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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 199 records · Page 11

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NASA NTRS1990

Adaptive truss structure

This paper discusses the research in adaptive structures conducted at NASA Langley Research Center. The objective in the research program on adaptive truss structures is to develop an integrated approach for the design, test, and evaluation of adaptive trusses. An adaptive structure must include sensors for measuring some of the states of the mechanism, a controller that processes the sensor information and generates command signals, and a device that will cause the struts in the mechanism to change length. Based on the results of the research program, it is concluded that alternative designs for future space applications are offered, and adaptive truss has been demonstrated to be effective for vibration suppression.

Horner, C. G.↗

NASA NTRS1990

Oscillating flow loss test results in Stirling engine heat exchangers

The results are presented for a test program designed to generate a database of oscillating flow loss information that is applicable to Stirling engine heat exchangers. The tests were performed on heater/cooler tubes of various lengths and entrance/exit configurations, on stacked and sintered screen regenerators of various wire diameters and on Brunswick and Metex random fiber regenerators. The test results were performed over a range of oscillating flow parameters consistent with Stirling engine heat exchanger experience. The tests were performed on the Sunpower oscillating flow loss rig which is based on a variable stroke and variable frequency linear drive motor. In general, the results are presented by comparing the measured oscillating flow losses to the calculated flow losses. The calculated losses are based on the cycle integration of steady flow friction factors and entrance/exit loss coefficients.

Koester, G.↗

NASA NTRS1998

Molecular Static Third-Order Polarizabilities of Carbon-Cage Fullerene and Their Correlation with Three Geometric Properties: Symmetry, Aromaticity, and Size

The static third-order polarizabilities (gamma) of C60, C70, five isomers of C78 and two isomers of C84 were analyzed in terms of three properties, from a geometric point of view: symmetry, aromaticity and size. The polarizability values were based on the finite field approximation using a semiempirical Hamiltonian (AM1) and applied to molecular structures obtained from density functional theory calculations. Symmetry was characterized by the molecular group order. The selection of 6-member rings as aromatic was determined from an analysis of bond lengths. Maximum interatomic distance and surface area were the parameters considered with respect to size. Based on triple linear regression analysis, it was found that the static linear polarizability (alpha) and gamma in these molecules respond differently to geometrical properties: alpha depends almost exclusively on surface area while gamma is affected by a combination of number of aromatic rings, length and group order, in decreasing importance. In the case of alpha, valence electron contributions provide the same information as all-electron estimates. For gamma, the best correlation coefficients are obtained when all-electron estimates are used and when the dependent parameter is ln(gamma) instead of gamma.

Moore, C. E.↗

NASA NTRS2018

Imaging X-Ray Polarimetry Explorer (IXPE) Risk Management

The Imaging X-ray Polarimetry Explorer (IXPE) project is an international collaboration to build and fly a polarization sensitive X-ray observatory. The IXPE Observatory consists of the spacecraft and payload. The payload is composed of three X-ray telescopes, each consisting of a mirror module optical assembly and a polarization-sensitive X-ray detector assembly; a deployable boom maintains the focal length between the optical assemblies and the detectors. The goal of the IXPE Mission is to provide new information about the origins of cosmic X-rays and their interactions with matter and gravity as they travel through space. IXPE will do this by exploiting its unique capability to measure the polarization of X-rays emitted by cosmic sources. The collaboration for IXPE involves national and international partners during design, fabrication, assembly, integration, test, and operations. The full collaboration includes NASA Marshall Space Flight Center (MSFC), Ball Aerospace, the Italian Space Agency (ASI), the Italian Institute of Astrophysics and Space Planetology (IAPS)/Italian National Institute of Astrophysics (INAF), the Italian National Institute for Nuclear Physics (INFN), the University of Colorado (CU) Laboratory for Atmospheric and Space Physics (LASP), Stanford University, McGill University, and the Massachusetts Institute of Technology. The goal of this paper is to discuss risk management as it applies to the IXPE project. The full IXPE Team participates in risk management providing both unique challenges and advantages for project risk management. Risk management is being employed in all phases of the IXPE Project, but is particularly important during planning and initial execution-the current phase of the IXPE Project. The discussion will address IXPE risk strategies and responsibilities, along with the IXPE management process which includes risk identification, risk assessment, risk response, and risk monitoring, control, and reporting.

