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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
All sourcesNASA NTRSDOE OSTI
NASA NTRS1951

Wind-tunnel Tests at Low Speed of Swept and Yawed Wings Having Various Plan Forms

Results are presented of wind-tunnel tests made at low speed of various small-scale models of sweptback, sweptforward, and yawed wings. The tests covered changes in aspect ratio, taper ratio, and tip shape. Some data were obtained with high-lift devices on sweptback wings and with ailerons on sweptforward wings. The data have been briefly analyzed and some comparisons have been made with the available theory.

HIGH LIFT DEVICES - COMPLETE WINGS↗
NASA NTRS1953

A note on the drag due to lift of delta wings at Mach numbers up to 2.0

In order to indicate the effects of Reynolds number and other variables on the drag due to lift of delta wings for Mach numbers up to 2.0, the results of several investigations of wing-body combinations employing delta wings with aspect ratios from 2 to 4 have been assembled for comparison. Effects of Reynolds number, leading-edge radius, and thickness ratio could be correlated with Reynolds number based on the leading-edge radius as a parameter. The results indicated that leading-edge Reynolds number effects were large at low speeds, but decreased with increases in Mach number. The effects of aspect ratio, wing modifications, and trim requirements are discussed.

MACH NUMBER EFFECTS - COMPLETE WINGS↗
NASA NTRS1993

A computer-controlled x-y offset guiding stage for the MLRS

The MLRS has experienced excellent success in its lunar and artificial satellite laser ranging operations during its many years of operation, in spite of its relatively small 'receive' aperture. We continue to strive, however, for a greater volume of data, together with better accuracy and precision. We have just now completed the design, construction, and implementation of a computer controlled x-y offset guiding stage for the MLRS, analogous to the manual one that had been a part of the original 2.7-m lunar laser ranging system on Mt. Locke at McDonald Observatory. In the past, we had been hampered by the lack of a satisfactory hardware design which could fit within the very cramped quarters of the MLRS telescope's tail piece. Recently, with funding support from the U.S. Naval Observatory and the design and construction expertise of DFM Engineering, Inc., a satisfactory instrument has been specified, designed, built, and installed. This instrument will greatly expand MLRS observational opportunities by allowing the observing crews to actively guide on visible off axis lunar surface features or background stars while the on-axis lunar surface retroreflector targets are in the dark. This paper describes this instrument and its present implementation at the MLRS.

Shelus, Peter J.↗
NASA NTRS1994

Feedback control laws for highly maneuverable aircraft

During the first half of the year, the investigators concentrated their efforts on completing the design of control laws for the longitudinal axis of the HARV. During the second half of the year they concentrated on the synthesis of control laws for the lateral-directional axes. The longitudinal control law design efforts can be briefly summarized as follows. Longitudinal control laws were developed for the HARV using mu synthesis design techniques coupled with dynamic inversion. An inner loop dynamic inversion controller was used to simplify the system dynamics by eliminating the aerodynamic nonlinearities and inertial cross coupling. Models of the errors resulting from uncertainties in the principal longitudinal aerodynamic terms were developed and included in the model of the HARV with the inner loop dynamic inversion controller. This resulted in an inner loop transfer function model which was an integrator with the modeling errors characterized as uncertainties in gain and phase. Outer loop controllers were then designed using mu synthesis to provide robustness to these modeling errors and give desired response to pilot inputs. Both pitch rate and angle of attack command following systems were designed. The following tasks have been accomplished for the lateral-directional controllers: inner and outer loop dynamic inversion controllers have been designed; an error model based on a linearized perturbation model of the inner loop system was derived; controllers for the inner loop system have been designed, using classical techniques, that control roll rate and Dutch roll response; the inner loop dynamic inversion and classical controllers have been implemented on the six degree of freedom simulation; and lateral-directional control allocation scheme has been developed based on minimizing required control effort.

