Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Flyby”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Preliminary Mariner 9 report on the geology of Mars.

Mariner 9 results indicate that Mars is geologically far more heterogeneous than previously suspected from earlier flyby missions; the surface has been shaped by volcanic, tectonic, erosional, and depositional activity. The equatorial region between 30 deg N and 30 deg S latitude is depicted in four geologic sketch maps, and seventeen geologic units are defined on the basis of their textural characteristics. The maps and the brief descriptions of geological units portrayed are followed by a series of more interpretive discussions dealing with topical problems and a summary geologic history. Topics covered include cratering, circular basins, volcanism, canyons, chaotic terrain, channels, and eolian activity.

Mccauley, J. F.↗
NASA NTRS1972

Nonlinear estimation theory applied to the interplanetary orbit determination problem.

The performance of a second order filter which is identical to the algorithm developed by Athans et al. (1968) for the scalar case is evaluated through numerical simulation of a Jupiter flyby mission. The observations used in the simulation are on-board measurements of the angle between Jupiter and a fixed star taken at discrete time intervals. In the numerical study, the influence of each of the second order terms is evaluated.

Tapley, B. D.↗
NASA NTRS1973

Ballistic mode Mercury orbiter missions.

The MVM'73 Mercury flyby mission will initiate exploration of this unique planet. No firm plans for follow-on investigations have materialized due to the difficult performance requirements of the next logical step, an orbiter mission. Previous investigations of ballistic mode flight opportunities have indicated requirements for a Saturn V class launch vehicle. Consequently, most recent effort has been oriented to use of solar electric propulsion. More comprehensive study of the ballistic flight mode utilizing Venus gravity-assist has resulted in identification of timely high-performance mission opportunities compatible with programmed launch vehicles and conventional spacecraft propulsion technologies. A likely candidate for an initial orbiter mission is a 1980 opportunity which offers net orbiter spacecraft mass of about 435 kg with the Titan IIIE/Centaur launch vehicle and single stage solid propulsion for orbit insertion.

Hollenbeck, G. R.↗
NASA NTRS1973

Oblique structure of Jupiter's bow shock.

Description of the Pioneer 10 flyby trajectory to the nominal bow shock of Jupiter. The analogy between the earth's and Jupiter's bow shocks is extended to include some structural features associated with oblique plasma shocks. A question of special interest to be answered by Pioneer 10 is to what extent results regarding the earth's bow shock structure can be extrapolated, qualitatively and quantitatively, to Jupiter's interaction with the solar wind.

Greenstadt, E. W.↗
NASA NTRS1972

The inference of temperature from the infrared spectra of planets.

The paper is concerned primarily with the determination of the temperature of planetary atmospheres from ground-based observations of the vibration-rotation spectra of their constituent gases. The paper is divided into two parts. The first is a discussion of the theoretical basis and analytical methods for the interpretation of planetary spectra formed by reflection of solar radiation, in the ideal case of a clear, nonscattering atmosphere; this is followed by a brief description of the effects of scattering in cloudy atmospheres on the formation of spectral lines and on the inferred temperatures. In the second part examples are given of the results which have been obtained for effective temperatures and thermal structures, for both the pure absorbing and the scattering cases, and these are compared with the results of flyby and entry probe measurements.

Farmer, C. B.↗
NASA NTRS1973

Interaction of the solar wind with the outer planets.

The hypersonic analog for the interaction of the solar wind with Jupiter, Saturn, Uranus, Neptune, and Pluto is used to provide estimates of shock shapes and locations, as well as average magnetosheath and/or ionosheath properties for these planets. Several representative spacecraft flyby trajectories (designed for outer-planet 'Grand Tour' simulations) are superimposed upon a series of figures in order to provide estimates of potential plasma and field parameters which may be encountered. Consideration is given first to the possibility that several of these planets have intrinsic magnetic fields and, secondly, to the interaction of the solar wind directly on the ionosphere should there actually be no intrinsic field. Saturn and Pluto are chosen as examples of this latter case.

Dryer, M.↗
NASA NTRS1973

Water and the Martian W cloud.

