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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 415 records · Page 23

Performance characterization of the Hubble Space Telescope Rate Gyro Assembly

An account is given of the design features and performance characteristics of the Rate Gyro Assembly employed by the Hubble Space Telescope's Pointing Control System to effect accurate spacecraft maneuvers and support fine pointing telescope operation, in conjunction with the fine guidance sensors. The rate sensor attitude quantization is 0.00025 arcsec. Fine-pointing stability is the driver for gyro noise performance, while spacecraft-pointing accuracy requirements at the end of maneuvers has driven the gyro scale factor and mechanical alignment stability performance.

Dougherty, H.↗

Instrument Thermal Test Bed - A unique two phase test facility

The Instrument Thermal Test Bed (ITTB) is a modular, large-scale test facility which provides a medium for ground testing and flight qualification of spacecraft thermal control components and system configurations. The initial 'shade-down' operations are discussed herein. Operational parameters and performance characteristics were determined and quantified on a preliminary basis. The ITTB was successfully operated at evaporator power loads ranging from 600 W to 9600 W as well as in both capillary pumped and series hybrid pumped modes.

Swanson, Theodore↗

Methodology for the passive control of orbital inclination and mean local time to meet sun-synchronous orbit requirements

The mean local time (MLT) of equatorial crossing of a sun-synchronous Earth-observing spacecraft orbit drifts with inclination; therefore, in order to maintain the MLT, the inclination must be controlled. Inclination may be maintained actively by costly out-of-plane maneuvers or passively by using the perturbing forces due to the sun and moon. This paper examines the passive control approach using the Earth Observing System (EOS) as a basis for the discussion. Applications to Landsat and National Oceanic and Atmospheric Administration (NOAA) spacecraft are presented for comparison. This technique is especially beneficial to spacecraft lacking propulsion systems. The results indicate that passive inclination control appears to be the preferable maintenance method when spacecraft weight restrictions, operational considerations, and scientific requirements apply.

Folta, David↗

Software for Simulating Air Traffic

Future Air Traffic Management Concepts Evaluation Tool (FACET) is a system of software for performing computational simulations for evaluating advanced concepts of advanced air-traffic management. FACET includes a program that generates a graphical user interface plus programs and databases that implement computational models of weather, airspace, airports, navigation aids, aircraft performance, and aircraft trajectories. Examples of concepts studied by use of FACET include aircraft self-separation for free flight; prediction of air-traffic-controller workload; decision support for direct routing; integration of spacecraft-launch operations into the U.S. national airspace system; and traffic- flow-management using rerouting, metering, and ground delays. Aircraft can be modeled as flying along either flight-plan routes or great-circle routes as they climb, cruise, and descend according to their individual performance models. The FACET software is modular and is written in the Java and C programming languages. The architecture of FACET strikes a balance between flexibility and fidelity; as a consequence, FACET can be used to model systemwide airspace operations over the contiguous U.S., involving as many as 10,000 aircraft, all on a single desktop or laptop computer running any of a variety of operating systems. Two notable applications of FACET include: (1) reroute conformance monitoring algorithms that have been implemented in one of the Federal Aviation Administration s nationally deployed, real-time, operational systems; and (2) the licensing and integration of FACET with the commercially available Flight Explorer, which is an Internet- based, real-time flight-tracking system.

Sridhar, Banavar↗

Design, Development, and Testing of a Water Vapor Exchanger for Spacecraft Life Support Systems

Thermal and environmental control systems for future exploration spacecraft must meet challenging requirements for efficient operation and conservation of resources. Maximizing the use of regenerative systems and conserving water are critical considerations. This paper describes the design, development, and testing of an innovative water vapor exchanger (WVX) that can minimize the amount of water absorbed in, and vented from, regenerative CO2 removal systems. Key design requirements for the WVX are high air flow capacity (suitable for a crew of six), very high water recovery, and very low pressure losses. We developed fabrication and assembly methods that enable high-efficiency mass transfer in a uniform and stable array of Nafion tubes. We also developed analysis and design methods to compute mass transfer and pressure losses. We built and tested subscale units sized for flow rates of 2 and 5 cu ft/min (3.4–8.5 cu m/hr). Durability testing demonstrated that a stable core geometry was sustained over many humid/dry cycles. Pressure losses were very low (less than 0.5 in. H2O (125 Pa) total) and met requirements at prototypical flow rates. We measured water recovery efficiency across a range of flow rates and humidity levels that simulate the range of possible cabin conditions. We measured water recovery efficiencies in the range of 80 to 90%, with the best efficiency at lower flow rates and higher cabin humidity levels. We compared performance of the WVX with similar units built using an unstructured Nafion tube bundle. The WVX achieves higher water recovery efficiency with nearly an order of magnitude lower pressure drop than unstructured tube bundles. These results show that the WVX provides uniform flow through flow channels for both the humid and dry streams and can meet requirements for service on future exploration spacecraft. The WVX technology will be best suited for long-duration exploration vehicles that require regenerative CO2 removal systems while needing to conserve water.

