What this body lifting ?

[Warzouz]

Since 1.0.5, I have a hard time putting my space station to LKO.

I looked into F12 and I discover a body lifting force far away from my rocket.

What is this body lifting force at the top of my rocket ?

[Snark]

Weird.

If I had to guess, maybe something to do with the big fairing? I seem to recall from the 1.0.5 release notes that they were tinkering with fairings to get them to work right with CoM, aero forces, etc. If they've been writing a bunch of new code in that area, I wouldn't be surprised if there's a bug in some edge case that's you've stumbled into.

Might be interesting to see what happens if you blow the fairing. Does the phantom lift stay there?

[Alshain]

I have noticed a similar issue on rockets that are far more simplistic and aerodynamically sound. I think there may be a bug in the fairings.

This was exceptionally difficult to launch and I had trouble determining why.

Edited November 15, 2015 by Alshain

[Claw]

Yes indeed, it's a bug with the CoL on the fairings (as also described here). Unfortunately it's not an edge case, and beware that the aero markers lie to you after jettisoning the fairing (until you cycle the overlay).

Not that I like saying "there's a mod for that," but if you aren't opposed to addons, I've fixed this in the latest release of bug fixes.

Otherwise the only "workaround" is to not use fairings, or design the craft in such a way as to still be controllable with a lever arm that far up.

Cheers,

~Claw

[Warzouz]

Thx Claw.

Is it only a display issue, or does it really affect flight ?

I find that in 1.0.5, rockets are much more unstable than in 1.0.4, even very big wings does help much. I mostly have to follow "prograde" only up to space.

[Claw]

Is it only a display issue, or does it really affect flight ?

There is more than one bug at play here. It's hard to explain exactly, because in some ways the overlay is wrong which muddles the important issues.

- The location of the vector before jettisoning the fairings is displaying correctly in the sense that this spot is where force is being applied. That's what is causing the rocket instability.

- After jettison of the fairing, the location of the vector is no longer correct. It doesn't move until the aero overlay is cycled. In this case, the overlay is incorrect.

- There's a third bug, which becomes apparent after jettisoning the fairing. Apparently for parts at the end of a stack that are wider than tall, the lift vector ends up negative. So you'll see in the overlay, the lift vector is pointing opposite of everything else. This is an actual error and not an overlay problem. This problem is an issue with the body lift calculations, and is not isolated to the fairings. You can see it on any part that's wider than tall (such as an FL-T100) that's at the top of a stack with it's top node exposed. (This isn't isn't pictured here, but I think is shown in the other thread.)

Hope that's clear enough.

Cheers,

~Claw