Results for “Lander” — Page 86

NASA NTRS2012

Characterizing of a Mid-Latitude Ice-Rich Landing Site on Mars to Enable in Situ Habitability Studies

We suggest an ice-rich landing site at 188.5E 46.16N within Amazonis Planitia as a candidate location to support a Mars lander mission equipped to study past habitability and regions capable of preserving the physical and chemical signs of life and organic matter. Studies of the ice-rich subsurface on Mars are critical for several reasons. The subsurface environment provides protection from radiation to shield organic and biologic compounds from destruction. The ice-rich substrate is also ideal for preserving organic and biologic molecules and provides a source of H2O for biologic activity. Examination of martian ground ice can test several hypotheses such as: 1) whether ground ice supports habitable conditions, 2) that ground ice can preserve and accumulate organic compounds, and 3) that ice contains biomolecules evident of past or present biological activity on Mars. This Amazonis site, located near the successful Viking Lander 2, shows indirect evidence of subsurface ice (ubiquitous defined polygonal ground, gamma ray spectrometer hydrogen signature, and numerical modeling of ice stability) and direct evidence of exposed subsurface ice. This site also provides surface conditions favorable to a safe landing including no boulders, low rock density, minimal rough topography, and few craters.

Heldmann, J.↗

NASA NTRS2012

Mars Sample Return: The Next Step Required to Revolutionize Knowledge of Martian Geological and Climatological History

The capability of scientific instrumentation flown on planetary orbiters and landers has made great advances since the signature Viking mission of the seventies. At some point, however, the science return from orbital remote sensing, and even in situ measurements, becomes incremental, rather than revolutionary. This is primarily caused by the low spatial resolution of such measurements, even for landed instrumentation, the incomplete mineralogical record derived from such measurements, the inability to do the detailed textural, mineralogical and compositional characterization needed to demonstrate equilibrium or reaction paths, and the lack of chronological characterization. For the foreseeable future, flight instruments will suffer from this limitation. In order to make the next revolutionary breakthrough in understanding the early geological and climatological history of Mars, samples must be available for interrogation using the full panoply of laboratory-housed analytical instrumentation. Laboratory studies of samples allow for determination of parageneses of rocks through microscopic identification of mineral assemblages, evaluation of equilibrium through electron microbeam analyses of mineral compositions and structures, determination of formation temperatures through secondary ion or thermal ionization mass spectrometry (SIMS or TIMS) analyses of stable isotope compositions. Such details are poorly constrained by orbital data (e.g. phyllosilicate formation at Mawrth Vallis), and incompletely described by in situ measurements (e.g. genesis of Burns formation sediments at Meridiani Planum). Laboratory studies can determine formation, metamorphism and/or alteration ages of samples through SIMS or TIMS of radiogenic isotope systems; a capability well-beyond flight instrumentation. Ideally, sample return should be from a location first scouted by landers such that fairly mature hypotheses have been formulated that can be tested. However, samples from clastic sediments derived from an extensive region of Mars can provide important, detailed understanding of early martian geological and climatological history. Interrogating clastic "sediments" from the Earth, Moon and asteroids has allowed discovery of new crustal units, identification of now-vanished crust, and determination of the geological history of extensive, remote regions. Returned sample of martian fluvial and/or aeolian sediments, for example from Gale crater, could be "read like a book" in terrestrial laboratories to provide truly revolutionary new insights into early martian geological and climatological evolution.

Mittlefehldt, D. W.↗

NASA NTRS2009

Nuclear Thermal Rocket/Vehicle Characteristics And Sensitivity Trades For NASA's Mars Design Reference Architecture (DRA) 5.0 Study

