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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 91 records · Page 5

The all electric airplane-benefits and challenges

The all electric aircraft considered in the present investigation is an aircraft which has digital flight crucial controls, electromechanical actuators, and electrical secondary power. There are no hydraulic or pneumatic systems. The characteristics of an all electric aircraft are related to reduced acquisition cost, reduced weight, reduced fuel consumption, increased reliability, reduced support equipment, simpler maintenance, an expanded flight envelope, and improved survivability. An additional benefit is the dramatically increased design flexibility and mission adaptability. However, the implementation of the all electric aircraft concept requires the resolution of a number of major technology issues. Issues in the digital flight controls area are related to achieving the required levels of safety and reliability in a cost effective manner. Other challenges which have to be met are concerned with electromechanical actuators, environmental control and ice protection systems, and engine technology.

Spitzer, C. R.↗

Time-Coordination Strategies and Control Laws for Multi-Agent Unmanned Systems

Time-critical coordination tools for unmanned systems can be employed to enforce the type of temporal constraints required in terminal control areas, ensure minimum distance requirements among vehicles are satisfied, and successfully perform coordinated missions. In comparison with previous literature, this paper presents an ampler spectrum of coordination and temporal specifications for unmanned systems, and proposes a general control law that can enforce this range of constraints. The constraint classification presented con- siders the nature of the desired arrival window and the permissible coordination errors to define six different types of time-coordination strategies. The resulting decentralized coordination control law allows the vehicles to negotiate their speeds along their paths in response to information exchanged over the communication network. This control law organizes the different members in the fleet hierarchically per their behavior and informational needs as reference agent, leaders, and followers. Examples and simulation results for all the coordination strategies presented demonstrate the applicability and efficacy of the coordination control law for multiple unmanned systems.

Puig-Navarro, Javier↗

Update on Area Production in Mixing of Supercritical Fluids

The focus of this research is on supercritical C7H16/N2 and O2/H2 mixing layers undergoing transitions to turbulence. The C7H16/N2 system serves as a simplified model of hydrocarbon/air systems in gas-turbine and diesel engines; the O2/H2 system is representative of liquid rocket engines. One goal of this research is to identify ways of controlling area production to increase disintegration of fluids and enhance combustion in such engines. As used in this research, "area production" signifies the fractional rate of change of surface area oriented perpendicular to the mass-fraction gradient of a mixing layer. In the study, a database of transitional states obtained from direct numerical simulations of the aforementioned mixing layers was analyzed to investigate global layer characteristics, phenomena in regions of high density-gradient magnitude (HDGM), irreversible entropy production and its relationship to the HDGM regions, and mechanisms leading to area production.

Okongo, Nora↗

An engine trade study for a supersonic STOVL fighter-attack aircraft, volume 1

The best main engine for an advanced STOVL aircraft flight demonstrator was studied. The STOVL aircraft uses ejectors powered by engine bypass flow together with vectored core exhaust to achieve vertical thrust capability. Bypass flow and core flow are exhausted through separate nozzles during wingborne flight. Six near term turbofan engines were examined for suitability for this aircraft concept. Fan pressure ratio, thrust split between bypass and core flow, and total thrust level were used to compare engines. One of the six candidate engines was selected for the flight demonstrator configuration. Propulsion related to this aircraft concept was studied. A preliminary candidate for the aircraft reaction control system for hover attitude control was selected. A mathematical model of transfer of bypass thrust from ejectors to aft directed nozzle during the transition to wingborne flight was developed. An equation to predict ejector secondary air flow rate and ram drag is derived. Additional topics discussed include: nozzle area control, ejector to engine inlet reingestion, bypass/core thrust split variation, and gyroscopic behavior during hover.

Beard, B. B.↗

Medical examinations for radiation workers

The NASA radiological protection policy allows an employee to be assigned work in a radiologically controlled area only if all of the following conditions are met: (1) The area must be radiologically safe for the intended operations; (2) the employee must be medically fit; (3) the employee must be properly trained; (4) appropriate radiation protection procedures must be prepared; (5) appropriate dosimetric, survey, surveillance and reporting procedures must be implemented; and (6) adequate controls and records must be established.

