Plugin for monitoring mechanical stress of parts at attachment nodes in flight scene

[fatcargo]

As this sounds both obvious in description and somewhat obscure in usability i will elaborate further : I was looking for a way to monitor parts of my craft for any stresses that MAY cause structural failures.

My wish is to use for KOS automation to react before unplanned disassemblies happen, but even for usual craft testing this would be a great help (think of trying to minimize strutting). and ofcourse, KOS should be able to read data from this plugin (possible by adding a context menu to part with this data).

[Axelord FTW]

Its a good idea. Maybe something like the AeroViz function out of FAR (which is actually quite close to structural stress readouts in Pontifex now that I think of it). Of course, here, it is the relation between two parts and not the parts themselves (alone).

In the meantime, Ferram's Kerbal Joint Reinforcement might help you make your flying rods harder.

[fatcargo]

Its a good idea. Maybe something like the AeroViz function out of FAR (which is actually quite close to structural stress readouts in Pontifex now that I think of it). Of course, here, it is the relation between two parts and not the parts themselves (alone).

In the meantime, Ferram's Kerbal Joint Reinforcement might help you make your flying rods harder.

Yes i already know about KJR. I would like to actually READ this data, though.

Hmmm now that (re)think of it... In it's simplest form it could be just a right-click menu item with labels, like "Stalled" reading on wings from FAR. For example "NodeA:50%" , "NodeB:35%" and "MaxStress:50kN" or similar (in part cfg there is crash tolerance definition in [m/s] units, but to me it looks weird to measure stress like that). Note that i don't know about KSP's physics engine, just a basic understanding of craft tree hierarchy.

I don't exactly know how are attachment nodes defined for radially attached parts. Does it make sense to measure stresses at both nodes or just root one ? I guess stress at child node is actually same as stress at root node of child part, so that is kind of same thing repeated twice.

[Axelord FTW]

Yes i already know about KJR. I would like to actually READ this data, though.

Hmmm now that (re)think of it... In it's simplest form it could be just a right-click menu item with labels, like "Stalled" reading on wings from FAR. For example "NodeA:50%" , "NodeB:35%" and "MaxStress:50kN" or similar (in part cfg there is crash tolerance definition in [m/s] units, but to me it looks weird to measure stress like that). Note that i don't know about KSP's physics engine, just a basic understanding of craft tree hierarchy.

I don't exactly know how are attachment nodes defined for radially attached parts. Does it make sense to measure stresses at both nodes or just root one ? I guess stress at child node is actually same as stress at root node of child part, so that is kind of same thing repeated twice.

I think stress is simply measured as a single force between two connections in KSP with breakage being initiated if the force exceed the capability of the nodes. I also think that in-between-part connection strength is based on the node size, or something like that. Parts have a simple crash tolerance thingy, which is valued for the part's ability to withstand impacts.

I'D rather have a visual effect (like I said, like FAR's AeroViz) than only a right-click tell (both are fine).

[fatcargo]

I agree for both for visual and numerical feedback. You can see what is being strained, and then you can right-click on part and see the exact value if you want to.

[illectro]

Indeed, I've been asking for this feature for a while, would also like a feature that switches into slow-motion timesteps if there's a stuctural failure so you can get instant slow mo when things break.

[wasml]

Indeed, I've been asking for this feature for a while, would also like a feature that switches into slow-motion timesteps if there's a stuctural failure so you can get instant slow mo when things break.

I like both these ideas - slow-motion and stress on parts. My thought would be to design and fly a rocket and then check MaxStress afterwards to see if the design was near it's limits/needed some redesign. While a right click display would be nice, a report would be nice too - could get tedious right clicking all parts on a large design.

[*Aqua*]

Physics in KSP work like this (simplified explanation):

Every object has a velocity and an angular velocity. Any forces applied to an object are used by the physics engine (PhysX by Nvidia) to recalculate these two values on the next physics update frames.

And the most important fact: PhysX in the Unity Engine seems to keep all the current force numbers and calculations etc. inside it. So far I didn't find any way to query any of that. It's a black box.

[fatcargo]

Thank you Aqua for clarifying this. At least we now know where we stand with this.

[illectro]

Physics in KSP work like this (simplified explanation):

Every object has a velocity and an angular velocity. Any forces applied to an object are used by the physics engine (PhysX by Nvidia) to recalculate these two values on the next physics update frames.

And the most important fact: PhysX in the Unity Engine seems to keep all the current force numbers and calculations etc. inside it. So far I didn't find any way to query any of that. It's a black box.

Can't you just measure an object's deviation from starting position relative to those object's it's joined to?

[*Aqua*]

It's possible. But that doesn't tell us how much stress there is and when the connection is about to break. That's calculated in the physics engine and stays in it.

Calculating this stress or force by a plugin would mean to reverse engineer PhysX (I don't think that's legal) and/or implement a programm which imitates the calculation of the physics engine (too much work; computationally intensive).

So far I don't see a way to get to know about forces.

Edited February 19, 2015 by *Aqua*

[fatcargo]

Hmmm so KSP itself gets from phyiscs engine a stream of data about part flexing and (eventual) breakage event, but nothing in between.

Part flex (or bend or whatever) is just a spatial value, not a force vector/value ?

[*Aqua*]

Exactly. I pretty sure there's somewhere a data structure which lists all the forces which are applied to a part. I know that because I found a way to add a force vector to a part. But there is no exposed method to query the added forces or the resulting force. It's not the fault of KSP, instead it's a limitation of Unity.

Maybe it has something to do with PhysX licensing or the way the physics engine works (maybe it doesn't store forces to allow to query them).