Pork Chop Essay

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Pork-chop plot
Pork-chop plot is a chart that shows contours of characteristic energy (C3) versus departure and arrival dates. The Pork-chop plot is essential to determine the initial launch parameters. Pork-chop plot is the graphical representation of lambert solution. Pork Chop plot of Earth-Venus trajectory (from Leela O’Brien, 2012)
Tisserand Graph
Tisserand graph is a very useful tool to investigate the feasibility of gravity-assist transfer trajectories. The Tisserand graph is the plot of orbital specific energy or orbital period versus the periapsis radius. Here, all the planets are assumed to have circular and coplanar orbits (Strange and Longuski, 2002). A flyby of a target body plotted on the Tisserand Graph is represented by a …show more content…

The graph shows that the inclination of the transfer orbit has increased initially and decreased later on. RAAN remains unchanged for the most part of the journey and only begin to fall when the spacecraft reaches the vicinity of the Venus. Semi-major axis has increased throughout the travel. There is an abrupt increase in mean anomaly initially and it begins to fall down for the rest of the journey. The interesting point is Argument of perigee increases as mean anomaly begins to fall.

The graph shows the orbital parameters during the journey of the spacecraft from Earth to Mars.
The graph shows that semi-major axis decreases gradually after the Venus flyby. RAAN falls down to 0 degrees after the flyby whereas inclination remains unchanged after the flyby. Mean anomaly falls to 0 degrees during May when the argument of perigee is at its maximum. Then, it increases abruptly to the maximum value (360 degrees) and decreases slightly for the rest of the journey. At the same time, argument of perigee falls abruptly to the minimum value (0 degrees) and increases slightly for the rest of the …show more content…

It is clear that Venus gravity assist trajectory requires slightly more delta V than direct trajectory. The clear advantage appears to be in terms of time of flight. Direct trajectory has TOF of 412 days, whereas Venus gravity assisted trajectory have TOF of 235 days. This makes Venus-gravity assisted trajectory appropriate for human mission. Time of flight can alter depending upon the departure date and phasing between Earth and Mars. The launch opportunity occurs every two years for direct trajectory whereas for Venus gravity-assisted trajectory, it occurs every 32 years. Therefore, there is a very less opportunity for Venus gravity-assisted

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