Planets causing acceleration?

[-RanZ-]

So last night during a KSPTV stream one of the guys had an elliptical orbit around a planet and while close to his perigee he couldn't exit to space center because his craft was accelerating... he also noticed his apogee was rising so something was causing his craft to accelerate while close to the planet. I am also experiencing this now, I have a probe on a polar elliptical orbit around Jool (230,000M x 1,300,000,000M) and when I get near the perigee my craft starts accelerating and my apogee rises. Something is causing acceleration.

[Bill Phil]

ALIENS, it's the only explanation...

But, probably a glitch.

[-RanZ-]

I can provide a quicksave persistence file if needed

[Findthepin1]

if it does that and you can't explain it, it is not a "glitch". it is a law of physics. this particular law of physics allows your kerbals to reach across the galaxy, which means you should keep it. figure out how to toggle it and use it anywhere in your orbit, and you've got warp drive. use it wisely.

-findthepin1

p.s. oh and if you can control the acceleration, you has to give everyone here the knowledge of exactly how the craft is made. we want to go to a(k)lph(k)a ce(k)nt(k)aur(k)i. (k). thx

Edited April 28, 2015 by Findthepin1
he must for the sake of the community

[Renegrade]

That's an OLD, longstanding bug.

The interior forces of the craft are out of balance, so it moves (all interior forces should vector-sum to zero at the end of the day unless engines are on)... it's basically a microscopic version of the k-drive.

Yay for single precision and SSE.

[-RanZ-]

I've never seen this before. It's a basic probe, has the new big ore scanner and 2 of the smaller scanners along with a fuel tank, engine, and some solar panels and batteries.

[igor_perusco]

It's obviously frame dragging.. try entering a retrograde orbit, it should help with landing attempts

On a more serious note, ghost (the ksptv streamer in question) had a 23km Pe and about 1000 Ap, it was not a case of rounding errors making the orbit jiggle ever so slightly

He went in twice around, you could tell he was in the atmosphere (and supposedly braking) because:

- You couldn't hear his voice from the deafening aero effects

- The camera was shaking vigorously

- The ship was on firee

- A chute was deployed (yes, really)

Still, his craft was accelerating (at periapsis) and apoapsis was increasing

[-RanZ-]

I wasn't even in the atmosphere... unless Jool has had its atmosphere increased from 200k. Hopefully the devs see this or another thread if one has been created.

[-RanZ-]

This is still broke in 1.0.2

[mikegarrison]

Is it possible this is a (broken) result of tidal forces? Maybe the internal forces caused by tidal stress are not correctly balanced out (floating point error?) and the result is that the game gives the ship a net acceleration.

[MartGonzo]

Glad to see this thread, I've had this bug so many times.

because I'd never seen it mentioned on the forum I always assumed it was some combination of mods causing escalating errors in the orbit calculations.

I'd usually just go into time warp until I got a bit away from the planet and the orbit would stabilize again.

If it's a stock bug hopefully it may get fixed

[Renegrade]

Is it possible this is a (broken) result of tidal forces? Maybe the internal forces caused by tidal stress are not correctly balanced out (floating point error?) and the result is that the game gives the ship a net acceleration.

Tidal force isn't simulated to the best of my knowledge. Wouldn't need that anyhow - if there's any sort of internal imbalance, acceleration would occur. Keep in mind that all parts are ALWAYS simulated as interacting physical bodies unless you're on rails (non-phys-warp, or not in the physics bubble/etc). They're always there, pushing on each other. IF any of the forces aren't perfectly and exactly cancelling out, you've got a net force and therefore accel.

I had a station back in 0.23 or thereabouts where it would accelerate in a given direction (and also turn rather violently); it had a net accel of 0.2m/s². That's pretty crazy.

(the Krakensbane system can help reduce this, but you gotta be going more than 750 m/s for it to kick in :/ )

One thing that trips up even experienced programmers is that floating point operations are non-associative. They LOOK like real numbers, but are in fact not.