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NASA NTRS1999

Soil Analysis Micro-Mission Concepts Derived from the MSP 2001 Mars Environmental Compatibility Assessment (MECA)

The Mars Environmental Compatibility Assessment (MECA) will evaluate the Martian environment for soil and dust-related hazards to human exploration as part of the Mars Surveyor Program 2001 Lander. The integrated MECA payload contains a wet-chemistry laboratory, a microscopy station, an electrometer to characterize the electrostatic environment, and arrays of material patches to study abrasion and adhesion. Heritage will be all-important for low cost micro-missions, and adaptations of instruments developed for the Pathfinder, '98 and '01 Landers should be strong contenders for '03 flights. This talk has three objectives: (1) Familiarize the audience with MECA instrument capabilities; (2) present concepts for stand-alone and/or mobile versions of MECA instruments; and (3) broaden the context of the MECA instruments from human exploration to a comprehensive scientific survey of Mars. Due to time limitations, emphasis will be on the chemistry and microscopy experiments. Ion-selective electrodes and related sensors in MECA's wet-chemistry laboratory will evaluate total dissolved solids, redox potential, pH, and the concentration of many soluble ions and gases in wet Martian soil. These electrodes can detect potentially dangerous heavy-metal ions, emitted pathogenic gases, and the soil's corrosive potential, and experiments will include cyclic voltammetry and anodic stripping. For experiments beyond 2001, enhancements could allow multiple use of the cells (for mobile experiments) and reagent addition (for quantitative mineralogical and exobiological analysis). MECA's microscopy station combines optical and atomic-force microscopy (AFM) in an actively focused, controlled illumination environment to image particles from millimeters to nanometers in size. Careful selection of substrates allows controlled experiments in adhesion, abrasion, hardness, aggregation, magnetic and other properties. Special tools allow primitive manipulation (brushing and scraping) of samples. Soil particle properties including size, shape, color, hardness, adhesive potential (electrostatic and magnetic), will be determined using an array of sample receptacles and collection substrates. The simple, rugged atomic-force microscope will image in the submicron size range and has the capability of performing a particle-by-particle analysis of the dust and soil. Future implementations might enhance the optical microscopy with spectroscopy, or incorporate advanced AFM techniques for thermogravimetric and chemical analysis.

Hecht, M. H.↗

NASA NTRS2000

Electrostatics of Granular Material (EGM): Space Station Experiment

Aggregates were observed to form very suddenly in a lab-contained dust cloud, transforming (within seconds) an opaque monodispersed cloud into a clear volume containing rapidly-settling, long hair-like aggregates. The implications of such a "phase change" led to a series of experiments progressing from the lab, to KC-135, followed by micro-g flights on USML-1 and USML-2, and now EGM slated for Space Station. We attribute the sudden "collapse" of a cloud to the effect of dipoles. This has significant ramifications for all types of cloud systems, and additionally implicates dipoles in the processes of cohesion and adhesion of granular matter. Notably, there is the inference that like-charged grains need not necessarily repel if they are close enough together: attraction or repulsion depends on intergranular distance (the dipole being more powerful at short range), and the D/M ratio for each grain, where D is the dipole moment and M is the net charge. We discovered that these ideas about dipoles, the likely pervasiveness of them in granular material, the significance of the D/M ratio, and the idea of mixed charges on individual grains resulting from tribological processes --are not universally recognized in electrostatics, granular material studies, and aerosol science, despite some early seminal work in the literature, and despite commercial applications of dipoles in such modern uses as "Krazy Glue", housecleaning dust cloths, and photocopying. The overarching goal of EGM is to empirically prove that (triboelectrically) charged dielectric grains of material have dipole moments that provide an "always attractive" intergranular force as a result of both positive and negative charges residing on the surfaces of individual grains. Microgravity is required for this experiment because sand grains can be suspended as a cloud for protracted periods, the grains are free to rotate to express their electrostatic character, and Coulombic forces are unmasked. Suspended grains will be "interrogated" by applied electrical fields. In one module, grains will be immersed in an inhomogeneous electric field and allowed to be attracted towards or repelled from the central electrode of the module: part of the grain's speed will be a function of its net charge (monopole), part will be a function of the dipole. Observed grain position vs. time will provide a curve that can be deconvolved into the dipole and monopole forces responsible, since both have distinctive radial dependencies. In a second approach, the inhomogeneous field will be alternated at low frequency (e.g., every 5-10 seconds) so that the grains are alternately attracted and repelled from the center of the field. The resulting "zigzag" grain motion will gradually drift inwards, then suddenly change to a unidirectional inward path when a critical radial distance is encountered (a sort of "Coulombic event horizon") at which the dipole strength supersedes the monopole strength --thus proving the presence of a dipole, while also quantifying the D/M ratio. In a second module, an homogeneous electric field eliminates dipole effects (both Coulombic and induced) to provide calibration of the monopole and to more readily evaluate net charge statistical variance. In both modules, the e-fields will be exponentially step-ramped in voltage during the experiment, so that the field "nominalizes" grain speed while spreading the response time --effectively forcing each grain to "wait its turn" to be measured. In addition to rigorously quantifying M, D, and the D/M ratio for many hundreds of grains, the experiment will also observe gross electrometric and RF discharge phenomena associated with grain activity. The parameter space will encompass grain charging levels (via intentional triboelectrification), grain size, cloud density, and material type. Results will prove or disprove the dipole hypothesis. In either case, light will be shed on the role of electrostatic forces in governing granular systems. Knowledge so gained can be applied to natural clouds such as protostellar and protoplanetary dust and debris systems, planetary rings, planetary dust palls and aerosols created by volcanic, impact, aeolian, firestorm, or nuclear winter processes. The data are also directly applicable to adhesion, cohesion, transport, dispersion, and collection of granular materials in industrial, agricultural, pharmaceutical applications, and in fields as diverse as dust contamination of space suits on Mars and crop spraying on Earth.

