What is craft "unloading" due to being farther that the "physics distance" from the "main craft"? What is the best way to deal with it? Can it be avoided?

I only find very sparse information on these subjects. "Unloading" is mentioned in this answer and is this Scott Manley video.

My problem is this: I have a craft with two probe command modules, one for the rocket and one for a rover. I sent it into orbit around a moon (Laythe). I sent the rover down to the surface. I switched to the space center. I switched to the tracking station. To my horror the rover is nowhere to be found, it has disappeared without a trace!

How can I switch away from my rover without it disappearing?

KSP version 0.90.0, Windows 8, career mode.

  • Did you land the rover before switching away from it? Commented Mar 15, 2015 at 2:38
  • @SevenSidedDie: Yeah. It was standing on the surface. I also made a quick save, luckily. I could load the quick save and continue exploring with the rover but I would prefer it if it didn't disappear at all.
    – Lii
    Commented Mar 15, 2015 at 10:25
  • It shouldn't be disappearing then—craft unload only has to do with part physics and graphics rendering, leaving the craft there but not simulated. So, if the rover is disappearing, there is something else wrong happening… Commented Mar 15, 2015 at 17:16
  • 1
    Those are talking about what happens when a craft is unloaded while moving in atmosphere. The game assumes that anything moving in-atmosphere that you're not controlling is going to crash, so it just destroys it immediately when its physics is unloaded. It's not relevant to a stationary rover, even on Laythe in atmosphere. That's why I asked if you had already landed it. Was it moving when you switched to the Space Centre? Did you leave it on a slope of any amount without the brakes on? Commented Mar 16, 2015 at 15:57
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    Oh, silly me. I had hid rovers by clicking at the icon in the tool bar at the top of the tracking station view. Thanks for you help. Anyway it would really be useful with some information about unloading around somewhere.
    – Lii
    Commented Mar 16, 2015 at 20:44

1 Answer 1


Things outside of physics range (2350 meters, or thereabout) is unloaded. This means that the physics engine isn't handling it anymore. Let's pretend that the tracking station takes control of it instead. Now, if it's in a situation where it would crash, such as in the atmosphere under 30000 meters, it would disappear and any onboard personnel would be listed as Missing.

However, I read in the devblog yersterday that they are tuning this up to 20km for stuff in the atmosphere in 1.0 (which is now in experimental).

To avoid unloading of the rover, you can:

a) Don't switch away from it when it's in an atmosphere or heading there b) Wait until your rover is landed and standing still c) Keep nearby

Update: As of 1.0.2, the physics range has indeed been increased to 20km when in atmosphere.

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