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

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At least 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Signal and Power Integrity Design Methodology for High-Performance Flight Computing Systems

Computing capabilities of space systems have in-creased onboard performance by orders of magnitude with the use of radiation-tolerant field-programmable gate arrays (FPGA)and processors. The incorporation of signal and power integrity analysis with printed circuit board (PCB) design in reliable computing architectures for space systems has become critical to enable future mission capabilities. Developers launch high-performance processors into a breadth of orbits and missions, running varying applications that create challenges for designing reliable computing hardware. Specifically, for these designs, academic and industry research has focused on component radiation performance, fault mitigation, and reliable architectures. How-ever, other design parameters including electromagnetic interference (EMI), PCB stackup, signal integrity (SI), voltage regulator module (VRM) design, and power distribution network (PDN)are often deprioritized or disregarded as the design matures. Since these characteristics are becoming more significant in high-performance processor designs, this research presents a hardware design and analysis methodology for high-performance, space-computing systems that focuses on a holistic design approach and PDN reliability. While these challenges exist across all space hardware, the reduced PCB dimensions imposed by SmallSats and CubeSats introduce additional hurdles, specifically to VRM and decoupling design. By examining the relationship between the PDN and radiation performance, an analytical relationship is developed that incorporates Total Ionizing Dose and Single-Event Transients to ensure reliability throughout the mission duration. The presented design methodology is applied to the SpaceCube v3.0 Mini, an FPGA-based on-board science data processing system developed at NASA Goddard Space Flight Center.

Advanced avionics↗
NASA NTRSDate not supplied

Surface Systems and Interface Standardization

Space exploration on planetary surfaces will require the use of various surface systems which will likely need to interface with one another. These systems must communicate and share data, as well as distribute power and transfer fluids for sustainable surface operations. Such systems can range from landers, surface habitats, mobility systems, cargo, and In-Situ Resource Utilizations (ISRUs). Previous and current programs have developed space interoperability standards that help aid in reducing potential risks of interface integration. One example of this is the International Deep Space Interoperability Standards (IDSIS) which focuses on deep space exploration. A goal of the Artemis program is to develop a sustained human presence on the lunar surface that would be a training ground for future Mars exploration. Therefore, it will be beneficial to identify interface standards between the surface assets which will help mitigate risk and reduce complexity in the harsh environments of space exploration. A key contribution to sustainability is commonality between hardware and software interfaces. Generic interfaces for data, power, and fluids will reduce risk, promote interoperability, and define standard interfaces across surface exploration projects and programs. Standardized interfaces would be advantageous for improving efficiency and reducing overall complexity, which are critical considerations for future space exploration. Furthermore, it will provide cost reductions to the Artemis programs over their life cycle (in Operations & Maintenance (O&M) and Logistics). Unique proprietary interfaces if considered or allowed would not only increase complexity but also add cost to the programs. Of course, understanding what will work and not work effectively in these unique environments such as the lunar surface is important. These unique environments require much needed intelligent design, prototyping, comprehensive testing, and field experience, utilizing consensus on common interface solutions.

Jaime Gomez↗
NASA NTRS2022

Pre-Installation Acceptance (PIA) Functional Performance of the Design Verification Test (DVT) Exploration Extra-vehicular Mobility Unit (xEMU)