Izenson, Michael G.↗

Thruster-Specific Force Estimation and Trending of Cassini Hydrazine Thrusters at Saturn

The Cassini spacecraft has been in orbit around Saturn since 2004 and has since been approved for both a first and second extended mission. As hardware reaches and exceeds its documented life expectancy, it becomes vital to closely monitor hardware performance. The performance of the 1-N hydrazine attitude control thrusters is especially important to study, because the spacecraft is currently operating on the back-up thruster branch. Early identification of hardware degradation allows more time to develop mitigation strategies. There is no direct measure of an individual thruster's thrust magnitude, but these values can be estimated by post-processing spacecraft telemetry. This paper develops an algorithm to calculate the individual thrust magnitudes using Euler's equation. The algorithm correctly shows the known degradation in the first thruster branch, validating the approach. Results for the current thruster branch show nominal performance as of August, 2015.

Stupik, Joan↗

Progress on LISA Colloid Microthruster Technology Development

Colloid microthrusters have been operated successfully in flight, providing drag-free and precision control for spacecraft that can be used for future applications such as gravity wave and exoplanet observatories. The Space Technology 7 Disturbance Reduction System (ST7- DRS) technology demonstration payload included eight Busek Colloid Micro-Newton Thrusters (CMNTs) as part of the Laser Interferometer Space Antenna (LISA) Pathfinder mission that launched in December of 2015. The CMNTs provided full attitude and precision drag-free control of the spacecraft with <10 nm/√Hz stability along the most sensitive axis during commissioning, nominal, and extended mission phases through April of 2017. Performance requirements (≤0.1 μN/√Hz) were met and models were validated based on on- orbit measurements of test mass motion and actuation during the 60-day nominal and 30-day extended missions. In 2018, the European Space Agency (ESA) selected LISA to be the agency’s next “large-class” mission, currently in Phase A, with a launch scheduled for 2034 and a 12.5-year duration, including the transfer (1.5 years), commissioning (1 year), nominal (4 or 6 years), and extended (6 or 4 years) phases of the mission, which sets the lifetime and consumables requirement. NASA is considering a significant contribution of hardware to the ESA-led mission, potentially including colloid microthrusters. In preparation, NASA is developing five technologies to TRL 5 and 6, including the colloid microthrusters, to be ready for infusion into LISA by the mission adoption review (MAR), currently scheduled for 2024. While ST7-DRS effectively brought the CMNTs to TRL 7, additional lower-TRL flow control components must be developed for full redundancy, reducing the system-level TRL back to 4. Key to the future of the colloid microthruster technology will be to use lessons learned and keep as much of the heritage from the ST7 design as possible while updating the system to support redundancy and lifetime requirements of a flagship-class mission. This paper describes the technology plan and progress to reach TRL 6 by the MAR, focusing on near- term plans to reach TRL 5 by the end of March 2022 for the LISA Colloid Microthrusters (CMTs). Work includes requirements development and sizing studies, breadboard and brassboard hardware developments at Busek, including relevant lifetime and environment testing, and lifetime modeling, verification and validation efforts at JPL, UCLA, and UCI.

Gamero-Castaño, Manuel↗

Use of microgravity sensors for quantification of space shuttle orbiter vernier reaction control system induced environments

In the modeling of spacecraft dynamics it is important to accurately characterize the environment in which the vehicle operates, including the environments induced by the vehicle itself. On the Space Shuttle these induced environmental factors include reaction control system plume. Knowledge of these environments is necessary for performance of control systems and loads analyses, estimation of disturbances due to thruster firings, and accurate state vector propagation. During the STS-71 mission, while the Orbiter was performing attitude control for the mated Orbiter/Mir stack, it was noted that the autopilot was limit cycling at a rate higher than expected from pre-flight simulations. Investigations during the mission resulted in the conjecture that an unmodelled plume impingement force was acting upon the orbiter elevons. The in-flight investigations were not successful in determining the actual magnitude of the impingement, resulting in several sequential post-flight investigations. Efforts performed to better quantify the vernier reaction control system induced plume impingement environment of the Space Shuttle orbiter are described in this paper, and background detailing circumstances which required the more detailed knowledge of the RCS self impingement forces, as well as a description of the resulting investigations and their results is presented. The investigations described in this paper applied microgravity acceleration data from two shuttle borne microgravity experiments, SAMS and OARE, to the solution of this particular problem. This solution, now used by shuttle analysts and mission planners, results in more accurate propellant consumption and attitude limit cycle estimates in preflight analyses, which are critical for pending International Space Station missions.