The diurnal brightening of the W cloud region of Mars during the flyby of Mariners 6 and 7 is likely due to the formation of water ice clouds. The water required in the cloud and as vapor in the atmosphere to produce the observed brightening is estimated to be roughly between 0.1 and 10 microns. Either a qualified local source with this daily production over the W cloud area or a more probable daily uplift and saturation of existing atmosphere are compatible with observations.

Peale, S. J.↗
NASA NTRS1973

Results of the flight noise measurement program using a standard and modified SH-3A helicopter

A field noise measurement program has been conducted using both a standard SH-3A helicopter and an SH-3A helicopter modified to reduce external noise levels. Modifications included reducing rotor speed, increasing the number of rotor blades, modifying the blade-tip shapes, and acoustically treating the engine air intakes and exhaust. The purpose of this study was to document the noise characteristics recorded on the ground of each helicopter during flyby, hover, landing, and take-off operations. Based on an analysis of the measured results, the average of the overhead, overall, ontrack noise levels was approximately 4 db lower for the modified helicopter than for the standard helicopter. The improved in-flight noise characteristics, and associated small footprint areas and time durations, were judged to be mainly due to tail-rotor noise reductions. The noise reductions were obtained at the expense of required power increases at airspeeds greater than 70 knots for the modified helicopter.

Pegg, R. J.↗
NASA NTRS1973

A study of the compatibility of science instruments with the solar electric propulsion space vehicle

Electromagnetic interference and field-of-view constraints are identified as the areas of most concern to science on solar electric propulsion space vehicles. Several areas are indicated which more detailed data on the space vehicle environment are needed. In addition, possible means to attain or demonstrate science/space vehicle compatibility are recommended for further iteration between space vehicle design and science payload considerations. The space vehicle design developed by the solar electric propulsion system integration technology effort is used. Two payload sets for comet Encke missions (a slow flyby and a rendezvous), as well as several instruments which are not included in the two payload sets, are analyzed to determine requirements on the space vehicle imposed by the instruments in order to meet their objectives. Environmental requirements for the sets of instruments are developed and compared to both the SEPSIT design criteria and the environment as it is presently understood.

Parker, R. H.↗
NASA NTRS1974

Studies of the major planet satellite systems

A summary is presented of the available data on the satellites of the major planets, including the currently most plausible models for several observed phenomena, for the planning of spacecraft missions to these objects. Some of the important questions likely to be solved by flyby and/or orbital missions to the giant planets are detailed, the importance of these studies to our understanding of the solar system as a whole is indicated.

Frey, H.↗
NASA NTRS1974

Pioneer 10 observations of the solar wind interation with Jupiter

Pioneer 10 Plasma Analyzer experiment flight data during the Jupiter flyby are presented. The observations show that the interaction of Jupiter's magnetic field with the solar wind is similar in many ways to that at earth, but the scale size is over 100 times larger. Jupiter is found to have a detached standing bow shock wave of high Alfven Mach number. Jupiter has a prominent magnetopause which deflects the magnetosheath plasma and excludes its direct entry into the Jovian magnetosphere. The sunward hemisphere of Jupiter's outer magnetosphere is found to be highly inflated with thermal plasma and a high beta region which is highly responsive to changes in solar wind dynamic pressure. Observational arguments are presented which tend to discount a thin disklike magnetosphere but, rather, favor a Jovian magnetosphere, albeit probabily considerably flattened as compared to the earth's magnetosphere, yet still with reasonable thickness. Results concerning the shock jump conditions, the magnetosheath flow field and inferred internal magnetospheric plasma are presented.

Wolfe, J. H.↗
NASA NTRS1974

Ephemeris data and error analysis in support of a Comet Encke intercept mission

Utilizing an orbit determination based upon 65 observations over the 1961 - 1973 interval, ephemeris data were generated for the 1976-77, 1980-81 and 1983-84 apparitions of short period comet Encke. For the 1980-81 apparition, results from a statistical error analysis are outlined. All ephemeris and error analysis computations include the effects of planetary perturbations as well as the nongravitational accelerations introduced by the outgassing cometary nucleus. In 1980, excellent observing conditions and a close approach of comet Encke to the earth permit relatively small uncertainties in the cometary position errors and provide an excellent opportunity for a close flyby of a physically interesting comet.