Garrard, William L.↗
NASA NTRS1992

Advanced Turbine Technology Applications Project (ATTAP)

ATTAP activities during the past year included test-bed engine design and development, ceramic component design, materials and component characterization, ceramic component process development and fabrication, ceramic component rig testing, and test-bed engine fabrication and testing. Significant technical challenges remain, but all areas exhibited progress. Test-bed engine design and development included engine mechanical design, combustion system design, alternate aerodynamic designs of gasifier scrolls, and engine system integration aimed at upgrading the AGT-5 from a 1038 C (1900 F) metal engine to a durable 1372 C (2500 F) structural ceramic component test-bed engine. ATTAP-defined ceramic and associated ceramic/metal component design activities completed include the ceramic gasifier turbine static structure, the ceramic gasifier turbine rotor, ceramic combustors, the ceramic regenerator disk, the ceramic power turbine rotors, and the ceramic/metal power turbine static structure. The material and component characterization efforts included the testing and evaluation of seven candidate materials and three development components. Ceramic component process development and fabrication proceeded for the gasifier turbine rotor, gasifier turbine scroll, gasifier turbine vanes and vane platform, extruded regenerator disks, and thermal insulation. Component rig activities included the development of both rigs and the necessary test procedures, and conduct of rig testing of the ceramic components and assemblies. Test-bed engine fabrication, testing, and development supported improvements in ceramic component technology that permit the achievement of both program performance and durability goals. Total test time in 1991 amounted to 847 hours, of which 128 hours were engine testing, and 719 were hot rig testing.

Source record↗
NASA NTRS1994

The Block V Receiver fast acquisition algorithm for the Galileo S-band mission

A fast acquisition algorithm for the Galileo suppressed carrier, subcarrier, and data symbol signals under low data rate, signal-to-noise ratio (SNR) and high carrier phase-noise conditions has been developed. The algorithm employs a two-arm fast Fourier transform (FFT) method utilizing both the in-phase and quadrature-phase channels of the carrier. The use of both channels results in an improved SNR in the FFT acquisition, enabling the use of a shorter FFT period over which the carrier instability is expected to be less significant. The use of a two-arm FFT also enables subcarrier and symbol acquisition before carrier acquisition. With the subcarrier and symbol loops locked first, the carrier can be acquired from an even shorter FFT period. Two-arm tracking loops are employed to lock the subcarrier and symbol loops parameter modification to achieve the final (high) loop SNR in the shortest time possible. The fast acquisition algorithm is implemented in the Block V Receiver (BVR). This article describes the complete algorithm design, the extensive computer simulation work done for verification of the design and the analysis, implementation issues in the BVR, and the acquisition times of the algorithm. In the expected case of the Galileo spacecraft at Jupiter orbit insertion PD/No equals 14.6 dB-Hz, R(sym) equals 16 symbols per sec, and the predicted acquisition time of the algorithm (to attain a 0.2-dB degradation from each loop to the output symbol SNR) is 38 sec.

Aung, M.↗
NASA NTRS1993

Technology integration box beam failure study

Composite structures have the potential to be cost-effective, structurally efficient primary aircraft structures. The Advanced Composites Technology (ACT) Program has the goal to develop the technology to exploit this potential for heavily loaded aircraft structures. As part of the ACT Program, Lockheed Aeronautical Systems Company completed the design and fabrication of the Technology Integration Box Beam (TIBB). The TIBB is an advanced composite prototype structure for the center wing section of the C-130 aircraft. Lockheed subjected the TIBB to downbending, upbending, torsion and combined upbending and torsion load conditions to verify the design. The TIBB failed at 83 percent of design ultimate load for the combined upbending and torsion load condition. The objective of this paper is to describe the mechanisms that led to the failure of the TIBB. The results of a comprehensive analytical and experimental study are presented. Analytical results include strain and deflection results from both a global analysis of the TIBB and a local analysis of the failure region. These analytical results are validated by experimental results from the TIBB tests. The analytical and experimental results from the TIBB tests are used to determine a sequence of events that resulted in failure of the TIBB. A potential cause of failure is high stresses in a stiffener runout region. Analytical and experimental results are also presented for a stiffener runout specimen that was used to simulate the TIBB failure mechanisms.

