Lagrange points are stable positions in a solar system, where the combined gravitational force between two large bodies equals the centripetal force required to orbit with them.

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Ignoring distance, lack of present technology to get there and supplies, what would be the implications of positioning a space station at Sun-Earth either L4 and L5 Lagrange points?

The purpose of the station(s) would be to do near space observations for unknown asteroids within the solar system.

Possible issues:

  • Heavy shielding to protect electronics and crew from solar radiation.
  • Orbiting space dust.
  • Heating / Cooling.
  • Would the station have to orbit the point or could it just occupy the exact point?
  • L4 has an asteroid, 2010 TK7, orbiting it. Would this be an advantage or a disadvantage?

closed as too broad by nitsua60, Aify, Jim2B, CAgrippa, Burki Mar 24 '16 at 7:58


  • $\begingroup$ Hi StainlessSteelRat. Welcome to Worldbuilding SE. As it stands, your question is a bit broad. We don't know what kind of space station you are thinking of, what kind of implications you are considering, etc. It would be good to focus the question a bit more. You can read the tour and the help center to get more information. $\endgroup$ – clem steredenn Mar 18 '16 at 22:05
  • $\begingroup$ Ditto ^^. Manned/unmanned? "What would be the implications" is unanswerably vague. As for 2010TK7 (and almost all things in life), there are many ways in which one could construe it as either an advantage or as a disadvantage. I suggest you peel apart this question into multiple answerable questions. There's no stigma against multiple postings here--in fact, it tends to help you get higher-quality answers as people can address parts they know without feeling beholden to answer all of your questions. I'm voting to put this on hold so that you can firm up the question a bit. $\endgroup$ – nitsua60 Mar 19 '16 at 3:51
  • $\begingroup$ (I know you mention a crew, but if the purpose is for asteroid detection one might argue unmanned is sufficient, which changes a lot of the other constraints.) $\endgroup$ – nitsua60 Mar 19 '16 at 3:53
  • $\begingroup$ As for peeling apart the question, I'd suggest (1) Are there any safety modifications that would have to be made for a manned space station at L4/5 as compared to ISS precautions; (2) How are the local environment and space weather different at L4/L5 as opposed to LEO; (3) How does one "park" at L4/5; (4) What uses could a manned space station at L4 put 2010TK7 to; (5) What uses could an unmanned space station at L4 put 2010TK7 to; (6) what are the dangers of parking a station at L4 due to 2010TK7? I may be over-slicing it, but those are the distinct questions I see above. I think the limit... $\endgroup$ – nitsua60 Mar 19 '16 at 3:59
  • $\begingroup$ ...is 10 questions a day, so have at it =) $\endgroup$ – nitsua60 Mar 19 '16 at 3:59

I'm going to answer these in no particular order.


L4 and L5 are stable Lagrange points. If an object at one of them was perturbed by some other body such that it moved away slightly from the point, it would move back to the point, thus ensuring stability. A good analogy is to picture these points as bowls, places of stable equilibrium. Imagine that the space station is a ball in the bowl. If the ball is somewhat jostled, it may roll up one of the sides a little, but it will come back down to its original stable position. So it's possible for an object to occupy the exact (well, it does depend on what you mean by "exact") point.

This is not true for all perturbations. There is a limit to the stability, generally reached if another body orbiting the Sun is massive enough and close enough. However, this is not the case for the Earth-Sun L4 and L5 points.

Orbiting space dust.

It has been conjectured that there is dust at these Lagrange points, called Kordylewski clouds. They are quite insubstantial and not at all dense; in fact, they are extremely hard to observe from Earth and their existence has not been definitely proven. Indeed, evidence for them is quite slim. The clouds might also be in an unstable orbit, again because of outside perturbations.

You can find a mention of the clouds here, though they are not referred to by name.


2010 TK7 has quite the odd orbit, moving closer to and farther from Earth over time. It oscillates in a way that takes it far enough away from L4 for it to be practical.

The other consideration is that 2010 TK7 has a very high orbital inclination, as illustrated here:

Image in the public domain.

This makes it very hard to access, so it would not be a good resource for a space station at L4

Heavy shielding to protect electronics and crew from solar radiation.

As far as I know, the precautions taken here would be the same as would be taken for any orbiting space station. The only differentiation factor between a space station at L4 or L5 and a space station orbiting Earth is that the space station at the Lagrangian points would always have one part facing the Sun; it would never be in shadow. This shouldn't pose a huge problem, though; simply rotate the space station.