IXPE↗

NASA NTRS2002

Verification of satellite radar remote sensing based estimates of boreal and subalpine growing seasons using an ecosystem process model and surface biophysical measurement network information

We employ daily surface Radar backscatter data from the SeaWinds Ku-band Scatterometer onboard Quikscat to estimate landscape freeze-thaw state and associated length of the seasonal non-frozen period as a surrogate for determining the annual growing season across boreal and subalpine regions of North America for 2000 and 2001.

boreal growing season radar monitoring boreal ecol↗

NASA NTRS2003

Time and Space Resolved Heat Transfer Measurements Under Nucleate Bubbles with Constant Heat Flux Boundary Conditions

Investigations into single bubble pool boiling phenomena are often complicated by the difficulties in obtaining time and space resolved information in the bubble region. This usually occurs because the heaters and diagnostics used to measure heat transfer data are often on the order of, or larger than, the bubble characteristic length or region of influence. This has contributed to the development of many different and sometimes contradictory models of pool boiling phenomena and dominant heat transfer mechanisms. Recent investigations by Yaddanapyddi and Kim and Demiray and Kim have obtained time and space resolved heat transfer information at the bubble/heater interface under constant temperature conditions using a novel micro-heater array (10x10 array, each heater 100 microns on a side) that is semi-transparent and doubles as a measurement sensor. By using active feedback to maintain a state of constant temperature at the heater surface, they showed that the area of influence of bubbles generated in FC-72 was much smaller than predicted by standard models and that micro-conduction/micro-convection due to re-wetting dominated heat transfer effects. This study seeks to expand on the previous work by making time and space resolved measurements under bubbles nucleating on a micro-heater array operated under constant heat flux conditions. In the planned investigation, wall temperature measurements made under a single bubble nucleation site will be synchronized with high-speed video to allow analysis of the bubble energy removal from the wall.

Myers, Jerry G.↗

NASA NTRS1981

Solar cycle signal in air temperature in North America - Amplitude, gradient, phase and distribution

The considered investigation was motivated by three factors. One is related to an extension of single-channel MESA to multi-channel by Strand (1977), Morf et al. (1978), and Jones (1978). MESA is a high-resolution signal processing and spectrum analysis technique due to Burg (1975). The considered developments resulted in the discovery of the 11-year solar cycle signal in the change of the length of day by Currie (1980, 1981). They also led Currie (1981) to study the phase spectrum of the 11-year term in height H of sea level. The investigation tries to clarify the phase relations among the involved parameters. The second factor is connected with an application of the linear time domain technique used by Currie (1981) to temperature records to obtain more accurate information regarding the signal amplitude. The third factor of motivation is related to increases in the number of stations available for an analysis, the greater average length of the records, and the more accurate data set.

Currie, R. G.↗

NASA NTRS1971

Nonsystematic convolutional codes for sequential decoding in space applications.

Description of a class of rate 1/2 nonsystematic convolutional codes with the following desirable properties: (1) an undetected decoding error probability verified by simulation to be much smaller than for the best systematic codes of the same constraint length; (2) computation behavior with sequential decoding verified by simulation to be virtually identical to that of the best systematic codes; (3) a ?quick-look-in' feature that permits recovery of the information sequence from the hard-decisioned received data without decoding simply by modulo-two addition of the received sequences; and (4) suitability for encoding by simple circuitry requiring less hardware than encoders for the best systematic codes of the same constraint length. Theoretical analyses are given. These codes have been adopted for use in several forthcoming space missions.

Massey, J. L.↗

NASA NTRS1974

Venus and Mercury as Planets

A general evolutionary history of the solar planetary system is given. The previously observed characteristics of Venus and Mercury (i.e. length of day, solar orbit, temperature) are discussed. The role of the Mariner 10 space probe in gathering scientific information on the two planets is briefly described.

Source record↗

NASA NTRS1990

Upper-Bound Estimates Of SEU in CMOS

Theory of single-event upsets (SEU) (changes in logic state caused by energetic charged subatomic particles) in complementary metal oxide/semiconductor (CMOS) logic devices extended to provide upper-bound estimates of rates of SEU when limited experimental information available and configuration and dimensions of SEU-sensitive regions of devices unknown. Based partly on chord-length-distribution method.

