Author Topic: Earth-Moon Lagrange Points: Best uses for them?  (Read 3026 times)

Online redliox

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Earth-Moon Lagrange Points: Best uses for them?
« on: 01/30/2018 07:48 AM »
As I believe most members here know, there are 5 Lagrange points.  We have space telescopes that operate in 4 of the Earth-Sun points (with only ES-3 unoccupied).  Currently it's the ARTEMIS (repurposed THEMIS) probes that occupy the first two Earth-Moon points to study how the Sun interacts with Luna.  On top of this, numerous plans for crew missions favor EM-2 especially, including the Deep Space Gateway station which could occupy either a halo orbit or NRO.

One of the hypothetical benefits the Gateway station would have is the ability to drift around either these points or lunar orbits.  If that's possible, it would be a boon since the station could essentially take on the role the space shuttle formerly did for LEO spacecraft except operating in high cislunar space.  While servicing something at the Solar Lagrange points would be a big safety stretch, the lunar ones have proximity on their side.

Basically I'm posing 2 questions in regards to the Lunar Lagrange points:
1) How much delta-v is needed to move between any of the points and NRO (DSG's presumed default parking spot orbit)?
2) Could any of the Lagrange points benefit any particular missions?
--In regards to the 2nd question, excluding crewed missions beyond Earth and more towards cislunar activity not regarding Lunar landings.
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Offline MATTBLAK

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« Last Edit: 01/30/2018 08:24 AM by MATTBLAK »
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Online redliox

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Re: Earth-Moon Lagrange Points: Best uses for them?
« Reply #2 on: 01/30/2018 03:33 PM »
Lagrange point 1 would be a good place for the Lunar Deep Space Gateway, I feel.

https://www.nasa.gov/pdf/604657main_4-%20GER%20Stakeholders%20Workshop%20Earth-Moon%20L1_L2%20Bobskill.pdf

Old but useful article on the track this tread is for.

The 4th and 5th Lagrange points have potential, mainly because they have greater stability than any other points.  Although the 2nd point would be a better gathering point for interplanetary missions, I'm still curious what benefits there could be for the others in fair comparison.
« Last Edit: 01/30/2018 03:34 PM by redliox »
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Offline Zed_Noir

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Re: Earth-Moon Lagrange Points: Best uses for them?
« Reply #3 on: 01/30/2018 06:06 PM »
Lagrange point 1 would be a good place for the Lunar Deep Space Gateway, I feel.

https://www.nasa.gov/pdf/604657main_4-%20GER%20Stakeholders%20Workshop%20Earth-Moon%20L1_L2%20Bobskill.pdf

Old but useful article on the track this tread is for.

The 4th and 5th Lagrange points have potential, mainly because they have greater stability than any other points.  Although the 2nd point would be a better gathering point for interplanetary missions, I'm still curious what benefits there could be for the others in fair comparison.

The 2nd point is not in view from the Earth. So don't get to see the Interplanetary missions lit up on departure. If for example a BFS flotilla is departing for destinations beyond Mars (in delta-V) from the 1st point. It will be very spectacular and memorable, especially for the relatives and friends of the departing crews.

Online Archibald

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Re: Earth-Moon Lagrange Points: Best uses for them?
« Reply #4 on: 01/30/2018 06:22 PM »
https://forum.nasaspaceflight.com/index.php?topic=1337.0

The very thread that got me hooked to libration points, notably EML-2.
...you have been found guilty by the elders of the forum of a (imaginary) vendetta against Saint Elon - BLAAASPHEMER !

Offline rakaydos

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Re: Earth-Moon Lagrange Points: Best uses for them?
« Reply #5 on: 01/31/2018 09:34 PM »
In the rotating frame of reference, L4 and L5 have flatter space than the other lagranges. Since zero-g manufacturing facilities are limited by tidal forces (if it gets too big, different parts of the factory are in different orbits, creating a gravitational gradent) using the flatter space in L4 and L5 allows you to build a larger facility.

Online redliox

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Re: Earth-Moon Lagrange Points: Best uses for them?
« Reply #6 on: 02/02/2018 03:49 AM »
The 2nd point is not in view from the Earth. So don't get to see the Interplanetary missions lit up on departure. If for example a BFS flotilla is departing for destinations beyond Mars (in delta-V) from the 1st point. It will be very spectacular and memorable, especially for the relatives and friends of the departing crews.

