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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS2018

GT SUITE Fuel Cell Model Validation with Power Module Test Data

The AES Modular Power Systems (AMPS) Fuel Cell team at the NASA Glenn Research Center (GRC) has created a Microsoft Excel model of a regenerative fuel cell (RFC) system for potential lunar and Martian applications. Due to some limitations of this model, including the ability to predict transient effects in the thermal and fluidic performance of the system, a system-level transient thermal/fluids model was desired. GT-SUITE is a transient multi-physics simulation tool that is popular in the automotive industry and has a built in template for proton exchange membrane (PEM) fuel cells. However, terrestrial fuel cells used in the automotive industry vary significantly from aerospace fuel cells. A validation effort was undertaken to compare GT SUITE model results to actual data collected during the 2015 AMPS Power Module Demonstration in which the AMPS team used a PEM fuel cell system to power a 478 kg rover assembly at the Dunes test site located at GRC. The purpose of the model was to evaluate the efficacy of using GT SUITE to model a non-flow through PEM fuel cell system. The validation effort examined electrochemical performance including fuel cell stack voltage and power supplied, the thermal performance of the stack namely stack temperature and heat rejection rates, and the fluidic performance of the system including pressures, reactant consumption, and water production rates.

Gilligan, Ryan↗
NASA NTRS2018

Fuel Cell Model Validation with Power Module Test Data

The AES Modular Power Systems (AMPS) Fuel Cell team at the NASA Glenn Research Center (GRC) has created a Microsoft Excel model of a regenerative fuel cell (RFC) system for potential lunar and Martian applications. Due to some limitations of this model, including the ability to predict transient effects in the thermal and fluidic performance of the system, a system-level transient thermal/fluids model was desired. GT-SUITE is a transient multi-physics simulation tool that is popular in the automotive industry and has a built-in template for proton exchange membrane (PEM) fuel cells. However, terrestrial fuel cells used in the automotive industry vary significantly from aerospace fuel cells. A validation effort was undertaken to compare GT SUITE model results to actual data collected during the 2015 AMPS (Advanced Exploration Systems (AES) Modular Power Systems) Power Module Demonstration in which the AMPS team used a PEM fuel cell system to power a 478 kilogram rover assembly at the Dunes test site located at GRC. The purpose of the model was to evaluate the efficacy of using GT SUITE to model a non-flow through PEM fuel cell system. The validation effort examined electrochemical performance including fuel cell stack voltage and power supplied, the thermal performance of the stack namely stack temperature and heat rejection rates, and the fluidic performance of the system including pressures, reactant consumption, and water production rates.

Model Validation↗
NASA NTRS2001

Stirling Technology Development at NASA GRC

The Department of Energy, Stirling Technology Company (STC), and NASA Glenn Research Center (NASA Glenn) are developing a free-piston Stirling convertor for a high efficiency Stirling Radioisotope Generator (SRG) for NASA Space Science missions. The SRG is being developed for multimission use, including providing electric power for unmanned Mars rovers and deep space missions. NASA Glenn is conducting an in-house technology project to assist in developing the convertor for space qualification and mission implementation. Recent testing of 55-We Technology Demonstration Convertors (TDCs) built by STC includes mapping of a second pair of TDCs, single TDC testing, and TDC electromagnetic interference and electromagnetic compatibility characterization on a nonmagnetic test stand. Launch environment tests of a single TDC without its pressure vessel to better understand the convertor internal structural dynamics and of dual-opposed TDCs with several engineering mounting structures with different natural frequencies have recently been completed. A preliminary life assessment has been completed for the TDC heater head, and creep testing of the IN718 material to be used for the flight convertors is underway. Long-term magnet aging tests are continuing to characterize any potential aging in the strength or demagnetization resistance of the magnets used in the linear alternator (LA). Evaluations are now beginning on key organic materials used in the LA and piston/rod surface coatings. NASA Glenn is also conducting finite element analyses for the LA, in part to look at the demagnetization margin on the permanent magnets. The world's first known integrated test of a dynamic power system with electric propulsion was achieved at NASA Glenn when a Hall-effect thruster was successfully operated with a free-piston Stirling power source. Cleveland State University is developing a multidimensional Stirling computational fluid dynamics code to significantly improve Stirling loss predictions and assist in identifying convertor areas for further improvements. This paper will update the status and results for these efforts.

