Astrodynamics research at MSFC
Earth-Moon, interplanetary, and model trajectories studies in astrodynamics
INTERPLANETARY TRAJECTORY↗
SEARCH · Search NASA
Results for “Trajectory Modeling”
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.
A wind tunnel free flight testing technique for nonplanar motion of spinning models.
Wind tunnel free-flight testing of reentry vehicle dynamics, noting capability for simultaneous two- dimensional viewing of model trajectories
TRAJECTORY ANALYSIS↗
An analytic guidance technique for planetary and lunar approach trajectories.
An explicit, analytic guidance technique is developed for the hyperbolic approach phases of interplanetary and lunar spacecraft trajectories. The guidance technique is based upon a first-order analytic solution for the perturbed planet-centered (or moon-centered) trajectory. This trajectory is represented as the sum of two components: (1) the unperturbed osculating hyperbola at pericenter, and (2) first-order position and velocity perturbations due to gravitational effects of the sun and other planets. A closed-form analytic approximation for these perturbations valid for the entire approach trajectory is derived, thereby eliminating the need for numerical integration of the equations of motion. By means of this analytic trajectory model, the approach guidance problem is reduced to an equivalent two-body problem. The guidance objectives are specified in terms of actual, attainable conditions at pericenter, and the required corrective velocity is determined explicitly for both fixed and variable times of arrival.
Carlson, N. A.↗
Rocket ascent G-limited moment-balanced optimization program (RAGMOP)
This document describes the RAGMOP (Rocket Ascent G-limited Momentbalanced Optimization Program) computer program for parametric ascent trajectory optimization. RAGMOP computes optimum polynomial-form attitude control histories, launch azimuth, engine burn-time, and gross liftoff weight for space shuttle type vehicles using a search-accelerated, gradient projection parameter optimization technique. The trajectory model available in RAGMOP includes a rotating oblate earth model, the option of input wind tables, discrete and/or continuous throttling for the purposes of limiting the thrust acceleration and/or the maximum dynamic pressure, limitation of the structural load indicators (the product of dynamic pressure with angle-of-attack and sideslip angle), and a wide selection of intermediate and terminal equality constraints.
Lyons, J. T.↗
An experimental simulation study of four crosswind landing gear concepts
An experimental investigation was conducted in order to evaluate several crosswind landing-gear concepts which have a potential application to tricycle-gear-configured, short take-off and landing (STOL) aircraft landing at crab or heading angles up to 30 deg. In this investigation, the landing gears were installed on a dynamic model which had a scaled mass distribution and gear spacing but no aerodynamic similarities when compared with a typical STOL aircraft. The model was operated as a free body with radio-control steering and was launched onto a runway sloped laterally in order to provide a simulated crosswind side force. During the landing rollout, the gear forces and the model trajectory were measured and the various concepts were compared with each other. Within the test limitations, the landing gear system, in which the gears were alined by the pilot and locked in the direction of motion prior to touchdown, gave the smoothest runout behavior with the vehicle maintaining its crab angle throughout the landing runout.
Stubbs, S. M.↗
Mission payloads subsystem description, revision 2
The Mission Payloads Subsystem (MPLS) which utilizes a simplified trajectory model to generate a list of missions for the Scheduling Algorithm for Mission Planning and Logistics Evaluation (SAMPLE) program is described. The MPLS is the mechanism that forms the basis of input for the other subsystems of SAMPLE and various post processors.
Williams, J. M.↗
The determination of the interplanetary orbits of Vikings 1 and 2
A description is presented of the navigation-related events of the Viking Mars mission. Orbit determination system fundamentals are discussed, taking into account the trajectory models, observation models, radio data models, range considerations, optical data models, filter models, the orbit determination process, critical orbit determination inputs, and orbit determination errors. Attention is also given to questions of orbit determination strategy, orbit determination results, optical measurements processing, aspects of approach orbit determination evaluation, and the orbit determination software system.
