Ep 484: Transfer Orbits and Gravitational Assists

This episode was recorded on Tuesday, March 20 at 8 pm EDT / 5 pm PDT / 0:00 UTC Wednesday.

If you want to get around in the Solar System, you’ll want to take advantage of natural gravitational speed boosts and transfer orbits. Whether you’re heading to the outer Solar System or you want to visit the Sun itself, the planets themselves can help you in your journey.

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Show Notes

Gravity Assist – only possible with a moving object
Gravitational Assist tutorial paper (Thanks W.Bacon for reference!)

Missions using gravity assists:
Mariner 10 was first.
Voyager 2 was biggest one – sling-shooting around Jupiter and shooting out past Neptune towards Uranus
Voyager 1 took another look at Jovian moons
Galileo studied Jupiter and moons by going by Venus and Earth
Ulysses from ESA used Jupiter to sling around and study polar regions of the Sun
MESSENGER used one flyby of Earth, two flybys of Venus, and three flybys of Mercury before finally arriving at Mercury
Cassini passed by Venus twice, then Earth, and finally Jupiter on the way to Saturn.
NASA’s Parker Solar Probe mission, scheduled for launch in 2018, will use multiple gravity assists at Venus to remove the Earth’s angular momentum from the orbit, in order to drop down to a distance of 8.5 solar radii (5.9 Gm) from the Sun. Parker Solar Probe’s mission will be the closest approach to the Sun by any space mission.
Transfer Orbits
Hohmann Transfer
Bi-elliptic transfer


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2 Responses to Ep 484: Transfer Orbits and Gravitational Assists

  1. Daryl McDaniel March 30, 2018 at 1:05 am #

    The fullraw file goes silent at about 39:15 and remains “dead air” for the remaining 19 minutes. The other file is fine.

  2. Jerel Smith April 12, 2018 at 6:21 am #

    The show notes look fine, but Pamela’s description of how the “slingshot” effect works is completely wrong. The time-integrated approach “more time is required to entering he gravitational field than exiting it” is wrong. This is a dead-symmetrical situation. A simple way to analyze the problem is to move into the planet’s frame of reference, (which subtracts the planet’s velocity in solar coordinates from the spacecrafts velocity in solar coodinates. Then describe the change of direction of the spacecraft in the planet’s gravitational potential.” In the planet’s frame of reference, the space craft leaved the planetary potential with the same speed and energy it entered, but with a change of direction. Shifting back into solar coordinates adds the planetary velocity to the “planet-centered” spacecraft’s new velocity. This generally has an enormous effect on the final velocity of the spacecraft in solar coordinates.

    I love this show, and never miss an episode. This was an “oops!”

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