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As others have mentioned, Kerbal Space Program uses two-body mechanics, ie. only one celestial body has gravitational influence on the spacecraft. And every gra

by exDM69 11y ago

As others have mentioned, Kerbal Space Program uses two-body mechanics, ie. only one celestial body has gravitational influence on the spacecraft. And every gravitational field has perfect spherical symmetry. In Orbiter, you can get restricted n-body dynamics and non-spherical gravitational fields so things such as Lagrangian points or Molnya orbits can be simulated. The solar system of KSP is a lot smaller in scale, the home planet is just 600 km and the atmosphere is 70 km thick. Liftoff to orbit takes just a few minutes (instead of 8-10 min) and a full orbit is about 30 min (instead of 90 min for LEO). KSP mods can add a level of realism and add more "scientific" tools to the game. "Kerbal Engineer" is a must-have addon because it adds some numeric data about the orbit that the game developers have intentionally left out (a decision I disagree with). MechJeb is a popular addon that adds all sorts of automation, similar to some Orbiter MFD modes. There are also mods to use the real solar system (in real scale) instead of the fictional universe. But no, overall, KSP is not nearly as realistic as Orbiter is. However, making any comparisons is pretty useless - they are both really fun games with a different emphasis and I play them both regularly.

Animats 11y ago
Kerbal's two-body mechanics thing is the worst limitation. Getting into orbit around Mun looks weird, as you suddenly snap from one gravitational system to another. Slightly non-spherical gravitational fields don't matter too much unless you're doing a lot of orbits.
- exDM69 11y ago
  > Slightly non-spherical gravitational fields don't matter too much unless you're doing a lot of orbits. Actually the effects of non spherical gravity is one or two orders of magnitude greater than the influence of all the other bodies in the solar system combined for low earth orbit satellite operations. It has a huge effect, causing a rotation of the orbital plane several degrees per day (up to 10 or so). The effect isn't as great for lunar or interplanetary trajectories, though.
MichaelGG 11y ago
Is the 2-body mechanics just a question of simulation speed? Or why wouldn't they compute based on the top N nearest-biggest objects?
- exDM69 11y ago
  > Is the 2-body mechanics just a question of simulation speed? No. 2 body dynamics can be predicted from initial conditions to an arbitrary time any time in the past or the future. N-body dynamics have to be numerically integrated timestep by timestep. But simulating n-body dynamics is not difficult or computationally expensive. Two things to understand: n is a very small number, around 20, the number of planets and moons in the solar system. And we're only interested in the restricted n-body problem, ie. movement of one massless particle (the spacecraft) in the gravity field of the planets and moons, so it's O(n) complexity, not O(n^2). Ultimately this was a game design decision. > Or why wouldn't they compute based on the top N nearest-biggest objects? For such a small number of bodies, this wouldn't save any time but would add a lot of complexity.

by exDM69 11y ago

Animats 11y ago

Kerbal's two-body mechanics thing is the worst limitation. Getting into orbit around Mun looks weird, as you suddenly snap from one gravitational system to another. Slightly non-spherical gravitational fields don't matter too much unless you're doing a lot of orbits.

exDM69 11y ago
> Slightly non-spherical gravitational fields don't matter too much unless you're doing a lot of orbits. Actually the effects of non spherical gravity is one or two orders of magnitude greater than the influence of all the other bodies in the solar system combined for low earth orbit satellite operations. It has a huge effect, causing a rotation of the orbital plane several degrees per day (up to 10 or so). The effect isn't as great for lunar or interplanetary trajectories, though.

MichaelGG 11y ago

Is the 2-body mechanics just a question of simulation speed? Or why wouldn't they compute based on the top N nearest-biggest objects?

exDM69 11y ago
> Is the 2-body mechanics just a question of simulation speed? No. 2 body dynamics can be predicted from initial conditions to an arbitrary time any time in the past or the future. N-body dynamics have to be numerically integrated timestep by timestep. But simulating n-body dynamics is not difficult or computationally expensive. Two things to understand: n is a very small number, around 20, the number of planets and moons in the solar system. And we're only interested in the restricted n-body problem, ie. movement of one massless particle (the spacecraft) in the gravity field of the planets and moons, so it's O(n) complexity, not O(n^2). Ultimately this was a game design decision. > Or why wouldn't they compute based on the top N nearest-biggest objects? For such a small number of bodies, this wouldn't save any time but would add a lot of complexity.