Marshall, J.↗

NASA NTRS2000

Increasing Importance of Material Electrical Interaction with the Space Environment

The electrical properties of materials have always been important for spacecraft in charging environments. However, in recent years consideration of interactions of materials and systems with the plasma environment has become more and more important in spacecraft design. This has primarily been driven by independent factors including increase in power and high voltage power systems, operation of tethered satellites, and science requirements for electrostatic clean spacecraft. Increased need for power has led to increased operating voltages for spacecraft. The Upper Atmospheric Research Satellite (UARS) was one of the first to operate at near 100 V solar array potential and demonstrate that the spacecraft floated nearly the entire voltage negative of the ionospheric plasma. The high voltage, 160 V, of the solar arrays on the International Space Station (ISS) led to the requirement to have a plasma contactor to control structure potential relative to the local plasma. Issues such as sputtering, dielectric breakdown, capacitive energy storage in the structure, space debris impact induced arcs and other arcing mechanisms had to be addressed. Recently commercial satellites, driven to higher voltages for efficiency, have experienced arcing problems which led to severe, permanent power degradation. The first tethered satellite, Tethered Satellite System (TSS), was deployed from the Space Shuttle. A conductive coating was developed which provided a low resistivity and also the required solar absorptivity and emittance. Other tether systems are being designed which will have similar requirements but also long life and "bare tether" designs are also being built for flight experiments. The wire requires an electrically conductive coating with proper thermal control properties, which a bare wire doesn't possess. Increasing sophistication of scientific instruments and measurements which scientists want to make have led to increasing requirements for conducting thermal control coatings to provide electrostatic cleanliness. These issues, which are increasing the importance of electrical interaction of materials to the space environment, will be discussed in this paper as well as research into material development to meet thermal and electrical requirements and research to understand phenomena regarding such interactions.

Carruth, M. R., Jr.↗

NASA NTRS2004

Electromagnetic Compatibility for the Space Shuttle

This slide presentation reviews the Space Shuttle electromagnetic compatibility (EMC). It includes an overview of the design of the shuttle with the areas that are of concern for the electromagnetic compatibility. It includes discussion of classical electromagnetic interference (EMI) and the work performed to control the electromagnetic interference. Another area of interest is electrostatic charging and the threat of electrostatic discharge and the attempts to reduce damage to the Shuttle from these possible hazards. The issue of electrical bonding is als reviewed. Lastly the presentation reviews the work performed to protect the shuttle from lightning, both in flight and on the ground.