Alexander, R. E.↗

Engineering information on an Analog Signal to Discrete Time Interval Converter (ASDT-IC)

An electronic control system for nondissipative dc power converters is presented which improves (1) the routinely attainable static output voltage accuracy to the order of + or - 1% for ambient temperatures from -55 to 100 C and (2) the dynamic stability by utilizing approximately one tenth of the feedback gain needed otherwise. Performance is due to a functional philosophy of deterministic pulse modulation based on pulse area control and to an autocompensated signal processing principle. The system can be implemented with commercially available unselected components.

Schwarz, F. C.↗

Solar Alpha Rotary Joint (SARJ) Lubrication Interval Test and Evaluation (LITE). Post-Test Grease Analysis

The Solar Alpha Rotary Joint (SARJ) is a mechanism of the International Space Station (ISS) that orients the solar power generating arrays toward the sun as the ISS orbits our planet. The orientation with the sun must be maintained to fully charge the ISS batteries and maintain all the other ISS electrical systems operating properly. In 2007, just a few months after full deployment, the starboard SARJ developed anomalies that warranted a full investigation including ISS Extravehicular Activity (EVA). The EVA uncovered unexpected debris that was due to degradation of a nitride layer on the SARJ bearing race. ISS personnel identified the failure root-cause and applied an aerospace grease to lubricate the area associated with the anomaly. The corrective action allowed the starboard SARJ to continue operating within the specified engineering parameters. The SARJ LITE (Lubrication Interval Test and Evaluation) program was initiated by NASA, Lockheed Martin, and Boeing to simulate the operation of the ISS SARJ for an extended time. The hardware was designed to test and evaluate the exact material components used aboard the ISS SARJ, but in a controlled area where engineers could continuously monitor the performance. After running the SARJ LITE test for an equivalent of 36+ years of continuous use, the test was opened to evaluate the metallography and lubrication. We have sampled the SARJ LITE rollers and plate to fully assess the grease used for lubrication. Chemical and thermal analysis of these samples has generated information that has allowed us to assess the location, migration, and current condition of the grease. The collective information will be key toward understanding and circumventing any performance deviations involving the ISS SARJ in the years to come.

Golden, Johnny L.↗

Communication

NASA s communication work for the UAS Command and Control area will build upon work currently being conducted under NASA Recovery Act funds. Communication portions of UAS NextGen ConOps, Stateof- the-Art assessment, and Gap Analysis. Preliminary simulations for UAS CNPC link scalability assessment. Surrogate UAS aircraft upgrades. This work will also leverage FY10 in-guide funding for communication link model development. UAS are currently managed through exceptions and are operating using DoD frequencies for line-of-sight (LOS) and satellite-based communications links, low-power LOS links in amateur bands, or unlicensed Instrument/Scientific/Medical (ISM) frequencies. None of these frequency bands are designated for Safety and Regularity of Flight. No radio-frequency (RF) spectrum has been allocated by the International Telecommunications Union (ITU) specifically for UAS command and control links, for either LOS or Beyond LOS (BLOS) communication.

Griner, James↗

Chile Wildland Fires: Augmenting Wildfire Risk Assessment Efforts with Satellite-based Measurements of Soil Moisture and Vegetation Health in Central and South-Central Chile

Since 2010, Central and South-Central Chile have recorded abnormally low annual precipitation, resulting in over a decade-long megadrought. This water deficit has driven more severe wildfires, which begin earlier in the year, last longer, and burn over significantly larger areas. Past studies indicated wildland fires propagate following vegetation stress and under certain soil moisture conditions. Our work further investigated the drivers of the unprecedented wildfire that devastated Central and South-Central Chile in 2017 and 2023. To that end, we leveraged NASA Earth observations from space to explore the link between terrestrial variables and wildland fires. We first delineated the burnt extent using data from Landsat 9 Operational Land Imager 2 (OLI-2), along with the combined information from Terra + Aqua Moderate Resolution Imaging Spectroradiometer (MODIS). Next, we analyzed vegetation health based on the Normalized Difference Vegetation Index (NDVI) and evapotranspiration (ET) products of Terra MODIS. Furthermore, we examined soil moisture data from the Soil Moisture Active Passive (SMAP) mission. As the megadrought continues, we found greater anomalies and stress in vegetation indices across the region. We also identified certain pre-fire conditions in soil moisture and evapotranspiration in the days and months leading to the recent wildfires. We compared these findings against control areas that were not impacted by wildfires. Using satellite-based NASA Earth observations, we were able to provide insights into potential indicators of wildfire risk, which can augment future risk assessment and management efforts.