Edmonds, Larry D.↗

NASA NTRS1998

Multipoint Measurements in an Axisymmetric Sudden Expansion

A flying wire system was utilized in conjunction with a rake of nine cross-wire probes to obtain simultaneous velocity measurements in an axisymmetric sudden expansion at a Reynolds number of 41,000. From these measurements, the correlation tensor could be calculated. Knowledge of the two-point correlation tensor reveals more in-depth information of the physical attributes of this flow. The two point correlation tensor allowed for calculation of the integrated length scales in both the radial and axial directions. This gives insight into the growth of structures with increasing downstream distance and at different radial locations through out the sudden expansion. The length scales were calculated by integrating the two-point correlation tensor in the radial direction from the centerline to the outer pipe wall and by integrating between several step heights for the axial direction. Calculated correlations at z/h = 8 and 9 at r/R = 0.46 showed a correlation length of 1/3 step height for the radial direction. It was found that length scales in the radial direction became larger with increasing radius with peaks at 0.70 e r/R c 0.81 but then decreased slightly towards the wall. Length scales in the axial direction yielded a recirculating bubble on the order of 3 step heights in the recirculating region. After the recirculating region, the length scales decreased to 1/4 of a step height.

Eaton, Erroll L.↗

NASA NTRS2006

Morphing: A Novel Approach to Astronaut Suit Sizing

The fitting of a spacesuit to an astronaut is an iterative process consisting of two parts. The first uses anthropometric data to provide an approximation of the suit components that will fit the astronaut. The second part is the subjective fitting, where small adjustments are made based on the astronaut s preference. By providing a better approximation of the correct suit components, the entire fit process time can be reduced significantly. The goals of this project are twofold: (1) To evaluate the effectiveness of the existing sizing algorithm for the Mark III Hybrid suit and (2) to determine what additional components are needed in order to provide adequate sizing for the existing astronaut population. A single subject was scanned using a 3D whole-body scanner (VITUS 3D) in the Mark III suit in eight different poses and four subjects in minimal clothing were also scanned in similar poses. The 3D external body scans of the suit and the subject are overlaid and visually aligned in a customized MATLAB program. The suit components were contracted or expanded linearly along the subjects limbs to match the subjects segmental lengths. Two independent measures were obtained from the morphing program on four subjects and compared with the existing sizing information. Two of the four subjects were in correspondence with the sizing algorithm and morphing results. The morphing outcome for a third subject, incompatible with the suit, suggested that an additional arm element at least 6 inches smaller than the existing smallest suit component would need to be acquired. The morphing result of the fourth subject, deemed incompatible with the suit using the sizing algorithm, indicated a different suit configuration which would be compatible. This configuration matched with the existing suit fit check data.

Margerum, Sarah↗

NASA NTRS1994

Airplane takeoff and landing performance monitoring system

The invention is a real-time takeoff and landing performance monitoring system for an aircraft which provides a pilot with graphic and metric information to assist in decisions related to achieving rotation speed (VR) within the safe zone of a runway, or stopping the aircraft on the runway after landing or take-off abort. The system processes information in two segments: a pretakeoff segment and a real-time segment. One-time inputs of ambient conditions and airplane configuration information are used in the pretakeoff segment to generate scheduled performance data. The real-time segment uses the scheduled performance data, runway length data and transducer measured parameters to monitor the performance of the airplane throughout the takeoff roll. Airplane acceleration and engine-performance anomalies are detected and annunciated. A novel and important feature of this segment is that it updates the estimated runway rolling friction coefficient. Airplane performance predictions also reflect changes in head wind occurring as the takeoff roll progresses. The system provides a head-down display and a head-up display. The head-up display is projected onto a partially reflective transparent surface through which the pilot views the runway. By comparing the present performance of the airplane with a continually predicted nominal performance based upon given conditions, performance deficiencies are detected by the system and conveyed to pilot in form of both elemental information and integrated information.

Middleton, David B.↗

NASA NTRS1996

Airplane takeoff and landing performance monitoring system

The invention is a real-time takeoff and landing performance monitoring system for an aircraft which provides a pilot with graphic and metric information to assist in decisions related to achieving rotation speed (V.sub.R) within the safe zone of a runway, or stopping the aircraft on the runway after landing or take-off abort. The system processes information in two segments: a pretakeoff segment and a real-time segment. One-time inputs of ambient conditions and airplane configuration information are used in the pretakeoff segment to generate scheduled performance data. The real-time segment uses the scheduled performance data, runway length data and transducer measured parameters to monitor the performance of the airplane throughout the takeoff roll. Airplane acceleration and engine-performance anomalies are detected and annunciated. A novel and important feature of this segment is that it updates the estimated runway rolling friction coefficient. Airplane performance predictions also reflect changes in head wind occurring as the takeoff roll progresses. The system provides a head-down display and a head-up display. The head-up display is projected onto a partially reflective transparent surface through which the pilot views the runway. By comparing the present performance of the airplane with a continually predicted nominal performance based upon given conditions, performance deficiencies are detected by the system and conveyed to pilot in form of both elemental information and integrated information.