This paper summarizes Phase I and II analysis results from NASA's recent Mars DRA 5.0 study which re-examined mission, payload and transportation system requirements for a human Mars landing mission in the post-2030 timeframe. Nuclear thermal rocket (NTR) propulsion was again identified as the preferred in-space transportation system over chemical/aerobrake because of its higher specific impulse (I(sub sp)) capability, increased tolerance to payload mass growth and architecture changes, and lower total initial mass in low Earth orbit (IMLEO) which is important for reducing the number of Ares-V heavy lift launches and overall mission cost. DRA 5.0 features a long surface stay (approximately 500 days) split mission using separate cargo and crewed Mars transfer vehicles (MTVs). All vehicles utilize a common core propulsion stage with three 25 klbf composite fuel NERVA-derived NTR engines (T(sub ex) approximately 2650 - 2700 K, p(sub ch) approximately 1000 psia, epsilon approximately 300:1, I(sub sp) approximately 900 - 910 s, engine thrust-toweight ratio approximately 3.43) to perform all primary mission maneuvers. Two cargo flights, utilizing 1-way minimum energy trajectories, pre-deploy a cargo lander to the surface and a habitat lander into a 24-hour elliptical Mars parking orbit where it remains until the arrival of the crewed MTV during the next mission opportunity (approximately 26 months later). The cargo payload elements aerocapture (AC) into Mars orbit and are enclosed within a large triconicshaped aeroshell which functions as payload shroud during launch, then as an aerobrake and thermal protection system during Mars orbit capture and subsequent entry, descent and landing (EDL) on Mars. The all propulsive crewed MTV is a 0-gE vehicle design that utilizes a fast conjunction trajectory that allows approximately 6-7 month 1-way transit times to and from Mars. Four 12.5 kW(sub e) per 125 square meter rectangular photovoltaic arrays provide the crewed MTV with approximately 50 kW(sub e) of electrical power in Mars orbit for crew life support and spacecraft subsystem needs. Vehicle assembly involves autonomous Earth orbit rendezvous and docking between the propulsion stages, in-line propellant tanks and payload elements. Nine Ares-V launches -- five for the two cargo MTVs and four for the crewed MTV -- deliver the key components for the three MTVs. Details on mission, payload, engine and vehicle characteristics and requirements are presented and the results of key trade studies are discussed.

Borowski, Stanley K.↗

NASA NTRS2009

Power Requirements for The NASA Mars Design Reference Architecture (DRA) 5.0

This paper summarizes the power systems analysis results from NASA s recent Mars DRA 5.0 study which examined three architecture options and resulting mission requirements for a human Mars landing mission in the post-2030 timeframe. DRA 5.0 features a long approximately 500 day surface stay split mission using separate cargo and crewed Mars transfer vehicles. Two cargo flights, utilizing minimum energy trajectories, pre-deploy a cargo lander to the surface and a habitat lander into a 24-hour elliptical Mars parking orbit where it remains until the arrival of the crew during the next mission opportunity approximately 26 months later. The pre-deployment of cargo poses unique challenges for set-up and emplacement of surface assets that results in the need for self or robotically deployed designs. Three surface architecture options were evaluated for breadth of science content, extent of exploration range/capability and variations in system concepts and technology. This paper describes the power requirements for the surface operations of the three mission options, power system analyses including discussion of the nuclear fission, solar photovoltaic and radioisotope concepts for main base power and long range mobility.

Cataldo, Robert L.↗

NASA NTRS2013

Ground Contact Modeling for the Morpheus Test Vehicle Simulation

The Morpheus vertical test vehicle is an autonomous robotic lander being developed at Johnson Space Center (JSC) to test hazard detection technology. Because the initial ground contact simulation model was not very realistic, it was decided to improve the model without making it too computationally expensive. The first development cycle added capability to define vehicle attachment points (AP) and to keep track of their states in the lander reference frame (LFRAME). These states are used with a spring damper model to compute an AP contact force. The lateral force is then overwritten, if necessary, by the Coulomb static or kinetic friction force. The second development cycle added capability to use the PolySurface class as the contact surface. The class can load CAD data in STL (Stereo Lithography) format, and use the data to compute line of sight (LOS) intercepts. A polygon frame (PFRAME) is computed from the facet intercept normal and used to convert the AP state to PFRAME. Three flat plane tests validate the transitions from kinetic to static, static to kinetic, and vertical impact. The hazardous terrain test will be used to test for visual reasonableness. The improved model is numerically inexpensive, robust, and produces results that are reasonable.