Friend, Robert B.↗

An Overview of the Formation and Attitude Control System for the Terrestrial Planet Finder Formation Flying Interferometer

The Terrestrial Planet Finder formation flying Interferometer (TPF-I) will be a five-spacecraft, precision formation operating near a Sun-Earth Lagrange point. As part of technology development for TPF-I, a formation and attitude control system (FACS) is being developed that achieves the precision and functionality associated with the TPF-I formation. This FACS will be demonstrated in a distributed, real-time simulation environment. In this paper we present an overview of the FACS and discuss in detail its constituent formation estimation, guidance and control architectures and algorithms. Since the FACS is currently being integrated into a high-fidelity simulation environment, component simulations demonstrating algorithm performance are presented.

Terrestrial Planet Finder (TPF)↗

NASA's Software Safety Standard

NASA (National Aeronautics and Space Administration) relies more and more on software to control, monitor, and verify its safety critical systems, facilities and operations. Since the 1960's there has hardly been a spacecraft (manned or unmanned) launched that did not have a computer on board that provided vital command and control services. Despite this growing dependence on software control and monitoring, there has been no consistent application of software safety practices and methodology to NASA's projects with safety critical software. Led by the NASA Headquarters Office of Safety and Mission Assurance, the NASA Software Safety Standard (STD-18l9.13B) has recently undergone a significant update in an attempt to provide that consistency. This paper will discuss the key features of the new NASA Software Safety Standard. It will start with a brief history of the use and development of software in safety critical applications at NASA. It will then give a brief overview of the NASA Software Working Group and the approach it took to revise the software engineering process across the Agency.

Ramsay, Christopher M.↗

MOOSE: Manned On-Orbit Servicing Equipment

The ability to service satellites has thus far been limited to low earth orbit platforms within reach of the Space Shuttle. Other orbits, such as geosynchronous orbits containing high-value spacecraft have not been attainable by a servicing vehicle. The useful life of a satellite can be extended by replacing spent propellant and damaged orbital replacement units, forestalling the need for eventual replacement. This growing need for satellite on-orbits servicing can be met by the Manned On-Orbit Servicing Equipment (MOOSE). Missions requiring orbit transfer capability, precision manipulation and maneuvering, and man-in-the-loop control can be accomplished using MOOSE. MOOSE is a flexible, reusable, single operator, aerobraking spacecraft designed to refuel, repair, and service orbiting spacecraft. MOOSE will be deployed from Space Station Freedom, (SSF), where it will be stored, resupplied, and refurbished.

Budinoff, J.↗

Passive Cooling for Mercury Surface Lander Electronics

A significant barrier to operation of a mission on the surface of Mercury is the temperature. At Mercury’s perihelion distance of 0.313 AU, the solar intensity is 10.6 times the solar flux at Earth orbit, and at the subsolar point, the maximum surface temperature reaches 427°C. For a mission landing on the surface of Mercury at latitude of 40°S, we analyzed using passive thermal control to reduce the temperature of the critical electronics to within the operation temperature limits of silicon devices. The thermal control requires reducing the thermal conductance and infrared flux from the high temperature surface and surrounding spacecraft, and moderating the solar heat input using a surface coating with high solar reflectivity, and maximizing thermal cooling with high infrared emissivity. Using this approach, we find that we can passively cool an electronics box to a temperature of 393K (120°C) using a radiator-white surface with solar absorptivity 0.11 and infrared emissivity 0.91. This temperature is well under 175C target we use for the limits of high-temperature silicon integrated circuits, including RAM and microcontrollers. We could further reduce this operating temperature to as low as 321K (48°C) with an advanced thermal coating, a temperature well within the operational limits of conventional electronics.

Mercury↗

Deep Space Network (DSN), Network Operations Control Center (NOCC) computer-human interfaces

The Network Operations Control Center (NOCC) of the DSN is responsible for scheduling the resources of DSN, and monitoring all multi-mission spacecraft tracking activities in real-time. Operations performs this job with computer systems at JPL connected to over 100 computers at Goldstone, Australia and Spain. The old computer system became obsolete, and the first version of the new system was installed in 1991. Significant improvements for the computer-human interfaces became the dominant theme for the replacement project. Major issues required innovating problem solving. Among these issues were: How to present several thousand data elements on displays without overloading the operator? What is the best graphical representation of DSN end-to-end data flow? How to operate the system without memorizing mnemonics of hundreds of operator directives? Which computing environment will meet the competing performance requirements? This paper presents the technical challenges, engineering solutions, and results of the NOCC computer-human interface design.