Scully, Robert C.↗

NASA NTRS2014

High Current ESD Test of Advanced Triple Junction Solar Array Coupon

Testing was conducted on an Advanced Triple Junction (ATJ) coupon that was part of a risk reduction effort in the development of a high-powered solar array design by Space Systems Loral, LLC (SSL). The ATJ coupon was a small, 4-cell, two-string configuration of flight-type design that has served as the basic test coupon design used in previous SSL environmental aging campaigns. The objective of the present test was to evaluate the performance of the coupon after being subjected to induced electrostatic discharge (ESD) testing at two string voltages (100 V, 150 V) and four string currents (1.65 A, 2.0 A, 2.475 A, and 3.3 A). An ESD test circuit, unique to SSL solar array design, was built that simulates the effect of missing cells and strings in a full solar panel with special primary arc flashover circuitry. A total of 73 primary arcs were obtained that included 7 temporary sustained arcs (TSA) events. The durations of the TSAs ranged from 50 micro-seconds to 2.75 milli-seconds. All TSAs occurred at a string voltage of 150 V. Post-ESD functional testing showed that no degradation occurred due to the TSA events. These test results point to a robust design for application to a high-current, high-power mission.

Wright, Kenneth H., Jr.↗

NASA NTRSDate not supplied

Heliophysics Environmental & Radiation Measurement Experiment Suite (HERMES): A Small External Payload for the Lunar Gateway with Big Challenges

Currently scheduled for liftoff in 2024, Gateway will be an outpost orbiting the moon for astronauts headed to and from the lunar surface and serve as a staging point for deep space exploration. In January of 2020 NASA headquarters contacted Goddard Space Flight Center to request that they develop a Heliophysics instrumentation package for Gateway. This package would later become known as HERMES-Heliophysics Environmental & Radiation Measurement Experiment Suite. HERMES consists of a Miniaturized Electron pRoton Telescope (MERIT), an Electron Electrostatic Analyzer (EEA), Solar Probe Analyzers (SPAN)-A-ions, and Noise Eliminating Magnetometer Instrument in a Small Integrated System (NEMISIS), which consists of one fluxgate and two Magneto-Inductive Magnetometers. From the beginning the HERMES mission faced a number of Challenges. It was constrained to fit in a small, half meter, cube and it was required to weigh no more than 25kg. A new boom design for the magnetometer would be required and for safety reasons it must be able to retract autonomously with power removed. To complicate matters the location of the SORI-Small ORU- (Orbital Replacement Unit) Robotics Interface, the primary interface for the HERMES platform to the Gateway elements, was undetermined. Also, the mechanical, thermal and electrical interfaces are not fully defined. The Canadian Space Agency is still in process of designing the version of the SORI that will be flown on the Power and Propulsion Element (PPE) and Habitation and Logistics Outpost (HALO) elements, each of which are being developed by different contractors. At the time of initiating the HERMES project, neither of the Gateway module providers were under contract. Additionally, we would later learn the ISS heritage SORI modules were not originally designed for launching on the Gateway elements with a payload directly attached but rather were intended to be brought up on a separate carrier outfitted with launch locks and specialized launch structures from which the robotic arm on Gateway would then be used to detach the payload and install it on the SORI adapters while on orbit. Launching the integrated Payload/SORI on the PPE and HALO elements complicates the stiffness requirements and coupled loads analysis. Adding to this are serious constraints on Field-Of-View (FOV) for solar viewing and severe radiation exposure considerations brought on by slowly raising the orbit through the Van Allen Belts. Just to make things a little more challenging the budget for the entire project was intended to be a low-cost tailored Class-D mission approach. Plus, the effects of Corona VIrus Disease 2019 (COVID-19) were not factored in from the beginning. This paper will discuss what’s being done to overcome these challenges and put HERMES on track for a 2024 Launch Readiness Date (LRD).

