Why not n-body physics?

[DAL59]

8 hours ago, Spricigo said:

will not drift away like it should.

Simulating the drifting would require n body though, unless something akin to the wind mod was implemented.  

[Spricigo]

21 hours ago, DAL59 said:

Simulating the drifting would require n body though, unless something akin to the wind mod was implemented.  

That is the point. Without a full fledged n-body physics it will be worse than patched conics.

[sevenperforce]

A stock update or mod for Faux Lagrange Points would be helpful.

For each moon (Gilly, Mun, Minmus, Ike, and the moons of Jool), define spherical regions of space at L1-5 with a radius roughly 10% that of the body itself, slightly outside the patched-conic SOI of that body. You could also do them for each planet relative to Kerbol.

Ships carrying an active Gravioli Detector will see these regions appear on their maps as little spiral symbols, similar to how asteroids look, which can then be targeted. If you enter that region and drop your target-relative velocity lower than some predetermined value (e.g., 50 m/s), you will remain in that region indefinitely, drifting randomly but never actually leaving. Subsequent ships can target that particular ship without having to have a Gravioli Detector and dock with it accordingly. Captured asteroids can also be brought into these regions like spacecraft.

This allows for orbital assembly at a predetermined, regular point without needing to enter into orbit around a particular body (e.g., the Mun) or match orbits with another spacecraft. I have been building a copy of the Deep Space Gateway and Deep Space Transport in polar Mun orbit for the Orion Style challenge and it is painful (and dV-expensive) to rendezvous every time after hitting Mun orbit.

Like patched conics does for n-body, this mimics the function of Lagrange points without being computationally expensive or hard to understand. It wouldn't cause any change in normal gameplay but could allow advanced and beginner players alike more freedom in orbital construction.

 

[Pand5461]

@sevenperforce

If you increase SOI radii for Mun and Minmus, you can get Kerbin-synchronous orbits there within the patched conics approximation. Can easily be done with Kopernicus and cfg tweaking. L3-5 are already stable and easily reachable.

Gilly's orbit is probably too elliptical to have stable L-points, and Jool system is too complex to have them stable.

And I disagree that adding faux L-point is not computationally complex. Given that I have a save with broken patched conics, I'm certain that adding new type of objects with weird dynamics is going to spawn countless bugs.

[Pand5461]

And, by the way, what's so difficult about matching orbits with another spacecraft? Yes, it requires more-than-usual mission planning. But hey, why do you think mission planning for getting to an L-point must be simple?

Another reason not to add the faux orbits is the educational mission of the game. For the educational purposes, the physics model must be scientifically sound, have the minimum of arbitrary assumptions (I will call them "magic" further on) and have good illustrative examples.

The model with the least magic is of course the true n-body physics. It has L-points, it has Keplerian orbits in the 2-body case, it has naturally occurring orbital resonances and the equations are really easy to write down. The only "magic" is the inverse-square law for forces. Unfortunately, it results in barely predictable and chaotic trajectories in reality and not amateur-friendly at all. The patched conics approximation mimics the problems of spaceflight quite accurately, inherits the Keplerian orbits and makes orbital paths more regular and more predictable. The trade-off is that we need another bit of magic - sphere of influence definition. But at least there is some scientific explanation for patched conics - it's what true physics reduces to if we only count the body with the strongest gravitational pull at the point spacecraft currently is. Introducing faux L-points without true n-body physics is just adding more magic for the sake of more magic. It's not the next approximation to the true n-body gravity after the patched conics, it's cherry-picking of some effect "we want to see in the game".

[DAL59]

Orbiter 2010 has n-body physics, and it is not much more difficult than ksp in terms of maneuvering, because of the highly versatile and clear displays.    

[Spricigo]

2 minutes ago, DAL59 said:

Orbiter 2010 has n-body physics, and it is not much more difficult than ksp in terms of maneuvering, because of the highly versatile and clear displays.    

From Orbiter forum:

Quote

Orbiter and KSP are aimed at different end goals, but mesh together nicely. They do not compare; they compliment each other

Notice,  is not about a game or another being more 'difficult' , 'realistic' or even 'interesting'. They are just different, and the apple/oranges kind of comparison that goes no where.

[UranianBlue]

We don't use n-body physics because it requires a lot of CPU's. Patched conics works fine.

[FreeThinker]

Edited July 27, 2020 by FreeThinker

[FreeThinker]

On 9/21/2017 at 6:57 PM, sevenperforce said:

A stock update or mod for Faux Lagrange Points would be helpful.

For each moon (Gilly, Mun, Minmus, Ike, and the moons of Jool), define spherical regions of space at L1-5 with a radius roughly 10% that of the body itself, slightly outside the patched-conic SOI of that body. You could also do them for each planet relative to Kerbol.

Ships carrying an active Gravioli Detector will see these regions appear on their maps as little spiral symbols, similar to how asteroids look, which can then be targeted. If you enter that region and drop your target-relative velocity lower than some predetermined value (e.g., 50 m/s), you will remain in that region indefinitely, drifting randomly but never actually leaving. Subsequent ships can target that particular ship without having to have a Gravioli Detector and dock with it accordingly. Captured asteroids can also be brought into these regions like spacecraft.

This allows for orbital assembly at a predetermined, regular point without needing to enter into orbit around a particular body (e.g., the Mun) or match orbits with another spacecraft. I have been building a copy of the Deep Space Gateway and Deep Space Transport in polar Mun orbit for the Orion Style challenge and it is painful (and dV-expensive) to rendezvous every time after hitting Mun orbit.

Like patched conics does for n-body, this mimics the function of Lagrange points without being computationally expensive or hard to understand. It wouldn't cause any change in normal gameplay but could allow advanced and beginner players alike more freedom in orbital construction.

 

This might be a long shot but I got an idea. What we could relatively easily implement is circumstantial N-Body Simulation at and near calculated Larange points. What this means that under normal condition, you use stock Physics and only once a vessel get close to a these stable larange point you gradualy switch to Background N-Body physics, allowing you to put vessel at an Larange Point.This might not be perfect but at least avoid most of the pitfalls while allowing to put  vessels stable at favoratable positions.

Edited July 28, 2020 by FreeThinker