Cordova, Luis↗

NASA NTRS2013

Using Combustion Synthesis to Reinforce Berms and Other Regolith Structures

The Moonraker Excavator and other tools under development for use on the Moon, Mars, and asteroids will be employed to construct a number of civil engineering projects and to mine the soil. Mounds of loose soil will be subject to the local transport mechanisms plus artificial mechanisms such as blast effects from landers and erosion from surface vehicles. Some of these structures will require some permanence, with a minimum of maintenance and upkeep. Combustion Synthesis (CS) is a family of processes and techniques whereby chemistry is used to transform materials, often creating flame in a hard vacuum. CS can be used to stabilize civil engineering works such as berms, habitat shielding, ramps, pads, roadways, and the like. The method is to unroll thin sheets of CS fabric between layers of regolith and then fire the fabric, creating a continuous sheet of crusty material to be interposed among layers of loose regolith. The combination of low-energy processes, ISRU (in situ resource utilization) excavator, and CS fabrics, seems compelling as a general method for establishing structures of some permanence and utility, especially in the role of robotic missions as precursors to manned exploration and settlement. In robotic precursory missions, excavator/ mobility ensembles mine the Lunar surface, erect constructions of soil, and dispense sheets of CS fabrics that are covered with layers of soil, fired, and then again covered with layers of soil, iterating until the desired dimensions and forms are achieved. At the base of each berm, for example, is a shallow trench lined with CS fabric, fired and filled, mounded, and then covered and fired, iteratively to provide a footing against lateral shear. A larger trench is host to a habitat module, backfilled, covered with fabric, covered with soil, and fired. Covering the applied CS fabric with layers of soil before firing allows the resulting matrix to incorporate soil both above and below the fabric ply into the fused layer, developing a very irregular surface which, like sandpaper, can provide an anchor for loose soil. CS fabrics employ a coarse fiberglass weave that persists as reinforcement for the fired material. The fiberglass softens at a temperature that exceeds the combustion temperature by factors of two to three, and withstands the installation process. This type of structure should be more resistant to rocket blast effects from Lunar landers.

Rodriquez, Gary↗

NASA NTRS2013

Possible Detection of Perchlorates by the Sample Analysis at Mars (SAM) Instrument: Comparison with Previous Missions

The first chemical analysis of soluble salts in the soil was carried out by the Phoenix Lander in the Martian Arctic [1]. Surprisingly, chlorine was present as magnesium or calcium perchlorate at 0.4 to 0.6 percent. Additional support for the identification of perchlorate came from the evolved gas analysis which detected the release of molecular oxygen at 350-550C [1]. When Mars-like soils from the Atacama Desert were spiked with magnesium perchlorate (1 percent) and heated using the Viking GC-MS protocol, nearly all the organics were combusted but a small amount was chlorinated, forming chloromethane and dichloromethane [2]. These chlorohydrocarbons were detected by the Viking GC-MS experiments when the Martian soil was analyzed but they were considered to be terrestrial contaminants [3]. Reinterpretation of the Viking results suggests <0.1 percent perchlorate and ppm levels of organic carbon at landing site 1 and 2 [2]. The suggestion of perchlorate in the Viking sites [2] has been challenged on the grounds that the detected compounds (CH3Cl and CH2Cl2) were carried from Earth [4]. Recently the Sample Analysis at Mars (SAM) instrument on board the Mars Science Laboratory (MSL) ran four samples from an aeolian bedform named Rocknest. The samples analyzed were portioned from the fifth scoop at this location. The samples were heated to 835C at 35C/min with a He flow. The SAM QMS detected a major oxygen release (300-500C) [5], coupled with the release of chlorinated hydrocarbons (chloromethane, dichloromethane, trichloromethane, and chloromethylpropene) detected both by SAM QMS and GC-MS derived from known Earth organic contaminants in the instrument [6]. Calcium perchlorate appears to be the best candidate for evolved O2 in the Rocknest samples at this time but other Cl species (e.g., chlorates) are possible and must be evaluated. The potential detection of perchlorates in Rocknest material adds weight to the argument that both Viking Landers measured signatures of perchlorates. Even if the source of the organic carbon detected is still unknown, the chlorine source was likely Martian. Two mechanisms have been hypothesized for the formation of soil perchlorate: (1) Atmospheric oxidation of chlorine; and (2) UV photooxidation of chlorides catalyzed by mineral catalysts [7]. The presence of soil perchlorates in the Martian surface has important implications for the detection of organics [2], carbonates [8] and nitrates [9] by SAM.

