switching to another vessel 500m away right after launch destroys the launching vessel?

[Drew Kerman]

from output log line #183218:

Vessel Model Rocket V5.1 was on-rails at 97.6 atm pressure and was destroyed

All I did was launch the rocket and then immediately press [ twice to switch thru the launch base left behind to another vessel I had parked on the ground 500m away. Why would that put this vessel on rails?

Recreated after stripping down to bare minimum for launching the rocket and switching to the crew vehicle: Squad + AIES + Remote Tech + KSO (crew bus only) + NearFuture Construction + Alchemy Technologies + Sounding Rockets

If this is correct behavior, I don't understand why if the physics loading distance is 22.5km (checked with kOS) that jumping to another craft within that range would put anything within that distance on rails

Edited August 24, 2015 by Gaiiden

[Dunbaratu]

There's two different distance ranges used by the stock game, "load" distance and "pack" distance. Load distance is well advertised but "pack" distance is a less well known phenomenon that's not mentioned much and you only find out about it by interacting with the underlying C# API. I'm only just finding out about it now as it's causing problems in the kOS mod because increasing the load distance doesn't seem to do a bit of good at all without also changing the "pack" distance, which we didn't know about.

Load distance appears to affect when the parts spawn into existence (the range at which the vessel goes from being a pinpoint dot in space to actually being a collection of parts you can see).

Pack distance, on the other hand, which tends to be much shorter than Load distance it seems, appears to affect the range at which the vessel freezes into position and refuses to respond to any changing its course or movement.

Maybe the stock game refuses to put a vessel into pack mode if the vessel is moving in atmosphere, and this auto-destruction is it's response to the attempt to do so?

At any rate, for a vessel to truly be properly movable requires that it be within BOTH load distance AND pack distance and pack distance seems to be much much shorter, even though it's not mentioned much.

[Drew Kerman]

this actually makes sense, since anything you'd want to remain off rails would normally be detached directly from your active vessel, and thus always be within the pack distance. Maybe I can try setting up a bunch of small vessels in a line I can hop along to get to my launch viewing point I hope you guys crack the pack distance and are able to add it to kOS' manipulative wonder.

Since you're here I should mention I also tried launching the rocket with kOS while I was already switched to the other vessel - so I started my launch script countdown, switched over to the vessel 500m away and when the counter ran down the launch base disappeared, the rocket engine lit but the rocket itself did not move and just stood there hanging in midair with its engine running

I've decided I can use BDArmory to get around this issue for now - which really isn't a issue I'll admit since it is what Squad coded the game to behave as. But under these circumstances, it is an issue. From the BDArmory FAQ:

Q: What's the deal with the physics range? I heard KSP now has a load range of 22.5km.

A: Stock KSP has an unload distance of 22.5km for vessels that are flying only. "Unload" meaning they have to be already loaded in order to remain active to that distance - it's designed for jettisoned stages. BDArmory extends loading, unloading, packing and unpacking ranges for landed, preflight, flight, orbit, suborbit, and splashed down situations. Whatever you set the load range to, it will never overwrite the default setting if the default is higher. For example, 5km is the default for BDArmory (which can be changed in the settings (alt-) but unload distance for flying vessels is still 22.5km minimum. Without the BDArmory extension, landed pack and unpack is like 200m or 300m which is why normally you can't switch to landed vessels when flying unless you're really close. There is, however, a maximum range for landed vessels of about 9-11km. I put this limit on because beyond that distance, landed vessels that aren't put on rails will fall through the terrain and crash into the "ocean".

Edited August 24, 2015 by Gaiiden