Capturing a moon: Process reality check

Background: I have an icy moon on a collision course with my fantasy world. Mages on this world have the ability to slow the speed of the moon gradually. I want them to use this power to lock the moon into orbit around the planet.

_{Note that 'moon' in this case refers to a moon-sized object, which is actually orbiting the sun like a comet.}

Based on my understanding of how to capture an asteroid (from here and here [for the visuals of the orbit]), the process the mages would follow goes something like this:

1. The mages slow the oncoming moon sufficiently for it to achieve a closed orbit around the planet.
2. The mages must wait for the moon to pass the planet once. This might result in aerobreaking.
3. Once the moon has passed the planet, the mages slow it more, gradually making its orbit more circular.

If this process is correct, there will be other questions about the second stage, so ignore for now any effects aerobraking or a close pass might have on the planet. The question is as follows:

Is this process correct? Do the mages have to wait for the moon to pass them to apply the third step, or can they achieve a closed orbit and immediately begin making it circular, thus avoiding the second step completely? That's my main concern. However, if there are other aspects (or all) of the process which are wrong, please let me know.

NOTES:

• I am not at this time interested in numbers or formulas. Those will come in following questions. This question deals only with the process to capture the moon via slowing it.
• Ignore the reasoning for such a plan. Don't worry about why the mages want to capture the moon, instead of just slowing it so that it bypasses the planet completely.
• Please back up your answer with explanations and/or links, but please phrase them in layman terms. Literally everything I know about orbital mechanics is in the above.

posted almost 6 years ago

Thomas Myron‭

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