Navarro-Gonzalex, Rafael↗

NASA NTRS2013

Assessing Habitability: Lessons from the Phoenix Mission

The Phoenix mission's key objective was to search for a habitable zone. The Phoenix lander carried a robotic arm with digging scoop to collect soil and icy material for analysis with an instrument payload that included volatile mineral and organic analysis(3) and soil ionic chemistry analysis (4). Results from Phoenix along with theoretical modeling and other previous mission results were used to evaluate the habitability of the landing site by considering four factors that characterize the environments ability to support life as we know it: the presence of liquid water, the presence of an energy source to support metabolism, the presence of nutrients containing the fundamental building blocks of life, and the absence of environmental conditions that are toxic to or preclude life. Phoenix observational evidence for the presence of liquid water (past or present) includes clean segregated ice, chemical etching of soil grains, calcite minerals in the soil and variable concentrations of soluble salts5. The maximum surface temperature measured was 260K so unfrozen water can form only in adsorbed films or saline brines but warmer climates occur cyclically on geologically short time scales due to variations in orbital parameters. During high obliquity periods, temperatures allowing metabolism extend nearly a meter into the subsurface. Phoenix discovered ~1%w/w perchlorate salt in the soil, a chemical energy source utilized by a wide range of microbes. Nutrient sources including C, H, N, O, P and S compounds are supplied by known atmospheric sources or global dust. Environmental conditions are within growth tolerance for terrestrial microbes. Summer daytime temperatures are sufficient for metabolic activity, the pH is 7.8 and is well buffered and the projected water activity of a wet soil will allow growth. In summary, martian permafrost in the north polar region is a viable location for modern life. Stoker et al. presented a formalism for comparing the habitability of various regions visited to date on Mars that involved computing a habitability probability, defined as the product of probabilities for the presence of liquid water (P(sub lw)), energy (P(sub e)), nutrients (P(sub ch)), and a benign environment (P(sub b)). Using this formalism, they argued that the Phoenix site was the most habitable of any site visited to date by landed missions and warranted a follow up mission to search for modern evidence of life. This paper will review that conclusion in view of more recent information from the Mars Exploration Rovers and Mars Science Lander missions.

Stoker, Carol R.↗

NASA NTRS2013

Relay Forward-Link File Management Services (MaROS Phase 2)

This software provides the service-level functionality to manage the delivery of files from a lander mission repository to an orbiter mission repository for eventual spacelink relay by the orbiter asset on a specific communications pass. It provides further functions to deliver and track a set of mission-defined messages detailing lander authorization instructions and orbiter data delivery state. All of the information concerning these transactions is persisted in a database providing a high level of accountability of the forward-link relay process.

Allard, Daniel A.↗

NASA NTRS2013

Smart-Divert Powered Descent Guidance to Avoid the Backshell Landing Dispersion Ellipse

A smart-divert capability has been added into the Powered Descent Guidance (PDG) software originally developed for Mars pinpoint and precision landing. The smart-divert algorithm accounts for the landing dispersions of the entry backshell, which separates from the lander vehicle at the end of the parachute descent phase and prior to powered descent. The smart-divert PDG algorithm utilizes the onboard fuel and vehicle thrust vectoring to mitigate landing error in an intelligent way: ensuring that the lander touches down with minimum- fuel usage at the minimum distance from the desired landing location that also avoids impact by the descending backshell. The smart-divert PDG software implements a computationally efficient, convex formulation of the powered-descent guidance problem to provide pinpoint or precision-landing guidance solutions that are fuel-optimal and satisfy physical thrust bound and pointing constraints, as well as position and speed constraints. The initial smart-divert implementation enforced a lateral-divert corridor parallel to the ground velocity vector; this was based on guidance requirements for MSL (Mars Science Laboratory) landings. This initial method was overly conservative since the divert corridor was infinite in the down-range direction despite the backshell landing inside a calculable dispersion ellipse. Basing the divert constraint instead on a local tangent to the backshell dispersion ellipse in the direction of the desired landing site provides a far less conservative constraint. The resulting enhanced smart-divert PDG algorithm avoids impact with the descending backshell and has reduced conservatism.