Thieme, Lanny G.↗
NASA NTRS2008

Embossed Teflon AF Laminate Membrane Microfluidic Diaphragm Valves

A microfluidic system has been designed to survive spaceflight and to function autonomously on the Martian surface. It manipulates microscopic quantities of liquid water and performs chemical analyses on these samples to assay for the presence of molecules associated with past or present living processes. This technology lies at the core of the Urey Instrument, which is scheduled for inclusion on the Pasteur Payload of the ESA ExoMars rover mission in 2013. Fabrication processes have been developed to make the microfabricated Teflon-AF microfluidic diaphragm pumps capable of surviving extreme temperature excursions before and after exposure to liquid water. Two glass wafers are etched with features and a continuous Teflon membrane is sandwiched between them (see figure). Single valves are constructed using this geometry. The microfabricated devices are then post processed by heating the assembled device while applying pneumatic pressure to force the Teflon diaphragm against the valve seat while it is softened. After cooling the device, the embossed membrane retains this new shape. This solves previous problems with bubble introduction into the fluid flow where deformations of the membrane at the valve seat occurred during device bonding at elevated temperatures (100-150 C). The use of laminated membranes containing commercial Teflon AF 2400 sheet sandwiched between spun Teflon AF 1600 layers performed best, and were less gas permeable than Teflon AF 1600 membranes on their own. Spinning Teflon AF 1600 solution (6 percent in FLOURINERT(Registered TradeMark) FC40 solvent, 3M Company) at 500 rpm for 1.5 seconds, followed by 1,000 rpm for 3 seconds onto Borofloat glass wafers, results in a 10-micron-thick film of extremely smooth Teflon AF. This spinning process is repeated several times on flat, blank, glass wafers in order to gradually build a thick, smooth membrane. After running this process at least five times, the wafer and Teflon coating are heated under vacuum at 220 C for one hour in order to drive off any residual solvent present in the composite film. After this, a second blank, glass wafer is brought down from above and the stack is held under vacuum at 3 atm mechanical pressure for ten 10 hours.

Willis, Peter↗
NASA NTRSDate not supplied

Post-flight Analysis of Atmospheric Properties from Mars 2020 Entry, Descent, and Landing

The Mars 2020 spacecraft landed the Perseverance rover and Ingenuity helicopter successfully in Jezero crater on Feb. 18, 2021. The entry, descent, and landing (EDL) sequence of the spacecraft largely leveraged the previous Mars Science Laboratory (MSL) mission. The atmospheric modeling approach for Mars 2020 was also borrowed from MSL, and consisted of utilizing two mesoscale atmospheric models of the landing site during the Martian season of landing, and using that data to create a statistical model of the pressure, density, temperature, and winds that Mars 2020 could have expected to encounter. Additionally, Mars 2020 contained an optical sensor - Landing Vision System (LVS) - that relied on taking pictures of the terrain, and was sensitive to the dust opacity of the atmosphere. This paper will briefly describe the pre-flight atmospheric models used for Mars 2020, but will focus on post-flight assessment of these models by comparing them to near-landing day orbiter sounder data and onboard atmospheric measurements. Suggestions for potential model changes will be also discussed.

