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Results for “Trajectory Design”

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 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Low-thrust mission risk analysis, with application to a 1980 rendezvous with the comet Encke

A computerized failure process simulation procedure is used to evaluate the risk in a solar electric space mission. The procedure uses currently available thrust-subsystem reliability data and performs approximate simulations of the thrust sybsystem burn operation, the system failure processes, and the retargeting operations. The method is applied to assess the risks in carrying out a 1980 rendezvous mission to the comet Encke. Analysis of the results and evaluation of the effects of various risk factors on the mission show that system component failure rates are the limiting factors in attaining a high mission relability. It is also shown that a well-designed trajectory and system operation mode can be used effectively to partially compensate for unreliable thruster performance.

Yen, C. L.↗
NASA NTRS1973

Low-thrust mission risk analysis.

A computerized multi-stage failure process simulation procedure is used to evaluate the risk in a solar electric space mission. The procedure uses currently available thrust-subsystem reliability data and performs approximate simulations of the thrust subsystem burn operation, the system failure processes, and the retargetting operations. The application of the method is used to assess the risks in carrying out a 1980 rendezvous mission to Comet Encke. Analysis of the results and evaluation of the effects of various risk factors on the mission show that system component failure rates is the limiting factor in attaining a high mission reliability. But it is also shown that a well-designed trajectory and system operation mode can be used effectively to partially compensate for unreliable thruster performance.

Yen, C. L.↗
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 NTRS1974

Investigation of new radar-data-reduction techniques used to determine drag characteristics of a free-flight vehicle

An investigation was conducted of new techniques used to determine the complete transonic drag characteristics of a series of free-flight drop-test models using principally radar tracking data. The full capabilities of the radar tracking and meteorological measurement systems were utilized. In addition, preflight trajectory design, exact kinematic equations, and visual-analytical filtering procedures were employed. The results of this study were compared with the results obtained from analysis of the onboard, accelerometer and pressure sensor data of the only drop-test model that was instrumented. The accelerometer-pressure drag curve was approximated by the radar-data drag curve. However, a small amplitude oscillation on the latter curve precluded a precise definition of its drag rise.

Woodbury, G. E.↗
NASA NTRS1974

Data handling and control of the Mariner Venus Mercury '73 spacecraft

Data handling and control subsystems are described for the MVM73 spacecraft, which demonstrated the feasibility of multiple-planet gravity-assist missions. In spite of strict budgetary constraints, MVM73 carried out experiments utilizing television, an IR radiometer, a UV spectrometer, a fluxgate magnetometer, a charged particle telescope, a modulation-demodulation unit, an X-band and S-band dual frequency communications system, a steerable high-gain antenna, a time-sharing digital articulation and pointing system, and moveable solar panels. The trajectory design and flight data system are described, and the systems governing articulation and pointing and attitude control are discussed.

Scull, J. R.↗
NASA NTRS1978

Viking first encounter of Phobos - Preliminary results

Viking Orbiter-1 (VO-1) made a series of close flybys of the Martian satellite Phobos in February and May 1977. A description is presented of the results obtained during the flybys in February. The flyby geometries for the encounter period in February are shown in a graph. The trajectory design gave flybys on the illuminated side of Phobos within 80 to 300 km during the entire encounter period. The primary encounter observations of Phobos included visual and infrared imaging as well as radio tracking of VO-1 while it was under the gravitational influence of Phobos. Visual imaging was obtained from two narrow-angle television cameras. Infrared observations were obtained from an infrared thermal mapper. Radio data included S- and X-band Doppler and ranging data to VO-1 with a 10-second Doppler count. Assuming for Phobos a volume of 500 + or - 900 cu km, a mean density of 1.9 + or - 0.6 g/cu cm is obtained for it on the basis of the processed data.

Tolson, R. H.↗
NASA NTRS1979

The first libration-point satellite - Mission overview and flight history

On August 12, 1978, a scientific spacecraft called International Sun-Earth Explorer-3 (ISEE-3) was launched towards the interior sun-earth libration point, L1. The spacecraft was placed into a 'halo orbit' around the L1 point on November 20, 1978, thus becoming the first libration-point satellite. During its 100-day transfer trajectory, ISEE-3 lingered in a region where the gravitational effects of the sun and the earth are comparable, leading to some interesting tradeoffs concerning the maneuver strategy for halo-orbit insertion. Following orbit insertion, stationkeeping maneuvers were required to maintain the delicate equilibrium in the halo orbit. Details are presented for all of the velocity change maneuvers that were executed prior to the completion of the first halo orbit on May 14, 1979. Orbit selection, trajectory design, and the scientific objectives of the ISEE-3 mission are also discussed.