Rourke, K. H.↗
Halley comet rendezvous with a SEPS vehicle
An analysis of the performance of a Solar Electric Propulsion System (SEPS) vehicle rendezvousing with Halley's comet just prior to its Frebruary 1986 perihelion is described. A calculus of variations mathematical formulation is used to maximize Halley arrival mass while giving effect to the influence of solar array size, launch date, arrival date, and insertion hyperbolic excess velocity. Numerical sensitivity relief, thrust system modeling, trajectory characteristics and ion engine operating conditions are discussed and illustrated. Results indicate a rendezvous is feasible with a minimal advance in solar cell and ion engine technology.
Burrows, R. R.↗
EDIN design study alternate space shuttle booster replacement concepts. Volume 1: Engineering analysis
The use of a recoverable liquid rocket booster (LRB) system to replace the existing solid rocket booster (SRB) system for the shuttle was studied. Historical weight estimating relationships were developed for the LRB using Saturn technology and modified as required. Mission performance was computed using February 1975 shuttle configuration groundrules to allow reasonable comparison of the existing shuttle with the study designs. The launch trajectory was constrained to pass through both the RTLS/AOA and main engine cut off points of the shuttle reference mission 1. Performance analysis is based on a point design trajectory model which optimizes initial tilt rate and exoatmospheric pitch profile. A gravity turn was employed during the boost phase in place of the shuttle angle of attack profile. Engine throttling add/or shutdown was used to constrain dynamic pressure and/or longitudinal acceleration where necessary. Four basic configurations were investigated: a parallel burn vehicle with an F-1 engine powered LRB; a parallel burn vehicle with a high pressure engine powered LRB; a series burn vehicle with a high pressure engine powered LRB. The relative sizes of the LRB and the ET are optimized to minimize GLOW in most cases.
Demakes, P. T.↗
EDIN design study alternate space shuttle booster replacement concepts. Volume 2: Design simulation results
Historical weight estimating relationships were developed for the liquid rocket booster (LRB) using Saturn technology, and modified as required to support the EDIN05 study. Mission performance was computed using February 1975 shuttle configuration groundrules to allow reasonable comparison of the existing shuttle with the EDIN05 designs. The launch trajectory was constrained to pass through both the RTLS/AOA and main engine cut-off points. Performance analysis was based on a point design trajectory model which optimized initial tilt rate and exo-atmospheric pitch profile. A gravity turn was employed during the boost phase in place of the shuttle angle-of-attack profile. Engine throttling add/or shutdown was used to constrain dynamic pressure and/or longitudinal acceleration where necessary.
Demakes, P. T.↗
Assessment of the use of space technology in the monitoring of oil spills and ocean pollution: Executive summary
The adequacy of current technology in terms of stage of maturity, of sensing, support systems, and information extraction was assessed relative to oil spills, waste pollution, and inputs to pollution trajectory models. Needs for advanced techniques are defined and the characteristics of a future satellite system are determined based on the requirements of U.S. agencies involved in pollution monitoring.
Alvarado, U. R.↗
Standing waves observed at the dayside magnetopause
Energetic (greater than 24 keV) ion distributions are used in remotely sounding an ion trapping boundary at the dayside magnetopause for two inbound crossings of ISEE-2 on days 347 and 312, 1977, at 0830 and 1100 LT. Applying single particle trajectory models to the observed temporal relationships between trapping boundary distance and orientation parameters, it is concluded that longitudinal standing waves occur on the boundary, having typical wavelengths of 1500-3000 km, amplitudes of 500 km, and periods of 200-400 sec. The standing wave nodes move along the node axis with velocities ranging from 1.5 to 6 km/sec. The data are found to be inconsistent with models of traveling waves moving tailward along the boundary.
