Question on decay of atmosphere-skimming objects

[Louella]

I have some objects, debris really, that are on high sub-orbital trajectories, with a periapsis of like 60+ km.

Now, I'd expect them to decay, slowly spiralling into the atmosphere and burning up. Which is fine.

But, do I have to be flying them actively during their time in atmosphere, so that the game physics updates their orbits each pass ? Or will they decay on their own, while I am actively controlling other spacecraft ?

[Superfluous J]

Things on rails do not interact with atmosphere in any way. If they get low enough, the game just deletes them. I don't know exactly what "low enough" on Kerbin is but it's somewhere near 20km. Anything with a Pe higher than that will just orbit forever. If you want them to decay naturally, you do indeed need to watch them the whole time.

I personally delete anything in the Tracking Station that interacts with any atmosphere, figuring it'd go away anyway if I wasted enough of my play time babysitting them.

[bewing]

You either have to be flying them, or you have to be within 22.5 km of them, or you have to have a "house rule" that says you must manually delete them if their Pe is in the atmosphere.

An object that is not within your "physics bubble" is in a state called "on rails". The only physics that applies to on-rails objects is gravity.

 

[Ty Tan Tu]

I suppose it is a feature that allows you to switch back to a ship before it crashes.

I sent a large solar array to Minmus (really large, 100 Kerbals large) with a sky crane and landed it. I separated the space crane and sent it on its merry way expecting it to run out of fuel and crash back to the surface. Mission accomplished. I went back to the VAB to build a rover, which I did launch into a Minmus' orbit. But then I discovered that here were TWO objects named 'Minimus Probe I'. I was pretty sure which one was my really big precious solar array. but I was not completely sure. So, I went back to the Tracking Station and zoomed into the one I was sure was not my solar array  - and sure enough it was the crane still suspended above the Minmus surface. I watched it until it finally did crash.

Now I have some debris I can visit with my new rover, and know where to land my rover. 

[Spricigo]

4 hours ago, Ty Tan Tu said:

I suppose it is a feature that allows you to switch back to a ship before it crashes.

It's 'a feature' as in "devs did it intentionally thus not a bug, a feature"  

But is not intended to give opportunities to avoid crashing.  Is just a mater of reducing the use of computer resources that would quickly become unmanageable if the game calculated all physics for all crafts out there.

The fact it may prevent a crash is only a side-effect, fortuitous or annoying depending on player perception. 

[Zhetaan]

@Louella:

You do have to fly them, though I would recommend you not bother.  A periapsis of 60+ km is going to be in the very thinnest part of the atmosphere and only for a minute, perhaps (unless the apoapsis is 70,001 m), but in any case, the amount of decay will be slight.  Add to that the fact that timewarp goes to real-time when you enter an atmosphere and in-atmosphere warp is limited to 4x physical timewarp, and you get to spend many hours watching a piece of useless space rubbish going round in circles rather than doing something interesting, such as playing the game.  If orbital decay is something you want to have so that you don't need to delete objects or because you think doing so is somewhat of a cheat, then there's a (slightly outdated) mod for that.