Teaching Physics (and more) with Niven

Notes


If you apply a thrust eastward (in the direction of your orbit), you put yourself in a higher orbit (you move Out)
If you apply a thrust Westward (against the direction of your orbit), you put yourself in a lower orbit (you move In)
If you apply a thrust outward, you put yourself in a slower orbit, so you move West relative to everything else in your old, faster orbit
If you apply a thrust inward, you put yourself in a faster orbit and you move East relative to everything else in your old, slower orbit

If you thrust to the left or right, you move to an orbit that is at an angle to your original orbit, but which intersects your original orbit at two points, one of which is the point at which you applied the thrust - hence you come back to where to started after half an orbit.
The “old saying” compressed all that knowledge into a few sentences, and it’s a useful mnemonic for students learning about orbital mechanics as well.

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