Soumyo Dutta↗
NASA NTRSDate not supplied

Post-flight Analysis of Atmospheric Properties from Mars 2020 Entry, Descent, and Landing

The Mars 2020 spacecraft landed the Perseverance rover and Ingenuity helicopter successfully in Jezero crater on Feb. 18, 2021. The entry, descent, and landing (EDL) sequence of the spacecraft largely leveraged the previous Mars Science Laboratory (MSL) mission. The atmospheric modeling approach for Mars 2020 was also borrowed from MSL, and consisted of utilizing two mesoscale atmospheric models of the landing site during the Martian season of landing, and using that data to create a statistical model of the pressure, density, temperature, and winds that Mars 2020 could have expected to encounter. Additionally, Mars 2020 contained an optical sensor - Landing Vision System (LVS) - that relied on taking pictures of the terrain, and was sensitive to the dust opacity of the atmosphere. This paper will briefly describe the pre-flight atmospheric models used for Mars 2020, but will focus on post-flight assessment of these models by comparing them to near-landing day orbiter sounder data and onboard atmospheric measurements. Suggestions for potential model changes will be also discussed.

Soumyo Dutta↗
NASA NTRS2015

Design and Demonstration of the Mars Organic Molecule Analyzer (MOMA) on the ExoMars 2018 Rover

The Mars Organic Molecule Analyzer (MOMA) investigation is a key astrobiology experiment scheduled to launch on the joint ESA-Roscosmos ExoMars 2018 rover mission. MOMA will examine the chemical composition of geological samples acquired from depths of up to two meters below the martian surface, where fragile organic molecules may be protected from destructive cosmic radiation and/or oxidative chemical reactions. The heart of the MOMA mass spectrometer subsystem (i.e., MOMA-MS) is a miniaturized linear ion trap (LIT) that supports two distinct modes of operation to detect: i) volatile and semi-volatile, low-to-moderate mass organics (less than or equal to 500 Da) via pyrolysis coupled with gas chromatography mass spectrometry (pyr/GCMS); and, ii) more refractory, moderate-to-high mass compounds (up to 1000 Da) via laser desorption (LDMS) at ambient Mars pressures. Additionally, the LIT mass analyzer enables selective ion trapping via multi-frequency waveform ion excitation (e.g., stored waveform inverse Fourier transform, or SWIFT), and structural characterization of complex molecules using tandem mass spectrometry (MSIMS). A high-fidelity Engineering Test Unit (ETU) of MOMAMS, including the LIT subassembly, dual-gun electron ionization source, micropirani pressure gauge, solenoid-driven aperture valve, redundant detection chains, and control electronics, has been built and tested at NASA GSFC under relevant operational conditions (pressure, temperature, etc.). Spaceflight qualifications of individual hardware components and integrated subassemblies have been validated through vibration, shock, thermal, lifetime, and performance evaluations. The ETU serves as a pathfinder for the flight model buildup, integration and test, as the ETU meets the form, fit and function of the flight unit that will be delivered to MPS in late 2015. To date, the ETU of MOMA-MS has been shown to meet or exceed all functional requirements, including mass range, resolution, accuracy, instrumental drift, and Iimit-of-detection specifications, thereby enabling the primary science objectives of the MOMA investigation and ExoMars 2018 mission.