Shuart, M. J.↗
NASA NTRS1995

Engineering development program of a closed aluminum-oxygen semi-cell system for an unmanned underwater vehicle: An update

Most emerging unmanned undersea vehicle (UUV) missions require significantly longer range and endurance than is achievable with existing battery technology. The Aluminum-Oxygen (Al-O2) semi-cell is a candidate technology capable of providing a significant improvement in endurance compared to the silver-zinc battery technology currently used in UUVs and compares favorably to other proposed UUV power systems not only in performance, but also in safety and logistics. An Al-O2 semi-cell system is under development by Loral Defense Systems-Akron (Loral) for the ARPA/Navy 44 in. diameter UUV test vehicle. The power plant consists of a cell stack, gas management, oxygen storage, electrolyte management, coolant and controller subsystems, designed to replace the existing silver-zinc battery and meet existing weight, volume, electrical and thermal requirements, therefore minimizing modifications to the UUV. A detailed system design is complete. A component and material endurance test to evaluate compatibility and reliability of various material arid components is complete. Sub scale (Short stack) system testing is completed. A full-scale demonstration unit is now under construction in the second half of 1995. The full scale demonstration test will simulate environmental conditions of the operational system. This paper summarizes the results of the extensive short stack and endurance test programs, describes the plan for full-scale testing, and concludes with a brief discussions of future directions for this technology. This program is sponsored by ARPA Maritime Systems Technology Office under NASA contract NAS3-26715.

Gregg, Dane W.↗
NASA NTRS1996

Engineering Development Program of a Closed Aluminum-Oxygen Semi-cell System for an Unmanned Underwater Vehicle: An Update

Most emerging unmanned undersea vehicle (UUV) missions require significantly longer range and endurance than is achievable with existing battery technology. The Aluminum-Oxygen (Al-O2) semi-cell is a candidate technology capable of providing a significant improvement in endurance compared to the silver-zinc battery technology currently in use in UUVs and compares favorably to other proposed UUV power systems not only in performance, but also in safety and logistics. An Al-O2 semi-cell system is under development, consisting of a cell stack, gas management, oxygen storage, electrolyte management coolant and controller subsystems. It is designed to replace the existing silver-zinc battery and meet existing weight, volume, electrical and thermal requirements, therefore minimizing modification to the UUV. A detailed system design is complete. A component and material endurance test to evaluate compatibility and reliability of various materials and components is complete. Sub=scale (short stack) system testing is complete. A full-scale demonstration unit is now under construction for testing in the second half of 1995. The full scale demonstration test will simulate environmental conditions of the operational system. This paper summarizes the results of the extensive short stack and endurance test programs, describes the plan for full-scale testing, and concludes with a brief discussion of future directions for this technology.

Gregg, Dane W.↗
NASA NTRS1997

Accurate Cold-Test Model of Helical TWT Slow-Wave Circuits

Recently, a method has been established to accurately calculate cold-test data for helical slow-wave structures using the three-dimensional electromagnetic computer code, MAFIA. Cold-test parameters have been calculated for several helical traveling-wave tube (TWT) slow-wave circuits possessing various support rod configurations, and results are presented here showing excellent agreement with experiment. The helical models include tape thickness, dielectric support shapes and material properties consistent with the actual circuits. The cold-test data from this helical model can be used as input into large-signal helical TWT interaction codes making it possible, for the first time, to design a complete TWT via computer simulation.

Kory, Carol L.↗
NASA NTRS1998

Accurate Cold-Test Model of Helical TWT Slow-Wave Circuits

Recently, a method has been established to accurately calculate cold-test data for helical slow-wave structures using the three-dimensional (3-D) electromagnetic computer code, MAFIA. Cold-test parameters have been calculated for several helical traveling-wave tube (TWT) slow-wave circuits possessing various support rod configurations, and results are presented here showing excellent agreement with experiment. The helical models include tape thickness, dielectric support shapes and material properties consistent with the actual circuits. The cold-test data from this helical model can be used as input into large-signal helical TWT interaction codes making it possible, for the first time, to design a complete TWT via computer simulation.