Carson, John M.↗

NASA NTRS2013

A Mission Concept: Re-Entry Hopper-Aero-Space-Craft System on-Mars (REARM-Mars)

Future missions to Mars that would need a sophisticated lander, hopper, or rover could benefit from the REARM Architecture. The mission concept REARM Architecture is designed to provide unprecedented capabilities for future Mars exploration missions, including human exploration and possible sample-return missions, as a reusable lander, ascend/descend vehicle, refuelable hopper, multiple-location sample-return collector, laboratory, and a cargo system for assets and humans. These could all be possible by adding just a single customized Re-Entry-Hopper-Aero-Space-Craft System, called REARM-spacecraft, and a docking station at the Martian orbit, called REARM-dock. REARM could dramatically decrease the time and the expense required to launch new exploratory missions on Mars by making them less dependent on Earth and by reusing the assets already designed, built, and sent to Mars. REARM would introduce a new class of Mars exploration missions, which could explore much larger expanses of Mars in a much faster fashion and with much more sophisticated lab instruments. The proposed REARM architecture consists of the following subsystems: REARM-dock, REARM-spacecraft, sky-crane, secure-attached-compartment, sample-return container, agile rover, scalable orbital lab, and on-the-road robotic handymen.

Davoodi, Faranak↗

NASA NTRS2014

Ground Contact Modeling for the Morpheus Test Vehicle Simulation

The Morpheus vertical test vehicle is an autonomous robotic lander being developed at Johnson Space Center (JSC) to test hazard detection technology. Because the initial ground contact simulation model was not very realistic, it was decided to improve the model without making it too computationally expensive. The first development cycle added capability to define vehicle attachment points (AP) and to keep track of their states in the lander reference frame (LFRAME). These states are used with a spring damper model to compute an AP contact force. The lateral force is then overwritten, if necessary, by the Coulomb static or kinetic friction force. The second development cycle added capability to use the PolySurface class as the contact surface. The class can load CAD data in STL (Stereo Lithography) format, and use the data to compute line of sight (LOS) intercepts. A polygon frame (PFRAME) is computed from the facet intercept normal and used to convert the AP state to PFRAME. Three flat plane tests validate the transitions from kinetic to static, static to kinetic, and vertical impact. The hazardous terrain test will be used to test for visual reasonableness. The improved model is numerically inexpensive, robust, and produces results that are reasonable.

Cordova, Luis↗

NASA NTRS2013

The Tailoring of Traditional Systems Engineering for the Morpheus Project

NASA's Morpheus Project has developed and tested a prototype planetary lander capable of vertical takeoff and landing that is designed to serve as a testbed for advanced spacecraft technologies. The lander vehicle, propelled by a LOX/Methane engine and sized to carry a 500kg payload to the lunar surface, provides a platform for bringing technologies from the laboratory into an integrated flight system at relatively low cost. From the beginning, one of goals for the Morpheus Project was to streamline agency processes and practices. The Morpheus project accepted a challenge to tailor the traditional NASA systems engineering approach in a way that would be appropriate for a lower cost, rapid prototype engineering effort, but retain the essence of the guiding principles. The team has produced innovative ways to create an infrastructure and approach that would challenge existing systems engineering processes while still enabling successful implementation of the current Morpheus Project. This paper describes the tailored systems engineering approach for the Morpheus project, including the processes, tools, and amount of rigor employed over the project's multiple lifecycles since the project began in FY11. Lessons learned from these trials have the potential to be scaled up and improve efficiency on a larger projects or programs.