In an effort that began with technology investment by NASA in a few key components during the Constellation Program and then evolved to demonstrate a packaged Portable Life Support System (PLSS) as part of the Advanced Exploration Systems (AES) Program, the next evolution of the PLSS is now a key component of the Exploration Extra-vehicular Mobility Unit (xEMU) and is assembled as a Design Verification Test (DVT) unit. The xEMU has been detailed with respect to completing a demonstration on the International Space Station (ISS) with support of units for initial lunar capability. The xEMU completed the Preliminary Design Review (PDR) with subsequent Safety Review Panel (SRP) Phase I reviews in 2019-2020. The objectives for DVT are to validate requirements, train the team, learn how to fabricate the hardware with appropriate process controls, assemble the hardware, test the hardware, determine the failure mechanisms/limits of the hardware design and buy down the most risk possible for the qualification and flight phases of the development. With completion of the assembly and initial functional testing of the DVT PLSS in laboratory ambient conditions and vacuum conditions the xEMU has progressed significantly into the DVT objectives. A key part of the test sequences for DVT and all future phases is the Pre-Installation Acceptance (PIA) functional testing which validates the performance of integrated systems including: primary thermal control, auxiliary thermal control, suit ventilation, primary oxygen, secondary oxygen, power distribution, as well as caution and warning all with respect to the applied requirements. This discussion will include an overview of the assembly, summary of the PIA functional testing, lessons learned, and corrective actions implemented moving forward into the remainder of the DVT phase for xEMU.

Colin Campbell↗
NASA NTRSDate not supplied

Comparison of Convective Heat Transfer Correlations and Their Application to Nuclear Thermal Propulsion Reactors

This study analyzes various Nusselt number and friction factor correlations and applies them to a Small Nuclear Rocket Engine model with a Sinusoidal power distribution profile to understand their effects on the temperatures and pressures inside the reactor. A nodal thermal hydraulic solver was used to determine the fluid and channel surface temperatures while also incorporating variable fluid properties and channel roughness. The results showed that the considered friction factors could essentially be used interchangeably given that their difference affected the pressure by less than 1%. However, large variations in the tube surface temperature were obtained for the different Nusselt numbers while the fluid temperature distribution was forced to remain the same. Supersonic flow conditions presented by Maynard Taylor are investigated to serve as a baseline for how experimental errors can lead to uncertainties in the reported empirical correlations. Detailed experimental investigation is necessary to determine the Nusselt number correlation that will provide the best prediction of the thermal hydraulic performance inside the reactor fluid flow channels.

Experiment↗
NASA NTRSDate not supplied

Comparison of Convective Heat Transfer Correlations and Their Application to NTP Reactors

This study analyzes various Nusselt number and friction factor correlations and applies them to a Small Nuclear Rocket Engine model with a Sinusoidal power distribution profile to understand their effects on the temperatures and pressures inside the reactor. A nodal thermal hydraulic solver was used to determine the fluid and channel surface temperatures while also incorporating variable fluid properties and channel roughness. The results showed that the considered friction factors could essentially be used interchangeably given that their difference affected the pressure by less than 1%. However, large variations in the tube surface temperature were obtained for the different Nusselt numbers while the fluid temperature distribution was forced to remain the same. Supersonic flow conditions presented by Maynard Taylor are investigated to serve as a baseline for how experimental errors can lead to uncertainties in the reported empirical correlations. Detailed experimental investigation is necessary to determine the Nusselt number correlation that will provide the best prediction of the thermal hydraulic performance inside the reactor fluid flow channels.

Nuclear Thermal Propulsion↗
NASA NTRSDate not supplied

Development of a Portable Stand-Alone 20 K Brayton Cycle Helium Refrigeration System

From 2012 to 2015, NASA funded development of the Ground Operations Demonstration Unit for Liquid Hydrogen (GODU-LH2) at Kennedy Space Center that scaled up and matured Integrated Refrigeration and Storage (IRAS) technology. IRAS involves the integration of an external helium refrigeration system with a cryogenic storage tank via an internal heat exchanger and allows advanced operations such as zero boiloff and densification of the liquid. The refrigeration system employed for GODU-LH2 was a Linde LR1620 piston-Brayton cycle machine with an RSX helium compressor. The GODU-LH2 system was installed in two separate shipping containers—one housing the cold-box, compressor, and gas management hardware, and the other the water chiller unit—with 480 VAC and 120 VAC electrical power fed from external hardware at the test site, and data capture and controls achieved using four different, independent software packages. From 2017 to 2019, in support of a densified hydrogen loading test program, the entire system was repackaged into a single, 40’ (12 m) shipping container, including the refrigeration system, water chiller, and electrical power distribution hardware, and controls were consolidated into a single Allen Bradley PanelView. Details regarding the design, build-out, and testing of the system will be presented and discussed.

