Lagrange Points

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1

Hello there,

as a huge Astronomy nerd and SciFi geek, this game has captured me instantly.
However, I was quite confused and a bit irritated about the implementation of Lagrange points.

In short:

It doesn’t make sense to have only one Lagrange points per planet, and they should be able to be orbited.

Longer:

Lagrange points are (quasi-)stable points in a two-body system (e.g. star and planet) at which the gravitational forces of the two bodies and the centrifugal force (in the co-rotating frame of the planet) perfectly cancel out: Lagrange point - Wikipedia

L1 and L2 are near the planet, L3 is always opposite, L4 and L5 are at an angle of 60° from the planet.
The one that shows up in game when you stabilize a planet’s Lagrange point is L5.

L4 and L5 are both “stable” points (as long as the mass ratio between the two bodies is large enough (>25x)), while L1 through L3 are nominally unstable.
So I could get behind only having L4 and L5 stabilizable, but since they are physically essentially equivalent, if one of them is in the game, the other should be as well.

In addition to that, it’s weird that they act as waypoints for fleets, but you can’t station anything there, because the Lagrange point will move away with the planet and any ships or stations you sent there will stay behind.
In reality, especially L4 and L5 can be orbited quite easily (that’s why Jupiter is collecting planetesimals there, the “greeks” and “trojans”), and even L1 to L3 have quasi-stable “halo orbits”: Halo orbit - Wikipedia
So even if a perfect placement is not possible and small corrections would be needed to stay exactly at the Lagrange point (e.g. JWST needs to do that to stay at L2, in the earth’s shadow), it should be possible for stations to remain roughly (in orbit) at the LP.

Afterword

I would be surprised if I was the first to bring this up, but I couldn’t find any discussion about this.
Please excuse if it’s a duplicate.

My qualifications:
I’m a PhD student in Astrophysics, and a huge nerd.

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This doesn’t nullify the overall suggestion, but since you didn’t mention it all and say you were confused about them: are you aware of the current in-game purpose of Lagrange points? They act as mini intra-system jump points for faster travel (if there are more than one present). The points we see in game are only the “jump-stable” Lagrange points, which is why not all planets have them and only one point appears per planet.

Since they are only slightly less important militarily as normal jump points, it would be great to be able to put stations on them, and it would make sense realism-wise as you described.

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Yes, I am aware of their in-game purpose.

What you describe is exactly what I wanted to do, which is what motivated me to write this suggestion in the first place

While it’s probably wildly overkill, I wanted to have defense (and possibly resupply) stations on at least one LP and was quite surprised when I saw the station I tugged there drifting off :smiley:

Also, my first idea was to use L3, L4 and L5 to set up equidistant stations in the Sol system, to get some redundancy because the change of relative planet locations can make it hard to be consistent there.

Of course you can just place some fleet waypoints and build stations that way, but that ruins my immersion a bit, since “stationary” doesn’t really work outside of an orbit.

4

Have you used Deep Space Populations, instead of waypoints? they don’t move.

5

I know that they are also an option (have another use in mind for them), but the “don’t move”-part is what’s bugging me (if you do that in reality, you just fall into the sun or onto whatever planet’s Hill radius you’re in)

6

I think the lore is that when you’re in orbit of a body, you’re in normal space, but when anywhere else, you’re at least partially in the fluidic trans-newtonian space. It either produces a friction-like force that opposes gravity, or when you’re in it you’re simply not affected by gravity.

Being able to “orbit” Lagrange points might be useful. In my current save I’ve put deep space tracking stations on some trojan asteroids to extend my sensor coverage around Jupiter’s orbit, which I think is similar to what you want. You can have stationary sensor buoys/stations, but since they don’t revolve about the star, they will sometimes have gaps in or overlapping sensor coverage with planet/moon based sensors. But even with the body, L3, L4, and L5 there are still gaps.