Benjamin D Goffin↗

An Integrated Architecture Study for Autonomous Lunar Construction

Lunar construction is an expanding field within NASA’s Moon to Mars objectives that presents many challenges and requires innovative and reliable forms of autonomous operations on the surface of the Moon to further the technologies needed for human space exploration. Marshal Space Flight Center’s (MSFC) Advanced Concepts Office (ACO) addressed Lunar Infrastructure Objective LI-4 l by developing a Pre-Phase A, integrated architecture to inform a demonstration for lunar construction operations. The ACO study traded three architectures that would survey and prepare a construction area to build a landing pad out of lunar regolith using MMPACT (Moon-to-Mars Planetary Autonomous Construction Technology) platforms, rovers, and navigation outposts. The main trades examined navigation for the system/architecture, options for rover navigation, battery vs continuous tether power for the MMPACT robotic arm, and assigning site prep functionality to the rovers vs the platforms. Results of the study determined that the best options for the scenario provided would be local navigation (more accurate and continuous), a combination of Light Detection and Ranging (LiDAR) for initial site mapping with subsequent Smart Video Guidance Sensors (SVGS) to save power for construction, and using tethered power to decrease mission duration. The team also concluded that assigning site prep functionality to either the rovers or the platforms has benefits and challenges; future studies could explore having that functionality on both the rovers and platforms. Lastly, the team provided a Concept of Operations (ConOps) timeline that can be used in real-time ground demonstrations to explore the mission timeline, construction processes, autonomous operations, and communication systems that can be tested using MSFC’s lunar regolith field and Lunar Utilization Control Area (LUCA).

Sarah Triana↗

Collaborative Arrival Planning: Data Sharing and User Preference Tools

Air traffic growth and air carrier economic pressures have motivated efforts to increase the flexibility of the air traffic management process and change the relationship between the air traffic control service provider and the system user. One of the most visible of these efforts is the U.S. government/industry "free flight" initiative, in which the service provider concentrates on safety and cross-airline fairness, and the user on their business objectives and operating preferences, including selecting their own path and speed in real-time. In the terminal arrival phase of flight, severe restrictions and rigid control are currently placed on system users, typically without regard for individual user operational preferences. Airborne delays applied to arriving aircraft into capacity constrained airports are imposed on a first-come, first-serve basis, and thus do not allow the system user to plan for or prioritize late arrivals, or to economically optimize their arrival sequence. A central tenant of the free-flight operating paradigm is collaboration between service providers and users in reaching air traffic management decisions. Such collaboration would be particularly beneficial to an airline's "hub" operation, where off-schedule arrival aircraft are a consistent problem, as they cause serious air-port ramp difficulties, rippling airline scheduling effects, and result in large economic inefficiencies. Greater collaboration can also lead to increased airport capacity and decrease the severity of over-capacity rush periods. In the NASA Collaborative Arrival Planning (CAP) project, both independent exchange of real-time data between the service provider and system user and collaborative decision support tools are addressed. Data exchange of real-time arrival scheduling, airspace management, and air carrier fleet data between the FAA service provider and an air carrier is being conducted and evaluated. Collaborative arrival decision support tools to allow intra-airline arrival preferences are being developed and simulated. The CAP project is part of and leveraged from the NASA/FAA Center TRACON Automation System (CTAS), a fielded set of decision support tools that provide computer generated advisories for both enroute and terminal area controllers to manage and control arrival traffic more efficiently. In this paper, the NASA Collaborative Arrival Planning project is outlined and recent results detailed, including the real-time use of CTAS arrival scheduling data by a major air carrier and simulations of tactical and strategic user preference decision support tools.

Zelenka, Richard E.↗

Surveyor surface sampler instrument

Operational capabilities, methods of deployment command and control, areas of lunar operation, and television viewability of Surveyor lunar surface sampler instrument

Clary, M. C.↗

Facilities and support systems for a 90-day test of a regenerative life support system

A 90-day test is reported of a regenerative life support system which was completed in a space station simulator. The long duration of the test and the fact that it was manned, imposed rigid reliability and safety requirements on the facility. Where adequate reliability could not be built into essential facility systems, either backup systems or components were provided. Awareness was intensified by: (1) placing signs on every piece of equipment that could affect the test, (2) painting switches on all breaker panels a bright contrasting color, (3) restricting access to the test control area, and (4) informing personnel in the facility (other than test personnel) of test activities. It is concluded that the basic facility is satisfactory for conducting long-duration manned tests, and it is recommended that all monitor and alarm functions be integrated into a single operation.

