Sub-Orbital Question

[Cyborg Pirate Ninja Jesus]

So on the KSP Wiki the definition of sub-orbital claims that a craft in sub-orbital orbit will eventually "collide with the body being orbited". That being said I've had a craft in sub-orbit for the past 13 days (In-game) but I've noticed no decrease in its orbit that would indicate it's orbit is decaying, which is what the wiki is suggesting imo. It could be that it just takes a lot longer than 13 days for this to become noticeable. Anyway my question is: Is the wiki correct and if so how long would it take for (very roughly) my craft to "collide" with the planet?

If it helps my craft is orbiting Kerbin, has a Periapsis of 66.077m and a Apoapsis of 559,665m.

Apologizes if this has been asked before, I tried a few searches but couldn't find anything related.

CPNJ

Edited May 9, 2015 by Cyborg Pirate Ninja Jesus

[Boomerang]

What I imagine happening is that you haven't been focused on that craft for those 13 days. So long as your periapsis is above something like 25-30km and you're focused on another craft or in the tracking station, the craft will be 'on rails' and atmospheric drag won't be calculated.

If you go to your sub-orbital craft and time warp, then each time you pass through the atmosphere around the periapsis, you'll notice your apoapsis drop due to drag and eventually the orbit will decay to the point that the craft crashes/burns up in reentry.

This is done so that the game isn't forced to do active physics calculations on -every- craft that you have floating around the system.

Edit - Also, at 66km, the atmosphere is going to be -very- thin and you're going to be traveling at quite a clip with that high of an apoapsis, so it will take quite a while for your orbit to decay significantly -if- you're even focused on it.

[Aser]

With a Periapsis of 66km, you're just barely inside the atmosphere. It'll slow you down a little bit each pass. The atmosphere is so thin that high up it will probably only be ~100 meters (wild guess) change in your apoapsis each pass.

^ninja

[Cyborg Pirate Ninja Jesus]

Ahh so the orbit will decay over time but only if I'm focused on the craft. Thats good to know as I was worried it might decay to the point of reentry whilst my attention is elsewhere.

Thanks for the speedy replies & info, much appreciated.

CPNJ

[KerikBalm]

Perapsis above 23km on kerbin, and no active craft nearby?

-Stable orbit.

If it gets to within "physics load range" of an active vessel, the atmosphere will start dragging it down.... which will happen fast at 24km...

66km? you are safe for a long, long time, even if it was the active vessel.