WTF? Engines falling off.

[Vanamonde]

The engines on the lander stage circled in red on the VAB pic (figure 1) fall off for no apparent reason (figure 2). You can see in the log (figure 3) that this is happening not during 2G takeoffs or any other violent manuever, but while the ship is coasting in orbit or on the way to Mun. Some time into the flight, the engines simply decide they'd rather not be part of the rocket anymore and just float away. There's no sound effect or explosion, so the first time it happened I didn't know the engines were gone until I was 500m from touchdown on Mun, ejected my booster stage, and found myself falling like a rock. This keeps happening to that ship design even after I added 3 struts between the engine and the fuel tank above it. Now is this a bug, a design flaw, or some aspect of .16 parts that I haven't encountered before?

Oh, snot. Can these attachments not be made bigger from here?

Edited August 4, 2012 by Vanamonde

[leopardenthusiast]

Upload the images to imgur, I have no idea what's going on in the images.

[Vanamonde]

Moderators: It seems this is happening to at least one other player, so would you like to move this thread to bug reports or shall I delete it and put a new post there? Either way, there are a couple of forum problems in addition to the glitch. Firstly, I get "invalid file" when I try to attach the .craft. Secondly, can attached images only be thumbnail sized now? The attachments screen doesn't seem to say anything about changing the size.

[softweir]

I'm not sure about the attachment limitations, but that's the sort of thing that gets adjusted as time goes by. In the meantime, if you can use a file-hosting website and link to your .craft file then we will be able to look at it and see what might be happening.

The Bug Report forums aren't operating as yet. Things are changing on this front.

[ccrraazzyyman]

The images are too small to make out what's going on

[Olsson]

This is happening to mee too. My engines along with those fuel tanks are placed exactly like mine and they fall off once I'm in zero G and get out of fast forwarding. This is a bug.

[Clouds]

I can't be sure, but make sure the fuel tanks below the engines are not intersecting the engines, nor the landing struts. In 0.16 it was changed so connected parts don't collide with each other, but once something is detached, it can be quite violent if it was previously intersecting - and landing gear/legs seem to be an exception, sometimes causing problems even if everything is still attached.

Or, when in doubt, add some struts between a weak part and the part to which it's attached. Even if they're at a useless angle, it will let the joint take more force.

[trekkie_]

yeah I would say lower those tanks directly below the engine, just a slight bit. it may be possible that the tanks aren't 100% structurally stable and wobble a tiny bit (even if you can't really see it) and it causes them to ever so slightly knock into the engines.

[Vanamonde]

Thanks for the suggestions, but I've tried both since posting those (tiny) pics. The engines are definitely not hitting anything below them since I moved them up, and even 3 struts apiece don't keep them in place. I haven't noticed if the problem is associated with warp because there's no notice or warning when it happens, so I only discover it when loose engines are floating around or preceding me to Mun. I'll try moving the landing legs, just to be sure.

[Vanamonde]

Excuse me while I experiment with the new forum stuff. Here's a pic of how the engines are mounted, though I shifted them up a little bit since this screenshot was taken to avoid collisions with the tanks below, and added three struts affixing each to the tank to which it's attached. http://i.imgur.com/y2Jhk.jpg As you can see here, they fall off and float away anyhow. http://i.imgur.com/eEtyw.png

Edited August 5, 2012 by Vanamonde

[MrMadGameplay]

That is weird

[Vanamonde]

I just got to Mun orbit and found that my engine had fallen off somewhere along the way. It was a completely different ship design, but that same model of 20-thrust engine. Is anyone beside me and Olsson seeing this happen? Is it happening with any other engine types? Does it always seem to happen somewhere between attaining Kerbin orbit and reaching Mun? Does it seem to be associated with warp? So far, it always seems to happen to those 20-thrust engines when they are not sitting atop a decoupler. Has anyone seen it happen under other circumstances? Any help folks could give in pinning down the circumstances of this glitch would be appreciated.

[Zephram Kerman]

It happens to me too. Just yesterday, in fact. The image is pretty tiny, but I think my lander is configured similarly to yours, except that I have those LV-909 engines running at launch. They disconnected consistently each flight after using time warp. After a lot of experimentation, the problem went away when I removed the engines, discarded them, and replaced them with the same type.

I'm not sure about this, but I think the problem appeared after I loaded the vessel. Those engines did not disconnect during the first few flights, only after loading the .craft file the next day. Since the problem went away after connecting the same engines with different PIDs, I suspect it has something to do with the saving or loading the .craft file.

[stanNL_97]

It happened to me too, I made a lander like that one.

When I went in time warp (50x) and I got to normal, I only heard a decoupler sound and the engines were gone...

[Vanamonde]

stanNL_97, were you also using the 20-thrust engines with no stage beneath them? I've never noticed a sound associated with it, though possibly because I'm usually watching the map view when it happens.

Okay guys, thanks for narrowing it down. I'm going to try going in and out of warp while watching the engines, and see if I can grab an output log just as they fall off.

[Ziff]

Vanamonde, I remember you posting this .craft file in another thread for some other reason and I remember downloading it, testing it, and commenting on it. I don't know if I mentioned it then, but I had those same 4 engines from your specific .craft file fall off. I remember it clearly, we were talking about design efficiency and I reached orbit with your craft, and then time warped to line up a Mun shot. Coming out of time warp all 4 engines just floated off into space, I think I even took a screenshot. I went back to the VAB, removed the engines, tanks, and associated parts, including the struts, saved it, and then rebuilt it exactly how it was. I launched the craft and the problem was gone. Actually, If there were struts trying to hold the engines on, I removed those. Otherwise everything else was the same.

[EDIT]:This confirms what I just read in Zephram's post, as I removed the offending parts and replaced them and the problem went away.

So yeah, something definitely quirky there. I wonder where that thread with that specific .craft link went? Maybe I can download and test it again.

[Vanamonde]

Thanks Ziff, I did remember that you did that in my "Wallows like a drunken cow" thread wherein I whined at length about how badly my crappy rocket design was flying. I cleared out a bunch of my old attachments to try to get my limit low enough to post logfiles, so I don't think that craft file is floating around here anymore. (Just as well; it wasn't a good design.) I think I will try the dismantle-and-rebuild trick, though, because I do like that layout for lander designs, if it could be made to work.