Malin, R. L.↗

Directional behavior of thermal emission from a rough lunar surface.

The directionality is studied of the infrared emission from the lunar surface. A rough surface is postulated where the roughness is characterized by a crater field on a plain surface. The contour of the craters is assumed to be spherical. This makes it possible to determine the thermal emission on the basis of the temperature distribution obtained analytically by Adorjan (1970). By integrating the radiosities of both the craters and plain surfaces over a control area, and for given solar elevation and observation angles, the brightness temperatures are determined. The obtained results are presented in diagrams and discussed.

Adorjan, A. S.↗

Time variation of Martian regional contrasts.

Observations of contrast changes in blue light on Mars in 1969 and 1971 are presented. Seasonal effects evidently can be evaluated from these data, although nonseasonal effects are also present. A diurnal variation is noted for certain features during both apparitions. This variation cannot be fully accounted for without considering meteorological effects. An example of a contrast reversal in ultraviolet light is presented. The suggestion is made that during the Martian season covered herein, variability of the bright areas controlled the apparent contrasts observed.

Thompson, D. T.↗

Study of genetic direct search algorithms for function optimization

The results are presented of a study to determine the performance of genetic direct search algorithms in solving function optimization problems arising in the optimal and adaptive control areas. The findings indicate that: (1) genetic algorithms can outperform standard algorithms in multimodal and/or noisy optimization situations, but suffer from lack of gradient exploitation facilities when gradient information can be utilized to guide the search. (2) For large populations, or low dimensional function spaces, mutation is a sufficient operator. However for small populations or high dimensional functions, crossover applied in about equal frequency with mutation is an optimum combination. (3) Complexity, in terms of storage space and running time, is significantly increased when population size is increased or the inversion operator, or the second level adaptation routine is added to the basic structure.

Zeigler, B. P.↗

Selenium in soils of the Lower Wasatch Formation, Campbell County, Wyoming: Geochemistry, distribution, and environmental hazards

The author has identified the following significant results. Seleniferous Shingle series soils and sandstone outcrops of section 27, T 48 N, R 71 W, Wyoming are mapped on aerial photography by their association with Astragalus bisulcatus. Chemical leachate analyses and atomic absorption methods reveal all studied Samsil and Shingle soils to contain acid, base, and water soluble selenium compounds, and that water extractions showed varied concentration behavior due to soil pH. Acid-soluble selenium is found to be associated with smectite. Statistical analyses confirm that A. bisulcatus presence has a weak influence on soil-lens organic selenium concentration, and determine the importance of other geobotanical factors for convertor presence. Environmental procedures of high selenium lens burial, convertor plant eradication, and revegetated site monitoring are recommended. Usage of density analysis and photographic enlargement are used to successfully produce both a control area and a Campbell County, Wyoming regional map of A. bisulcatus supportive soils and outcrops using Skylab photography.

Kolm, K. E.↗

Effects of a 2X gravity environment on the ultrastructure of the gerbil parathyroid gland

A number of studies concerning the effects of hypergravity on bone have shown increases in bone mass or bone dimensions. Correlative studies, which could provide clues to the mechanism for such a response, have been lacking. The purpose of the present study was to evaluate the ultrastructure of parathyroid glands of Mongolian gerbils exposed to a continuous 2 X gravity force for 60 d. It was found that the experimental animals had parathyroid glands which had a greater percentage of chief cells in the active stage of their secretory cycle when compared with control animals. This result was interpreted to indicate an increase in parathyroid gland secretory activity and, hence, an increase in parathyroid hormone release. It was suggested that increased parathyroid secretory activity was necessary to maintain serum calcium levels of hypergravity animals within normal limits. Cellular forms resembling water clear cells and highly compact, degenerating cells were described in experimental animals but not in controls. Areas suggestive of cellular dissolution and disorganization were also reported in experimental parathyroids.

Sannes, P. L.↗