Can the distance above which the ship's physics calculation stops be changed?

[Cesrate]

I would like to see all the ships below the atmospheric height getting drag calculation so their orbit could decay like the real case. Instead of only when you are several kilometers away.

[flightmaster]

Is this the current case? I didn't realise it was currently like this, I thought if you put an object in an orbit that intercepted the atmosphere, it would decay, whether you were there or not...

[Millitron]

It CAN be increased, but not enough to solve the decaying orbits problem. The Buran Shuttle mod comes with a .dll which, among other things, bumps the limit up significantly, 100km if I remember correctly.

[Cesrate]

Is that a very hard problem?

We can use the simple drag model, just to make sure it could decay, no matter how unrealistic it could be.

[flyfire2002]

Is this the current case? I didn't realise it was currently like this, I thought if you put an object in an orbit that intercepted the atmosphere, it would decay, whether you were there or not...

Yes, it is. I've seem too many ICBMs running across 20k height with a speed more than 3KM/S when i'm doing interceptions...

[flightmaster]

Yes, it is. I've seem too many ICBMs running across 20k height with a speed more than 3KM/S when i'm doing interceptions...

So if you switch to them when they're at their 20km PE, would drag suddenly kick in?

[flyfire2002]

So if you switch to them when they're at their 20km PE, would drag suddenly kick in?

never tried before. 20k is too far away for [ or ]. I can use lazor to change vessel under control but i've never tried it before.

[chainedlupine]

Doesn't the game auto-delete debris that goes below 25km altitude on Kerbin?

Not sure about the other planets/moons. I doubt it does this for planets with no atmosphere.

Update: Sometimes it doesn't seem to work properly. Such as...

[RawChicken]

Yeah, this also bugs me. I hope this is issued in next updates

[flyfire2002]

if the PE of falling object dont go below kerbin surface, it won't be deleted

[NannerManCan]

I thought squad didn't want the game to calculate the other objects because it would cause to much lag

[FluffyBob]

From the Wiki:

"If a ship is "on rails" (meaning it's further than 2.25 km from the actively-controlled ship) and its orbit passes through a planet's atmosphere, one of two things will happen based on atmospheric pressure at the ship's altitude:

below 0.01 atm: no atmospheric drag will occur  the ship will be completely unaffected

0.01 atm or above: the ship will disappear "

[Millitron]

NannerManCan, its not that it causes lag. The problem is floating-point math inaccuracies. All physics in game is calculated relative to the current vessel. As another vessel gets further away from the current one, the physics calculations get increasingly inaccurate due to rounding errors. A piece of debris re-entering on the opposite side of Kerbin for instance, would be so far away the calculations would be complete nonsense. This means orbital decay cannot use any drag model which requires physics calculations, which means the current drag model, and any future drag models are pretty much out of the question.

From the Wiki:

"If a ship is "on rails" (meaning it's further than 2.25 km from the actively-controlled ship) and its orbit passes through a planet's atmosphere, one of two things will happen based on atmospheric pressure at the ship's altitude:

below 0.01 atm: no atmospheric drag will occur  the ship will be completely unaffected

0.01 atm or above: the ship will disappear "

That simply isn't the case. Try it yourself, launch a ship, put it in orbit with a periapsis around 30km, then put another ship in orbit. Timewarp watching the orbital ship, and you will see the sub-orbital one is never deleted. There are multiple levels to "on-rails", Vessels go from physics being active, to only the textures being loaded, to none of it being loaded. It seems that if it is not loaded, I.E. the vessel is beyond the draw distance (further than 10km, don't know the exact value), then that vessel is never checked. Remember, draw distance is different than the on-rails difference. A ship can be on-rails, but still within the draw distance.

Edited April 23, 2013 by Millitron

[Amaroq]

That simply isn't the case. Try it yourself, launch a ship, put it in orbit with a periapsis around 30km, then put another ship in orbit. Timewarp watching the orbital ship, and you will see the sub-orbital one is never deleted.

How does that contradict what FluffyBob cross-posted from the wiki? The wiki also states that atmospheric pressure on Kerbin can be calculated as

P = e^{-altitude/5000}

By my calculations, your 30km periapsis comes out at 0.002 atmosphere, so "unaffected" is the expected outcome according to the wiki.

Running the math, you'd need a periapsis below 23km to reach 0.01 atmosphere, and that does match my experience -- I make sure to decouple my main boost stage when my periapsis is about 20km, even if it still has a tiny amount of fuel left, just to ensure that it falls properly and doesn't become orbital debris.

- - - -

That said, I'd love to see "orbital decay" modeled for anything which falls into an atmosphere while "on rails", but I think the solution would have to be along the lines of "for an orbit with a periapsis of X km, apply Y amount of drag that reduces orbital velocity, and therefore both periapsis and apoapsis for the next 'lap'."

Edited April 23, 2013 by Amaroq