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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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NASA NTRS2013

Enhanced Contact Graph Routing (ECGR) MACHETE Simulation Model

Contact Graph Routing (CGR) for Delay/Disruption Tolerant Networking (DTN) space-based networks makes use of the predictable nature of node contacts to make real-time routing decisions given unpredictable traffic patterns. The contact graph will have been disseminated to all nodes before the start of route computation. CGR was designed for space-based networking environments where future contact plans are known or are independently computable (e.g., using known orbital dynamics). For each data item (known as a bundle in DTN), a node independently performs route selection by examining possible paths to the destination. Route computation could conceivably run thousands of times a second, so computational load is important. This work refers to the simulation software model of Enhanced Contact Graph Routing (ECGR) for DTN Bundle Protocol in JPL's MACHETE simulation tool. The simulation model was used for performance analysis of CGR and led to several performance enhancements. The simulation model was used to demonstrate the improvements of ECGR over CGR as well as other routing methods in space network scenarios. ECGR moved to using earliest arrival time because it is a global monotonically increasing metric that guarantees the safety properties needed for the solution's correctness since route re-computation occurs at each node to accommodate unpredicted changes (e.g., traffic pattern, link quality). Furthermore, using earliest arrival time enabled the use of the standard Dijkstra algorithm for path selection. The Dijkstra algorithm for path selection has a well-known inexpensive computational cost. These enhancements have been integrated into the open source CGR implementation. The ECGR model is also useful for route metric experimentation and comparisons with other DTN routing protocols particularly when combined with MACHETE's space networking models and Delay Tolerant Link State Routing (DTLSR) model.

Segui, John S.↗
NASA NTRS1993

Simulated space environmental effects on a polyetherimide and its carbon fiber-reinforced composites

The selection of materials for spacecraft construction requires identification of candidate materials which can perform reliably in the space environment. Understanding the effects of the space environment on the materials is an important step in the selection of candidate materials. This work examines the effects of energetic electrons, thermal cycling, electron radiation in conjunction with thermal cycling, and atomic oxygen on a thermoplastic polyetherimide and its carbon-fiber-reinforced composites. Composite materials made with non-sized fibers as well as materials made with fibers sized with an epoxy were evaluated. The mechanical and thermomechanical properties of the materials were studied and spectroscopic techniques were used to investigate the mechanisms for the observed effects. Considerations for future material development are suggested.

Kern, Kristen T.↗
NASA NTRS1974

High temperature antenna development for space shuttle, volume 2

An S-band antenna system and a group of off-the-shelf aircraft antenna were exposed to temperatures simulating shuttle orbital cold soak and entry heating. Radiation pattern and impedance measurements before and after exposure to the thermal environments were used to evaluate the electrical performance. The results of the electrical and thermal testing are given. Test data showed minor changes in electrical performance and established the capability of these antenna to withstand both the low temperatures of space flight and the high temperatures of entry.

Kuhlman, E. A.↗
NASA NTRS1993

Marshall Space Flight Center's Virtual Reality Applications Program 1993

A Virtual Reality (VR) applications program has been under development at the Marshall Space Flight Center (MSFC) since 1989. Other NASA Centers, most notably Ames Research Center (ARC), have contributed to the development of the VR enabling technologies and VR systems. This VR technology development has now reached a level of maturity where specific applications of VR as a tool can be considered. The objectives of the MSFC VR Applications Program are to develop, validate, and utilize VR as a Human Factors design and operations analysis tool and to assess and evaluate VR as a tool in other applications (e.g., training, operations development, mission support, teleoperations planning, etc.). The long-term goals of this technology program is to enable specialized Human Factors analyses earlier in the hardware and operations development process and develop more effective training and mission support systems. The capability to perform specialized Human Factors analyses earlier in the hardware and operations development process is required to better refine and validate requirements during the requirements definition phase. This leads to a more efficient design process where perturbations caused by late-occurring requirements changes are minimized. A validated set of VR analytical tools must be developed to enable a more efficient process for the design and development of space systems and operations. Similarly, training and mission support systems must exploit state-of-the-art computer-based technologies to maximize training effectiveness and enhance mission support. The approach of the VR Applications Program is to develop and validate appropriate virtual environments and associated object kinematic and behavior attributes for specific classes of applications. These application-specific environments and associated simulations will be validated, where possible, through empirical comparisons with existing, accepted tools and methodologies. These validated VR analytical tools will then be available for use in the design and development of space systems and operations and in training and mission support systems.

