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I expect KSP will finally get a real N-body simulator! My mun orbit insertion will be even harder!

by xgbi 7y ago

Sanzig 7y ago
There already is a pretty good one available as a mod: https://github.com/mockingbirdnest/Principia https://github.com/mockingbirdnest/Principia
perl4ever 7y ago
When I read that KSP didn't use "real" N-body physics, I lost interest in trying it. Maybe it doesn't make a big difference, but I don't understand how it would save any noticeable amount of cpu cycles. I mean, there aren't that many objects in the game, are there? It's not like it involves galaxies or star clusters.
- antepodius 7y ago
  I can think of a few reasons why it was a pain to add at any given point, (and then you just have to imagine some dev inertia/laziness/other priorities to ge tthe rest of the way): The game started off with only on body, Kerbin (earth knockoff), with the sun going around it. They then added the Mun and put in spheres of influence. As they added more planets, if, at any point, they had changed from the simple model to the true one, it would have broken all tutorials, delta-v calculations, extant saves, etc. It would also have required more changes to make the game properly playable. In KSP, players will often leave vessels in orbits on timewarp while focusing on something else- they'll have 10 missions ongoing at once. This works well when orbits aren't being perturbed, but in real life/real physics, you can't just leave a vessel in orbit around the moon for a year without course correction- it'll crash. The problem is, the game has no way to automate course correction/stationholding, and that would be far less trivial to add than merely changing the gravity model from one system to another. I'm not apologising for the devs not having done it right, really. KSP didn't really live up to all its promises, though it is pretty good.
- wcoenen 7y ago
  That's because N-body physics implies unstable orbits. For the planet scale objects, the game designers would have to make sure that the orbits don't go crazy (over times that can be explored at maximum time warp). But then if the goal is to keep those orbits stable, why not just save all the dev effort and just keep them on Keplerian rails? For the smaller objects launched by the player, unstable orbits aren't necessarily desirable either. Imagine going on a multi-decade mission and returning home to find your favorite space station missing. Game devs aren't going to spend effort on complicated features that will just piss off most players.

I expect KSP will finally get a real N-body simulator! My mun orbit insertion will be even harder!

by xgbi 7y ago

I expect KSP will finally get a real N-body simulator! My mun orbit insertion will be even harder!

There already is a pretty good one available as a mod: https://github.com/mockingbirdnest/Principia https://github.com/mockingbirdnest/Principia

perl4ever 7y ago

When I read that KSP didn't use "real" N-body physics, I lost interest in trying it. Maybe it doesn't make a big difference, but I don't understand how it would save any noticeable amount of cpu cycles. I mean, there aren't that many objects in the game, are there? It's not like it involves galaxies or star clusters.

antepodius 7y ago
I can think of a few reasons why it was a pain to add at any given point, (and then you just have to imagine some dev inertia/laziness/other priorities to ge tthe rest of the way): The game started off with only on body, Kerbin (earth knockoff), with the sun going around it. They then added the Mun and put in spheres of influence. As they added more planets, if, at any point, they had changed from the simple model to the true one, it would have broken all tutorials, delta-v calculations, extant saves, etc. It would also have required more changes to make the game properly playable. In KSP, players will often leave vessels in orbits on timewarp while focusing on something else- they'll have 10 missions ongoing at once. This works well when orbits aren't being perturbed, but in real life/real physics, you can't just leave a vessel in orbit around the moon for a year without course correction- it'll crash. The problem is, the game has no way to automate course correction/stationholding, and that would be far less trivial to add than merely changing the gravity model from one system to another. I'm not apologising for the devs not having done it right, really. KSP didn't really live up to all its promises, though it is pretty good.
wcoenen 7y ago
That's because N-body physics implies unstable orbits. For the planet scale objects, the game designers would have to make sure that the orbits don't go crazy (over times that can be explored at maximum time warp). But then if the goal is to keep those orbits stable, why not just save all the dev effort and just keep them on Keplerian rails? For the smaller objects launched by the player, unstable orbits aren't necessarily desirable either. Imagine going on a multi-decade mission and returning home to find your favorite space station missing. Game devs aren't going to spend effort on complicated features that will just piss off most players.