Results for “Unit Testing” — Page 7

NASA NTRS2014

Thermal Model Predictions of Advanced Stirling Radioisotope Generator Performance

This paper presents recent thermal model results of the Advanced Stirling Radioisotope Generator (ASRG). The three-dimensional (3D) ASRG thermal power model was built using the Thermal Desktop(trademark) thermal analyzer. The model was correlated with ASRG engineering unit test data and ASRG flight unit predictions from Lockheed Martin's (LM's) I-deas(trademark) TMG thermal model. The auxiliary cooling system (ACS) of the ASRG is also included in the ASRG thermal model. The ACS is designed to remove waste heat from the ASRG so that it can be used to heat spacecraft components. The performance of the ACS is reported under nominal conditions and during a Venus flyby scenario. The results for the nominal case are validated with data from Lockheed Martin. Transient thermal analysis results of ASRG for a Venus flyby with a representative trajectory are also presented. In addition, model results of an ASRG mounted on a Cassini-like spacecraft with a sunshade are presented to show a way to mitigate the high temperatures of a Venus flyby. It was predicted that the sunshade can lower the temperature of the ASRG alternator by 20 C for the representative Venus flyby trajectory. The 3D model also was modified to predict generator performance after a single Advanced Stirling Convertor failure. The geometry of the Microtherm HT insulation block on the outboard side was modified to match deformation and shrinkage observed during testing of a prototypic ASRG test fixture by LM. Test conditions and test data were used to correlate the model by adjusting the thermal conductivity of the deformed insulation to match the post-heat-dump steady state temperatures. Results for these conditions showed that the performance of the still-functioning inboard ACS was unaffected.

radioisotope power system↗

NASA NTRS2011

Software Testing and Verification in Climate Model Development

Over the past 30 years most climate models have grown from relatively simple representations of a few atmospheric processes to a complex multi-disciplinary system. Computer infrastructure over that period has gone from punch card mainframes to modem parallel clusters. Model implementations have become complex, brittle, and increasingly difficult to extend and maintain. Existing verification processes for model implementations rely almost exclusively upon some combination of detailed analysis of output from full climate simulations and system-level regression tests. In additional to being quite costly in terms of developer time and computing resources, these testing methodologies are limited in terms of the types of defects that can be detected, isolated and diagnosed. Mitigating these weaknesses of coarse-grained testing with finer-grained "unit" tests has been perceived as cumbersome and counter-productive. In the commercial software sector, recent advances in tools and methodology have led to a renaissance for systematic fine-grained testing. We discuss the availability of analogous tools for scientific software and examine benefits that similar testing methodologies could bring to climate modeling software. We describe the unique challenges faced when testing complex numerical algorithms and suggest techniques to minimize and/or eliminate the difficulties.

Clune, Thomas L.↗

NASA NTRS1971

Post test inspection of three Brayton rotating units

Post test inspection of Brayton Rotating Unit for closed Brayton cycle electric power conversion system for long space missions

Dunn, J. H.↗

NASA NTRS2001

Addressing EO-1 Spacecraft Pulsed Plasma Thruster EMI Concerns

The Pulsed Plasma Thruster (PPT) Experiment on the Earth Observing One (EO-1) spacecraft has been designed to demonstrate the capability of a new generation PPT to perform spacecraft attitude control. Results from PPT unit level radiated electromagnetic interference (EMI) tests led to concerns about potential interference problems with other spacecraft subsystems. Initial plans to address these concerns included firing the PPT at the spacecraft level both in atmosphere, with special ground support equipment. and in vacuum. During the spacecraft level tests, additional concerns where raised about potential harm to the Advanced Land Imager (ALI). The inadequacy of standard radiated emission test protocol to address pulsed electromagnetic discharges and the lack of resources required to perform compatibility tests between the PPT and an ALI test unit led to changes in the spacecraft level validation plan. An EMI shield box for the PPT was constructed and validated for spacecraft level ambient testing. Spacecraft level vacuum tests of the PPT were deleted. Implementation of the shield box allowed for successful spacecraft level testing of the PPT while eliminating any risk to the ALI. The ALI demonstration will precede the PPT demonstration to eliminate any possible risk of damage of ALI from PPT operation.