Hale, Joseph P., II↗
NASA NTRS1989

An assessment of the structural dynamic effects on the microgravity environment of a reference Space Station

An interim 'Permanently Manned Capability' Space Station configuration and one designated 'Assembly Complete' are modeled by FEM techniques in order to select forcing functions for modal transient response analysis and illustrate sample waveforms. In all, 114 applied-force cases have been executed to simulate such expected operational disturbances as crewmembers' treadmill exercises and EVAs. The present discussion of the results obtained give attention to the acceleration-response environment of the U.S. Laboratory's center grid-point. The magnitude of the acceleration responses obtained indicate that attenuation systems must be incorporated, or operational constraints must be instituted.

Del Basso, Steve↗
NASA NTRS1991

A navigation and control system for an autonomous rescue vehicle in the space station environment

A navigation and control system was designed and implemented for an orbital autonomous rescue vehicle envisioned to retrieve astronauts or equipment in the case that they become disengaged from the space station. The rescue vehicle, termed the Extra-Vehicular Activity Retriever (EVAR), has an on-board inertial measurement unit ahd GPS receivers for self state estimation, a laser range imager (LRI) and cameras for object state estimation, and a data link for reception of space station state information. The states of the retriever and objects (obstacles and the target object) are estimated by inertial state propagation which is corrected via measurements from the GPS, the LRI system, or the camera system. Kalman filters are utilized to perform sensor fusion and estimate the state propagation errors. Control actuation is performed by a Manned Maneuvering Unit (MMU). Phase plane control techniques are used to control the rotational and translational state of the retriever. The translational controller provides station-keeping or motion along either Clohessy-Wiltshire trajectories or straight line trajectories in the LVLH frame of any sufficiently observed object or of the space station. The software was used to successfully control a prototype EVAR on an air bearing floor facility, and a simulated EVAR operating in a simulated orbital environment. The design of the navigation system and the control system are presented. Also discussed are the hardware systems and the overall software architecture.

Merkel, Lawrence↗
NASA NTRS1966

Biology and the Exploration of Mars

Until recent years the origin of life and its possible occurrence elsewhere in the universe have been matters for speculation only. The rapid growth of molecular biology since 1940 has, to be sure, made it possible to discuss life's origins in far more precise and explicit terms than was possible earlier; and the subject entered a new experimental phase in the 1950's with successful abiogenic synthesis of important biochemical substances in conditions simulating the presumptive environment of the primitive Earth. But the real transformation that the subject has undergone stems from the spectacular growth of space technology in the last decade. The possibility of life's origin and occurrence on planets other than ours is no longer limited to idle speculation: it has entered the realm of the testable, of science in the strict sense. Given the rockets now available, and especially those available by 1969, it has become fully realistic to consider plans for the biological exploration of Mars. The study that this report seeks to interpret was initiated in June, 1964, by the Space Science Board of the National Academy of Sciences to examine this possibility. The working group comprised 36 people representing a broad spectrum of scientific interests: evolutionary biology, genetics, microbiology, biochemistry and molecular biology, animal physiology, soil chemistry, organic chemistry, planetary astronomy, geochemistry, and theoretical physics. The participants included some with considerable prior involvement in problems of space exploration and others with none. Advice was also sought outside the group of immediate participants on the potentialities of selected analytical methods for the experimental study of extraterrestrial life and its environment. More than 30 individuals contributed in this fashion written assessments of techniques in which they were particularly well versed. Our task was to examine the scientific foundations and merits of the proposal to undertake a biological exploration of Mars. What are the potential scientific yields? How valuable, if attained, would they be? What, in fact, is the possibility of life occurring on Mars? And of our detecting it with available and foreseeable technology? What could be achieved by further astronomical work from Earth? by Martian fly-by missions? by Martian orbiters? and Martian Landers? What payloads would we recommend for planetary missions? What timing and over-all strategy would we recommend for Martian exploration were we to consider it worthwhile at all? In brief, the over-all purpose was to recommend to. the government, through the Academy's Space Science Board, whether or not a biological exploration of Mars should be included in the nation's space program over the next few decades; and, further, to outline what that program, if any, should be.