Mars Organic Molecule Analyzer↗
NASA NTRS2000

The Mars Project: Avoiding Decompression Sickness on a Distant Planet

A cost-effective approach for Mars exploration is to use available resources, such as water and atmospheric gases. Nitrogen (N2) and argon (Ar) are available and could form the inert gas component of a habitat atmosphere at 8.0, 9.0, or 10.0 pounds per square inch (psia). The habitat and space suit are designed as an integrated system: a comfortable living environment about 85% of the time and a safe working environment about 15% of the time. A goal is to provide a system that permits unrestricted exploration of Mars, but the risk of decompression sickness (DCS) during the extravehicular activity in a 3.75-psia suit, after exposure to any of the three habitat conditions, may limit unrestricted exploration. I evaluate here the risk of DCS since a significant proportion of a trinary breathing gas in the habitat might contain Ar. I draw on past experience and published information to extrapolate into untested, multivariable conditions to evaluate risk. A rigorous assessment of risk as a probability of DCS for each habitat condition is not yet possible. Based on many assumptions about Ar in hypobaric decompressions, I conclude that the presence of Ar significantly increases the risk of DCS. The risk is significant even with the best habitat option: 2.56 psia oxygen, 3.41 psia N2, and 2.20 psia Ar. Several hours of prebreathing 100% 02, a higher suit pressure, or a combination of other important variables such as limited exposure time on the surface or exercise during prebreathe would be necessary to reduce the risk of DCS to an acceptable level. The acceptable level for DCS risk on Mars has not yet been determined. Mars is a great distance from Earth and therefore from primary medical care. The acceptable risk would necessarily be defined by the capability to treat DCS in the Rover vehicle, in the habitat, or both.

Conkin, Johnny↗
NASA NTRS2002

Stirling Technology Development at NASA GRC

The Department of Energy, Stirling Technology Company (STC), and NASA Glenn Research Center (NASA Glenn) are developing a free-piston Stirling convertor for a high-efficiency Stirling Radioisotope Generator (SRG) for NASA Space Science missions. The SRG is being developed for multimission use, including providing electric power for unmanned Mars rovers and deep space missions. NASA Glenn is conducting an in-house technology project to assist in developing the convertor for space qualification and mission implementation. Recent testing, of 55-We Technology Demonstration Convertors (TDC's) built by STC includes mapping, of a second pair of TDC's, single TDC testing, and TDC electromagnetic interference and electromagnetic compatibility characterization on a nonmagnetic test stand. Launch environment tests of a single TDC without its pressure vessel to better understand the convertor internal structural dynamics and of dual-opposed TDC's with several engineering mounting structures with different natural frequencies have recently been completed. A preliminary life assessment has been completed for the TDC heater head, and creep testing of the IN718 material to be used for the flight convertors is underway. Long-term magnet aging tests are continuing to characterize any potential aging in the strength or demagnetization resistance of the magnets used in the linear alternator (LA). Evaluations are now beginning on key organic materials used in the LA and piston/rod surface coatings. NASA Glenn is also conducting finite element analyses for the LA, in part to look at the demagnetization margin on the permanent magnets. The world's first known integrated test of a dynamic power system with electric propulsion was achieved at NASA Glenn when a Hall-effect thruster was successfully operated with a free-piston Stirling power source. Cleveland State University is developing a multidimensional Stirling computational fluid dynamics code to significantly improve Stirling loss predictions and assist in identifying convertor areas for further improvements. This paper will update the status and results for these efforts.

Thieme, Lanny G.↗
NASA NTRSDate not supplied

Mars 2020 Reconstructed Aerothermal Environments and Design Margins

The Mars 2020 aeroshell's thermal protection system was nearly identical to the Mars Science Laboratory system that successfully completed its mission for the Curiosity rover's landing in 2012. It was predicted that, like Mars Science Laboratory, the Mars 2020 heatshield would experience boundary layer transition and that the thermal protection system would provide sufficient material thickness margins against the aerothermal environments, even after adding radiative heating that was not included for Mars Science Laboratory. The Mars 2020 flight instrumentation suite included heatshield sensors similar to Mars Science Laboratory and new backshell measurements. A full set of surface pressure and in-depth temperature data were collected during atmospheric entry. This paper provides an initial analysis of the flight data and focuses on the reconstructed total surface heat flux inferred from the measured temperatures. Turbulent boundary layer conditions again were observed on the Mars 2020 heatshield, and the temperatures at all eleven heatshield and six backshell thermocouple in-depth sensor locations were well within system capabilities due to favorable entry conditions and conservative uncertainties. New computational fluid dynamics results on the reconstructed entry trajectory are compared to the measured surface pressures and reconstructed total heat fluxes. The predicted heatshield surface pressures at six locations match the data qualitatively and quantitatively well, as expected. Smooth-wall laminar heating predictions prior to boundary layer transition fall above the reconstructed heating on the heatshield. After the observed boundary layer transition time, total heat flux based on algebraic turbulence model calculations generally match the heat flux trends relative to one another. The convective heat flux was predicted to constitute the majority of the total heating. On the backshell, smooth-wall laminar total heat flux predictions generally exceed the reconstructed total heating at six locations. At each of these locations, it is estimated that radiative heating provided almost all of the total heating. The Mars 2020 as-flown aerothermal environments were well below the design levels for all measurement locations due to conservative design assumptions and a stressing design trajectory.