Yes and no.  Technically speaking objects would be in a halo orbit around the various points, so most orbits around L2 would actually be visible and serve as a relay point for the Lunar farside.
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Re: Earth-Moon Lagrange Points: Best uses for them?
« Reply #7 on: 02/18/2018 02:55 AM »
As I understand it, L4 and L5 are more stable over the very long term where as L1, L2, and L3 (and even most lunar orbits) would require station-keeping fuel reserves (although potentially this could be done with solar sails).  In any case, the larger the space station is, the more likely you'll want it in L4 or L5.

 

Offline speedevil

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Re: Earth-Moon Lagrange Points: Best uses for them?
« Reply #8 on: 02/18/2018 11:46 AM »
As I understand it, L4 and L5 are more stable over the very long term where as L1, L2, and L3 (and even most lunar orbits) would require station-keeping fuel reserves (although potentially this could be done with solar sails).  In any case, the larger the space station is, the more likely you'll want it in L4 or L5.

I have extreme problems imagining a scenario where you care about stationkeeping fuel that is in under a meter or so a second every year, possibly even managable by radiation pressure alone.
Especially in a future where you actually have 'large space stations', or refuelling depots, or the need for them.

Online mikelepage

Re: Earth-Moon Lagrange Points: Best uses for them?
« Reply #9 on: 02/21/2018 11:21 AM »
As I understand it, L4 and L5 are more stable over the very long term where as L1, L2, and L3 (and even most lunar orbits) would require station-keeping fuel reserves (although potentially this could be done with solar sails).  In any case, the larger the space station is, the more likely you'll want it in L4 or L5.

I have extreme problems imagining a scenario where you care about stationkeeping fuel that is in under a meter or so a second every year, possibly even managable by radiation pressure alone.
Especially in a future where you actually have 'large space stations', or refuelling depots, or the need for them.

If it is so little, then I agree.  I thought it was quite a bit larger than that.

Offline speedevil

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Re: Earth-Moon Lagrange Points: Best uses for them?
« Reply #10 on: 02/21/2018 01:02 PM »
If it is so little, then I agree.  I thought it was quite a bit larger than that.

For some of the L* points, it is indeed under a meter/s a year.

https://forum.nasaspaceflight.com/index.php?topic=37745.msg1791068#msg1791068

DSCOVR at the moment is needing (at L2)  4m/s for stationkeeping, with another 1m/s per year for momentum management.
(and 26m/s/year to keep 4 degrees away from the sun)

Offline AncientU

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Re: Earth-Moon Lagrange Points: Best uses for them?
« Reply #11 on: 02/21/2018 07:53 PM »
For the Moon, EML-1 and 2 offer access to anywhere on the lunar surface, almost any time you want to go.  This makes them opportune locations for fuel, supply depots, habs, and as mentioned above, the DSG.  They are also much lower delta-v destinations than LLO (or even GEO) as jumping off points for departing spacecraft.  For flights preparing to depart Cis-Lunar space for Mars, for instance, they are almost out of the Earth gravity well, and can maximize the boost available from an Oberth burn for departure.

I personally would like to see EML-1 as the maintenance, supplies, and fueling node for Lunar operations, and EML-2 as the staging location for the Mars 'fleet'.  EML-4/5 could be used for space industrial areas such as resource extraction, etc. where considerable debris may be generated.
« Last Edit: 02/21/2018 07:54 PM by AncientU »
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Offline TrevorMonty

Re: Earth-Moon Lagrange Points: Best uses for them?
« Reply #12 on: 02/21/2018 10:12 PM »
For the Moon, EML-1 and 2 offer access to anywhere on the lunar surface, almost any time you want to go.  This makes them opportune locations for fuel, supply depots, habs, and as mentioned above, the DSG.  They are also much lower delta-v destinations than LLO (or even GEO) as jumping off points for departing spacecraft.  For flights preparing to depart Cis-Lunar space for Mars, for instance, they are almost out of the Earth gravity well, and can maximize the boost available from an Oberth burn for departure.

I personally would like to see EML-1 as the maintenance, supplies, and fueling node for Lunar operations, and EML-2 as the staging location for the Mars 'fleet'.  EML-4/5 could be used for space industrial areas such as resource extraction, etc. where considerable debris may be generated.
ULA cislunar 1000 chart shows EML1 as their fuel depot location which makes sense if supplying lunar fuel to GEO and LEO.

For DSG NRO gives good comms coverage to one of poles for most of its orbit time. Lander access is also good from NRO to target pole.

Offline Hop_David

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Re: Earth-Moon Lagrange Points: Best uses for them?
« Reply #13 on: 02/26/2018 02:45 PM »
https://forum.nasaspaceflight.com/index.php?topic=1337.0

The very thread that got me hooked to libration points, notably EML-2.

Same here. See my EML2 blog post.

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