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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 NTRS2010

Thermal Analysis of the Advanced Technology Large Aperture Space Telescope (ATLAST) 8 Meter Primary Mirror

The Advanced Technology Large Aperture Space Telescope (ATLAST) preliminary design concept consists of an 8 meter diameter monolithic primary mirror enclosed in an insulated, optical tube with stray light baffles and a sunshade. ATLAST will be placed in orbit about the Sun-Earth L2 and will experience constant exposure to the sun. The insulation on the optical tube and sunshade serve to cold bias the telescope which helps to minimize thermal gradients. The primary mirror will be maintained at 280K with an active thermal control system. The geometric model of the primary mirror, optical tube, sun baffles, and sunshade was developed using Thermal Desktop(R) SINDA/FLUINT(R) was used for the thermal analysis and the radiation environment was analyzed using RADCAD(R). A XX node model was executed in order to characterize the static performance and thermal stability of the mirror during maneuvers. This is important because long exposure observations, such as extra-solar terrestrial planet finding and characterization, require a very stable observatory wave front. Steady state thermal analyses served to predict mirror temperatures for several different sun angles. Transient analyses were performed in order to predict thermal time constant of the primary mirror for a 20 degree slew or 30 degree roll maneuver. This paper describes the thermal model and provides details of the geometry, thermo-optical properties, and the environment which influences the thermal performance. All assumptions that were used in the analysis are also documented. Parametric analyses are summarized for design parameters including primary mirror coatings and sunshade configuration. Estimates of mirror heater power requirements are reported. The thermal model demonstrates results for the primary mirror heated from the back side and edges using a heater system with multiple independently controlled zones.

Hornsby, Linda↗
NASA NTRS1990

Functional description of a command and control language tutor

The status of an ongoing project to explore the application of Intelligent Tutoring System (ITS) technology to NASA command and control languages is described. The primary objective of the current phase of the project is to develop a user interface for an ITS to assist NASA control center personnel in learning Systems Test and Operations Language (STOL). Although this ITS will be developed for Gamma Ray Observatory operators, it will be designed with sufficient flexibility so that its modules may serve as an ITS for other control languages such as the User Interface Language (UIL). The focus of this phase is to develop at least one other form of STOL representation to complement the operational STOL interface. Such an alternative representation would be adaptively employed during the tutoring session to facilitate the learning process. This is a key feature of this ITS which distinguishes it from a simulator that is only capable of representing the operational environment.

Elke, David R.↗
NASA NTRS2006

Control Surface Interaction Effects of the Active Aeroelastic Wing Wind Tunnel Model

This paper presents results from testing the Active Aeroelastic Wing wind tunnel model in NASA Langley s Transonic Dynamics Tunnel. The wind tunnel test provided an opportunity to study aeroelastic system behavior under combined control surface deflections, testing for control surface interaction effects. Control surface interactions were observed in both static control surface actuation testing and dynamic control surface oscillation testing. The primary method of evaluating interactions was examination of the goodness of the linear superposition assumptions. Responses produced by independently actuating single control surfaces were combined and compared with those produced by simultaneously actuating and oscillating multiple control surfaces. Adjustments to the data were required to isolate the control surface influences. Using dynamic data, the task increases, as both the amplitude and phase have to be considered in the data corrections. The goodness of static linear superposition was examined and analysis of variance was used to evaluate significant factors influencing that goodness. The dynamic data showed interaction effects in both the aerodynamic measurements and the structural measurements.

Heeg, Jennifer↗
NASA NTRS1973

Teleoperators and EVA for Shuttle missions

Review of the methods currently being contemplated for enabling the Space Shuttle to perform the Shuttle and payload support missions. Two general approaches to carrying out such activity are discussed - namely, the use of teleoperators and astronaut extravehicular activity (EVA). Detailed descriptions are given of an attached manipulator system (AMS) and a free-flying teleoperator (FFTO), noting the applications, capabilities, and limitations of each. The primary technology development areas for the AMS are in the areas of stabilization, structure, and manual control, while the technology areas of primary concern in the case of the FFTO include the manipulator-grappler system, the control system, the video system, and the mobility system. Four modes of EVA that are possible for the Shuttle are cited, noting the unlikelihood of direct applicability of EVA to payload deployment and retrieval and its feasibility for payload servicing and experiment support.

