Engineering topics

Chadwick, C.

Publications and source records attributed to Chadwick, C..

6 records

NASA NTRS1986

High-accuracy computation of Delta V magnitude probability densities - Preliminary remarks

This paper describes an algorithm for the high accuracy computation of some statistical quantities of the magnitude of a random trajectory correction maneuver (TCM). The trajectory correction velocity increment Delta V is assumed to be a three-component random vector with each component being a normally distributed random scalar having a possibly nonzero mean. Knowledge of the statitiscal properties of the magnitude of a random TCM is important in the planning and execution of maneuver strategies for deep-space missions such as Galileo. The current algorithm involves the numerical integration of a set of differential equations. This approach allows the computation of density functions for specific Delta V magnitude distributions to high accuracy without first having to generate large numbers of random samples. Possible applications of the algorithm to maneuver planning, planetary quarantine evaluation, and guidance success probability calculations are described.

Chadwick, C.↗

NASA NTRS1986

Precision maneuver determination for trajectory corrections

The interplanetary navigation of a spacecraft requires precise calculation of trajectory correction maneuver parameters. Velocity increments must be found which make the required corrections, minimize propellant consumption, and do not violate hardware design constraints or scientific objectives. This process is illustrated by its application to the Galileo Mission. The paper describes inflight analysis techniques, mathematical modeling, and computational algorithms used in the precision maneuver calculation scenario.

Hintz, G. R.↗

NASA NTRS1984

Computing approximate random Delta v magnitude probability densities

This paper describes the development and use of an algorithm to compute approximate statistics of the magnitude of a single random trajectory correction maneuver (TCM) Delta v vector. The TCM Delta v vector is modeled as a three component Cartesian vector each of whose components is a random variable having a normal (Gaussian) distribution with zero mean and possibly unequal standard deviations. The algorithm uses these standard deviations as input to produce approximations to (1) the mean and standard deviation of the magnitude of Delta v, (2) points of the probability density function of the magnitude of Delta v, and (3) points of the cumulative and inverse cumulative distribution functions of Delta v. The approximates are based on Monte Carlo techniques developed in a previous paper by the author and extended here. The algorithm described is expected to be useful in both pre-flight planning and in-flight analysis of maneuver propellant requirements for space missions.

Chadwick, C.↗

NASA NTRS1984

Design and analysis techniques for trajectory correction maneuvers

Selecting a spacecraft maneuver strategy usually involves tradeoffs of many competing factors. This paper describes such a tradeoff process. The method uses parametric data to cope with targeting requirements, thruster configuration and performance, hardware constraints, operational considerations, propellant optimization demands, and expected execution and orbit determination errors, while remaining flexible to react to new conditions.

Hintz, G. R.↗

NASA NTRS1982

Statistics of Delta v magnitude for a trajectory correction maneuver containing deterministic and random components

A number of interplanetary missions now being planned involve placing deterministic maneuvers along the flight path to alter the trajectory. Lee and Boain (1973) examined the statistics of trajectory correction maneuver (TCM) magnitude with no deterministic ('bias') component. The Delta v vector magnitude statistics were generated for several values of random Delta v standard deviations using expansions in terms of infinite hypergeometric series. The present investigation uses a different technique (Monte Carlo simulation) to generate Delta v magnitude statistics for a wider selection of random Delta v standard deviations and also extends the analysis to the case of nonzero deterministic Delta v's. These Delta v magnitude statistics are plotted parametrically. The plots are useful in assisting the analyst in quickly answering questions about the statistics of Delta v magnitude for single TCM's consisting of both a deterministic and a random component. The plots provide quick insight into the nature of the Delta v magnitude distribution for the TCM.

Bollman, W. E.↗

NASA NTRS1977

Voyager navigation strategy and accuracy

The paper presents the results of the prelaunch navigation studies conducted for the Mariner spacecraft launched toward encounters with the giant planets. The navigation system and the strategy for using this system are described. The requirements on the navigation system demanded by the goals of the project are mentioned, and the predicted navigational capability relative to each of the requirements is discussed. Baseline navigation results for three possible trajectories are analyzed.

Jones, J. B.↗