Farquhar, R. W.↗
NASA NTRS1980

The Voyager spacecraft /James Watt International Gold Medal Lecture/

The Voyager Project background is reviewed with emphasis on selected features of the Voyager spacecraft. Investigations by the Thermo-electric Outer Planets Spacecraft Project are discussed, including trajectories, design requirements, and the development of a Self Test and Repair computer, and a Computer Accessed Telemetry System. The design and configuration of the spacecraft are described, including long range communications, attitude control, solar independent power, sequencing and control data handling, and spacecraft propulsion. The development program, maintained by JPL, experienced a variety of problems such as design deficiencies, and process control and manufacturing problems. Finally, the spacecraft encounter with Jupiter is discussed, and expectations for the Saturn encounter are expressed.

Heacock, R. L.↗
NASA NTRS1981

Aerobraking techniques for planetary missions

Aerobraking techniques are applied to trajectory design for the VOIR (Venus Orbiting Imaging Radar) mission to enhance overall mission performance. The approach can be used for other planetary missions such as a Titan orbiter or a Mars sample return to earth. The orientation of the elliptical insertion orbit must be chosen in such a way that the combined effects of solar gravity, central-body harmonics, and drag on periapsis altitude are minimized to avoid frequent maneuvers. The selection of the base and width of a corridor for periapsis altitude depends upon the temperature and integrated heat of the aerobrake shield, the atmospheric density profile, the duration of aerobraking, the number of maneuvers, the time available between maneuvers, and uncertainties in the central-body gravity field and atmospheric density. Flight path profiles for an aerodynamically stable spacecraft and an inertially fixed spacecraft passing through the free molecular flow regime, as well as the transitional flow regime, are illustrated

Tang, C. C. H.↗
NASA NTRS1982

A combined Halley flyby/Galileo mission

The Galileo mission to Jupiter utilizes change of velocity earth gravity assist trajectories which leave earth in 1985 on 2-year orbits, have maneuvers of approximately 500 m/sec near aphelion, and then use earth flybys to send the spacecraft to Jupiter. It was noted that in Nov. 1985, one family of these trajectories passes fairly close to Halleys comet near its preperihelion node. It is shown that an arbitrarily close flyby of Halley can be added to these trajectories for about a 500 m/sec increase in the aphelion maneuver. Optimal trajectory design and mission performance as a function of launch vehicle capability are discussed in detail.

Byrnes, D. V.↗
NASA NTRS1985

A Mars sample return mission using a rover for sample acquisition

Mission and vehicle concepts are discussed for obtaining surface and subsurface samples of Mars, acquired by a roving vehicle, and returning those samples to earth for detailed analyses in scientific laboratories. Mission options that were traded off in order to arrive at a baseline mission considered most worthy of further study comprised the following: (1) direct entry vs entry out of Mars orbit; (2) direct return from the Mars surface vs rendezvous in Mars orbit and return to earth from there; and (3) propulsive orbit injection and aeroballistic entry (similar to Viking) vs aerocapture into Mars orbit and aeromaneuvering entry. After a comparison of relative merits - based primarily on mass and cost estimates and secondarily on configurational constraints - a baseline mission was selected: out-of-orbit entry, return after Mars orbit rendezvous, and aerocapture/aeromaneuvering. Trajectory design is based on the 1996 launch opportunity. Launch mass requirements for eight mission options, a mission and vehicle description for the baseline mission, and the outline of a mission sequence of events are presented.

De Vries, J. P.↗
NASA NTRS1988

Ascent Guidance for a Winged Boost Vehicle

The objective of the advanced ascent guidance study was to investigate guidance concepts which could contribute to increased autonomy during ascent operations in a winged boost vehicle such as the proposed Shuttle II. The guidance scheme was required to yield near a full-optimal ascent in the presence of vehicle system and environmental dispersions. The study included consideration of trajectory shaping issues, trajectory design, closed loop and predictive adaptive guidance techniques and control of dynamic pressure by throttling. An extensive ascent vehicle simulation capability was developed for use in the study.