Mars 2020↗
NASA NTRSDate not supplied

Mars 2020 Reconstructed Aerothermal Environments and Design Margins

The Mars 2020 aeroshell's thermal protection system was nearly identical to the Mars Science Laboratory system that successfully completed its mission for the Curiosity rover's landing in 2012. It was predicted that, like Mars Science Laboratory, the Mars 2020 heatshield would experience boundary layer transition and that the thermal protection system would provide sufficient material thickness margins against the aerothermal environments, even after adding radiative heating that was not included for Mars Science Laboratory. The Mars 2020 flight instrumentation suite included heatshield sensors similar to Mars Science Laboratory and new backshell measurements. A full set of surface pressure and in-depth temperature data were collected during atmospheric entry. This paper provides an initial analysis of the flight data and focuses on the reconstructed total surface heat flux inferred from the measured temperatures. Turbulent boundary layer conditions again were observed on the Mars 2020 heatshield, and the temperatures at all eleven heatshield and six backshell thermocouple in-depth sensor locations were well within system capabilities due to favorable entry conditions and conservative uncertainties. New computational fluid dynamics results on the reconstructed entry trajectory are compared to the measured surface pressures and reconstructed total heat fluxes. The predicted heatshield surface pressures at six locations match the data qualitatively and quantitatively well, as expected. Smooth-wall laminar heating predictions prior to boundary layer transition fall above the reconstructed heating on the heatshield. After the observed boundary layer transition time, total heat flux based on algebraic turbulence model calculations generally match the heat flux trends relative to one another. The convective heat flux was predicted to constitute the majority of the total heating. On the backshell, smooth-wall laminar total heat flux predictions generally exceed the reconstructed total heating at six locations. At each of these locations, it is estimated that radiative heating provided almost all of the total heating. The Mars 2020 as-flown aerothermal environments were well below the design levels for all measurement locations due to conservative design assumptions and a stressing design trajectory.

Mars 2020↗
NASA NTRS2008

Advanced Stirling Convertor Heater Head Durability and Reliability Quantification

The National Aeronautics and Space Administration (NASA) has identified the high efficiency Advanced Stirling Radioisotope Generator (ASRG) as a candidate power source for long duration Science missions, such as lunar applications, Mars rovers, and deep space missions, that require reliable design lifetimes of up to 17 years. Resistance to creep deformation of the MarM-247 heater head (HH), a structurally critical component of the ASRG Advanced Stirling Convertor (ASC), under high temperatures (up to 850 C) is a key design driver for durability. Inherent uncertainties in the creep behavior of the thin-walled HH and the variations in the wall thickness, control temperature, and working gas pressure need to be accounted for in the life and reliability prediction. Due to the availability of very limited test data, assuring life and reliability of the HH is a challenging task. The NASA Glenn Research Center (GRC) has adopted an integrated approach combining available uniaxial MarM-247 material behavior testing, HH benchmark testing and advanced analysis in order to demonstrate the integrity, life and reliability of the HH under expected mission conditions. The proposed paper describes analytical aspects of the deterministic and probabilistic approaches and results. The deterministic approach involves development of the creep constitutive model for the MarM-247 (akin to the Oak Ridge National Laboratory master curve model used previously for Inconel 718 (Special Metals Corporation)) and nonlinear finite element analysis to predict the mean life. The probabilistic approach includes evaluation of the effect of design variable uncertainties in material creep behavior, geometry and operating conditions on life and reliability for the expected life. The sensitivity of the uncertainties in the design variables on the HH reliability is also quantified, and guidelines to improve reliability are discussed.