Devolites, Jennifer L.↗

NASA NTRS2012

Ground Contact Model for Mars Science Laboratory Mission Simulations

The Program to Optimize Simulated Trajectories II (POST 2) has been successful in simulating the flight of launch vehicles and entry bodies on earth and other planets. POST 2 has been the primary simulation tool for the Entry Descent, and Landing (EDL) phase of numerous Mars lander missions such as Mars Pathfinder in 1997, the twin Mars Exploration Rovers (MER-A and MER-B) in 2004, Mars Phoenix lander in 2007, and it is now the main trajectory simulation tool for Mars Science Laboratory (MSL) in 2012. In all previous missions, the POST 2 simulation ended before ground impact, and a tool other than POST 2 simulated landing dynamics. It would be ideal for one tool to simulate the entire EDL sequence, thus avoiding errors that could be introduced by handing off position, velocity, or other fight parameters from one simulation to the other. The desire to have one continuous end-to-end simulation was the motivation for developing the ground interaction model in POST 2. Rover landing, including the detection of the postlanding state, is a very critical part of the MSL mission, as the EDL landing sequence continues for a few seconds after landing. The method explained in this paper illustrates how a simple ground force interaction model has been added to POST 2, which allows simulation of the entire EDL from atmospheric entry through touchdown.

Raiszadeh, Behzad↗

NASA NTRS2014

Morpheus Vertical Test Bed Flight Testing

NASA's Morpheus Project has developed and tested a prototype planetary lander capable of vertical takeoff and landing, that is designed to serve as a testbed for advanced spacecraft technologies. The lander vehicle, propelled by a LOX/Methane engine and sized to carry a 500kg payload to the lunar surface, provides a platform for bringing technologies from the laboratory into an integrated flight system at relatively low cost. Morpheus onboard software is autonomous from ignition all the way through landing, and is designed to be capable of executing a variety of flight trajectories, with onboard fault checks and automatic contingency responses. The Morpheus 1.5A vehicle performed 26 integrated vehicle test flights including hot-fire tests, tethered tests, and two attempted freeflights between April 2011 and August 2012. The final flight of Morpheus 1.5A resulted in a loss of the vehicle. In September 2012, development began on the Morpheus 1.5B vehicle, which subsequently followed a similar test campaign culminating in free-flights at a simulated planetary landscape built at Kennedy Space Center's Shuttle Landing Facility. This paper describes the integrated test campaign, including successes and setbacks, and how the system design for handling faults and failures evolved over the course of the project.

Hart, Jeremy↗

NASA NTRS2013

Variable Conductance Heat Pipe Cooling of Stirling Convertor and General Purpose Heat Source

In a Stirling Radioisotope Power System (RPS), heat must be continuously removed from the General Purpose Heat Source (GPHS) modules to maintain the modules and surrounding insulation at acceptable temperatures. The Stirling convertor normally provides this cooling. If the Stirling convertor stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS at the cost of an early termination of the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) can be used to passively allow multiple stops and restarts of the Stirling convertor. In a previous NASA SBIR Program, Advanced Cooling Technologies, Inc. (ACT) developed a series of sodium VCHPs as backup cooling systems for Stirling RPS. The operation of these VCHPs was demonstrated using Stirling heater head simulators and GPHS simulators. In the most recent effort, a sodium VCHP with a stainless steel envelope was designed, fabricated and tested at NASA Glenn Research Center (GRC) with a Stirling convertor for two concepts; one for the Advanced Stirling Radioisotope Generator (ASRG) back up cooling system and one for the Long-lived Venus Lander thermal management system. The VCHP is designed to activate and remove heat from the stopped convertor at a 19 degC temperature increase from the nominal vapor temperature. The 19 degC temperature increase from nominal is low enough to avoid risking standard ASRG operation and spoiling of the Multi-Layer Insulation (MLI). In addition, the same backup cooling system can be applied to the Stirling convertor used for the refrigeration system of the Long-lived Venus Lander. The VCHP will allow the refrigeration system to: 1) rest during transit at a lower temperature than nominal; 2) pre-cool the modules to an even lower temperature before the entry in Venus atmosphere; 3) work at nominal temperature on Venus surface; 4) briefly stop multiple times on the Venus surface to allow scientific measurements. This paper presents the experimental results from integrating the VCHP with an operating Stirling convertor and describes the methodology used to achieve their successful combined operation.