Malone, T. B.↗
NASA NTRS1996

Advanced Intelligent System Application to Load Forecasting and Control for Hybrid Electric Bus

The primary motivation for this research emanates from providing a decision support system to the electric bus operators in the municipal and urban localities which will guide the operators to maintain an optimal compromise among the noise level, pollution level, fuel usage etc. This study is backed up by our previous studies on study of battery characteristics, permanent magnet DC motor studies and electric traction motor size studies completed in the first year. The operator of the Hybrid Electric Car must determine optimal power management schedule to meet a given load demand for different weather and road conditions. The decision support system for the bus operator comprises three sub-tasks viz. forecast of the electrical load for the route to be traversed divided into specified time periods (few minutes); deriving an optimal 'plan' or 'preschedule' based on the load forecast for the entire time-horizon (i.e., for all time periods) ahead of time; and finally employing corrective control action to monitor and modify the optimal plan in real-time. A fully connected artificial neural network (ANN) model is developed for forecasting the kW requirement for hybrid electric bus based on inputs like climatic conditions, passenger load, road inclination, etc. The ANN model is trained using back-propagation algorithm employing improved optimization techniques like projected Lagrangian technique. The pre-scheduler is based on a Goal-Programming (GP) optimization model with noise, pollution and fuel usage as the three objectives. GP has the capability of analyzing the trade-off among the conflicting objectives and arriving at the optimal activity levels, e.g., throttle settings. The corrective control action or the third sub-task is formulated as an optimal control model with inputs from the real-time data base as well as the GP model to minimize the error (or deviation) from the optimal plan. These three activities linked with the ANN forecaster proving the output to the GP model which in turn produces the pre-schedule of the optimal control model. Some preliminary results based on a hypothetical test case will be presented for the load forecasting module. The computer codes for the three modules will be made available fe adoption by bus operating agencies. Sample results will be provided using these models. The software will be a useful tool for supporting the control systems for the Electric Bus project of NASA.

Momoh, James↗
NASA NTRS1989

Error-Compensated Telescope

Proposed reflecting telescope includes large, low-precision primary mirror stage and small, precise correcting mirror. Correcting mirror machined under computer control to compensate for error in primary mirror. Correcting mirror machined by diamond cutting tool. Computer analyzes interferometric measurements of primary mirror to determine shape of surface of correcting mirror needed to compensate for errors in wave front reflected from primary mirror and commands position and movement of cutting tool accordingly.

Meinel, Aden B.↗
NASA NTRS1986

The large deployable reflector: A NASA submillimeter-infrared orbiting observatory

The Large Deployable Reflector (LDR) concept is outlined. The LDR telescope is based on a 20-m diameter reflector. The primary mirror is a filled aperture made up of 84 hexagonal panels, each 2 m edge-to-edge. The panels are based on lightweight structural composite materials. The optical configuration is a four mirror two stage system. The primary mirror is passive. The active optical elements for figure control are at the quaternary mirror. The primary mirror panels are supported by a deployable PAC truss backup structure at the vertices of each hexagon. The four focal plane instruments covering the range of 30 to 1000 microns are located near the vertex of the primary mirror. Some instruments will be cooled with stored cryogens to liquid helium temperatures, others to liquid nitrogen temperatures. The spacecraft functions will be located in a resource module behind the primary mirror. The LDR will be transferred to orbit by the space transportation system and assembled and tested at the space station. It will then be boosted to an orbit of greater than or = 700 km as a free flyer.

Swanson, Paul N.↗
NASA NTRS2009

Benefits Assessment of Algorithmically Combining Generic High Altitude Airspace Sectors

In today's air traffic control operations, sectors that have traffic demand below capacity are combined so that fewer controller teams are required to manage air traffic. Controllers in current operations are certified to control a group of six to eight sectors, known as an area of specialization. Sector combinations are restricted to occur within areas of specialization. Since there are few sector combination possibilities in each area of specialization, human supervisors can effectively make sector combination decisions. In the future, automation and procedures will allow any appropriately trained controller to control any of a large set of generic sectors. The primary benefit of this will be increased controller staffing flexibility. Generic sectors will also allow more options for combining sectors, making sector combination decisions difficult for human supervisors. A sector-combining algorithm can assist supervisors as they make generic sector combination decisions. A heuristic algorithm for combining under-utilized air space sectors to conserve air traffic control resources has been described and analyzed. Analysis of the algorithm and comparisons with operational sector combinations indicate that this algorithm could more efficiently utilize air traffic control resources than current sector combinations. This paper investigates the benefits of using the sector-combining algorithm proposed in previous research to combine high altitude generic airspace sectors. Simulations are conducted in which all the high altitude sectors in a center are allowed to combine, as will be possible in generic high altitude airspace. Furthermore, the algorithm is adjusted to use a version of the simplified dynamic density (SDD) workload metric that has been modified to account for workload reductions due to automatic handoffs and Automatic Dependent Surveillance Broadcast (ADS-B). This modified metric is referred to here as future simplified dynamic density (FSDD). Finally, traffic demand sets with increased air traffic demand are used in the simulations to capture the expected growth in air traffic demand by the mid-term.