Krause, David L.↗
NASA NTRSDate not supplied

Variable Pressure - Scanning Electron Microscopy (VP-SEM)

Variable Pressure (or Environmental) Scanning Electron Microscopy (VP-SEM) combined with Energy Dispersive X-ray Spectroscopy (EDS) is one of the most powerful methods for characterizing the sub-micron topography and chemical composition of uncoated samples. Terrestrially, VP-SEM is extensively used to non-destructively study geologic and manufactured materials with high spatial resolution (tens of nanometers) and large depth-of-field. An SEM offers a geologist a first survey of microscopic mineral phases via secondary electron imaging (SEI), which provides a topographic look at a sample, as well as backscattered electron (BEI) imaging, which contrasts the phases present based on their geochemistry (atomic number). A VP-SEM utilizes a gas in the sample chamber as a charge dissipation and signal amplification method, allowing analysis of a sample without preparation in the form of a conductive coating. A miniaturized VP-SEM operating in-situ on a lander or rover would be able to use the CO2-rich Martian atmosphere (e.g., Nier et al., 1976; Williams 2016) as an imaging medium for this purpose. Adaptation of a VP-SEM for in-situ Mars surface studies will provide a new imaging capability (via SEI) that is at least an order of magnitude higher resolution than the Mars Hand Lens Imager (MAHLI) on the Mars Science Laboratory (Williams et al., 2015), and equal to or better than the achieved resolution of the Atomic Force Microscope on the Phoenix Mars lander (Pike et al., 2011). In addition, the MVP-SEM is capable of BSI and simultaneous chemical analysis of the imaged region. In this sense, the MVP-SEM can be regarded as an instrument suite that will provide a new set of information not achievable by any other instrument. The Miniaturized Variable Pressure Scanning Electron Microscope (MVP-SEM) was designed, built, and benchtop tested by a team at NASA’s Marshall Space Flight Center and Jet Propulsion Laboratory (JPL), Jacobs Space Exploration Group, Applied Physics Technologies, Inc. (AP-Tech), and Creare LLC, working with a team of technical and science collaborators. Benchtop testing was successful, proving concept feasibility. To date, the MVP-SEM has achieved an imaging resolution of <100 nm in the lab, and with continued optimization, even better performance (~50 nm resolution) is possible. Use in-situ on the lunar or other planetary surfaces would require some redesign to optimize instrument performance, but such an instrument would be equally useful.

Variable Pressure Scanning Electron Microscopy↗
NASA NTRSDate not supplied

Miniature Variable Pressure - Scanning Electron Microscopy (MVP-SEM)

