thrusting not changing orbit

[deltak]

I am trying to bring a large (2000t) asteroid into orbit around Kerbin, using a nuclear engine and using mining equipment to convert the asteroid into fuel. This has involved long slow burns, involving a very low acceleration of around 0.0175m/s^2. To bring it into orbit I would need a deltaV of around 400m/s. The method works fine for the first 100m/s of deltaV, decreasing the velocity of the asteroid by 0.1 m/s every 5-6 seconds as expected from that acceleration. However, after the asteroid reaches an orbital velocity of 750.0m/s thrusting the engine no longer has any affect on the orbital velocity, and it is not decreasing by the 0.1m/s every 5-6 seconds. I'm not sure if this is a bug or what, but it has happened consistently, even after re loading from a previous save file multiple times.

When re-loading the save file, sometimes the asteroid loads rotating, and I'm not sure why this happens either, but this is less concerning to me.

I'm running version 1.04.861 on a mac, OS 10.7.5. I'll attach the save file for right before this happens, so the asteroid can still decelerate for a few tenths of a m/s before thrusting stops having any effect.

https://www.dropbox.com/sh/xo4pjj6v84t3fcq/AACLC1hvZGBapoXru9SXWXifa?dl=0

Thanks!

Update: even if I wait till periapsis, and my orbital velocity increases to 752.0m/s and then burn, the speed changes just fine until 750.0m/s,where it stops changing again (other than changes due to the orbit itself)--It's like there's a speed limit under which thrusting does nothing.

Edited September 8, 2015 by deltak

[sal_vager]

Hi Deltak, I cannot load the save file as it appears to be a shortcut to your file, not the file itself.

[deltak]

Thanks for checking sal_vager, I changed the file so it should work now. Not sure why that happened.

I'm still curious about the bug, but since then I've worked around it by letting the asteroid pass through the system and orbit Kerbol, and re-rendezvousing with Kerbin and bringing it into orbit using many aerobrakes... but who knows when that will strike again. Again, many thanks for looking into it.

[Padishar]

Whenever any issue involves a change of behaviour around 750m/s it is almost certainly related to the mechanism called krakensbane which only operates above 750m/s. This continually shifts the origin of the coordinate system used by the game to remain centered on the vessel to eliminate some very odd effects caused by moving quickly. Certain parts of the game not correctly allowing for the side-effects of krakensbane (or allowing for them when it isn't actually being used) has been the underlying cause of a number of bugs in older versions.

The problem is most likely related to either the claw or to the asteroid (and you have to have a claw for an asteroid to be part of your vessel). You should consider installing (at least the ModuleGrappleNodeFix part of) the "stock bug fixes mod" as it fixes a number of issues with the claw that can result in vessels spontaneously exploding or doing other wacky things and can also corrupt the whole save game.

As for loading of saves sometimes going weird, there is a long-standing bug where quickloading doesn't always load every part of the game state correctly. This can be most easily seen when you make a quicksave at one point in an orbit (it may need to be a very large and eccentric orbit) and then reload the save after you have travelled to a significantly different point on the orbit and your ship is pointing (and travelling) in a considerably different direction. After the quickload you may see that the ship has not been loaded in the orientation it was in when saved, instead being left in the orientation it was just before you loaded. Quickloading again should then load it correctly. So, if you think there is something weird after quickloading then immediately do another quickload of the same file and it may well be better.

Edit: Are you only using a single nuke engine? When I was messing with class E asteroids I was using a tug that had 18 LV-Ns and the burns still took ages. This was in 0.23.5 when asteroids and the claw were first introduced and the LV-N still used LF+O so it needs a major redesign for 1.0+

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Because the burns were so slow (and the pusher arrangement is so hard to control and using multiple claws for the RCS pods makes the claw issues worse) I also created a version that used 6 mainsails in a puller arrangement. I've used this one fine in 1.0.4 even though it is a highly non-aerodynamic, asparagus pancake...

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Edited September 18, 2015 by Padishar

[deltak]

Thanks for the help Padishar--It's back! I'm still having the issue after using the ModuleGrappleNodeFix. This time I'm trying to adjust my orbital inclination, once I'm in orbit around kerbin at an altitude of 115km (using a much bigger engine this time). It's not at 750 m/s this time either... I've included a new quicksave file right before this happens--once I try to carry out the maneuver.

Also thanks for the quicksave tip. I found the rotation less of an issue if I retracted the mining drill before saving. It turns out that rotation isn't even encoded in the save file, only orientation. At least as far as I could tell by mucking around with the save file.