Violent Spinning While Deorbiting Debris

[cgwhite4]

I recently sent up a "janitor" ship to grab several pieces of space junk with a claw, and then dispose of them by putting them into suborbital trajectories.  One of the pieces was from a large craft that uses a system of boosters to lift off from Kerbin, specifically, part of one of its boosters (one of two large fuel tanks and a nose cone apparently broke off when it impacted some other object during jettison).  The junk in question consists of the largest fuel tank, a mammoth engine, a horizontal stack separator, and three of the extra large fins resembling shuttle wings, (which are all on the same side of the booster (one of four boosters in a symmetrical arrangement) arranged so that there is less than a 90 degree angle between the two fins on the outside, and the other is halfway between.  After setting all junk on suborbital trajectories and bringing home the capsule from the "janitor" ship, I began de-orbiting the junk by focusing on it and allowing aerobraking to either bring it down to collide with Kerbin or cause it to overheat.

When I attempted this for the piece of junk I described above, everything went normally at first.  Then, the mammoth engine overheated at an altitude in the 20k range, and the remaining pieces of the junk began tumbling.  Eventually the piece of junk began to spin rapidly, and the velocity began dropping faster than normal.  The spinning became so rapid that the navball appeared to be having trouble keeping up and the screen was shaking.  I expected that this would cease upon impact with the ground, but velocity dropped to zero before impact with the ground, and then the piece of junk began inexplicably going back up faster and faster.  I tried resetting to a point before the junk in question entered the atmosphere and trying again, but twice I got the same result.

Although I do have MM, KAS, and EL, this piece of debris does not contain any parts from any of these mods, nor do I have any reason to believe that any of them could be causing the problem.

Edit: By engaging the physics time warp (which I usually avoid doing), I was able to induce failure of the connections between the fuel tank and the shuttle wings (which occurred just after the mammoth engine's Rapid Unscheduled Disassembly), and the spinning issue did not occur, so physics time warp can serve as a workaround.

Edited April 5, 2017 by cgwhite4
successful workaround

[Capt. Hunt]

Another option might be to not ride it in.  KSP automatically removes any unfocused object that drops below 25 km if it isn't already on the ground.

[cgwhite4]

Unfortunately, the trajectory I had placed this piece of junk in had a "Kerbal perigee" of about 40km.  Due to the 200m physics calculation range, I therefore needed to "ride it in" in order to bring the piece the rest of the way down via aerobraking.  Switching away from a piece that is in the process of aerobraking is not allowed (the game would revert me to before the aerobraking had started), and only one aerobraking pass was required to bring the piece down.

Had I lowered the Kerbal perigee of the junk in question to below 25km, then following it from the tracking station instead of "riding" it would have been an option, but I would have needed to know this would happen when making the disposal dive maneuver with my "janitor" ship (which had enough fuel to do this and pull up safely, but unfortunately performed this maneuver well before the quicksave I was using when bringing in this piece: in the interim, other pieces of junk were put into their disposal trajectories and/or brought down).  Of course there is also the most obvious workaround: issuing the "range safety" command to the problematic junk, but if were going to do this, I would not even have needed the janitor ship in the first place.

I'll keep this in mind for future space junk removal operations.