Variable Pressure (or Environmental) Scanning Electron Microscopy (VP-SEM) combined with Energy Dispersive X-ray Spectroscopy (EDS) is one of the most powerful methods for characterizing the sub-micron topography and chemical composition of uncoated samples. Terrestrially, VP-SEM is extensively used to non-destructively study geologic and manufactured materials with high spatial resolution (tens of nanometers) and large depth-of-field. An SEM offers a geologist a first survey of microscopic mineral phases via secondary electron imaging (SEI), which provides a topographic look at a sample, as well as backscattered electron (BEI) imaging, which contrasts the phases present based on their geochemistry (atomic number). A VP-SEM utilizes a gas in the sample chamber as a charge dissipation and signal amplification method, allowing analysis of a sample without preparation in the form of a conductive coating. A miniaturized VP-SEM operating in-situ on a lander or rover would be able to use the CO2-rich Martian atmosphere (e.g., Nier et al., 1976; Williams 2016) as an imaging medium for this purpose. Adaptation of a VP-SEM for in-situ Mars surface studies will provide a new imaging capability (via SEI) that is at least an order of magnitude higher resolution than the Mars Hand Lens Imager (MAHLI) on the Mars Science Laboratory (Williams et al., 2015), and equal to or better than the achieved resolution of the Atomic Force Microscope on the Phoenix Mars lander (Pike et al., 2011). In addition, the MVP-SEM is capable of BSI and simultaneous chemical analysis of the imaged region. In this sense, the MVP-SEM can be regarded as an instrument suite that will provide a new set of information not achievable by any other instrument. The Miniaturized Variable Pressure Scanning Electron Microscope (MVP-SEM) was designed, built, and benchtop tested by a team at NASA’s Marshall Space Flight Center and Jet Propulsion Laboratory (JPL), Jacobs Space Exploration Group, Applied Physics Technologies, Inc. (AP-Tech), and Creare LLC, working with a team of technical and science collaborators. Benchtop testing was successful, proving concept feasibility. To date, the MVP-SEM has achieved an imaging resolution of <100 nm in the lab, and with continued optimization, even better performance (~50 nm resolution) is possible. Use in-situ on the lunar or other planetary surfaces would require some redesign to optimize instrument performance, but such an instrument would be equally useful.

Variable Pressure Scanning Electron Microscopy↗
NASA NTRS2011

GeoLab's First Field Trials, 2010 Desert RATS: Evaluating Tools for Early Sample Characterization

As part of an accelerated prototyping project to support science operations tests for future exploration missions, we designed and built a geological laboratory, GeoLab, that was integrated into NASA's first generation Habitat Demonstration Unit-1/Pressurized Excursion Module (HDU1-PEM). GeoLab includes a pressurized glovebox for transferring and handling samples collected on geological traverses, and a suite of instruments for collecting preliminary data to help characterize those samples. The GeoLab and the HDU1-PEM were tested for the first time as part of the 2010 Desert Research and Technology Studies (DRATS), NASA's analog field exercise for testing mission technologies. The HDU1- PEM and GeoLab participated in two weeks of joint operations in northern Arizona with two crewed rovers and the DRATS science team.

Evans, Cindy A.↗
NASA NTRS2012

Mars Science Laboratory Rover Integrated Pump Assembly Bellows Jamming Failure

The Mars Science Laboratory rover and spacecraft utilize two mechanically pumped fluid loops for heat transfer to and from the internal electronics assemblies and the Radioisotope Thermo-Electric Generator (RTG). The heat transfer fluid is Freon R-11 (CFC-11) which has a large coefficient of thermal expansion. The Freon within the heat transfer system must have a volume for safe expansion of the fluid as the system temperature rises. The device used for this function is a gas-over-liquid accumulator. The accumulator uses a metal bellows to separate the fluid and gas sections. During expansion and contraction of the fluid in the system, the bellows extends and retracts to provide the needed volume change. During final testing of a spare unit, the bellows would not extend the full distance required to provide the needed expansion volume. Increasing the fluid pressure did not loosen the jammed bellows either. No amount of stroking the bellows back and forth would get it to pass the jamming point. This type of failure, if it occurred during flight, would result in significant overpressure of the heat transfer system leading to a burst failure at some point in the system piping. A loss of the Freon fluid would soon result in a loss of the mission. The determination of the source of the jamming of the bellows was quite elusive, leading to an extensive series of tests and analyses. The testing and analyses did indicate the root cause of the failure, qualitatively. The results did not provide a set of dimensional limits for the existing hardware design that would guarantee proper operation of the accumulator. In the end, a new design was developed that relied on good engineering judgment combined with the test results to select a reliable enough solution that still met other physical constraints of the hardware, the schedule, and the rover system.