W F Reaves↗
NASA NTRS2024

A Uniform Analysis of Debris Disks with the Gemini Planet Imager. I. An Empirical Search for Perturbations from Planetary Companions in Polarized Light Images

The Gemini Planet Imager (GPI) has excelled in imaging debris disks in the near-infrared. The GPI Exoplanet Survey imaged 24 debris disks in polarized H-band light, while other programs observed half of these disks in polarized J and/or K1 bands. Using these data, we present a uniform analysis of the morphology of each disk to find asymmetries suggestive of perturbations, particularly those due to planet–disk interactions. The multiwavelength surface brightness, disk color, and geometry permit the identification of any asymmetries such as warps or disk offsets from the central star. We find that 19 of the disks in this sample exhibit asymmetries in surface brightness, disk color, disk geometry, or a combination of the three, suggesting that for this sample, perturbations, as seen in scattered light, are common. The relationship between these perturbations and potential planets in the system is discussed. We also explore correlations among stellar temperatures, ages, disk properties, and observed perturbations. We find significant trends between the vertical aspect ratio and the stellar temperature, disk radial extent, and the dust grain size distribution power law, q. We also confirm a trend between the disk color and stellar effective temperature, where the disk becomes increasingly red/neutral with increasing temperature. Such results have important implications for the evolution of debris disk systems around stars of various spectral types.

Katie A Crotts↗
NASA NTRS1976

Single phase inverter for a three phase power generation and distribution system

A breadboard design of a single-phase inverter with sinusoidal output voltage for a three-phase power generation and distribution system was developed. The three-phase system consists of three single-phase inverters, whose output voltages are connected in a delta configuration. Upon failure of one inverter the two remaining inverters will continue to deliver three-phase power. Parallel redundancy as offered by two three-phase inverters is substituted by one three-phase inverter assembly with high savings in volume, weight, components count and complexity, and a considerable increase in reliability. The following requirements must be met: (1) Each single-phase, current-fed inverter must be capable of being synchronized to a three-phase reference system such that its output voltage remains phaselocked to its respective reference voltage. (2) Each single-phase, current-fed inverter must be capable of accepting leading and lagging power factors over a range from -0.7 through 1 to +0.7.

Lindena, S. J.↗
NASA NTRS1994

Is a data set distributed as a power law? A test, with application to gamma-ray burst brightnesses

We present a method to determine whether an observed sample of data is drawn from a parent distribution that is pure power law. The method starts from a class of statistics which have zero expectation value under the null hypothesis, H(sub 0), that the distribution is a pure power law: F(x) varies as x(exp -alpha). We study one simple member of the class, named the `bending statistic' B, in detail. It is most effective for detection a type of deviation from a power law where the power-law slope varies slowly and monotonically as a function of x. Our estimator of B has a distribution under H(sub 0) that depends only on the size of the sample, not on the parameters of the parent population, and is approximated well by a normal distribution even for modest sample sizes. The bending statistic can therefore be used to test a set of numbers is drawn from any power-law parent population. Since many measurable quantities in astrophysics have distriibutions that are approximately power laws, and since deviations from the ideal power law often provide interesting information about the object of study (e.g., a `bend' or `break' in a luminosity function, a line in an X- or gamma-ray spectrum), we believe that a test of this type will be useful in many different contexts. In the present paper, we apply our test to various subsamples of gamma-ray burst brightness from the first-year Burst and Transient Source Experiment (BATSE) catalog and show that we can only marginally detect the expected steepening of the log (N (greater than C(sub max))) - log (C(sub max)) distribution.

