Isn't it weird that you can't land on asteroids, but Gilly, a captured asteroid, can be landed on? in KSP Discussion Posted April 15 · Edited April 15 by Dunbaratu "Why" as in "What is the mechanical difference in how the game implements them?" or "Why" as in "What was the reason for choosing the implementation that has this limitation"? I can answer the first, but the second is harder as that requires dev insider knowledge. The mechanical difference is that Gilly, being a moon, is modeled as a kind of CelestialBody, while asteroids are a type of Vessel, much like flags are a type of Vessel and Kerbals floating in their EVA suits are a type of Vessel. The game does not calculate the effects of a vessel pulling on another vessel due to gravity, since most of the time a vessel's mass is so small that the effect isn't worth the computing time it would take to bother. Also, when you go into time-warp mode, the game doesn't *really* use Newtonian gravity from a celestial body to pull on the ship anymore, it instead just uses Kepler's ellipse formulas to decide where along the orbit path the vessel would be at time=t. To do that in the stock game model requires that the body you are orbiting be your sphere of influence center point. So that answers the first kind of "why". As to the second kind of "why", now I have to speculate about what was in the dev's heads. But I'll do that. I just want to throw the caveat that at this point I'm trying to read their minds and this is not definitive: So here goes: To do gravity with asteroids using the stock system, those asteroids would all have to be modeled as tiny planets with their own little spheres of influence. The sphere of influence model really breaks down at that point, as you have to be SUPER close to the asteroid before it's gravity is strong enough to treat it like its own little pocket reference frame that ignores perturbations from the sun. I suspect they didn't bother because it's an organizational mess to have that many asteroids being modeled as planetary bodies instead of as vessels, especially when for the smaller ones their spheres of influence wouldn't even be above their ground altitude. Imagine if it treated them as planets what the map view would look like with all those little orbit lines. I think before it becomes even possible to do it well, the game would first have to leave behind the sphere of influence model and use an N-body model like Principia mod does. And a change like that is *massive* and breaks some other parts of how the game is meant to be simple for players.