Spacecraft Rotation During Timewarp

[Enorats]

So, I'm trying to wrap my head around this and totally failing. All logic tells me that this shouldn't be happening, or well.. it should, but not remotely at the rate that it is. Here's the issue:

I'm using Kerbal Health as a "life support" type of mod. Even with the power drains cut in half in the .cfg's it's still utterly insane and I should probably cut them down to more like 1/10th. My station is currently powered by six mod solar panels from BDB that are similar to the large stock ones, but smaller and slightly weaker. I rotate my station to point the panels at the sun at 100% exposure. As I orbit Kerbin I expect that my panels will stay at that same exposure, as my ship should not rotate in its orbit - there is no force acting on it making it rotate. Eventually, after enough time passes Kerbin will move far enough in it's orbit that I'll slowly need to adjust my orientation, but that should only require something like half to three quarters of a degree a day.

What I'm finding though is that when I time warp I stay around 100% exposure, then drop behind Kerbin.. and when I come back to the day side I'm only at ~80%.. go back around to night, and on day side I'm at 50%.. then 20%.. With each "sunrise" I've somehow rotated ~20-30 degrees for no apparent reason, causing my solar panels to fail to recharge my batteries I go back to the night side, causing my life support systems to fail.

Now, am I right in assuming that this is not supposed to happen? Thankfully the simple solution of just putting more batteries and panels facing in the other two directions as well takes care of the issue.. but this uber-fast complete 360 rotation in a day thing is breaking the part of my brain that thinks about physics.

[Streetwind]

While I don't know what causes it or how to fix it, there may be a potential workaround for you if your station uses solar panels that can rotate on their mounts.

Note the direction your station is rotating in, then position it so that the axis is the same as that of your solar panels. That way, even when the station comes out of the shadow of the planet at a totally different angle, your solar panels will simply rotate themselves back to full exposure.

People use this technique all the time for geostationary satellites that need consistent sun exposure at any point of Kerbin's orbit around the sun.

[Tex_NL]

@Streetwind might not know what's causing your issues, I do. The problem is not rotation, it is the complete lack thereof.

During timewarp ALL rotation is halted in ANY frame of reference. You can clearly see this as you look at your station while it is orbiting around Kerbin. It always faces the same way.
But what you're forgetting is that Kerbin is also rotating around the sun. Every day Kerbin progresses a few degrees in its own orbit and your station 'inherits' this movement. As a result the sun is in a slightly different position every day. Over time this will be enough to rotate your solar panels out of alignment.

Solution: As @Streetwind suggested, place rotating solar panels on the Z axis in order for them to track the sun.

[Streetwind]

@Tex_NL I don't think that's it. if you read his post carefully, you'll see he reports rotation of >20 degrees for a single Kerbin orbit.

[Enorats]

Yeah, I know that over long periods of time I should slowly drift out of alignment as Kerbin orbits. It should only be something like 360/ (days in a kerbal year) degrees per day though. Since Kerbin takes well over 400 days (450 something maybe?) I should be seeing less than a degree per day of alignment loss. Instead I'm seeing 20+ degrees every time I go around Kerbin. It seems the problem gets worse the higher the timewarp gets too, if I keep it at a lower time warp I only see a couple degrees per orbit. That's still an order of magnitude more rotation than I should see though, as an orbit only takes less than an hour (1/6 of a day, so I should see (360/(days in kerbal year))/6) at my altitude. If I use the higher time warps granted by the Better Time Warp mod (which lets you warp faster near bodies) it gets absolutely insane.

I like that solution though Streetwind. I'll have to give that a try.

Edited July 15, 2017 by Enorats

[Nicias]

The game uses a reference frame tied to the rotation of the planet for low orbits. So if you are in a Low kerbin orbit, with a period of about 20 minutes, then in the time it takes you to do one orbit (20 minutes) Kerbin has rotated 360*(20/6*60)=20 degrees. 

The solution is as given, align the axis of your solar panels N-S, or move to a higher orbit.