Bloem, Michael↗
NASA NTRS2000

Influence of microgravity on ultrastructure and storage reserves in seeds of Brassica rapa L

Successful plant reproduction under spaceflight conditions has been problematic in the past. During a 122 d opportunity on the Mir space station, full life cycles of Brassica rapa L. were completed in microgravity in a series of three experiments in the Svet greenhouse. Ultrastructural and cytochemical analyses of storage reserves in mature dry seeds produced in these experiments were compared with those of seeds produced during a high-fidelity ground control. Additional analyses were performed on developing Brassica embryos, 15 d post pollination, which were produced during a separate experiment on the Shuttle (STS-87). Seeds produced on Mir had less than 20% of the cotyledon cell number found in seeds harvested from the ground control. Cytochemical localization of storage reserves in mature cotyledons showed that starch was retained in the spaceflight material, whereas protein and lipid were the primary storage reserves in ground control seeds. Protein bodies in mature cotyledons produced in space were 44% smaller than those in the ground control seeds. Fifteen days after pollination, cotyledon cells from mature embryos formed in space had large numbers of starch grains, and protein bodies were absent, while in developing ground control seeds at the same stage, protein bodies had already formed and fewer starch grains were evident. These data suggest that both the late stage of seed development and maturation are changed in Brassica by growth in a microgravity environment. While gravity is not absolutely required for any step in the plant life cycle, seed quality in Brassica is compromised by development in microgravity.

NASA Experiment Number 9600004↗
NASA NTRS1993

Fluidic scale model multi-plane thrust vector control test results

An experimental investigation has been conducted at the NASA Langley 16-Foot Transonic Tunnel Static Test Facility to determine the concept feasibility of using fluidics to achieve multiplane thrust vector control in a 2D convergent-divergent (2D-CD) fixed aperture nozzle. Pitch thrust vector control is achieved by injection of flow through a slot in the divergent flap into the primary nozzle flow stream. Yaw vector control results from secondary air delivered tangentially to vertical Coanda flaps. These flaps are offset laterally and aligned parallel to the primary nozzle side walls. All tests were conducted at static (no external flow) conditions. Flow visualization was conducted using a paint flow technique and Focus Schlieren. Significant levels of pitch deflection angles (19 deg) were achieved at low pressure ratios and practical levels (14 deg) resulted at typical intermediate power settings. The ability of the Coanda surface blowing concept to produce yaw deflection was limited to NPR not greater than 4.

Chiarelli, Charles↗
NASA NTRS2007

Flight Test Results on the Stability and Control of the F-15B Quiet Spike Aircraft

The Quiet Spike (QS) flight research program was an aerodynamic and structural proof-of-concept of a telescoping sonic-boom suppressing nose boom on an F-15 B aircraft. The program goal was to collect flight data for model validation up to 1.8 Mach. The primary test philosophy was maintaining safety of flight. In the area of stability and controls the primary concerns were to assess the potential destabilizing effect of the spike on the stability, controllability, and handling qualities of the aircraft and to ensure adequate stability margins across the entire QS flight envelop. This paper reports on the stability and control methods used for flight envelope clearance and flight test results of the F-15B Quiet Spike. Also discussed are the flight test approach, the criteria to proceed to the next flight condition, brief pilot commentary on typical piloting tasks, approach and landing, and refueling task, and air data sensitivity to the flight control system.

Moua, Cheng↗
NASA NTRS1975

Mechanization of and experience with a triplex fly-by-wire backup control system

A redundant three-axis analog control system was designed and developed to back up a digital fly-by-wire control system for an F-8C airplane. Forty-two flights, involving 58 hours of flight time, were flown by six pilots. The mechanization and operational experience with the backup control system, the problems involved in synchronizing it with the primary system, and the reliability of the system are discussed. The backup control system was dissimilar to the primary system, and it provided satisfactory handling through the flight envelope evaluated. Limited flight tests of a variety of control tasks showed that control was also satisfactory when the backup control system was controlled by a minimum-displacement (force) side stick. The operational reliability of the F-8 digital fly-by-wire control system was satisfactory, with no unintentional downmodes to the backup control system in flight. The ground and flight reliability of the system's components is discussed.

Lock, W. P.↗
NASA NTRS1976

Mechanization of and experience with a triplex fly-by-wire backup control system

A redundant three axis analog control system was designed and developed to back up a digital fly by wire control system for an F-8C airplane. The mechanization and operational experience with the backup control system, the problems involved in synchronizing it with the primary system, and the reliability of the system are discussed. The backup control system was dissimilar to the primary system, and it provided satisfactory handling through the flight envelope evaluated. Limited flight tests of a variety of control tasks showed that control was also satisfactory when the backup control system was controlled by a minimum displacement (force) side stick. The operational reliability of the F-8 digital fly by wire control system was satisfactory, with no unintentional downmodes to the backup control system in flight. The ground and flight reliability of the system's components is discussed.