bellows↗
DOE OSTI2022

In situ recording of Mars soundscape

Abstract Before the Perseverance rover landing, the acoustic environment of Mars was unknown. Models predicted that: (1) atmospheric turbulence changes at centimetre scales or smaller at the point where molecular viscosity converts kinetic energy into heat 1 , (2) the speed of sound varies at the surface with frequency 2,3 and (3) high-frequency waves are strongly attenuated with distance in CO 2 (refs. 2–4 ). However, theoretical models were uncertain because of a lack of experimental data at low pressure and the difficulty to characterize turbulence or attenuation in a closed environment. Here, using Perseverance microphone recordings, we present the first characterization of the acoustic environment on Mars and pressure fluctuations in the audible range and beyond, from 20 Hz to 50 kHz. We find that atmospheric sounds extend measurements of pressure variations down to 1,000 times smaller scales than ever observed before, showing a dissipative regime extending over five orders of magnitude in energy. Using point sources of sound (Ingenuity rotorcraft, laser-induced sparks), we highlight two distinct values for the speed of sound that are about 10 m s −1 apart below and above 240 Hz, a unique characteristic of low-pressure CO 2 -dominated atmosphere. We also provide the acoustic attenuation with distance above 2 kHz, allowing us to explain the large contribution of the CO 2 vibrational relaxation in the audible range. These results establish a ground truth for the modelling of acoustic processes, which is critical for studies in atmospheres such as those of Mars and Venus.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2012

Calibration and Sequence Development Status for the Sample Analysis at Mars Investigation on the Mars Science Laboratory

The measurement goals of the Sample Analysis at Mars (SAM) instrument suite on the "Curiosity" Rover of the Mars Science Laboratory (MSL) include chemical and isotopic analysis of organic and inorganic volatiles for both atmospheric and solid samples [1,2]. SAM directly supports the ambitious goals of the MSL mission to provide a quantitative assessment of habitability and preservation in Gale crater by means of a range of chemical and geological measurements [3]. The SAM FM combined calibration and environmental testing took place primarily in 2010 with a limited set of tests implemented after integration into the rover in January 2011. The scope of SAM FM testing was limited both to preserve SAM consumables such as life time of its electromechanical elements and to minimize the level of terrestrial contamination in the SAM instrument. A more comprehensive calibration of a SAM-like suite of instruments will be implemented in 2012 with calibration runs planned for the SAM testbed. The SAM Testbed is nearly identical to the SAM FM and operates in a ambient pressure chamber. The SAM Instrument Suite: SAM's instruments are a Quadrupole Mass Spectrometer (QMS), a 6-column Gas Chromatograph (GC), and a 2-channel Tunable Laser Spectrometer (TLS). Gas Chromatography Mass Spectrometry is designed for identification of even trace organic compounds. The TLS [5] secures the C, H, and O isotopic composition in carbon dioxide, water, and methane. Sieved materials are delivered from the MSL sample acquisition and processing system to one of68 cups of the Sample Manipulation System (SMS). 59 of these cups are fabricated from inert quartz. After sample delivery, a cup is inserted into one of 2 ovens for evolved gas analysis (EGA ambient to >9500C) by the QMS and TLS. A portion of the gas released can be trapped and subsequently analyzed by GCMS. Nine sealed cups contain liquid solvents and chemical derivatization or thermochemolysis agents to extract and transform polar molecules such as amino acids, nucleobases, and carboxylic acids into compounds that are sufficiently volatile to transmit through the GC columns. The remaining 6 cups contain calibrants. SAM FM Calibration Overview: The SAM FM calibration in the Mars chamber employed a variety of pure gases, gas mixtures, and solid materials. Isotope calibration runs for the TLS utilized 13C enriched C02 standards and 0 enriched CH4. A variety of fluorocarbon compounds that spanned the entire mass range of the QMS as well as C3-C6 hydrocarbons were utilized for calibration of the GCMS. Solid samples consisting of a mixture of calcite, melanterite, and inert silica glass either doped or not with fluorocarbons were introduced into the SAM FM cups through the SAM inlet funnel/tube system.

Mahaffy, Paul R.↗