Irving Joseph Burt↗

NASA NTRSDate not supplied

The Influence of Chemical Descriptors on the Reactivity of Potential Hypergolic Fuels With Hydrogen Peroxide

The state-of-the-art for storable hypergolic bipropellant systems is monomethylhydrazine (MMH) and mixed oxides of nitrogen (MON). While MMH and MON provide fast and highly reliable hypergolic ignition with excellent propulsive performance, they suffer from safety concerns impacting their production, cost, and supply to various test and launch facilities. In contrast, identifying and demonstrating low-toxicity fuels hypergolic with rocket grade hydrogen peroxide (H2O2) has been challenging with long ignition delay (IDT) and low propulsive performance affecting their deployment in flight systems. This work describes a preliminary observational study to assess the effects of molecular descriptors suspected to predict the reactivity and hypergolicity of compounds within the same chemical class (i.e., thioamide). The approach centered on evaluating functional groups, electrostatic potential, number of carbons, dipole moment, and adiabatic ionization energy. Thiourea is hypergolic with 89.2 wt.% H2O2 (minimum IDT of 21.9 ms) and was selected as a core fuel to study the reactivity of derived fuels with different functionalities. Additionally, the chemical properties were calculated with the Gaussian16 suite. The results showed that group substitution and generally increased number of carbons on thiourea increases IDT. It was observed that a more positively charged sulfur atom in the thioamide does not increase the reactivity towards H2O2. The dipole moment analysis revealed an overall trend of decreasing IDT due to increasing dipole moment. Finally, a lower adiabatic ionization energy related to increased IDTs for most cases. Additional chemical classes comprising a wider range of functionalities and electrophilic attributes are being investigated in on-going work.

Propellant↗

NASA NTRS2014

High Current ESD Test of Advanced Triple Junction Solar Array Coupon

A test was conducted on an Advanced Triple Junction (ATJ) coupon that was part of a risk reduction effort in the development of a high-powered solar array design by SSL. The ATJ coupon was a small, 4-cell, two-string configuration that has served as the basic test coupon design used in previous SSL environmental aging campaigns. The coupon has many attributes of the flight design; e.g., substrate structure with graphite face sheets, integrated by-pass diodes, cell interconnects, RTV grout, wire routing, etc. The objective of the present test was to evaluate the performance of the coupon after being subjected to induced electrostatic discharge testing at two string voltages (100 V, 150 V) and four array current (1.65 A, 2.0 A, 2.475 A, and 3.3 A). An ESD test circuit, unique to SSL solar array design, was built that simulates the effect of missing cells and strings in a full solar panel with special primary arc flashover circuitry. A total of 73 primary arcs were obtained that included 7 temporary sustained arcs (TSA) events. The durations of the TSAs ranged from 50 μs to 2.9 ms. All TSAs occurred at a string voltage of 150 V. Post-test Large Area Pulsed Solar Simulator (LAPSS), Dark I-V, and By-Pass Diode tests showed that no degradation occurred due to the TSA events. In addition, the post-test insulation resistance measured was > 50 G-ohms between cells and substrate. These test results indicate a robust design for application to a high-current, high-power mission application.

Wright, K. H.↗

NASA NTRS2014

High Current ESD Test of Advanced Triple Junction Solar Array Coupon

Testing was conducted on an Advanced Triple Junction (ATJ) coupon that was part of a risk reduction effort in the development of a high-powered solar array design by Space Systems/Loral, LLC (SSL). The ATJ coupon was a small, 4-cell, two-string configuration that has served as the basic test coupon design used in previous SSL environmental aging campaigns. The coupon has many attributes of the flight design; e.g., substrate structure with graphite face sheets, integrated by-pass diodes, cell interconnects, RTV grout, wire routing, etc. The objective of the present test was to evaluate the performance of the coupon after being subjected to induced electrostatic discharge (ESD) testing at two string voltages (100 V, 150 V) and four array currents (1.65 A, 2.0 A, 2.475 A, and 3.3 A). An ESD test circuit, unique to SSL solar array design, was built that simulates the effect of missing cells and strings in a full solar panel with special primary arc flashover circuitry. A total of 73 primary arcs were obtained that included 7 temporary sustained arcs (TSA) events. The durations of the TSAs ranged from 50 micro-seconds to 2.75 milli-seconds. All TSAs occurred at a string voltage of 150 V. Post-test Large Area Pulsed Solar Simulator (LAPSS), Dark I-V, and By-Pass Diode tests showed that no degradation occurred due to the TSA events. In addition, the post-test insulation resistance measured was > 50 G-ohms between cells and substrate. These test results indicate a robust design for application to a high-current, high-power mission.