Zakrzwski, C. M.↗

NASA NTRS2019

Overview of the Development and Testing of the Heatshield for Extreme Entry Environment Technology (HEEET) TPS

Over the last 5 years, the Heatshield for Extreme Entry Environment Technology (HEEET) project has been working to mature a 3-D Woven Thermal Protection System (TPS) to Technical Readiness Level (TRL) 6 to support future NASA missions to destinations such as Venus and Saturn. A key aspect of the project has been the development of the manufacturing and integration processes/procedures necessary to build a heat shield utilizing the HEEET 3D-woven material. This has culminated in the building of a 1-meter diameter Engineering Test Unit (ETU) representative of what would be used for a Saturn probe. The present talk provides an overview of recent testing of NASA's Heatshield for Extreme Entry Environment Technology (HEEET) 3D Woven TPS. Under the current program, the ETU has been subjected to Thermal and Mechanical loads typical of deep space mission to Saturn. Thermal testing of HEEET coupons has performance up to 4,500 watts per centimeter squared at 5 atmospheres stagnation pressure and successful shear performance up to 3000 pascals at 1,650 watts per centimeter squared at 2.6 atmospheres pressure.

HEEET↗

NASA NTRS1971

A Saturn launched X-ray astronomy experiment. Volume 1: S-027

The S-027 X-Ray Astronomy Experiment originally proposed in early 1966, was developed to detect X-rays in the 2 keV to 10 keV range. Both a prototype unit and flight unit were constructed with the prototype unit also serving as the engineering model, the qualification test unit, and after refurbishment, as the back-up flight unit. Two Ground Support Equipment consoles were built to verify the experiment operation. A photograph of one experiment package with its Ground Support Equipment is shown. The S-027 experiment was scheduled for launch in 1968/69 and although both units were completed and tested to the extent that either would be ready for the scheduled launch, delays in the space program resulted in a launch date slip of several years. When the 1968/69 launch delay became official, provisions were made for storage of the two experiment packages at SCI Electronics in Huntsville, Alabama until a new launch date could be established.

Source record↗

NASA NTRS1988

Development of an electronically-scanned pressure module for operation at cryogenic temperatures

Pressure and temperature characteristics were measured for a number of multichannel electronically scanned pressure sensors. The tests were made on commercially available units designed to operate in a controlled temperature environment. Measurements of zero shift, sensitivity, and nonlinearity for each transducer were taken over a temperature range from 100 K to 340 K using a computer controlled data acquisition system. The units tested failed to meet accuracy specifications over the complete temperature range, which was expected. However, the sensors showed acceptable and predictable behavior over the temperature range from approximately -40 C (233 K) to 70 C (343 K). It was determined that a combination of local heating and accurate temperature monitoring can result in a device that can be compensated for temperature as well as its other physical properties. The design of a prototype for operation in a cryogenic environment is proposed, and a method for compensation is developed.

Johnson, Preston B.↗

NASA NTRS1989

Validation of NSSC-I software for the Hubble Space Telescope

This paper describes the simulation and test methods used to ensure that the NASA Standard Spacecraft Computer, Model 1, (NSSC-I) flight software for the Hubble Space Telescope properly carries out its requirements for control of scientific observations and for monitoring the health and safety of the payload. The hardware and software test environment is discussed. The different kinds of tests (unit, special real time, and stress tests) that are performed before the software is incorporated into the flight system are described, and the kinds of errors that each test category is best suited to find are listed. Finally, the limitations of the tests are discussed, and current plans for enhancing the test environment are outlined.

Foley, Glenn↗

NASA NTRS2003

Thermal Vacuum Testing of a Novel Loop Heat Pipe Design for the Swift BAT Instrument

An advanced thermal control system for the Burst Alert Telescope on the Swift satellite has been designed and an engineering test unit (ETU) has been built and tested in a thermal vacuum chamber. The ETU assembly consists of a propylene loop heat pipe, two constant conductance heat pipes, a variable conductance heat pipe (VCHP), which is used for rough temperature control of the system, and a radiator. The entire assembly was tested in a thermal vacuum chamber at NASA/GSFC in early 2002. Tests were performed with thermal mass to represent the instrument and with electrical resistance heaters providing the heat to be transferred. Start-up and heat transfer of over 300 W was demonstrated with both steady and variable condenser sink temperatures. Radiator sink temperatures ranged from a high of approximately 273 K, to a low of approximately 83 K, and the system was held at a constant operating temperature of 278 K throughout most of the testing. A novel LHP temperature control methodology using both temperature-controlled electrical resistance heaters and a small VCHP was demonstrated. This paper describes the system and the tests performed and includes a discussion of the test results.