CONFERENCE↗
NASA NTRS1973

Chemical and morphological changes of reusable surface insulation coatings as a function of convectively heated cyclic testing

The effects of convective heating upon reusable surface insulation coatings were studied utilizing scanning electron microscopy, X-ray fluorescence, and X-ray diffraction. Samples of coated silica, mullite, and ceramic mullite fiber were cycled in an arc plasma stream up to 15 times for 15 minutes per cycle at surface temperatures simulating those on the space shuttle vehicle. The surfaces of ceramic mullite fiber and mullite coatings were roughened substantially by the convectively heated environment while the silica was significantly smoothed after testing. Scanning electron microscopy also showed surface cracking of varying degrees in all of the coatings. The surface chemistry of the coatings as examined by X-ray fluorescence revealed that significant changes in composition were occurring during cycling, particularly within the mullite coating.

Leiser, D. B.↗
NASA NTRS1979

Performance verification and system parameter identification of spacecraft tape recorder control servo

Design adequacy of the lead-lag compensator of the frequency loop, accuracy checking of the analytical expression for the electrical motor transfer function, and performance evaluation of the speed control servo of the digital tape recorder used on-board the 1976 Viking Mars Orbiters and Voyager 1977 Jupiter-Saturn flyby spacecraft are analyzed. The transfer functions of the most important parts of a simplified frequency loop used for test simulation are described and ten simulation cases are reported. The first four of these cases illustrate the method of selecting the most suitable transfer function for the hysteresis synchronous motor, while the rest verify and determine the servo performance parameters and alternative servo compensation schemes. It is concluded that the linear methods provide a starting point for the final verification/refinement of servo design by nonlinear time response simulation and that the variation of the parameters of the static/dynamic Coulomb friction is as expected in a long-life space mission environment.

Mukhopadhyay, A. K.↗
NASA NTRS1989

Simulation of the low earth orbital atomic oxygen interaction with materials by means of an oxygen ion beam

Atomic oxygen is the predominant species in low-Earth orbit between the altitudes of 180 and 650 km. These highly reactive atoms are a result of photodissociation of diatomic oxygen molecules from solar photons having a wavelength less than or equal to 2430A. Spacecraft in low-Earth orbit collide with atomic oxygen in the 3P ground state at impact energies of approximately 4.2 to 4.5 eV. As a consequence, organic materials previously used for high altitude geosynchronous spacecraft are severely oxidized in the low-Earth orbital environment. The evaluation of materials durability to atomic oxygen requires ground simulation of this environment to cost effectively screen materials for durability. Directed broad beam oxygen sources are necessary to evaluate potential spacecraft materials performance before and after exposure to the simulated low-Earth orbital environment. This paper presents a description of a low energy, broad oxygen ion beam source used to simulate the low-Earth orbital atomic oxygen environment. The results of materials interaction with this beam and comparison with actual in-space tests of the same meterials will be discussed. Resulting surface morphologies appear to closely replicate those observed in space tests.

Banks, Bruce A.↗
NASA NTRS1988

Position and force control of coordinated multiple arms

A technique is presented for controlling multiple manipulators which are holding a single object and therefore form a closed kinematic chain. The object, which may or may not be in contact with a rigid environment, is assumed to be held rigidly by n robot end-effectors. The derivation is based on setting up constraint equations which reduce the 6 x n degrees of freedom of n manipulators each having six joints. Additional constraint equations are considered when one or more degrees of freedom of the object are reduced due to external constraints. Utilizing the operational space dynamic equations, a decoupling controller is designed to control both the position and the interaction forces of the object with the environment. Simulation results for the control of a pair of two-link manipulators are presented.