Kory, Carol L.↗
NASA NTRS2000

Overview of Conceptual Design of Early VentureStar(TM) Configurations

One of NASA's goals is to enable commercial access to space at a cost of $1000/lb (an order of magnitude less than today's cost) by approximately 2010. Based on results from the 1994 Congressionally mandated, NASA led, Access-to-Space Study, an all rocket-powered single-stage-to-orbit reusable launch vehicle was, selected as the best option for meeting the goal. To address the technology development issues and the follow-on development of an operational vehicle, NASA initiated the X-33 program. The focus of this paper is on the contributions made by the NASA Langley Research Center (LaRC), from 1997-1998, to the conceptual design of the Lockheed Martin Skunk Work's (LMSW) operational reusable single-stage-to-orbit VentureStar(sup TM) vehicle. The LaRC effort has been in direct support of LMSW and NASA Marshall Space Flight Center (MSFC). The primary objectives have been to reduce vehicle dry weight and improve flyability of the VentureStar(sup TM) concepts. This paper will briefly describe the analysis methods used and will present several of the concepts analyzed and design trades completed.

Lockwood, M. K.↗
NASA NTRS1999

Near Earth Asteroid Rendezvous (NEAR) Revised Eros Orbit Phase Trajectory Design

Trajectory design of the orbit phase of the NEAR mission involves a new process that departs significantly from those procedures used in previous missions. In most cases, a precise spacecraft ephemeris is designed well in advance of arrival at the target body. For NEAR, the uncertainty in the dynamic environment around Eros does not allow the luxury of a precise spacecraft trajectory to be defined in advance. The principal cause of this uncertainty is the limited knowledge oi' the gravity field a,-id rotational state of Eros. As a result, the concept for the NEAR trajectory design is to define a number of rules for satisfying spacecraft, mission, and science constraints, and then apply these rules to various assumptions for the model of Eros. Nominal, high, and low Eros mass models are used for testing the trajectory design strategy and to bracket the ranges of parameter variations that are expected upon arrival at the asteroid. The final design is completed after arrival at Eros and determination of the actual gravity field and rotational state. As a result of the unplanned termination of the deep space rendezvous maneuver on December 20, 1998, the NEAR spacecraft passed within 3830 km of Eros on December 23, 1998. This flyby provided a brief glimpse of Eros, and allowed for a more accurate model of the rotational parameters and gravity field uncertainty. Furthermore, after the termination of the deep space rendezvous burn, contact with the spacecraft was lost and the NEAR spacecraft lost attitude control. During the subsequent gyrations of the spacecraft, hydrazine thruster firings were used to regain attitude control. This unplanned thruster activity used Much of the fuel margin allocated for the orbit phase. Consequently, minimizing fuel consumption is now even more important.

Helfrich, J↗
NASA NTRS2000

The Test and Evaluation of a Non-Chromate Finishing Agent

This research is focused on the design, development and implementation of an industry, military and commercial standard testing cell for surface coatings, which focuses on advanced non-chromate materials technology and their commercialization. Currently, within both private and commercial sectors, chromates are used in the corrosion prevention. processes. However, there is a great demand for chromate-free systems that are able to provide equal protection. At the end of this effort, it is intended that a patented alternative to chromate conversion coatings would be tested and processed for commercialization. Thus far, research studies have been concerned primarily with current corrosion knowledge and testing methods. Corrosion can be classified into five categories: The first type is uniform corrosion which is dominated by a uniform thinning due to an even and regular loss of metal. The second type is called localized corrosion in which most of the loss occurs in discrete areas. The third type, metallurgically influenced corrosion is a form of attack where metallurgy plays a significant role. The fourth type, titled mechanically assisted degradation is a form of attack where velocity, abrasion, and hydrodynamics control the corrosion process. The last type of corrosion is defined as environmentally induced cracking which occurs when cracks are produced under specific, premeditated stress. Oddly enough, with these varying classifications, there are not as many standardized corrosion testing sites. Two of the most common testing methods for corrosion are salt spray testing and filiform. Although neither has proven to be absolute, in terms of the resulting observations, our research aims to help provide data that may be used to support the standardization for corrosion testing. We would acquire and use a Singleton Cyclic Corrosion Testing Chamber. Singleton test chambers perform a wide range of commonly used catalytic corrosion tests. They are used throughout the industry, some of which are - automotive, aerospace, electronic and many more. In addition to this, Singleton test chambers are fully expandable to accommodate cyclic corrosion testing needs. Singleton chambers are also designed for complete compliance and conformity with ASTM (American Society for Testing and Materials), military and commercial standards.

