
Nasa Is Building a Space Station in a Weird Orbit - oedmarap
https://hackaday.com/2019/02/25/nasa-is-building-a-space-station-in-a-weird-orbit-heres-why/
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asteli
It's astonishing to me that you can orbit a _point in space_ between two
planetary bodies. There's nothing on Earth that would give you that intuitive
understanding.

I'm curious if over the next hundreds of years if the Lagrange points will
become contentious regions of space, perhaps the subject of territorial
disputes. It's perhaps cynical to project humanity's pettiness into the future
but if the L* points are as valuable for lunar access as the article says,
it's not unthinkable.

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penagwin
This fascinates me.

On a side note, can somebody much smarted then me tell me if it's possible to
"sling shot" (Gravity assist?) Off a Lagrange point?

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sandworm101
Yes, if coming from outside the 2-body system. But you aren't really getting
an assist from the L point. You are being accelerated by the pair of bodies
that create the point. Such an assist is very very slight, not worth the
effort in comparison to using either of the bodies directly.

Unless you are an interstellar traveler looking for an assist from a pair of
binary stars that you really do not want to get too close to. That is scifi
territory atm.

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mLuby
I found Robert Zubrin's case _against_ LOP-G and in favor of a polar Moon base
quite compelling.
[https://www.youtube.com/watch?v=buLzhqgQbpA](https://www.youtube.com/watch?v=buLzhqgQbpA)

We have twenty years of experience with space stations but no experience with
an extra-terrestrial base. Yes, Antarctica or Biosphere come close in some
ways, and yes there's still plenty to learn from space habitation outside our
magnetosphere, but to me that pales in comparison to the skills we'd learn
establishing an actual human outpost on another celestial body!

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zeckalpha
Much more than 20. Nearly 50 years.

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hyperion2010
Cool orbit. The criticisms [1] of the project are pretty telling though. The
most glaring of which IMO is why one would consider putting unshielded humans
in a tin can rather than under a bunch of rock on the ground.

1\. [https://en.wikipedia.org/wiki/Lunar_Orbital_Platform-
Gateway...](https://en.wikipedia.org/wiki/Lunar_Orbital_Platform-
Gateway#Criticisms)

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foxyv
Probably a need for Solar power throughout the month. A lunar base would need
a nuclear generator for 15 days a month or one heck of a battery system. Also
probably easier to maintain a structure in microG.

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jcriddle4
A low earth orbit, like the current space station, has roughly half the sky
blocked out by earth plus the magnetic field of earth to somewhat protect it.
Getting to the lunar gateway's weird orbit, if you were already on the moon,
could take several days versus less delta-v to just go to low earth orbit
which can be done at any time.

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ak217
Article does not actually explain why mid-latitudes were inaccessible to
Apollo; anybody care to explain?

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btilly
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.

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haberman
> 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?

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cmsmith
It 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)

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btilly
Exactly. 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/moonpossible...](https://hackadaycom.files.wordpress.com/2019/02/moonpossiblelandings.png)

You see the landings on the equator, and also the strip going over the pole.

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haberman
But what makes the orbit turn? What is accelerating the satellite?

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MPSimmons
It uses the equatorial bulge to process the orbit.

[https://space.stackexchange.com/questions/5312/why-would-
sun...](https://space.stackexchange.com/questions/5312/why-would-sun-
synchronous-orbits-be-impossible-around-perfectly-spherical-bodies)

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veddox
> Sure, it’s rocket science, but so is playing Kerbal Space Program.

Best sentence in the article :D

On a serious note, I remember a university friend telling me about how they
had been working on figuring out this orbit. Interesting to see it written up
here now.

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thisisweirdok
Oh thank god hackaday redesigned

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PunksATawnyFill
Who’s “Nasa?”

