Porkchop plot

Porkchop plot

Porkchop plot (also pork-chop plot) is a chart that depicts orbital trajectories for spacecraft. It is named for the characteristically porkchop-shaped contours that display combinations of launch date and arrival date characteristics of an interplanetary flight path for a given launch opportunity to Mars or any other planet.cite web
author=Goldman, Elliot
url=http://ccar.colorado.edu/asen5050/projects/projects_2003/goldman/
title=Launch Window Optimization: The 2005 Mars Reconnaissance Orbiter (MRO) Mission"
publisher=Colorado Center for Astrodynamics Research
accessdate=2007-12-30]

By examining the results of the porkchop plot, engineers can determine when launch opportunities exist to make use of special low-energy orbits needed to send payloads outwards using the lowest characteristic energy (C3), which allows for lower fuel usage and/or larger payloads. [ [http://mars.jpl.nasa.gov/spotlight/porkchopAll.html "Porkchop" is the First Menu Item on a Trip to Mars] , NASA. Accessed December 30, 2007.] A given contour, called a porkchop curve, represents constant C3, and the center of the porkchop the optimal minimum C3. The orbital elements of the solution, where the fixed values are the departure date, the arrival date, and the length of the flight, were first solved mathematically in 1761 by Johann Heinrich Lambert, and the equation is generally known as "Lambert's problem" (or "theorem").

For the Voyager program, engineers at JPL plotted around 10,000 potential trajectories using porkchop plots, from which they selected around 100 that were optimal for the mission objectives. The plots allowed them to reduce or eliminate planetary encounters taking place over the Thanksgiving or Christmas holidays, and to plan the completion of the mission's primary goals before the end of the fiscal year 1981. [cite book
url=http://books.google.com/books?id=UYlfQvFHn7MC&pg=PA27&dq=pork.chop+curve&ie=ISO-8859-1&sig=X9Wj1DIPV3L3xQv72XdQvt_CHzA#PPA21,M1
title=Into the Black: JPL and the American Space Program, 1976-2004
author=Peter J. Westwick
year=2007
publisher=Yale University Press
isbn=0300110758]

References

External links

* [http://marsprogram.jpl.nasa.gov/spotlight/porkchopAll.html JPL Introduction to Porkchop plots]


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