Lock, W. P.↗
NASA NTRS1985

Impurities in silicon solar cells

Metallic impurities, both singly and in combinations, affect the performance of silicon solar cells. Czochralski silicon web crystals were grown with controlled additions of secondary impurities. The primary electrical dopants were boron and phosphorus. The silicon test ingots were grown under controlled and carefully monitored conditions from high-purity charge and dopant material to minimize unintentional contamination. Following growth, each crystal was characterized by chemical, microstructural, electrical, and solar cell tests to provide a detailed and internally consistent description of the relationships between silicon impurity concentration and solar cell performance. Deep-level spectroscopy measurements were used to measure impurity concentrations at levels below the detectability of other techniques and to study thermally-induced changes in impurity activity. For the majority of contaminants, impurity-induced performance loss is due to a reduction of the base diffusion length. From these observations, a semi-empirical model which predicts cell performance as a function of metal impurity concentration was formulated. The model was then used successfully to predict the behavior of solar cells bearing as many as 11 different impurities.

Hopkins, R. H.↗
NASA NTRS2005

AOCS Performance and Stability Validation for a 160-m Solar Sail with Control-Structure Interactions

Future solar sail missions, such as NASA's Solar Polar Imager Vision, will require sails with dimensions on the order of 50-500 m. We are examining a square sail design with moving mass (trim control mass, TCM) and quadrant rotation primary actuators plus pulsed plasma thrusters (PPTs) at the mast tips for backup attitude control. Quadrant rotation is achieved via roll stabilizer bars (RSB) at the mast tips. At these sizes, given the gossamer nature of the sail supporting structures, flexible modes may be low enough to interact with the control system, especially as these actuators are located on the flexible structure itself and not on the rigid core. This paper develops a practical analysis of the flexible interactions using state-space systems and modal data from finite element models of the system. Torsion and bending of the masts during maneuvers could significantly affect the function of the actuators while activation of the membrane modes could adversely affect the thrust vector direction and magnitude. Analysis of the RSB and TCM dynamics for developing high-fidelity simulations is included. For control analysis of the flexible system, standard finite-element models of the flexible sail body are loaded and the modal data is used to create a modal coordinate state-space system. Key parameters include which modes to include, which nodes are of interest for force inputs and displacement outputs, connecting nodes through which external forces and torques are applied from the flex body to the core, any nominal momentum in the system, and any steady rates. The system is linearized about the nominal attitude and rate. The state-space plant can then be analyzed with a state-space controller, and Bode, Nyquist, step and impulse responses generated. The approach is general for any rigid core with a flexible appendage. This paper develops a compensator for a simple two-mass flex system and extrapolates the results to the solar sail. A finite element model of the 20 m solar sail by ATK Space Systems, recently validated in ground tests, is used to demonstrate the sail analysis approach.

Wie, Bong↗
NASA NTRS2013

Progress in Operational Analysis of Launch Vehicles in Nonstationary Flight

This paper presents recent results in an ongoing effort to understand and develop techniques to process launch vehicle data, which is extremely challenging for modal parameter identification. The primary source of difficulty is due to the nonstationary nature of the situation. The system is changing, the environment is not steady, and there is an active control system operating. Hence, the primary tool for producing clean operational results (significant data lengths and data averaging) is not available to the user. This work reported herein uses a correlation-based two step operational modal analysis approach to process the relevant data sets for understanding and development of processes. A significant drawback for such processing of short time histories is a series of beating phenomena due to the inability to average out random modal excitations. A recursive correlation process coupled to a new convergence metric (designed to mitigate the beating phenomena) is the object of this study. It has been found in limited studies that this process creates clean modal frequency estimates but numerically alters the damping.

James, George↗
NASA NTRS1972

Heat pipe thermal control system concept for the space station.

A program was undertaken to design and evaluate a high reliability, long life thermal control system for Space Station application. The program consisted of three sequential steps including the investigation of many thermal control elements to select the most reliable. The elements are combined into several system concepts. The most desirable approach is then selected and its characteristics are determined. The result of this project is a conceptual thermal control system design that employs heat pipes as primary components, both for heat transport and variable temperature control.

Scollon, T. R., Jr.↗
NASA NTRS1976

Resume and analysis of NACA lateral control research

An analysis of the principal results of recent lateral control research is made. Two things are considered of primary importance in judging the effectiveness of different control devices: The (calculated) banking and yawing motion of a typical small airplane caused by a deflection of the control, and the stick force required to produce this deflection. The report includes a table in which a number of different lateral control devices are compared on these bases. Test flights demonstrated that satisfactory lateral control at high angles of attack depends as much on the retention of stability as on aileron effectiveness.

Weick, F. E.↗