N-body simulation software?

[KerikBalm]

So I've modified my game system, and I'd like to know if it is more or less stable than the stock system...

I'd like to do a simulation like shown in this video:

but the link to the software is no longer valid.

Does anyone know how I could go about doing this simulation?

[Gargamel]

3 hours ago, KerikBalm said:

more or less stable than the stock system...

I believe that I have read that the stock Jool system is highly unstable, and would result in a couple of the moons getting flung out, and the remaining ones falling into resonant orbits.     .....Hey just like the video shows....    Although if the simulation continued, I wonder if Vaal would have been recaptured. 

[Kerbart]

You could do it in pretty much any language. Making the simulation numerically stable might be a challenge.

[steuben]

I found one years ago doing research on an idea for story that I had. The verse hasn't gone anywhere, and i think i lost the sowftare...

however i did just find these

http://www.orbitsimulator.com/ 

http://www.gravitation3d.com/

The problem is the search space has a fair bit of false positive results.

Kerbart, rolling your own is pretty heavy lifting both code wise and math wise. 

[Bill Phil]

Chebyshev polynomials?

[Fraston]

Poor Vall... It had so much fun with it’s brothers and sisters... now it got flung out from the family.

[ThatGuyWithALongUsername]

1 hour ago, Fraston said:

Poor Vall... It had so much fun with it’s brothers and sisters... now it got flung out from the family.

Flung out 'nothin... look a bit closer at some of those encounters. I don't think Vall would have made it...

[KerikBalm]

So in my system I started with Sigma dimensions to do a 3x rescale...

Dres did not get scaled up, and had its surface gravity decreased. Minmus was moved to an orbit similar to that of dres. A vesta analogue was added.

Jool's surface gravity was increased from 0.8 g (like saturn) to 2.5 g (more like Jupiter), so its influence on a moon relative to the influence of the other moons is greater. On top of that, I only scaled up the moons by... 2x I think it was instead of 3x, and decreased their surface gravity, so they should disturb each other less, and Jool has a tighter grip on them.

Duna I made a moon of my mod planet Rald, which is 3 or 4 x the mass of Duna, Ike became a distance moon around the two... I wonder if its a stable system, or if Jool plus Ike's influence would make them collide.

Then... I added a Mun sized body to Kerbin's psuedo L5 point (60 degrees behind Kerbin, same SMA +0.01 meters for purposes of not breaking the sentinel telescope wich will pick a body to map based on the next closest SMA that is greater than the crafts SMA).

This one I also want to know if its stable... L5 points should be stable...

https://en.wikipedia.org/wiki/Giant-impact_hypothesis#Possible_origin_of_Theia

Quote

Two-dimensional computer models suggest that the stability of Theia's proposed trojan orbit would have been affected when its growing mass exceeded a threshold of approximately 10% of the Earth's mass (the mass of Mars).^[46] In this scenario, gravitational perturbations by planetesimals caused Theia to depart from its stable Lagrangian location, and subsequent interactions with proto-Earth led to a collision between the two bodies.

I'd like to know if my mun sized body there is stable (not really any planetesimals here to work with, but still other planets), or if I've doomed Kerbin, and they really need to get to Rald and Laythe fast, and be prepared to stay there a long time.

[YNM]

35 minutes ago, KerikBalm said:

L5 points should be stable...

They're a point equilibrium, which means it's not stable. Even spacecrafts only orbits around it.

[KerikBalm]

https://en.wikipedia.org/wiki/Lagrangian_point#Stability

Quote

Although the L₁, L₂, and L₃points are nominally unstable, there are (unstable) periodic orbits called "halo" orbits around these points in a three-body system. A full n-body dynamical system such as the Solar System does not contain these periodic orbits, but does contain quasi-periodic (i.e. bounded but not precisely repeating) orbits following Lissajous-curve trajectories. These quasi-periodic Lissajous orbits are what most of Lagrangian-point space missions have used until now. Although they are not perfectly stable, a modest effort of station keeping keeps a spacecraft in a desired Lissajous orbit for a long time. Also, for Sun–Earth-L₁ missions, it is preferable for the spacecraft to be in a large-amplitude (100,000–200,000 km or 62,000–124,000 mi) Lissajous orbit around L₁ than to stay at L₁, because the line between Sun and Earth has increased solar interference on Earth–spacecraft communications. Similarly, a large-amplitude Lissajous orbit around L₂ keeps a probe out of Earth's shadow and therefore ensures continuous illumination of its solar panels.

The L₄ and L₅ points are stable provided that the mass of the primary body (e.g. the Earth) is at least 25^{[note 1]} times the mass of the secondary body (e.g. the Moon).^[17][18] The Earth is over 81 times the mass of the Moon (the Moon is 1.23% of the mass of the Earth^[19]). Although the L₄ and L₅ points are found at the top of a "hill", as in the effective potential contour plot above, they are nonetheless stable. The reason for the stability is a second-order effect: as a body moves away from the exact Lagrange position, Coriolis acceleration (which depends on the velocity of an orbiting object and cannot be modeled as a contour map)^[18]curves the trajectory into a path around (rather than away from) the point.

Its why we find lots of examples of "trojan asteroids" and such at Sun-Jupiter L4 and L5, but no example of them at L1 or L2, nor L3 really. The closest to an L3 asteroid are the Hildas:

https://en.wikipedia.org/wiki/Hilda_asteroid

By stable, I mean... its not a danger to Kerbin/ it won't do what they think Theia did- as I said " I'd like to know if... I've doomed Kerbin "

Edited April 24, 2019 by KerikBalm

[Nightside]

Have you tried to install Principia and see what happens?

[KerikBalm]

18 hours ago, steuben said:

http://www.gravitation3d.com/

I'm trying this one, its a bit clunky to do everything in X Y Z, I wish I could specify orbital paramaters like SMA, eccentricity, etc, but it seems to be ok... still need to "build" more of the system, so far I've got Moho, Eve, Kerbin, and Kerbin's Trojan Eki entered into it... seems stable so far

6 hours ago, Nightside said:

Have you tried to install Principia and see what happens?

I didin't realize that it took planets off rails, I thought it was just the craft... I think even Orbiter puts the planets on rails... does Principia use a lot more CPU power?

[Nightside]

I haven’t used it for a while now, but a lean install ran well enough on my old laptop.

their wiki is also very interesting to read.