Middleton, David B.↗

NASA NTRS2014

Flash Infrared Thermography Contrast Data Analysis Technique

This paper provides information on an IR Contrast technique that involves extracting normalized contrast versus time evolutions from the flash thermography inspection infrared video data. The analysis calculates thermal measurement features from the contrast evolution. In addition, simulation of the contrast evolution is achieved through calibration on measured contrast evolutions from many flat-bottom holes in the subject material. The measurement features and the contrast simulation are used to evaluate flash thermography data in order to characterize delamination-like anomalies. The thermal measurement features relate to the anomaly characteristics. The contrast evolution simulation is matched to the measured contrast evolution over an anomaly to provide an assessment of the anomaly depth and width which correspond to the depth and diameter of the equivalent flat-bottom hole (EFBH) similar to that used as input to the simulation. A similar analysis, in terms of diameter and depth of an equivalent uniform gap (EUG) providing a best match with the measured contrast evolution, is also provided. An edge detection technique called the half-max is used to measure width and length of the anomaly. Results of the half-max width and the EFBH/EUG diameter are compared to evaluate the anomaly. The information provided here is geared towards explaining the IR Contrast technique. Results from a limited amount of validation data on reinforced carbon-carbon (RCC) hardware are included in this paper.

Koshti, Ajay↗

NASA NTRS1990

Preliminary error budget for an optical ranging system: Range, range rate, and differenced range observables

Future missions to the outer solar system or human exploration of Mars may use telemetry systems based on optical rather than radio transmitters. Pulsed laser transmission can be used to deliver telemetry rates of about 100 kbits/sec with an efficiency of several bits for each detected photon. Navigational observables that can be derived from timing pulsed laser signals are discussed. Error budgets are presented based on nominal ground stations and spacecraft-transceiver designs. Assuming a pulsed optical uplink signal, two-way range accuracy may approach the few centimeter level imposed by the troposphere uncertainty. Angular information can be achieved from differenced one-way range using two ground stations with the accuracy limited by the length of the available baseline and by clock synchronization and troposphere errors. A method of synchronizing the ground station clocks using optical ranging measurements is presented. This could allow differenced range accuracy to reach the few centimeter troposphere limit.

Folkner, W. M.↗

NASA NTRS1992

Global geodesy using GPS without fiducial sites

Baseline lengths and geocentric radii have been determined from GPS data without the use of fiducial sites. Data from the first GPS experiment for the IERS and Geodynamics (GIG '91) have been analyzed with a no-fiducial strategy. A baseline length daily repeatability of 2 mm + 4 parts per billion was obtained for baselines in the Northern Hemisphere. Comparison of baseline lengths from GPS and the global VLBI solution GLB659 (Caprette et al. 1990) show rms agreement of 2.1 parts per billion. The geocentric radius mean daily repeatability for all sites was 15 cm. Comparison of geocentric radii from GPS and SV5 (Murray et al. 1990) show rms agreement of 3.8 cm. Given n globally distributed stations, the n(n - 1)/2 baseline lengths and n geocentric radii uniquely define a rigid closed polyhedron with a well-defined center of mass. Geodetic information can be obtained by examining the structure of the polyhedron and its change with time.

Heflin, Michael↗

NASA NTRS1993

Design of multiple-ply laminated composite tapered beams

A study of a special case of symmetric laminated composite cantilever beams is presented. The approach models beams that are tapered both in depth and width and investigates the effect of the ply layup angle and the ply taper on bending and interlaminar shearing stresses. For the determination of stresses and deflections, the beam stiffness matrices are expressed as linear functions of the beam length. Using classical lamination theory (CLT) the stiffness matrices are determined and assembled at strategic locations along the length of the beam. They are then inverted and necessary stiffness parameters are obtained numerically and extracted for determination of design information at each location chosen. Several ply layup configurations are investigated, and design considerations are presented based on the findings. Finally, recommendations for the design of these beams are presented, and a means for anticipating the location of highest stresses is offered.

Rodriguez, P.↗