Ottenstein, Laura↗

NASA NTRS2012

RESOLVE Project

The RESOLVE project is a lunar prospecting mission whose primary goal is to characterize water and other volatiles in lunar regolith. The Lunar Advanced Volatiles Analysis (LAVA) subsystem is comprised of a fluid subsystem that transports flow to the gas chromatograph- mass spectrometer (GC-MS) instruments that characterize volatiles and the Water Droplet Demonstration (WDD) that will capture and display water condensation in the gas stream. The LAVA Engineering Test Unit (ETU) is undergoing risk reduction testing this summer and fall within a vacuum chamber to understand and characterize C!Jmponent and integrated system performance. Ray will be assisting with component testing of line heaters, printed circuit heaters, pressure transducers, temperature sensors, regulators, and valves in atmospheric and vacuum environments. He will be developing procedures to guide these tests and test reports to analyze and draw conclusions from the data. In addition, he will gain experience with preparing a vacuum chamber with fluid and electrical connections. Further testing will include integrated testing of the fluid subsystem with the gas supply system, near-infrared spectrometer, WDD, Sample Delivery System, and GC-MS in the vacuum chamber. This testing will provide hands-on exposure to a flight forward spaceflight subsystem, the processes associated with testing equipment in a vacuum chamber, and experience working in a laboratory setting. Examples of specific analysis Ray will conduct include: pneumatic analysis to calculate the WOO's efficiency at extracting water vapor from the gas stream to form condensation; thermal analysis of the conduction and radiation along a line connecting two thermal masses; and proportional-integral-derivative (PID) heater control analysis. In this Research and Technology environment, Ray will be asked to problem solve real-time as issues arise. Since LAVA is a scientific subsystem, Ray will be utilizing his chemical engineering background to operate the near-infrared spectrometer and GC-MS instruments during ETU testing. Ray will be working with Modified Commercial off the Shelf (MCOTS) instruments and characterizing their analytical behavior for optimization. Ray will be offered the opportunity to suggest testing modifications or configuration changes at any time to improve the experimental effectiveness. He will gain many skills needed for working in a technical team setting requiring flexibility and critical thinking.

Parker, Ray O.↗

NASA NTRS2013

RESOLVE Project

The RESOLVE project is a lunar prospecting mission whose primary goal is to characterize water and other volatiles in lunar regolith. The Lunar Advanced Volatiles Analysis (LAVA) subsystem is comprised of a fluid subsystem that transports flow to the gas chromatograph - mass spectrometer (GC-MS) instruments that characterize volatiles and the Water Droplet Demonstration (WDD) that will capture and display water condensation in the gas stream. The LAVA Engineering Test Unit (ETU) is undergoing risk reduction testing this summer and fall within a vacuum chamber to understand and characterize component and integrated system performance. Testing of line heaters, printed circuit heaters, pressure transducers, temperature sensors, regulators, and valves in atmospheric and vacuum environments was done. Test procedures were developed to guide experimental tests and test reports to analyze and draw conclusions from the data. In addition, knowledge and experience was gained with preparing a vacuum chamber with fluid and electrical connections. Further testing will include integrated testing of the fluid subsystem with the gas supply system, near-infrared spectrometer, WDD, Sample Delivery System, and GC-MS in the vacuum chamber. This testing will provide hands-on exposure to a flight forward spaceflight subsystem, the processes associated with testing equipment in a vacuum chamber, and experience working in a laboratory setting. Examples of specific analysis conducted include: pneumatic analysis to calculate the WDD's efficiency at extracting water vapor from the gas stream to form condensation; thermal analysis of the conduction and radiation along a line connecting two thermal masses; and proportional-integral-derivative (PID) heater control analysis. Since LAVA is a scientific subsystem, the near-infrared spectrometer and GC-MS instruments will be tested during the ETU testing phase.