Heating / Cooling.

See the above.


The primary implications might be political rather than technological.

Anyone building a long term space station at the L4 or L5 points will presumably have developed some sort of space based infrastructure in order to deal with the various technological issues that were raised (shielding, closed life support systems, etc.), by bringing material from the Moon or Near Earth Objects (NEO's) for building and charging the ecosystem. Their primary goal would be to reduce the immense energy and financial costs of bringing materials from the Earth's deep gravity well, but they will have become independent from Earth for most practical purposes.

How the Earth reacts to what are essentially independent city states at L4 and L5 will depend on factors like the political situation on Earth at the time, who or what is responsible for building the stations and what the real and imagined goals of the station builders are.

The constant factors which will probably drive Earth's nations to a frenzy are the fact that there are potentially two independent "powers" on the geopolitical scene which are not "beholden" to the nations of Earth, and that they have the real and potential ability to manipulate very large amounts of energy. This isn't just the solar power they can gather with solar panels of arbitrary size, but the energy from masses of building and life support materials they can import to their stations.

A body orbiting the Earth is moving at incredible velocities. The ISS, if it were to pass overhead as you fired a .45 ACP round from a pistol at a target would travel the length of a football field before your bullet went 10 yards. The kinetic energy of even a small piece of space debris moving at that speed would be enormous, so Earth nations looking at tons of materials being moved "overhead" at speeds ranging up to 72 miles per second (the fastest an unpowered object can move in the solar system without escaping the sun's gravity) will be seeing potential weapons with destructive energies greater than the dinosaur killer asteroid which caused the great extinction. And since these items are under intelligent control, this means the spacers living at L4 and L5 could target individual cities, destroy carrier battle groups at sea or vaporize dams with controlled artificial meteor strikes. The Chelyabinsk meteor which disintegrated over Russia is estimated to have a Kinetic energy on entry of 500KT. The estimated yield of strategic nuclear weapons used today is usually estimated to be in the 300KT yield range, for comparison.

I would expect to see the Earth organize some sort of "Space Guard" to watch for and carefully examine every object being sent to and from the L4 and L5 stations, with orders to destroy anything on an intersecting orbit with Earth. No pussyfooting around either, hit it with a nuke, use more nukes to ensure nothing is on an intercept course with Earth then launch either more nukes or Space Marines to destroy or capture the stations. The interesting question is will the stations try to arrange for alliances with Earth nations, use deadly force to protect themselves or find alternative solutions?


Your main issue will be logistics. It will be very costly and difficult to get a rocket from Earth to that station. Since it's travelling at the same orbital speed as Earth, you'll have to speed up (or slow down) to catch it and then reverse that when you arrive. There's no areobreaking or other tricks as used in planetary missions. So you'll have to carry fuel for use at the destination. Being manned, you'll need the same return capability! The rocket size grows exponentially. The journey each way will be slow, taking years.

from xkcd what-if "voyager"

Yes, solar activity will be a problem on any interplanetary mission. You'll need a "storm celler" to hide out a storm. Look at designs for interplanetary craft for manned missions, as the issues are the same.

Building a base on an asteroid might be a big advantage. You can use it as a shield and dig into it.

Since the Earth's orbit is not a perfect circle, it moves faster and slower at different points in its orbit. A station at L4 will be in a different point of its orbit, thus moving faster and slower at different times than the Earth. Thus, it will move around in a cycle and will not stay at the point.

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    $\begingroup$ I feel like some sort of attribution/credit, or even just a hyperlink, would be proper for the picture. I know its provenance on-sight, but perhaps not everyone does. Plus, it's just polite to send him a bit more traffic if anyone curious clicks. $\endgroup$ – nitsua60 Mar 19 '16 at 3:47
  • $\begingroup$ There is attribution: Look at the source code, if it doesn't appear on hover in your browser. :) $\endgroup$ – JDługosz Mar 19 '16 at 3:50
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    $\begingroup$ Rather, I get the imgur address from my browser; nothing appears as an alt-text or tooltip on hover. I see where you've put it into the source, but either it's browser-dependent and not appearing for me (chrome) or the syntax isn't doing what you expect. But even if that works, users may never hover; I still maintain it'd be polite to attribute in a way that's as visible as the image itself. $\endgroup$ – nitsua60 Mar 19 '16 at 4:03