Yeomans, D. K.↗
NASA NTRS1973

The evolution of the SEP stage /SEPS/ concept

The features of a solar electric propulsion (SEP) stage are examined. An SEP stage (SEPS) contains all of the subsystems required to deliver separable payloads to the desired target and to support its own operations. These include attitude control, communications, data handling, and computer subsystems in addition to the solar array and thrust subsystems required for electric propulsion. SEPS can provide subsystem support to attached payloads for comet flyby and asteroid rendezvous. It can accommodate both planetary and geosynchronous missions by the use of mission-peculiar modules. In addition SEPS can assist the shuttle tug transportation system in earth-orbital applications. Aspects of mission analysis are discussed together with details of the electric propulsion system including solar array considerations.

Gilbert, J.↗
NASA NTRS1973

Trajectory analysis and performance for SEP Comet Encke missions

A summary of the performance of Solar Electric Propulsion spacecraft for Comet Encke missions for the 1980, 1984 and 1987 mission opportunities is presented together with a description of the spacecraft trajectory for each opportunity. Included is data for rendezvous trajectories for all three opportunities and data for a slow flyby mission during the 1980 opportunity. A range of propulsion system input powers of 10 to 20 kW are considered together with a constant spacecraft power requirement of 400 watts. The performance presented in this paper is indicative of that using 30 cm Mercury electron bombardment thrusters that are currently being developed. Performance is given in terms of final spacecraft mass and is thus independent of any particular spacecraft design concept.

Sauer, C. G., Jr.↗
NASA NTRS1973

Thruster array thermal control

This paper presents the results of a preliminary investigation of the thermal interactions between elements in the thruster array for a proposed Encke flyby mission. A clustered eight-thruster array was considered as the trial configuration in the current study. Electrically heated dummy thrusters were calibrated to represent the thruster thermal performance. The thermal behavior of the thruster array thermal mockup and the effects of thermal coating applications were investigated. Temperature measurements of the thruster array mockup were performed under various operational modes to substantiate the analytical results. A resultant analytical thermal network model was established to provide pertinent information for thruster array design tradeoff studies.

Wen, L.↗
NASA NTRS1973

Computation and analysis of satellite opportunities for the Mariner Jupiter/Saturn 1977 mission

The MJS77 mission provides the United States with the first opportunity to study the large satellites of Jupiter and Saturn at close range. Techniques are presented which allow the mission analyst to generate single and multiple satellite encounters at Jupiter and Saturn, and to incorporate satellite gravity assist into the targeting problem. These methods are applied to the MJS77 mission to generate, parametrically, the single and multiple satellite opportunities and characteristics at both flyby planets. An interesting consequence of this study is that a close encounter with a Galilean satellite increases the flexibility of a trajectory design which would otherwise require sizable post-Jupiter trajectory correction maneuvers to achieve the desired Saturn arrival date timing. In addition the Saturn studies revealed that as many as four satellites can be encountered on a single trajectory.

Beerer, J. G.↗
NASA NTRS1973

The Jupiter orbiter satellite tour mission

Consideration of the problem of exploring the Jupiter-Galilean satellite system by a spacecraft in orbit about the planet. A simple patched conic algorithm is developed which identifies Jupiter orbiter trajectories that utilize gravity assist flybys of the Galilean satellites. A detailed reference mission is designed against specific science criteria for satellite exploration to demonstrate the possible science return of utilizing close satellite encounters. A navigation strategy is developed, including both planet and satellite relative orbit determination and a maneuver analysis; spacecraft delivery statistics are determined in the barycentric Jupiter-Galilean satellite coordinate system and mapped to the satellite target planes to determine feasibility. A simple maneuver sequence is employed which yields acceptable velocity requirements.

Beckman, J. C.↗