How to define multiple nozzles when modding an engine

[Kerbolox]

Hi everyone ,

I've got a little story to tell you that will end with a couple of questions on how the configuration of engines with multiple nozzles works. But before I start, here is a...

TLDR: How can I configure an engine with multiple nozzles in KSP? And is it possible to tamper with the multi-nozzle configurations of stock engines by modifying their config file? If yes, how does it work?

Okay, so I have been a little dissatisfied with the stock Launch Escape System for quite some time.
It does its job when aborting mid-flight, even although in many such occasions it would also be sufficient to simply shut down all engines and decouple the command pod; but the LES's miniscule amount of propellant gives it far too little burn time to be useful for an abort on the launch pad. Instead, if it had more fuel, it could really be used in those situations where one builds a far too big and too unstable rocket that spontaneously disassembles itself right on the pad, to pull the capsule to a height large enough to deploy the parachutes and land safely back on the ground.

Thus, in my KSP 1.8.1 install, I decided to give a look at the LES's config file and see what I could do to "improve" it. I have little to no experience with KSP modding, but still, increasing the amount of fuel in the LES was simple enough for me to manage that. However it then turned out that there is a problem created by the fact that the net thrust generated by the LES is angled with respect to its vertical axis. Once the burn time of the LES is more than fractions of a second, this will lead to the capsule spinning out of control quickly and stop it from gaining height after a pad abort. Therefore, I gave the config another look to figure out what I could do to reduce the amount of torque the LES induces. Unfortunately, I haven't been able to find anything that I can do to modify the center of thrust or the angle of the thrust the LES generates.

My feeling is that the direction of the thrust the LES generates is computed internally by adding up the thrust of all its five nozzles, and therefore there is no single variable that determines the direction of the net thrust. Then, I'd only have to modify the configuration of the LES's off-center nozzle at the top to make it less off-center. Unfortunately, I haven't been able to find anything in the config file that seems to configure the multiple nozzles, their position, rotation, etc. and moreover, I also haven't been able to find any information on that anywhere else. So, in case someone reads this who knows how to configure multi-nozzle engines, I'd be very happy if you could explain it to me. Maybe it is configured somewhere else than in the LES's config file? Maybe it is not even possible to tamper with the multi-nozzle configurations of stock engines? Or maybe I'm just blind ? I just don't know and I'd appreciate any hints that you can give me.

At least I am pretty sure that multiple nozzles have to be configured somewhere. I have RealPlume with stock configs in my install and for the LES it only configures a single plume which is automatically attached to each of the five nozzles. And here is a second issue that I am having: I find the plumes way to underwhelming for the thrust the LES generates, and I would like to make them much larger and longer. However, increasing the size of the plume also increases the size of the plume emerging from the little nozzle at the top, which I don't want. So I am guessing that what I could do, is to remove the top nozzle from the config and then manually add a small plume to it in a similar way it is done, for instance, with the turbopump exhaust plumes of various engines (like the ones in the ReStock mod for example). But before I can do that, again, I have to know where the multiple nozzles are configured.

So, if you have any answers to my questions or any other suggestions you can give me on those problems, I'd love to hear them!

[wasml]

The thrust is configured with a thrust transform that's part of the model in the .mu file - not something you can change in the cfg file. It is possible to fix but you would need to import the model into a 3D editor and fix the thrust transforms and then change the model back to a .mu file (doable with taniwha's Blender .mu importer/exporter I think) or run the model through Unity.

[JadeOfMaar]

The LES's offset thrust is by design. It's meant to pull the crewed pod out of the path of the remaining vehicle, otherwise they'll meet again and the crew will get splattered. Try shifting the CoM or you'll have to roll your own LES (by welding things, making a sub-assembly, or using 3D modelling skills and sculpting your own)

This is the key to use and an example of where it goes in a config.

PART
{
  	CoMOffset = 0, 0, 0 // x, y, z coordinates in meters
}