Fahnenstiel, S. C.↗
Effects of Titan on trapped particles in Saturn's magnetosphere
Magnetic field data from Voyager 1 magnetometer experiment are used with angular distribution data from the same spacecraft's low energy charged particle experiment to investigate the influences of Titan on the magnetosphere energetic particle distributions, with attention to the pitch angle distributions of ions and electrons. Titan appears to disrupt the corotation motion of the ions, since, while the fluxes of the ions in the corotation direction are of diminished intensity, those observed in the equatorial plane perpendicular to this direction are almost unaffected. The resulting distribution and trajectory modeling conclusions suggest that the convection electric field is absent in the wake of Titan, and that the presence of Titan produces a reduction in the fluxes of the electrons and flatter distributions with pitch angle.
Maclennan, C. G.↗
Extended atmospheres of outer planet satellites and comets
The cometary hydrogen particle-trajectory model was used successfully to analyze observations of Comet P/Encke. The Pioneer Venus Orbiter Ultraviolet Spectrometer observed the comet at 1216A (hydrogen Lyman-alpha) on 15 April 1984, when the comet was .58 AU from the Sun and 1.02 AU from Venus. The analysis implies a production rate at .58 AU of 3.3 x 10 to the 28th power/sec of the water molecules which photodissociate to produce the observed hydrogen.
Smyth, W. H.↗
An optimized rotation-axis model-following controller for STS orbiter attitude maneuvers
This paper describes a new controller for automatic attitude maneuvers of the Space Shuttle Orbiter. The controller incorporates a new solution algorithm for partially linearized, fuel-optimal maneuvers for RCS jet controlled spacecraft. These solutions provide model trajectories and jet commands that are easily tracked using a feed-forward, feedback controller structure. The result is a substantial performance improvement over the current Orbiter attitude maneuver controller. The paper discusses optimal maneuvers for this type of vehicle, giving detail of the solution algorithm. Closed-loop controller design and implementation is discussed. Detailed performance results are presented.
Redding, D. C.↗
Extended atmospheres of outer planet satellites and comets
The new cometary hydrogen particle-trajectory model, completed last year, has been used successfully to analyze observations of Comet P/Giacobini-Zinner. The Pioneer Venus Orbiter Ultraviolet Spectrometer observed the comet at 1216 A (hydrogen Lyman-a) on 11 September 1985 when the comet was 1.03 AU from the Sun and 1.09 AU from Venus. The analysis implies a production rate at 1.03 AU 2.3 x 10 to the 28th power/sec of the water molecules which photodissociate to produce the observed hydrogen. An upper limit for the H2O production rate of Comet P/Halley of 5 x 10 to the 28th power/sec at 2.60 AU was also obtained from the Pioneer Venus instrument.
Smyth, W. H.↗
Pioneer Venus Lyman-alpha observations of Comet P/Giacobini-Zinner and the life expectancy of cometary hydrogen
Results are given of the Pioneer Venus observation of the hydrogen coma of Comet P/Giacobini-Zinner on September 11, 1985 during the fly-by conducted by the International Cometary Explorer (ICE). Analysis of the data with a time-dependent 3-D particle-trajectory model implies a water production rate of 2.2 x 10 to the 28 per second on that day. The model includes the irregular variations in the H lifetime and the H Lyman-alpha fluorescence rate determined from simultaneous measurements of the solar wind by ICE and of the solar UV by the Solar Mesosphere Explorer (SME), respectively. The H lifetime varied from 2 x 10 to the 5 to 3 x 10 to the 6 seconds during the 42 days preceding the observation.
Combi, M. R.↗
Neutral cometary atmospheres. V - C2 and CN in comets
The radial Haser scale lengths for the production and destruction of C2 and CN are calculated on the basis of brightness profiles for comets Bennett 1970 II and Kohoutek 1973 XII, applying the Monte Carlo particle-trajectory model of Combi and Delsemme (1980). Findings reported include C2/CN ratio independent of heliocentric distance, C2 ejection velocity from its parent molecule about 0.5 km/s, and 1-AU photochemical lifetime 31,000 s for the C2 parent molecule and 120,000 s for C2.
Combi, M. R.↗