Hayati, Samad A.↗
NASA NTRS1991

Atomic oxygen stimulated outgassing

The passive Long Duration Exposure Facility (LDEF) Experiment A0034, Atomic Oxygen Simulated Outgassing, consisted of two identical one-sixth tray modules, exposing selected thermal control coatings to atomic oxygen and the combined space environment on the leading edge and, for reference, to the relative wake environment on the trailing edge. Optical mirrors were included adjacent to the thermal coatings for deposition of outgassing products. Ultraviolet grade windows and metal covers were provided for additional assessment of the effects of the various environmental factors. Preliminary results indicate that orbital atomic oxygen is both a degrading and a optically restorative factor in the thermo-optical properties of selected thermal coatings. There is evidence of more severe optical degradation on collector mirrors adjacent to coatings that were exposed to the RAM-impinging atomic oxygen. This evidence of atomic oxygen stimulated outgassing is discussed in relation to alternative factors that could affect degradation. The general effects of the space environment on the experiment hardware as well as the specimens are discussed.

Linton, Roger C.↗
NASA NTRS1991

Tele-existence and/or cybernetic interface studies in Japan

Tele-existence aims at a natural and efficient remote control of robots by providing the operator with a real time sensation of presence. It is an advaced type of teleoperation system which enables a human operator at the controls to perform remote manipulation tasks dexterously with the feeling that he or she exists in one of the remote anthropomorphic robots in the remote environment, e.g., in a hostile environment such as those of nuclear radiation, high temperature, and deep space. In order to study the use of the tele-existence system in the artificially constructed environment, the visual tele-existence simulator has been designed, a pseudo-real-time binocular solid model robot simulator has been made, and its feasibility has been experimentally evaluated. An anthropomorphic robot mechanism with an arm having seven degrees of freedom has been designed and developed as a slave robot for feasibility experiments of teleoperation using the tele-existence method. An impedance controlled active display mechanism and a head mounted display have also been designed and developed as the display subsystem for the master. The robot's structural dimensions are set very close to those of humans.

Tachi, Susumu↗
NASA NTRS1994

Simulation of Shuttle launch G forces and acoustic loads using the NASA Ames Research Center 20G centrifuge

The high cost and long times required to develop research packages for space flight can often be offset by using ground test techniques. This paper describes a space shuttle launch and reentry simulating using the NASA Ames Research Center's 20G centrifuge facility. The combined G-forces and acoustic environment during shuttle launch and landing were simulated to evaluate the effect on a payload of laboratory rates. The launch G force and acoustic profiles are matched to actual shuttle launch data to produce the required G-forces and acoustic spectrum in the centrifuge test cab where the rats were caged on a free-swinging platform. For reentry, only G force is simulated as the aero-acoustic noise is insignificant compared to that during launch. The shuttle G-force profiles of launch and landing are achieved by programming the centrifuge drive computer to continuously adjust centrifuge rotational speed to obtain the correct launch and landing G forces. The shuttle launch acoustic environment is simulated using a high-power, low-frequency audio system. Accelerometer data from STS-56 and microphone data from STS-1 through STS-5 are used as baselines for the simulations. This paper provides a description of the test setup and the results of the simulation with recommendations for follow-on simulations.

Shaw, T. L.↗
NASA NTRS2001

Space Environmental Effects Testing and Characterization of the Candidate Solar Sail Material Aluminized Mylar

The usage of solar sails as a propellantless propulsion system has been proposed for many years. The technical challenges associated with solar sails are fabrication of ultralightweight films, deploying the sails and controlling the spacecraft. Integral to all these challenges is the mechanical property integrity of the sail while exposed to the harsh environment of space. This paper describes testing and characterization of a candidate solar sail material, Aluminized Mylar. This material was exposed to a simulated Geosynchronous Transfer Orbit (GTO) and evaluated by measuring thermooptical and mechanical property changes. Testing procedures and results are presented.

Edwards, D. L.↗
NASA NTRS2010

Gravity-Off-loading System for Large-Displacement Ground Testing of Spacecraft Mechanisms

Gravity-off-loading of deployable spacecraft mechanisms during ground testing is a long-standing problem. Deployable structures which are usually too weak to support their own weight under gravity require a means of gravity-off-loading as they unfurl. Conventional solutions to this problem have been helium-filled balloons or mechanical pulley/counterweight systems. These approaches, however, suffer from the deleterious effects of added inertia or friction forces. The changing form factor of the deployable structure itself and the need to track the trajectory of the center of gravity also pose a challenge to these conventional technologies. This paper presents a novel testing apparatus for high-fidelity zero-gravity simulation for special application to deployable space structures such as solar arrays, magnetometer booms, and robotic arms in class 100,000 clean room environments

Han, Olyvia↗