Corvin, Michael Alexander↗
NASA NTRS1988

Cassini - A mission to the Saturnian system

This international (NASA/ESA) mission, planned for a Titan IV/Centaur G-prime launch in the 1995-1997 era, consists of a Saturn Orbiter (a U.S. Mariner Mark II spacecraft) and a Titan Atmospheric Entry Probe (an ESA product). The mission profile is highly sophisticated in its astrodynamic aspects - a deep space Delta-V maneuver, followed by earth and Jupiter gravity assist flybys, with asteroid encounter(s) along the way. Saturn arrival is characterized by further multiple maneuvers resulting in the Titan probe delivery and a close orbiter flyby, to be followed by a 4-year Saturn system tour. Details of the trajectory design process are discussed.

Sergeyevsky, Andrey B.↗
NASA NTRS1989

The Voyager Neptune travel guide

The Voyager mission to the giant outer planets of our solar system is described. Scientific highlights include interplanetary cruise, Jupiter, Saturn, Uranus, and their vast satellite and ring systems. Detailed plans are provided for the August 1989 Neptune encounter and subsequent interstellar journey to reach the heliopause. As background, the elements of an unmanned space mission are explained, with emphasis on the capabilities of the spacecraft and the scientific sensors. Other topics include the Voyager Grand Tour trajectory design, deep-space navigation, and gravity-assist concepts. The Neptune flyby is animated through the use of computer-generated, flip-page movie frames that appear in the corners of the publication. Useful historical information is also presented, including facts associated with the Voyager mission. Finally, short summaries are provided to describe the major objectives and schedules for several space missions planned for the remainder of the 20th century.

Kohlhase, Charles↗
NASA NTRS1989

Icarus lander

Icarus is one of the earth-crossing asteroids. It has a semi-major axis of 1.078 AU, giving it a period of 1.12 years, and an eccentricity of 0.827. The perihelion distance is thus 0.187 AU. The inclination of Icarus's orbit is 23 deg. Although it is a small body, it is still massive enough to be essentially immune to non-gravitational forces. These orbital and physical qualities make it an attractive target for testing General Relativity. The close passage to the sun means that it will be subject to a large relativistic perihelion precession; the high eccentricity makes the precession easy to measure; the high inclination allows the solar quadrupole moment (J sub 2) to be simultaneously determined via the nodal precession it predicts. The degeneracy between the relativistic effect and the effect of J sub 2 in the perihelion precession may thus be broken. Results are presented from a preliminary study of a possible trajectory design for an Icarus lander and from a covariance study of the scientific return to be expected from such a mission.

Hellings, Ronald W.↗
NASA NTRS1988

Galileo: Earth avoidance study report

The 1989 Galileo mission to Jupiter is based on a VEEGA (Venus Earth Earth-Gravity Assist) trajectory which uses two flybys of Earth and one of Venus to achieve the necessary energy and shaping to reach Jupiter. These encounters are needed because the Centaur upper stage is not now being used on this mission. Since the Galileo spacecraft uses radioisotope thermoelectric generators (RTGs) for electrical power, the question arises as to whether there is any chance of an inadvertent atmospheric entry of the spacecraft during either of the two Earth flybys. A study was performed which determined the necessary actions, in both spacecraft and trajectory design as well as in operations, to insure that the probability of such reentry is made very small, and to provide a quantitative assessment of the probability of reentry.

Mitchell, R. T.↗
NASA NTRS1989

THREAD: A programming environment for interactive planning-level robotics applications

THREAD programming language, which was developed to meet the needs of researchers in developing robotics applications that perform such tasks as grasp, trajectory design, sensor data analysis, and interfacing with external subsystems in order to perform servo-level control of manipulators and real time sensing is discussed. The philosophy behind THREAD, the issues which entered into its design, and the features of the language are discussed from the viewpoint of researchers who want to develop algorithms in a simulation environment, and from those who want to implement physical robotics systems. The detailed functions of the many complex robotics algorithms and tools which are part of the language are not explained, but an overall impression of their capability is given.

Beahan, John J., Jr.↗