Thruster Component acting unexpectedly regardless of its rotation


I’m having some problem with trying to control/understand the thruster component. Basically i attach a thruster to the root mesh of a blueprint, set the X axis accordingly and when i hit play it starts to spin like a headless chicken. I tried a couple of other options and recorded a 2 min. video that explains the situation better:

The white spinning mesh in the background is a static mesh set to movable and simulate physics and a thruster attached to it inside the level, but as you see it acts the same way. Do thrusters require super precision on where you place it on a mesh to make it move straight or is this a possible bug?

Let me know if you need more information.


Edit: Currently i’m using 4.3 but i had the same result with 4.2 a couple of weeks ago.

Hey, Jacky.

So I’ve looked into the issue and I’m seeing the same result you are. A PhysicsThruster just causes the ship to flip around and meander off, rather than flying neatly and smoothly. The reason for that is that the origin of the ship isn’t its exact center of mass. You’ve got a few options to fix this.

  1. If you find the EXACT center of mass of the ship, you can put the thruster there and it should stop flipping. The problem with this solution is that it’s very difficult to do, and if something causes the ship to turn even a little bit, it’ll start flipping again.

  2. You could, rather than using a single PhysicsThruster, use several and balance them so that they prevent the flipping. This would still be pretty hard to calibrate, so I personally would choose to…

  3. Not use a PhysicsThruster for this. In order to get the smooth sort of movement you probably want from a spaceship (like the spaceship you fly by default in this level), it’s easier to directly change its velocity or position in the blueprint, ignoring physics simulation. Simulating physics with a Thruster will be very likely to result in unintended side effects like this flipping.



Hey Jonathan,

Thanks for the answer! And the answer was something i was afraid of, but it makes sense. The reason i wanted to try thruster for movement was to avoid gimbal lock behavior we see in flying template while looping but i’ll have to find another way around it i guess.

Thanks again!

Old thread I know but adding this as it popped up on recent searches for me. if you want good physics you generally want to avoid setting velocities directly, instead use AddForce. This works on the centre of mass and allows the physics system to combine acceleration and collisions gracefully.

Thanks for the input! It’s also worth adding that we have access to center of mass of the objects since 4.6 or 7 i think.