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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 1,171 records · Page 65
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

The challenges of modelling antibody repertoire dynamics in HIV infection

Antibody affinity maturation by somatic hypermutation of B-cell immunoglobulin variable region genes has been studied for decades in various model systems using well-defined antigens. While much is known about the molecular details of the process, our understanding of the selective forces that generate affinity maturation are less well developed, particularly in the case of a co-evolving pathogen such as HIV. Despite this gap in understanding, high-throughput antibody sequence data are increasingly being collected to investigate the evolutionary trajectories of antibody lineages in HIV-infected individuals. Here, we review what is known in controlled experimental systems about the mechanisms underlying antibody selection and compare this to the observed temporal patterns of antibody evolution in HIV infection. In addition, we describe how our current understanding of antibody selection mechanisms leaves questions about antibody dynamics in HIV infection unanswered. Without a mechanistic understanding of antibody selection in the context of a co-evolving viral population, modelling and analysis of antibody sequences in HIV-infected individuals will be limited in their interpretation and predictive ability.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Advanced Intra-Cycle Detection of Pre-Ignition Events through Phase-Space Transforms of Cylinder Pressure Data

The widespread adoption of boosted, downsized SI engines has brought pre-ignition phenomena into greater focus, as the knock events resulting from pre-ignitions can cause significant hardware damage. Much attention has been given to understanding the causes of pre-ignition and identify lubricant or fuel properties and engine design and calibration considerations that impact its frequency. This helps to shift the pre-ignition limit to higher specific loads and allow further downsizing but does not fundamentally eliminate the problem. Real-time detection and mitigation of pre-ignition would thus be desirable to allow safe engine operation in pre-ignition-prone conditions. This study focuses on advancing the time of detection of pre-ignition in an engine cycle where it occurs. Furthermore, phase space transforms through time-delay embedding of cylinder pressure and principal component analysis were applied to same-cycle detection of pre-ignition and shown to enable detection on the order of a crank degree earlier than deviation in cylinder pressure can be identified through direct statistical observation of the pressure data. Additionally, it appears that the deviation of the trajectory in phase space may offer the opportunity to extend this method to further extend the detection window and allow more time for mitigation actions to occur.

42 ENGINEERING↗
NASA NTRS1962

HYPERSONIC AERODYNAMIC PROBLEMS OF THE FUTURE

Blunt shapes were of interest for the speed regime of ballistic missiles and satellite vehicles, in the main, as a result of the necessity for minimizing convective heating. But as speeds exceed escape speed, the heating due to air radiation assumes an even more important role than does the convective heating. It is shown that this change revives interest in the more slender configurations and that when the speed of a vehicle entering the atmosphere of a planet becomes sufficiently great, it may be economical to decelerate in part by retrorocket rather than entirely by aerodynamic braking. The factors discussed determine the speed limit for which retrorocket braking becomes desirable. The change in the basic characteristics of flow brought about by gas radiation at speeds well in excess of escape speed are then analyzed. It is shown that when the gas radiation energy becomes a significant part of the total energy of the flow, it is no longer possible to analyze aerodynamic flow fields with the assumption that the energy of elemental volumes remains constant, since for such cases a transfer of energy by radiation from one elemental volume to another significantly alters the flow. The increase in complexity in the analytical approaches to the problems of these hypersonic flows necessitates, more than ever, continued experimental research, even though such experiments are exceedingly difficult to perform. Extension of our experimental knowledge of these hypersonic flows is shown to be possible by study of tracked trajectories of bright meteors. Some analyses of meteor tracking data are presented which demonstrate that the tracking camera systems employed at present can provide sufficiently accurate results to yield useful aerodynamic heating information.

SATELLITE↗
NASA NTRS1971

Fast Mars communication geometry program

Computer program calculates trajectories of orbiting spacecraft and lander vehicles simultaneously. Using data from both vehicles, program calculates communications geometry which consists of orbiting spacecraft cone/clock angle, lander cone/clock angle, range, range rate and acceleration, and fade, reflective, and system margins.

