (MER) landed on the surface of Mars to begin their mission as robotic geologists. A year prior to these historic landings, both rovers and the spacecraft that delivered them to Mars, were completing a series of environmental tests in facilities at the Jet Propulsion Laboratory. This paper describes the test program undertaken to validate the thermal design and verify the workmanship integrity of both rovers and the spacecraft. The spacecraft, which contained the rover within the aeroshell, were tested in a 7.5 m diameter thermal vacuum chamber. Thermal balance was performed for the near earth (hot case) condition and for the near Mars (cold case) condition. A solar simulator was used to provide the solar boundary condition on the solar array. IR lamps were used to simulate the solar heat load on the aeroshell for the off-sun attitudes experienced by the spacecraft during its cruise to Mars.

As part of the Mars Exploration Rover (MER) project, the National Aeronautics and Space Administration (NASA) launched two rovers in June and July of 2003 and successfully landed both of them on Mars in January of 2004. The cruise stage of each spacecraft (S/C) housed most of the hardware needed to complete the cruise from Earth to Mars, including the propulsion system. Propulsion lines brought hydrazine propellant from tanks under the cruise stage to attitude-control thrusters located on the periphery of the cruise stage. Hydrazine will freeze in the propellant lines if it reaches temperatures below 1.7°C. Thermal control of the propulsion lines was a mission critical function of the thermal subsystem; a frozen propellant line could have resulted in loss of attitude control and complete loss of the S/C.

This paper describes a study on the capillary limit of a loop heat pipe (LHP) with two evaporators and two condensers. Both theoretical analysis and experimental investigation are performed. Experimental tests conducted include heat load to one evaporator only, even heat loads to both evaporators, and uneven heat loads to both evaporators. Test results show that after the capillary limit is exceeded, vapor will penetrate through the wick of the weaker evaporator, and the compensation chamber (CC) of that evaporator will control the loop operating temperature regardless of which CC has been in control prior to the event. Because the evaporator can tolerate vapor bubbles, the loop can continue to work after vapor penetration. As the loop operating temperature increases, the system pressure drop actually decreases due to a decrease in liquid and vapor viscosities. Thus, the loop may reach a new steady state at a higher operating temperature after vapor penetration.

Development of a second generation Electronic Nose at JPL is focusing on optimization of the sensing films to increase sensitivity and optimization of the array. Toward this goal, studies have focused on sources of noise in the films, alternatives to carbon black as conductive medium, measurement techniques, and development of an analytical approach to polymer selection to maximize the abilities of the array to distinguish among compounds.

Candidate Aeroshell Test models composed of a quasi-isotropic Carbon/Carbon(C/C) front face sheet (F/S), eggcrate core, C/C back F/S, Carbon Aerogel insulation, C/C radiation shield and the C/C close-out were constructed based on the analytical temperature predictions presented in Part One of this work[1]. The analytical results obtained for a simulated Mars entry of a 2.9 meter diameter cone shaped Carbon-Carbon Aeroshell demonstrated the feasibility of the design. These results showed that the maximum temperature the front F/S reached during the decent was 1752 °C with the resulting rear temperature reaching 326 °C in the thermal model. Part Two of this work documents the thermal modeling and correlation for the Mars Aeroshell test sample and fixture. A finite difference, SINDA/G, thermal math model of the test fixture and sample was generated and correlated to data from an arc jet test conducted at the NASA Ames Research Center's interactive heating facility.

Radiators will be used on Mars to reject excess heat from various processes and surfaces and will help temper the climate of any future manned habitats. Radiator performance is a function of the radiator size (area), the emissivity, ε, of the radiator surface, the radiator temperature, local environmental conditions, and the effective sky temperature to which it radiates. The effective sky temperature of Mars is not known. Previous estimates have ranged between 80 K to 170 K. Also, it is not known how dust accumulation and other environmental effects act to change the performance of a radiator as a function of time. The MTERC Experiment is designed to gather data to address these unknowns. This paper will describe the operational theory and the configuration of the MTERC experiment hardware and will discuss results of MTERC performance testing.

Human exploration of Mars as well as unmanned sample return missions from Mars can benefit greatly from the use of propellants produced from the resources available from the atmosphere of Mars. The first major step of any in-situ propellant production (ISPP) system is to acquire carbon dioxide (CO2) from the Mars atmosphere and compress it for further chemical processing. One system that performs this step is called a Mars Atmosphere Acquisition and Compression (MAAC) unit. A simple prototype MAAC was developed by JPL as part of the Mars ISPP Precursor (MIP) experiment package for inclusion on the Mars 2001 Surveyor Lander. The MAAC consists of a valved enclosure packed with a sorbent material which selectively adsorbs CO2 from the Mars atmosphere (valves open), desorbs and compresses the acquired CO2 by heating (valves closed) and then delivers the pressurized CO2 to an oxygen generating system where the CO2 is electrolyzed to produce oxygen.

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 Sojourner Rover landed on the surface of Mars on July 4, 1997 as part of the Mars Pathfinder Mission. The mission lasted almost three months during which the thermal design of the Rover was tested. This paper summarizes the Rover's design and performance as well as post-mission model correlation.