How much of a big deal would it be for lunar orbiters to take a 90deg turn so that their orbit avoids the dark side, the comms blackout etc?

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How much of a big deal would it be for lunar orbiters to take a 90deg turn so that their orbit avoids the dark side, the comms blackout etc?

In: Physics
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To do it once, it’s not a huge deal. That’s called an “inclination change” and it’s among the more efficient types of orbit change, but it still requires a change in velocity (not speed, but direction) and that requires fuel. And fuel is heavy and expensive to get to the moon, so precious.

The issue is that flipping to a 90 degree orbit only temporarily solves the problem, because the moon is rotating so an orbit that avoids the dark side will be right over the dark side in a week (1/4 rotation). You need to get into what’s called a “sun-synchronous” orbit, which is slightly angled so that your orbit precesses just enough to oppose the moon’s rotation. You can do it, but it’s a very specific orbit, not just a simple inclination change.