Garner, W. R.↗
NASA NTRS1973

Atlas/Centaur Pioneer G operations summary

Specifications of the Pioneer G and Atlas/Centaur 30 Launch Vehicle are provided, along with information concerning mission objectives. The Atlas/Centaur engine group will generate a 431,383 lb. thrust for an injection velocity of approximately 32,400 miles per hour using liquid oxygen and RP-1 propellants. In addition to detailed diagrams of equipment aboard the Pioneer G, an account is given of intended investigations of the interplanetary medium beyond the orbit of Mars, the nature of the asteroid belt, and the environmental and atmospheric characteristics of Jupiter. Pertinent data regarding the option of a Saturn-oriented trajectory are also reviewed and evaluated.

Source record↗
NASA NTRS1973

Coordinated observations of chemical releases from the ground and from aircraft at high latitudes

The ground observations of the Na-Li trail released from a Nike-Apache rocket obtained by the Geophysical Institute are discussed. By using the nominal trajectory for a 60 pound payload and the particular rocket, a best fit trajectory was determined based on the Ester Dome photographic data, launch time and earth-sun geometrical shadow height. From these calculations, the height of obvious features along the trail were determined and their velocity estimated. A clockwise rotation of the velocity vector with increasing height was observed. Velocities deduced at various altitudes were then compared to meter radar data also obtained during this period. The comparisons of these two neutral wind measurements techniques are satisfactory.

Romick, G. J.↗
NASA NTRS1971

NASA-GSFC ionospheric corrections to satellite tracking data

An overview is presented of the development, verification, and recent implementation of the NASA-GSFC ionospheric model for satellite tracking data corrections. This model was incorporated into the Goddard Trajectory Determination System which is providing continuous trajectory computation support for the lunar orbiting Radio Astronomy Explorer-B launched on 10 June 1973.

Schmid, P. E.↗
NASA NTRS1973

Solar radio bursts at kilometer wavelengths

The potential value of traveling solar radio bursts for investigating energetic particle propagation, and for probing the interplanetary medium is discussed. A general survey of the characteristics of type 3 radio phenomena observed at hectometer and kilometer wavelengths is presented along with a brief discussion of the relationships among type 1 meter noise storms, decametric continuum, and type 3 hectometric storms. Type 3 bursts are analyzed to show how these data provide information about the average energy, dispersion, and trajectory of energetic particles, the interplanetary scale, and magnetic field configuration. The recent observations of type 2 shock wave phenomena at kilometer wavelengths are described, and current research and the direction of future observation are outlined.

Stone, R. G.↗
NASA NTRS1976

Geocentric gravitational constant determined from spacecraft radiometric data

The value of the geocentric gravitational constant was determined from the analysis of Doppler and range data during the near-earth phases of the trajectories of Mariners 9 and 10. Geocentric gravitational constant values (in units of cu km/sq s) for the two spacecraft were found to be: 398,600.7 plus or minus 0.2 for Mariner 9 and 398,600.6 plus or minus 0.2 for Mariner 10.

Esposito, P. B.↗
NASA NTRS1976

Missions to Titan /1983-2000/ - An analysis of orbiters and entry vehicles

Mission Analysis data is presented which forms a basis for planning future missions to Titan, the seventh moon of Saturn. Four Titan mission options are studied: orbiters, probes, penetrators and landers. The generated data supports these mission modes. A comprehensive launch and trajectory analysis of earth to Saturn opportunities from 1983 to 2000 is given. Direct ballistic and Delta VEGA trajectory modes are evaluated. Orbital insertion, orbital trim, entry vehicle deployment options are all studied in parametric detail.

Hendricks, T. C.↗
NASA NTRS1979

Goddard trajectory determination

Goddard Trajectory Determination System (GTDS), programs designed to support Earth, lunar and interplanetary missions are used as research and development tool. Program displays research and development used in trajectory determination, preflight and postflight analyses, simulation of tracking data, ephemeris generation, and related tasks.

