Engineering topics

Williams, S. N.

Publications and source records attributed to Williams, S. N..

6 records

NASA NTRS1998

New Results in Astrodynamics Using Genetic Algorithms

Generic algorithms have gained popularity as an effective procedure for obtaining solutions to traditionally difficult space mission optimization problems. In this paper, a brief survey of the use of genetic algorithms to solve astrodynamics problems is presented and is followed by new results obtained from applying a Pareto genetic algorithm to the optimization of low-thrust interplanetary spacecraft missions.

generic algorithms optimization problems astrodyna↗

NASA NTRS1998

Mission Design for Deep Space 1: A Low-Thrust Technology Validation Mission

Deep Space 1 (DS1), scheduled for launch in July 1998, is the first mission of NASA's New Millennium program, chartered to flight validate high-risk, advanced technologies important for future space and Earth Science programs.

Mission↗

NASA NTRS1996

Better, Faster, Cheaper Planetary Missions Using Solar Electric Propulsion

Planetary missions of the future will have increasingly greater energy requirements due to the desire for in-situ investigations and faster flight times. Solar electric propulsion provides a means of more effectively accomplishing these types of missions.

planetary missions new missions propulsion systems↗

NASA NTRS1992

Interplanetary mission design for the Comet Rendezvous Asteroid Flyby mission

As part of the CRAF/Cassini Project, the Comet Rendezvous Asteroid Flyby (CRAF) mission will explore primitive solar system bodies. CRAF is unique in that there are a number of scientifically acceptable targets from which to choose. In principle, each may be reached with several types of trajectories. This results in a large number of potential mission opportunities which must be considered. The various mission modes being considered will be discussed along with the criteria by which these missions are evaluated in order to reduce them to a smaller set. Also, the current primary and backup missions will be discussed.

Williams, S. N.↗

NASA NTRS1991

The last grand tour opportunity to Pluto

An automated mission design program permits a thorough examination of gravity-assist trajectories such as the Voyager II flight to Jupiter, Saturn, Uranus and Neptune. The program is applied to the automated design of multiple encounter trajectories to the far outer planets. The most significant result is that the last four-planet grand tour opportunity occurs in 1996 and includes encounters with Jupiter, Uranus, Neptune and Pluto. Other mission designs include Jupiter and one or two other planets and have characteristically short flight times.

Longuski, J. M.↗

NASA NTRS1991

Low energy trajectories to Mars via gravity assist from Venus to earth

The analytical determination of launch dates and proposed trajectories is reviewed with respect to the search for a low-energy trajectory to Mars with gravitational assist from Venus for the years 1995-2024. Both Ballistic and Venus-Earth gravity assist (VEGA) trajectories are calculated with an automated design tool by the authors (1990). The trajectories are modeled as conic sections from one gravitating body to the next, and gravity assist is considered to act impulsively. VEGA trajectories to Mars require similar launch energies for 6 years listed and have moderate arrival C3s, with the lowest C3 requirement in 2015. The flight time and arrival energies of the trajectories are found to be larger than those of ballistic trajectories, but the low-energy launch window makes them desirable for unmanned Mars missions, in particular.

Williams, S. N.↗