Gulley, H.↗
NASA NTRS1997

Evaluation of Flight Attendant Technical Knowledge

Accident and incident reports have indicated that flight attendants have numerous opportunities to provide the flight-deck crew with operational information that may prevent or lessen the severity of a potential problem. Additionally, as carrier fleets transition from three person to two person flight-deck crews, the reliance upon the cabin crew for the transfer of this information may increase further. Recent research indicates that flight attendants do not feel confident in their ability to describe mechanical parts or malfunctions of the aircraft, and the lack of flight attendant technical training has been referenced in a number of recent reports. Chute and Wiener describe five factors which may produce communication barriers between cockpit and cabin crews: the historical background of aviation, the physical separation of the two crews, psychosocial issues, regulatory factors, and organizational factors. By examining these areas of division we can identify possible bridges and address the implications of deficient cockpit/cabin communication on flight safety. Flight attendant operational knowledge may provide some mitigation of these barriers. The present study explored both flight attendant technical knowledge and flight attendant and pilot expectations of flight attendant technical knowledge. To assess the technical knowledge of cabin crewmembers, 177 current flight attendants from two U.S. carriers voluntarily completed a 13-item technical quiz. To investigate expectations of flight attendant technical knowledge, 181 pilots and a second sample of 96 flight attendants, from the same two airlines, completed surveys designed to capture each group's expectations of operational knowledge required of flight attendants. Analyses revealed several discrepancies between the present level of flight attendant operational knowledge and pilots' and flight attendants' expected and desired levels of technical knowledge. Implications for training will be discussed.

Dunbar, Melisa G.↗
NASA NTRS2001

Nutrient Stress Detection in Corn, Using Neural Networks and AVIRIS Hyperspectral Imagery

The US Department of Agriculture (USDA) Agricultural Research Service (ARS) Variable Rate (VRAT) Nitrogen Application site in Shelton, Nebraska, represents a well-documented, corn-growing quarter section. The USDA VRAT site is used to systematically study nutrient stress in corn by varying sub-plot application of fertilizer. The field has four replicates of five blocks that vary by nitrogen treatment from 0-kg/ha to 200-kg/ha in 50-kg/ha increments. The treatment blocks are set out in a randomized, complete block design. Typically, the VRAT is planted in a ridge till, monoculture corn and is watered by a central pivot irrigation system on a three-day period. Since water stress can increase spectral reflectance from corn leaves, it is important that the N-application plots be adequately watered so that only nutrient-related stress will predominate. A figure shows imagery of the USDA VRAT site with the fertilizer amounts for each block shown. Low-altitude Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) hyperspectral imagery was acquired over the Shelton, Nebraska, VRAT site on July 22, 1999. The overflight produced 3-meter pixels with 224 spectral bands. Ground personnel supported the mission with measurements at the time of the overflight. The image data was pre-processed at JPL before being sent out to an investigator. The data arrived radiometrically corrected, allowing ready application of an atmospheric correction procedure. The Atmosphere Removal Program (ATREM) was used to perform an atmospheric correction. The AVIRIS imagery after ATREM correction was output as relative reflectance. This relative reflectance file was scaled by an empirical line procedure to provide reflectances that matched closely those measured in the field.

Estep, Lee↗