Stirling Radioisotope Power System↗

NASA NTRS2013

Alkali Metal Backup Cooling for Stirling Systems - Experimental Results

In a Stirling Radioisotope Power System (RPS), heat must be continuously removed from the General Purpose Heat Source (GPHS) modules to maintain the modules and surrounding insulation at acceptable temperatures. The Stirling convertor normally provides this cooling. If the Stirling convertor stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS at the cost of an early termination of the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) can be used to passively allow multiple stops and restarts of the Stirling convertor. In a previous NASA SBIR Program, Advanced Cooling Technologies, Inc. (ACT) developed a series of sodium VCHPs as backup cooling systems for Stirling RPS. The operation of these VCHPs was demonstrated using Stirling heater head simulators and GPHS simulators. In the most recent effort, a sodium VCHP with a stainless steel envelope was designed, fabricated and tested at NASA Glenn Research Center (GRC) with a Stirling convertor for two concepts; one for the Advanced Stirling Radioisotope Generator (ASRG) back up cooling system and one for the Long-lived Venus Lander thermal management system. The VCHP is designed to activate and remove heat from the stopped convertor at a 19 degC temperature increase from the nominal vapor temperature. The 19 degC temperature increase from nominal is low enough to avoid risking standard ASRG operation and spoiling of the Multi-Layer Insulation (MLI). In addition, the same backup cooling system can be applied to the Stirling convertor used for the refrigeration system of the Long-lived Venus Lander. The VCHP will allow the refrigeration system to: 1) rest during transit at a lower temperature than nominal; 2) pre-cool the modules to an even lower temperature before the entry in Venus atmosphere; 3) work at nominal temperature on Venus surface; 4) briefly stop multiple times on the Venus surface to allow scientific measurements. This paper presents the experimental results from integrating the VCHP with an operating Stirling convertor and describes the methodology used to achieve their successful combined operation.

Stirling Convertor↗

NASA NTRS2013

Variable Conductance Heat Pipe Cooling of Stirling Convertor and General Purpose Heat Source

In a Stirling Radioisotope Power System (RPS), heat must be continuously removed from the General Purpose Heat Source (GPHS) modules to maintain the modules and surrounding insulation at acceptable temperatures. The Stirling convertor normally provides this cooling. If the Stirling convertor stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS at the cost of an early termination of the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) can be used to passively allow multiple stops and restarts of the Stirling convertor. In a previous NASA SBIR Program, Advanced Cooling Technologies, Inc. (ACT) developed a series of sodium VCHPs as backup cooling systems for Stirling RPS. The operation of these VCHPs was demonstrated using Stirling heater head simulators and GPHS simulators. In the most recent effort, a sodium VCHP with a stainless steel envelope was designed, fabricated and tested at NASA Glenn Research Center (GRC) with a Stirling convertor for two concepts; one for the Advanced Stirling Radioisotope Generator (ASRG) back up cooling system and one for the Long-lived Venus Lander thermal management system. The VCHP is designed to activate and remove heat from the stopped convertor at a 19 degC temperature increase from the nominal vapor temperature. The 19 degC temperature increase from nominal is low enough to avoid risking standard ASRG operation and spoiling of the Multi-Layer Insulation (MLI). In addition, the same backup cooling system can be applied to the Stirling convertor used for the refrigeration system of the Long-lived Venus Lander. The VCHP will allow the refrigeration system to: 1) rest during transit at a lower temperature than nominal; 2) pre-cool the modules to an even lower temperature before the entry in Venus atmosphere; 3) work at nominal temperature on Venus surface; 4) briefly stop multiple times on the Venus surface to allow scientific measurements. This paper presents the experimental results from integrating the VCHP with an operating Stirling convertor and describes the methodology used to achieve their successful combined operation.

Tarau, Calin↗