Wright, Kenneth H., Jr.↗

NASA NTRS2015

Space Environment Testing of Photovoltaic Array Systems at NASA's Marshall Space Flight Center

CubeSats, Communication Satellites, and Outer Planet Science Satellites all share one thing in common: Mission success depends on maintaining power in the harsh space environment. For a vast majority of satellites, spacecraft power is sourced by a photovoltaic (PV) array system. Built around PV cells, the array systems also include wiring, substrates, connectors, and protection diodes. Each of these components must function properly throughout the mission in order for power production to remain at nominal levels. Failure of even one component can lead to a crippling loss of power. To help ensure PV array systems do not suffer failures on-orbit due to the space environment, NASA's Marshall Space Flight Center (MSFC) has developed a wide ranging test and evaluation capability. Key elements of this capability include: Testing: a. Ultraviolet (UV) Exposure b. Charged Particle Radiation (Electron and Proton) c. Thermal Cycling d. Plasma and Beam Environments Evaluation: a. Electrostatic Discharge (ESD) Screening b. Optical Inspection and easurement c. PV Power Output including Large Area Pulsed Solar Simulator (LAPSS) measurements This paper will describe the elements of the space environment which particularly impact PV array systems. MSFC test capabilities will be described to show how the relevant space environments can be applied to PV array systems in the laboratory. A discussion of MSFC evaluation capabilities will also be provided. The sample evaluation capabilities offer test engineers a means to quantify the effects of the space environment on their PV array system or component. Finally, examples will be shown of the effects of the space environment on actual PV array materials tested at MSFC.

Schneider, Todd A.↗

NASA NTRS2015

High Current ESD Test of Advanced Triple Junction Solar Array Coupon

A test was conducted on an Advanced Triple Junction (ATJ) coupon that was part of a risk reduction effort in the development of a high-powered solar array design by SSL. The ATJ coupon was a small, 4-cell, two-string configuration that has served as the basic test coupon design used in previous SSL environmental aging campaigns. The coupon has many attributes of the flight design; e.g., substrate structure with graphite face sheets, integrated by-pass diodes, cell interconnects, RTV grout, wire routing, etc. The objective of the present test was to evaluate the performance of the coupon after being subjected to induced electrostatic discharge testing at two string voltages (100 V, 150 V) and four array current (1.65 A, 2.0 A, 2.475 A, and 3.3 A). An ESD test circuit, unique to SSL solar array design, was built that simulates the effect of missing cells and strings in a full solar panel with special primary arc flashover circuitry. A total of 73 primary arcs were obtained that included 7 temporary sustained arcs (TSA) events. The durations of the TSAs ranged from 50 micros to 2.9 ms. All TSAs occurred at a string voltage of 150 V. Post-test Large Area Pulsed Solar Simulator (LAPSS), Dark I-V, and By-Pass Diode tests showed that no degradation occurred due to the TSA events. In addition, the post-test insulation resistance measured was > 50 G-ohms between cells and substrate. These test results indicate a robust design for application to a high-current, high-power mission application.

Wright, Kenneth H., Jr.↗

NASA NTRS1998

MEMS Louvers for Thermal Control

Mechanical louvers have frequently been used for spacecraft and instrument thermal control purposes. These devices typically consist of parallel or radial vanes, which can be opened or closed to vary the effective emissivity of the underlying surface. This project demonstrates the feasibility of using Micro-Electromechanical Systems (MEMS) technology to miniaturize louvers for such purposes. This concept offers the possibility of substituting the smaller, lighter weight, more rugged, and less costly MEMS devices for such mechanical louvers. In effect, a smart skin that self adjusts in response to environmental influences could be developed composed of arrays of thousands of miniaturized louvers. Several orders of magnitude size, weight, and volume decreases are potentially achieved using micro-electromechanical techniques. The use of this technology offers substantial benefits in spacecraft/instrument design, integration and testing, and flight operations. It will be particularly beneficial for the emerging smaller spacecraft and instruments of the future. In addition, this MEMS thermal louver technology can form the basis for related spacecraft instrument applications. The specific goal of this effort was to develop a preliminary MEMS device capable of modulating the effective emissivity of radiators on spacecraft. The concept pursued uses hinged panels, or louvers, in a manner such that heat emitted from the radiators is a function of louver angle. An electrostatic comb drive or other such actuator can control the louver position. The initial design calls for the louvers to be gold coated while the underlying surface is of high emissivity. Since, the base MEMS material, silicon, is transparent in the InfraRed (IR) spectrum, the device has a minimum emissivity when closed and a maximum emissivity when open. An initial set of polysilicon louver devices was designed at the Johns Hopkins Applied Physics Laboratory in conjunction with the Thermal Engineering Branch at NASA's Goddard Space Flight Center.

