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I believe that it is about getting from the lander to the orbital vehicle. If you go into an equatorial orbit, then every orbit of the orbital vehicle gives yo
by btilly 8y ago
I believe that it is about getting from the lander to the orbital vehicle.
If you go into an equatorial orbit, then every orbit of the orbital vehicle gives you a chance to get the lander back.
There is also a stable polar orbit where the orbiter stays lined up between the Earth and the Moon. Since the surface is tidally locked you again get the lander back easily. This orbit takes more energy to get into and out of for the orbital vehicle. But gives you mid latitudes with the Earth high in the sky.
What is hard is getting to mid latitudes on the side of the Moon. Now what happens is that the object on the surface turns away from the orbital vehicle making it hard to line up everything for the return trip. The lander therefore has to be much more capable to land and return at will, rather than waiting weeks for things to line up right.
- deleted 8y ago[deleted]
- haberman 8y ago> There is also a stable polar orbit where the orbiter stays lined up between the Earth and the Moon. Since the surface is tidally locked you again get the lander back easily. Wait, what keeps the polar orbit lined up with the Earth? If the orbit just stayed constant, it would deviate from being lined up from the Earth, right?
- cmsmith 8y agoIt wouldn't be exactly a polar orbit, but slightly offset from one - like a sun-synchronous orbit around the earth https://en.wikipedia.org/wiki/Sun-synchronous_orbit https://en.wikipedia.org/wiki/Sun-synchronous_orbit
- btilly 8y agoExactly. And since the orbit turns at the same speed as the Moon does, it works. That is why in the article they offer a map of where the landing could have been and came up with https://hackadaycom.files.wordpress.com/2019/02/moonpossiblelandings.png https://hackadaycom.files.wordpress.com/2019/02/moonpossible... You see the landings on the equator, and also the strip going over the pole.
- haberman 8y agoBut what makes the orbit turn? What is accelerating the satellite?
- MPSimmons 8y agoIt uses the equatorial bulge to process the orbit. https://space.stackexchange.com/questions/5312/why-would-sun-synchronous-orbits-be-impossible-around-perfectly-spherical-bodies https://space.stackexchange.com/questions/5312/why-would-sun...
- deleted 8y ago[deleted]