Ellman, Alvin↗

Lunar transfer vehicle design issues with electric propulsion systems

This paper describes parametric design studies of electric propulsion lunar transfer vehicles. In designing a lunar transfer vehicle, selecting the 'best' operating points for the design parameters allows significant reductions in the mass in low earth orbit (LEO) for the mission. These parameters include the specific impulse, the power level, and the propulsion technology. Many of the decisions regarding the operating points are controlled by the propulsion and power system technologies that are available for the spacecraft. The relationship between these technologies is discussed and analyzed here. It is found that both ion and MPD propulsion offer significant LEO mass reductions over O2/H2 for lunar transfer vehicle missions. The recommended operating points for the lunar transfer vehicle are an I(sp) of 5000 lb(f)-s/lb(m) and a 1 MW power level. For large lunar missions, krypton may be the best choice for ion propulsion.

Palaszewski, Bryan↗

An Overview of the Formation and Attitude Control System for the Terrestrial Planet Finder Formation Flying Interferometer

The Terrestrial Planet Finder formation flying Interferometer (TPF-I) will be a five-spacecraft, precision formation operating near the second Sun-Earth Lagrange point. As part of technology development for TPF-I, a formation and attitude control system (FACS) is being developed that achieves the precision and functionality needed for the TPF-I formation and that will be demonstrated in a distributed, real-time simulation environment. In this paper we present an overview of FACS and discuss in detail its formation estimation, guidance and control architectures and algorithms. Since FACS is currently being integrated into a high-fidelity simulation environment, component simulations demonstrating algorithm performance are presented.

Scharf, Daniel P.↗

The Fate of Trace Contaminants in a Crewed Spacecraft Cabin Environment

Trace chemical contaminants produced via equipment offgassing, human metabolic sources, and vehicle operations are removed from the cabin atmosphere by active contamination control equipment and incidental removal by other air quality control equipment. The fate of representative trace contaminants commonly observed in spacecraft cabin atmospheres is explored. Removal mechanisms are described and predictive mass balance techniques are reviewed. Results from the predictive techniques are compared to cabin air quality analysis results. Considerations are discussed for an integrated trace contaminant control architecture suitable for long duration crewed space exploration missions.

Perry, Jay L.↗

Conjunction Assessment and Deconfliction Paradigm for Co-Located Satellite Constellations With on-Spacecraft “Autonomous” Flight Dynamics Control

Satellite constellations that employ on-spacecraft flight dynamics and conjunction assessment (CA) approaches face particular challenges. First, they must arrange to obtain and upload to the constellation satellite close approach information, such as Conjunction Data Messages, so that their on-board systems will have the data they need to make informed CA decisions. Second, given current latencies in obtaining CA screening information, such systems often cannot obtain dedicated screenings of their proposed maneuvers before they are executed. Third, they usually cannot engage in real time with owner/operators (O/Os) with whom they may come into conjunction, relying instead on pre-arranged courses of action that may or may not fit a given situation well. Despite these difficulties, it is nonetheless possible, as operators such as SpaceX have demonstrated, to operate safely using on-board CA calculations, in the presence of a largely collaborative operating environment. The situation breaks down, however, when two constellations that operate with such a paradigm are placed in the same orbital region and will experience conjunctions with each other. Each may have a vague idea of where the other’s satellites are, or perhaps even a somewhat precise idea if they exchange O/O ephemerides, but neither will know the other’s more immediate maneuver intentions, especially for situations in which they are in a high-risk conjunction with each other and a mitigation maneuver is required. As there is no formalized way for these automated systems to ascertain each other’s intentions for this type of conjunction, it is quite possible that each spacecraft may choose a maneuver that results in the two objects’ colliding. An opportunity to develop a solution to this problem was presented by the NASA “Starling” project, a small experimental constellation developed to demonstrate autonomous satellite control and constellation reconfiguration and for which a launch was obtained that, serendipitously, will place this constellation close to the SpaceX Starlink constellation. Because the NASA constellation is experimental, an extended mission part of the mission has been negotiated to implement and test mechanisms for resolving the problem of co-located constellations with on-board flight dynamics control. For the last eighteen months, a consortium among NASA Ames (the Starling satellite providers), NASA CARA (the Agency organization responsible for conjunction assessment), Space X, and the Department of Commerce (in observer status) has met regularly to assemble a concept of operations for a robust solution to this problem and has developed a prototype ground node that will serve as a needed CA screening and information dispensary. The approach and methods, as well as the active employment of the developed ground node, will be tested both in simulation before actual use and then in actual spacecraft operations, which are anticipated to begin in January 2024. This paper will describe the co-located autonomously-controlled constellation problem and the developed solution in detail, outlining what ground node (i.e., government) infrastructure and features are required, what particular capabilities are needed by the constellations themselves in order to make use of this deconfliction paradigm, and the migration path forward to allow such a capability set to be incorporated by the Department of Commerce’s space traffic coordination system.

Conjunction Assessment↗