Dixon, B.↗
NASA NTRS1980

Static and transient performance of YF-102 engine with up to 14 percent core airbleed for the quiet short-haul research aircraft

An outdoor static test stand was used to measure the steady-state and transient performance of the YF-102 turbofan engine with core airbleed. The test configuration included a bellmouth inlet and a confluent-flow exhaust system similar in size to the quiet short-haul research aircraft (QSRA) exhaust system. For the steady-state tests, the engine operated satisfactorily with core bleed up to 14 percent of the core inlet flow. For the transient tests the engine accelerated and decelerated satisfactorily with no core bleed and with core bleed up to 11 percent of the core inlet flow (maximum tested). For some of the tests the core-bleed flow rate was scheduled to vary with fan discharge pressure, to simulate the QSRA bleed requirements. No stability, surge, stall, overtemperature, combustor flameout, or other operating problems were encountered in any of the tests. Steady-state and transient engine performance data are presented in graphs, and fuel-control trajectories for typical transient tests are shown.

Mcardle, J. G.↗
NASA NTRS1980

STS-1 operational flight profile. Volume 4: Onorbit profile-cycle 3.1.1

The orbital flight test (OFT) phase of the shuttle program consists of four orbital flights beginning in November 1980and continuing through 1981. The major purpose of the OFT program is to demonstrate and verify shuttle systems and flight capabilities by satisfying the OFT requirements, is presented. The onorbit portion of the operational flight profile (OFP) for the first Space Transportation System-1 (STS-1) flight is presented. This onorbit document (volume 4) is one in a series that, taken together, will define the STS-1 OFP. This OFP onorbit document represents a combination of the STS-1 ground rules and constraints and the initialization data. The STS-1 flight activities described reflect the trajectory, consumable, crew activity, and flight requirement baseline as of May 1, 1980. Flight plans for the ascent, onorbit, and descent phases of the test flight are presented.

Source record↗
NASA NTRS1981

Comparison data for Seasat altimetry in the western North Atlantic

The radar altimeter flown on Seasat in 1978 collected approximately 1,000 orbits of high quality data (5-8 precision). In the western North Atlantic these data were combined with a detailed gravimetric geoid in an attempt to produce profiles of dynamic topography. In order to provide a basis for evaluation of these profiles, available oceanographic observations in the Gulf Stream/Sargasso Sea region have been compiled into a series of biweekly maps. The data include XBT's, satellite infrared imagery, and selected trajectories of surface drifters and sub-surface SOFAR floats. The maps document the known locations of the Gulf Stream, cyclonic and anticyclonic rings, and mid-ocean eddies during the period July to October 1978.

Cheney, R. E.↗
NASA NTRS1981

The ESA mission to Comet Halley

The Europeon Space Agency's approximately Giotto mission plans for a launch in July 1985 with a Halley encounter in mid-March 1986 4 weeks after the comet's perihelion passage. Giotto carries 10 scientific experiments, a camera, neutral, ion and dust mass spectrometers, a dust impact detector system, various plasma analyzers, a magnetometer and an optical probe. The instruments are described, the principles on which they are based are described, and the experiment key performance data are summarized. The launch constraints the helicentric transfer trajectory, and the encounter scenario are analyzed. The Giotto spacecraft major design criteria, spacecraft subsystem and the ground system are described. The problem of hypervelocity dust particle impacts in the innermost part of the coma, the problem of spacecraft survival, and the adverse effects of impact-generated plasma aroung the spacecraft are considered.

Reinhard, R.↗
NASA NTRS1984

Definitive orbit determination for the HEAO-2 spacecraft

Precise ephemerides for the High Energy Astronomy Observatory-2 (HEAO-2) were computed to assist in the Charles Stark Draper Laboratory development of an onboard orbit determination technique. Weighted least-squares, batch orbit solutions were calculated using a high-precision earth gravity model and an approximate model for intermittent spacecraft thrusting. With these improvements, orbit solution consistencies at the 50- to 100-meter level were attained using the Goddard Trajectory Determination System and NASA S-band tracking data.

Smith, R. L.↗
NASA NTRS1988

A catalog of interplanetary type III storms

A catalog describing the characteristics of all the interplanetary type III storms observed at kilometric wavelengths by the radio astronomy experiment on the ISEE-3 spacecraft between September 1978 and October 1982 is presented. Three-dimensional trajectories have been determined for about one-third of these storms using radio techniques. Solar coordinate and solar wind parameters derived from the trajectories are also tabulated. A statistical summary of the data is included.

Kayser, S. E.↗