Parker, Ray↗

NASA NTRS2015

RESOLVE (Regolith & Environmental Science Oxygen & Lunar Volatile Extraction) Project

The RESOLVE Project is a lunar prospecting mission whose primary goal is to characterize water and other volatiles in lunar regolith. The Lunar Advanced Volatiles Analysis (LAVA) subsystem is comprised of a fluid subsystem that transports flow to the gas chromatograph - mass spectrometer (GC-MS) instruments that characterize volatiles and the Water Droplet Demonstration (WDD) that will capture and display water condensation in the gas stream. The LAVA Engineering Test Unit (ETU) is undergoing risk reduction testing this summer and fall within a vacuum chamber to understand and characterize component and integrated system performance. Testing of line heaters, printed circuit heaters, pressure transducers, temperature sensors, regulators, and valves in atmospheric and vacuum environments was done. Test procedures were developed to guide experimental tests and test reports to analyze and draw conclusions from the data. In addition, knowledge and experience was gained with preparing a vacuum chamber with fluid and electrical connections. Further testing will include integrated testing of the fluid subsystem with the gas supply system, near-infrared spectrometer for the Surge Tank (NIRST), WDD, Sample Delivery System, and GC-MS in the vacuum chamber. Since LAVA is a scientific subsystem, the near infrared spectrometer and GC-MS instruments will be tested during the ETU testing phase.

LAVA↗

NASA NTRSDate not supplied

Analysis and Optimization of Test Plans for Advanced Exploration Systems Reliability and Supportability

Future crewed exploration missions beyond Low Earth Orbit (LEO) will operate farther from Earth and be logistically isolated for longer than any previous human spaceflight mission. Under these conditions, supportability and reliability willbestronger drivers of mission mass and risk than they have been in the past. Items with high failure rates, or uncertain failure rates, can result in high spares mass requirements and/or high risk on deep space missions. Testing is a critical element of system development which provides the opportunity to identify and resolve design issues, defects, or other failure modes before they cause problems during a mission. Reliability growth programs can reduce failure rates by identifying and remove failure modes via design changes, and long-duration life testing can provide valuable data to reduce failure rate estimate uncertainty and verify (to some level of confidence) that components are as reliable as expected. Testing activities take time and resources, however, and must be incorporated into program plans in order to be fully effective. This paper presents an integrated reliability test plan analysis and optimization methodology, which has been used to inform Advanced Exploration Systems (AES) Life Support Systems (LSS) ground test planning for future missions. The methodology determines the optimal number of test units to purchase and allocation of test time –split between reliability growth and uncertainty reduction testing –across a given set of items in order to minimize spares mass for a given mission under constraints on total test cost and schedule. Model outputs also include expected spares mass after testing and the expected number of modifications or refurbishments during testing, both of which can inform program planning. Discussion of the model, conclusions, and future work are also presented.

Testing↗

NASA NTRSDate not supplied

Analysis and Optimization of Test Plans for Advanced Exploration Systems Reliability and Supportability

Future crewed exploration missions beyond Low Earth Orbit (LEO) will operate farther from Earth and be logistically isolated for longer than any previous human spaceflight mission. Under these conditions, supportability and reliability willbestronger drivers of mission mass and risk than they have been in the past. Items with high failure rates, or uncertain failure rates, can result in high spares mass requirements and/or high risk on deep space missions. Testing is a critical element of system development which provides the opportunity to identify and resolve design issues, defects, or other failure modes before they cause problems during a mission. Reliability growth programs can reduce failure rates by identifying and remove failure modes via design changes, and long-duration life testing can provide valuable data to reduce failure rate estimate uncertainty and verify (to some level of confidence) that components are as reliable as expected. Testing activities take time and resources, however, and must be incorporated into program plans in order to be fully effective. This paper presents an integrated reliability test plan analysis and optimization methodology, which has been used to inform Advanced Exploration Systems (AES) Life Support Systems (LSS) ground test planning for future missions. The methodology determines the optimal number of test units to purchase and allocation of test time –split between reliability growth and uncertainty reduction testing –across a given set of items in order to minimize spares mass for a given mission under constraints on total test cost and schedule. Model outputs also include expected spares mass after testing and the expected number of modifications or refurbishments during testing, both of which can inform program planning. Discussion of the model, conclusions, and future work are also presented.