Wijers, Ralph A. M. J.↗
NASA NTRS1992

Load converter interactions with the secondary system in the Space Station Freedom power management and distribution DC test bed

The NASA LeRC in Cleveland, Ohio, is responsible for the design, development, and assembly of the Space Station Freedom (SSF) Electrical Power System (EPS). In order to identify and understand system level issues during the SSF Program design and development phases, a system Power Management and Distribution (PMAD) DC test bed was assembled. Some of the objectives of this test bed facility are the evaluation of, system efficiency, power quality, system stability, and system protection and reconfiguration schemes. In order to provide a realistic operating scenario, dc Load Converter Units are used in the PMAD dc test bed to characterize the user interface with the power system. These units are dc to dc converters that provide the final system regulation before power is delivered to the load. This final regulation is required on the actual space station because the majority of user loads will require voltage levels different from the secondary bus voltage. This paper describes the testing of load converters in an end to end system environment (from solar array to loads) where their interactions and compatibility with other system components are considered. Some of the system effects of interest that are presented include load converters transient behavior interactions with protective current limiting switchgear, load converters ripple effects, and the effects of load converter constant power behavior with protective features such as foldback.

Lebron, Ramon C.↗
NASA NTRS1992

Load converter interactions with the secondary system in the Space Station Freedom power management and distribution dc test bed

The NASA LeRC in Cleveland, Ohio, is responsible for the design, development, and assembly of the Space Station Freedom (SSF) Electrical Power System (EPS). In order to identify and understand system level issues during the SSF program design and development phases, a system Power Management and Distribution (PMAD) dc test bed was assembled. Some of the objectives of this test bed facility are the evaluation of, system efficiency, power quality, system stability, and system protection and reconfiguration schemes. In order to provide a realistic operating scenario, dc Load Converter Units are used in the PMAD dc test bed to characterize the user interface with the power system. These units are dc to dc converters that provide the final system regulation before power is delivered to the load. This final regulation is required on the actual space station because the majority of user loads will require voltage levels different from the secondary bus voltage. This paper describes the testing of load converters in an end to end system environment (from solar array to loads) where their interactions and compatibility with other system components are considered. Some of the system effects of interest that are presented include load converters transient behavior interactions with protective current limiting switchgear, load converters ripple effects, and the effects of load converter constant power behavior with protective features such as foldback.

Lebron, Ramon C.↗
NASA NTRS1996

AlGaN Channel Transistors for Power Management and Distribution

Contained within is the Final report of a Phase 1 SBIR program to develop AlGaN channel junction field effect transistors (JFET). The report summarizes our work to design, deposit, and fabricate JFETS using molecular beam epitaxy growth AlGaN. Nitride growth is described using a RF atomic nitrogen plasma source. Processing steps needed to fabricate the device such as ohmic source-drain contacts, reactive ion etching, gate formation, and air bride fabrication are documented. SEM photographs of fabricated power FETS are shown. Recommendations are made to continue the effort in a Phase 2 Program.

ENERGY MANAGEMENT↗
NASA NTRS1985

Controlling Solar-Power Systems With Distributed Processors

System undergoing development uses distributed microprocessors to monitor and control photovoltaic power system. Equipment increases life expectancy and reliability of power system and decreases costs. Adapted to vehicular, residential, and commercial solar and nonsolar power systems. Equipment especially desirable in systems with overall power levels above few kilowatts.

Imamura, M. S.↗
NASA NTRS1992

An environmental testing facility for Space Station Freedom power management and distribution hardware

The plans for a new test facility, including new environmental test systems, which are presently under construction, and the major environmental Test Support Equipment (TSE) used therein are addressed. This all-new Rocketdyne facility will perform space simulation environmental tests on Power Management and Distribution (PMAD) hardware to Space Station Freedom (SSF) at the Engineering Model, Qualification Model, and Flight Model levels of fidelity. Testing will include Random Vibration in three axes - Thermal Vacuum, Thermal Cycling and Thermal Burn-in - as well as numerous electrical functional tests. The facility is designed to support a relatively high throughput of hardware under test, while maintaining the high standards required for a man-rated space program.

Jackola, Arthur S.↗