Timewarp and aircraft: what's going on with the physics?

[Klapaucius]

Can someone explain to me why timewarp seems to alter flight characteristics?  In space flight, the timewarp simply accelerates you to a certain point by a certain factor (or at least, that is how it seems to work). But if I am flying a plane around Kerbin and I turn on timewarp, I find that often the plane will start turning for no reason, start shaking, noses down and/or come apart.  I was flying the stock Ravenspear, and when I turned on timewarp the engines kept flaming out.  With the Albatross and when I turned on timewarp, the wings warped considerably.  It is almost as if my time acceleration is more like simple acceleration and all the forces acting on the aircraft are compounded. 

Thoughts?

Edited May 10, 2018 by Klapaucius

[Shadowmage]

33 minutes ago, Klapaucius said:

It is almost as if my time acceleration is more like simple acceleration and all the forces acting on the aircraft are compounded.

That is exactly what goes on when you enable 'physics warp'.  Its not doing more calculations, rather its doing the same calcs with 2x, 3x, or 4x the change rate (delta).

If you think on that for a bit, it should be a bit obvious why this causes issues in atmo (lots more 'forces' in play in atmo compared to in orbit).

Physics warp has never been good for aircraft, or rovers.  Sometimes you can 'get away' with a 2x warp, but often even that will cause issues.

[pincushionman]

In space (more specifically, when there are no outside forces acting on the craft OR the craft is in the “landed” state), timewarp puts the craft “on rails” and it is allowed to travel along its orbital path without having to deal with pesky physics calculations.

In the atmosphere, however, you always have forces aerodynamics and engines) acting on the craft, so standard timewarp is disallowed. Instead, you have what we often call “physics time warp,” which is accomplished by increasing the time step of the physics calculations. Not only does this decrease the fidelity of the trajectory, it also causes the parts to deform more under load (because the forces act for a longer time before the forces and stiffnesses are re-evaluated). So the state of the aircraft can quickly move beyond the limits of normal deformation before the simulation can stabilize, especially at high speeds or loads.

This can, as you have seen, be quite dangerous to your aircraft. It used to be there was a warning on-screen the first time you engaged physics warp in a game; don’t know if it’s still there or not.

By the way, you can engage physics warp at any time by using the Alt key with your warp up/down keys. It’s limited to 4x.

EDIT: Ninja’d!

Edited May 10, 2018 by pincushionman

[Klapaucius]

Thanks both of you.  That clarifies things.  However, it does make around the world flights rather long. 

[blakemw]

You can use autostruts (and actually, just normal struts) to stiffen up planes, the restoring forces provided by struts aren't vulnerable to physics warp in the same way as normal inter-part connections.

Also if you're into mods, then Atmospheric Autopilot (the fly by wire function) results in rock-solid handling even at 4x physics warp.

[Geonovast]

1 hour ago, Klapaucius said:

Thanks both of you.  That clarifies things.  However, it does make around the world flights rather long. 

Set the cruise and go get a pizza.

[Klapaucius]

15 minutes ago, Geonovast said:

Set the cruise and go get a pizza.

Perfect! Will it work in 1.4.3?

[blakemw]

2 minutes ago, Klapaucius said:

Perfect! Will it work in 1.4.3?

Works great for me.