Champion, J. L.↗

NASA NTRS2013

Robust Platinum Resistor Thermometer (PRT) Sensors and Reliable Bonding for Space Missions

Platinum resistance thermometers (PRTs) provide accurate temperature measurements over a wide temperature range and are used extensively on space missions due to their simplicity and linearity. A standard on spacecraft, PRTs are used to provide precision temperature control and vehicle health assessment. This paper reviews the extensive reliability testing of platinum resistor thermometer sensors (PRTs) and bonding methods used on the Mars Science Laboratory (MSL) mission and for the upcoming Soil Moisture Active Passive (SMAP) mission. During the Mars Exploration Rover (MER) mission, several key, JPL-packaged PRTs failed on those rovers prior to and within 1-Sol of landing due to thermally induced stresses. Similar failures can be traced back to other JPL missions dating back thirty years. As a result, MSL sought out a PRT more forgiving to the packaging configurations used at JPL, and extensively tested the Honeywell HRTS-5760-B-U-0-12 sensor to successfully demonstrate suitable robustness to thermal cycling. Specifically, this PRT was cycled 2,000 times, simulating three Martian winters and summers. The PRTs were bonded to six substrate materials (Aluminum 7050, treated Magnesium AZ231-B, Stainless Steel 304, Albemet, Titanium 6AL4V, and G-10), using four different aerospace adhesives--two epoxies and two silicones--that conformed to MSL's low out-gassing requirements. An additional epoxy was tested in a shorter environmental cycling test, when the need for a different temperature range adhesive was necessary for mobility and actuator hardware late in the fabrication process. All of this testing, along with electrostatic discharge (ESD) and destructive part analyses, demonstrate that this PRT is highly robust, and not subject to the failure of PRTs on previous missions. While there were two PRTs that failed during fabrication, to date there have been no in-flight PRT failures on MSL, including those on the Curiosity rover. Since MSL, the sensor has gone through a change in construction such that the manufacturer significantly restricts the minimum temperature. However, significant subsequent testing was performed with this new version of the part to show that it indeed is still robust to at least Mars minimum temperatures of -135(sup o)C. The additional completed testing will be described. This work has resulted in a successful sensor package qualification and a reliable bonding method suitable for use over large temperature extremes.

dectector↗

NASA NTRS2013

Robust Platinum Resistor Thermometer (PRT) Sensors and Reliable Bonding for Space Missions

Platinum resistance thermometers (PRTs) provide accurate temperature measurements over a wide temperature range and are used extensively on space missions due to their simplicity and linearity. A standard on spacecraft, PRTs are used to provide precision temperature control and vehicle health assessment. This paper reviews the extensive reliability testing of platinum resistor thermometer sensors (PRTs) and bonding methods used on the Mars Science Laboratory (MSL) mission and for the upcoming Soil Moisture Active Passive (SMAP) mission. During the Mars Exploration Rover (MER) mission, several key, JPL-packaged PRTs failed on those rovers prior to and within 1-Sol of landing due to thermally induced stresses. Similar failures can be traced back to other JPL missions dating back thirty years. As a result, MSL sought out a PRT more forgiving to the packaging configurations used at JPL, and extensively tested the Honeywell HRTS-5760-B-U-0-12 sensor to successfully demonstrate suitable robustness to thermal cycling. Specifically, this PRT was cycled 2,000 times, simulating three Martian winters and summers. The PRTs were bonded to six substrate materials (Aluminum 7050, treated Magnesium AZ231-B, Stainless Steel 304, Albemet, Titanium 6AL4V, and G-10), using four different aerospace adhesives--two epoxies and two silicones--that conformed to MSL's low out-gassing requirements. An additional epoxy was tested in a shorter environmental cycling test, when the need for a different temperature range adhesive was necessary for mobility and actuator hardware late in the fabrication process. All of this testing, along with electrostatic discharge (ESD) and destructive part analyses, demonstrate that this PRT is highly robust, and not subject to the failure of PRTs on previous missions. While there were two PRTs that failed during fabrication, to date there have been no in-flight PRT failures on MSL, including those on the Curiosity rover. Since MSL, the sensor has gone through a change in construction such that the manufacturer significantly restricts the minimum temperature. However, significant subsequent testing was performed with this new version of the part to show that it indeed is still robust to at least Mars minimum temperatures of -135 degrees Centigrade. The additional completed testing will be described. This work has resulted in a successful sensor package qualification and a reliable bonding method suitable for use over large temperature extremes

