recovering first stages

[farmerben]

I've been trying to minimize orbital debris by dropping my stages before PE reaches 70km, but it's not working.  In the tracking station I discovered I had 99 pieces of debris most of which had a PE between 50-70km.  I watched from the tracking station and the orbits did not change, several pieces had been orbiting for more than 5 years.  I clicked on fly for a few pieces and they burned up or crashed as expected, others I just terminated.  Also I was surprised to find very few pieces on Kerbin surface, because I sometimes put parachutes on stages.

I believe there is a mod to help with this, but I can't find it just now.  Help please.

[linuxgurugamer]

Orbital decay

[bewing]

The other mod that allows the recovery of stages that have parachutes attached is called Stage Recovery.

Besides that, parachutes never open unless they are on the focused vessel, or within physics range (25km) of the focused vessel. So just putting on a parachute is not enough, if you don't watch it come down.

If an unfocused object is outside physics range and goes below about 25km, it will be autodeleted.

 

[Snark]

6 hours ago, farmerben said:

I've been trying to minimize orbital debris by dropping my stages before PE reaches 70km, but it's not working.  In the tracking station I discovered I had 99 pieces of debris most of which had a PE between 50-70km.  I watched from the tracking station and the orbits did not change, several pieces had been orbiting for more than 5 years.

Correct.  That's because drag doesn't happen to objects that are "on rails" (i.e.  not in current physics range).  Unless you're actually "flying" them yourself, they blithely ignore the atmosphere; they'll orbit forever, with no orbital decay at all.

6 hours ago, farmerben said:

I clicked on fly for a few pieces and they burned up or crashed as expected

Yep.  That works because while you're flying them, they're no longer on rails, which means that they experience drag and will burn up as desired.

 

"But that seems silly," I hear you cry.  "Everything completely ignores atmosphere unless you're flying it?"

Well, yes and no.  Yes, it is a little "silly", in terms of realism, but it's a necessary programming compromise.  That's because actually doing all the calculations for drag, and applying them to moving ships, is heavily processor-intensive.  There's no way your computer could keep up if the game tried to do a full physics simulation of the potentially hundreds of objects flying around-- that's why "running on rails" is a thing.  So they basically have to "cheat" and make them ignore atmosphere when they're on rails.

That said, though, it would be silly if objects got down into "the soup" (i.e. the thick, lower atmosphere) and were never affected, and the game uses a simplified model for this, as well:  anything that gets "too low" when on rails will simply vanish and be deleted.  The threshold for "too low" is "higher than 0.01 atmosphere pressure), which on Kerbin happens at an altitude of about 23 km.

So, on Kerbin, it works this way for things on rails:

• Anything above 23 km is completely unaffected and acts as if the atmosphere doesn't exist.
• Anything below 23 km is instantly and silently deleted, and vanishes into thin air.

6 hours ago, farmerben said:

I had 99 pieces of debris most of which had a PE between 50-70km

Yes-- that's because their Pe is above the magic 23 km threshold.

6 hours ago, farmerben said:

Also I was surprised to find very few pieces on Kerbin surface, because I sometimes put parachutes on stages.

Correct-- and the reason for that is the same as above.  After you jettisoned those pieces, then as soon as your ship got far enough away from them to be outside physics range, they went "on rails" and thus were immediately deleted (because they were under 23 km altitude).

Basically, if you want something to land on a parachute, you have to "fly" it all the way to the ground, yourself.

6 hours ago, farmerben said:

I believe there is a mod to help with this, but I can't find it just now.  Help please.

I believe there's an orbital decay mod for getting rid of those pieces that are in atmosphere, but I don't know anything about it.

As for landing stuff:  there are some stage-recovery mods that (I believe) don't actually land your pieces, but if you equip them with parachutes will cause them to get recovered (for a refund) instead of just vanishing.

If you want stuff to land on parachutes, I believe you pretty much have to just land them manually that way, i.e. while flying them.  Haven't heard of any mod to do this (doesn't necessarily mean it doesn't exist, just that I haven't heard of it).