Testing↗

NASA NTRSDate not supplied

Obtaining cryogenic molecular transport data for analysis

The James Webb Space Telescope (JWST) has a primary mirror, made of 18 segments, and a secondary mirror (SM) that are used to direct the light of desired targets. While on orbit, the secondary mirror assembly (SMA) was stowed for approximately 10 days and was subject to molecular contamination outgassing from the cavity of the secondary mirror support structure (SMSS) in-board hinge (IBH) which contains cables, motors, resolvers, and coatings. The main concern during this period before SMA deployment is the accumulation of ice due to the lack of a heater on the SMA. The temperature differentials between the IBH surfaces and SMA could cause redistribution of contaminants. To address this concern, single layer insulation (SLI) was used to create adequate venting and path redirection of outgassing from the IBH. Two separate thermal vacuum tests were performed to quantify this contamination: one Z307 ASTM E 1559 materials test of the radiator paint used on the motor of the IBH and a separate test on a primary mirror backplane assembly (PMBA) qualification engineering test unit (ETU) of the IBH. These tests approximately followed the predicted SMA pre-deployment thermal environment. To quantify source rates in case of a leak, the motor and resolver sides were separated and quartz crystal microbalances (QCM) were used to measure the deposition of water. The SLI redesign and implementation and outgassing measurements to understand leak effects from the IBH were essential to mitigate the deposition of contamination on the SMA.

James Webb Space Telescope, contamination, cleanro↗

NASA NTRSDate not supplied

Obtaining Cryogenic Molecular Transport Data for Analysis

The James Webb Space Telescope (JWST) has a primary mirror, made of 18 segments, and a secondary mirror (SM) that are used to direct the light of desired targets. While on orbit, the secondary mirror assembly (SMA) was stowed for approximately 10 days and was subject to molecular contamination outgassing from the cavity of the secondary mirror support structure (SMSS) in-board hinge (IBH) which contains cables, motors, resolvers, and coatings. The main concern during this period before SMA deployment is the accumulation of ice due to the lack of a heater on the SMA. The temperature differentials between the IBH surfaces and SMA could cause redistribution of contaminants. To address this concern, single layer insulation (SLI) was used to create adequate venting and path redirection of outgassing from the IBH. Two separate thermal vacuum tests were performed to quantify this contamination: one Z307 ASTM E 1559 materials test of the radiator paint used on the motor of the IBH and a separate test on a primary mirror backplane assembly (PMBA) qualification engineering test unit (ETU) of the IBH. These tests approximately followed the predicted SMA pre-deployment thermal environment. To quantify source rates in case of a leak, the motor and resolver sides were separated and quartz crystal microbalances (QCM) were used to measure the deposition of water. The SLI redesign and implementation and outgassing measurements to understand leak effects from the IBH were essential to mitigate the deposition of contamination on the SMA. "

James Webb Space Telescope↗

NASA NTRSDate not supplied

Initial Testing Results and Forward Design Considerations for the Tri-Rotor Hand Controller

The Lunar Terrain Vehicle (LTV) is one of the key elements of NASA’s Artemis return to the Moon. As an unpressurized rover, the LTV hand controller must take into account the limitations of the spacesuit worn by the crew as well as lessons learned operating the Apollo Lunar Roving Vehicle and preliminary NASA simulations. Because the NASA Ground Test Unit (GTU) design features omnidirectional steering, NASA engineers developed the TriRotor is an innovation to minimize crew fatigue and discomfort. NASA conducted a series of tests, initially with 3D printed mockup controllers, and expanding to a functional prototype used in an LTV video wall simulation. The Tri-Rotor compared favorably with legacy Apollo T-Handles, though numerous test subject comments were collected to improve the controller’s usability. Several options to improve the Tri-Rotor’s usability are also discussed, along with opportunities to test the Tri-Rotor in Virtual Reality, a motion table, and in field analogs.

Hand Controller↗

NASA NTRS2020

Characterization of Nancy Grace Roman Space Telescope Slitless Spectrometer (grism)

We have published the optical design and early test results of the Roman Space Telescope grism spectrometer in previous SPIE proceedings. We report the follow-on activity of the spectral and radiometric calibrations, including the calibration methods, experiment designs, and test equipment calibration, such as the light source and detectors used in the test. The grism calibration includes the throughput versus wavelength, which is largely determined by the diffraction efficiency of the two diffractive surfaces. It also includes spectral resolution, point spread function, and relative radiometric measurements. The measured results are presented. The comparisons between the test data and the theoretical simulations are also presented. The tests and results presented are from the engineering test unit in ambient room temperature environment. The thermal/vacuum tests are planned to verify the results when the flight unit is ready.

Qian Gong↗