Platinum Resistor Thermometer (PRT)↗

NASA NTRS2019

NEXT Single String Integration Tests in Support of the Double Asteroid Redirection Test Mission

A system integration test has been performed utilizing a prototype model NEXT ion thruster, an engineering model power processing unit, and a laboratory model command and data handling system. The objectives of the test were to: a) verify that the integrated system meets performance requirements, b) demonstrate that the integrated system is functional across the anticipated thermal, power processor, and Xe propellant ranges for the DART mission, and to c) evaluate fault detection and operation of the command and data handling system. Measurements made during this test included: thruster performance, PPU input voltages, PPU electrical and thermal telemetry, software states, and fault flags. Additionally, a far-field electrostatic probe diagnostic was used to infer relative changes in the thrust vector across the various propellant flow splits. This manuscript presents the results of these tests, which include integrated ion propulsion system demonstrations of performance, details on the execution of DART flight algorithms, and software fault handling.

Thomas, Robert E.↗

NASA NTRS2019

NEXT Single String Integration Tests in Support of the Double Asteroid Redirection Test Mission

Thomas, Robert↗

NASA NTRS1990

EMI testing adequacy and flight anomaly history

The effects of electromagnetic interference (EMI) and the space environment on the performance of long-duration spacecraft hardware are surveyed, and the implications for prelaunch test procedures are indicated. Topics addressed include the need for onboard environmental monitoring devices to aid in the identification of environmentally induced anomalies, environmental modeling methods, the existing spacecraft-anomaly data bases, electrostatic discharges, radiation effects, magnetic-field effects, and terrestrial sources of EMI. Statistical data on EMI-induced anomalies are presented in graphs and discussed in detail. It is recommended that testing beyond the current MIL-STD levels be performed on equipment for long-term missions such as the Space Station.

Kuberry, Richard W.↗

NASA NTRS2015

Space Environment Testing of Photovoltaic Array Systems at NASA's Marshall Space Flight Center

To successfully operate a photovoltaic (PV) array system in space requires planning and testing to account for the effects of the space environment. It is critical to understand space environment interactions not only on the PV components, but also the array substrate materials, wiring harnesses, connectors, and protection circuitry (e.g. blocking diodes). Key elements of the space environment which must be accounted for in a PV system design include: Solar Photon Radiation, Charged Particle Radiation, Plasma, and Thermal Cycling. While solar photon radiation is central to generating power in PV systems, the complete spectrum includes short wavelength ultraviolet components, which photo-ionize materials, as well as long wavelength infrared which heat materials. High energy electron radiation has been demonstrated to significantly reduce the output power of III-V type PV cells; and proton radiation damages material surfaces - often impacting coverglasses and antireflective coatings. Plasma environments influence electrostatic charging of PV array materials, and must be understood to ensure that long duration arcs do not form and potentially destroy PV cells. Thermal cycling impacts all components on a PV array by inducing stresses due to thermal expansion and contraction. Given such demanding environments, and the complexity of structures and materials that form a PV array system, mission success can only be ensured through realistic testing in the laboratory. NASA's Marshall Space Flight Center has developed a broad space environment test capability to allow PV array designers and manufacturers to verify their system's integrity and avoid costly on-orbit failures. The Marshall Space Flight Center test capabilities are available to government, commercial, and university customers. Test solutions are tailored to meet the customer's needs, and can include performance assessments, such as flash testing in the case of PV cells.

Phillips, Brandon S.↗