Refuel and resupply stations, if orbiting Lagrange points, will always be a fixed distance from their planet which might be useful in some situations. Usually you’d want something like that to be a fixed distance from a jump point, though.

7

I think lagrange points should be added to the secondary components of a multi-star system. If a superjovian has a lagrange point then a companion star should as well.

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I think lagrange points should be added to the secondary components of a multi-star system. If a superjovian has a lagrange point then a companion star should as well.

Depends on the mass ratios, since the physics can get quite complicated if the assumption of one body being a lot more massive than the other no longer holds.

Binary systems in general are fascinating, since you can also have circumbinary planets that orbit both stars (stable distance is usually at minimum around ~3 binary separations), and even coorbital planets! (I did my Master’s thesis on that .-.)

But that’s probably it’s own topic, since that is already a quite advanced topic.
But if you’d want to include proper N-body simulations for that end, I can recommend Rebound by Hanno Rein

9

@Serathos.
Which is the level of your deep space tracking stations?
Keeping them on Earth, with the right development, their tracking range can go well beyond Pluto. So, it isn’t strictly necessary to scatter them around.
Unless your jump points are very far from the Sun.
But, in that case, you can place some sensor buoys next each JP.

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There are three points raised in the thread:

  1. Why not have all five Lagrange points

  2. Why no Lagrange points for stars.

  3. Why don’t things at a Lagrange point remain there

For the first one, that was a conscious decision. Aurora is a game, rather than an astrophysics simulator. It uses astronomical objects as a mechanic to add interesting gameplay. I didn’t want a lot of Lagrange points cluttering up the map, especially as players would go mad trying to figure out the best movement paths through a system.

L1 and L2 would be too close to the parent body anyway, as they would allow someone to avoid an approach battle. You can add a Lagrange point to a moon and achieve a similar situation, but that is a deliberate player choice.

L4 and L5 are more interesting in terms of gameplay, adding a jump location within a system, but not too close to the planets, so I decided to use one of those. They add a new tactical dimension and allow travel between distant solar systems, without adding the movement and tactical complexity of all five.

I didn’t add them to companion stars because the Lagrange point is no closer to the companion star than the primary. I guess they could be useful in trinaries with close orbiting B and C components, but that is very rare anyway.

The last point is different. Adding Lagrange points as a location, like a system body, is simply a lot of work :slight_smile:. Fleets, Wrecks, Missile Salvos, Waypoints and Deep Space Populations all track which body they are orbiting. Anytime one of those objects is created or updated, the status of the ‘orbit body’ is checked. Anything derived from those objects is checked for its relationship to the orbit body. Any movement order related to the object might also relate to the body they orbit, etc. Staying in position during orbital movement is very minor in comparison.

Even so, it is something I should have tackled a while ago so I went ahead and spent a few hours on it today. I’ll post the update in the v2.8 Changes thread, but in essence, Fleets, Wrecks, Waypoint, Missiles and Deep Space Populations at a Lagrange point will now move with it. I’ve changed the code in over a hundred different places, so there will likely be some bugs to squish over the next few weeks.

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Hi Steve!

Thanks for the in-depth answer!

I understand wanting to not overcrowd the systems with all 5 LPs, although i’d still petition for L4 to be there as well, for symmetry reasons ^^ ships mostly determine which paths to use themselves anyway, right?
But I get that astrophysics isn’t the focus of the game, I’m mainly interested in “realism” because it feels great to be able to use real-world knowledge in such in-depth games :slight_smile:

I am very hyped that you are making them into proper Locations!
Thanks so much for your work!

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Eh, it’s less about “is it necessary” and more that I just enjoy building up the infrastructure and redundancy, almost for rp reasons, I guess.
I put up small station clusters with Defense Platforms, Refueling Stations and Maintenance Stations, and a Recreational Station in multiple spots scattered around, so a “spearhead” strike against my main planet doesn’t cripple everything.

Is it necessary? Probably not.
But I enjoy it ^^