Particle system thruster to move in opposite direction to ship - non Rigidbody


I’m trying to make my particle system thruster move in exactly the opposite direction to an object that I am dragging with the mouse (not using Rigidbodies). The particle system is a child object of the ship. Currently, I’m changing the Velocity Over Lifetime values and setting them the opposite direction to that of the ship. It’s working well in terms of changing to the correct direction, however, it’s changing the direction of all of the emitted particles in the system, rather than just the ‘new’ ones being emitted at the back of the ship.

Any help would be great - current code:

    public GameObject Particles;
    private ParticleSystem pSystem;
    private ParticleSystem.VelocityOverLifetimeModule velocityModule;
    Vector3 prevPos;

    private void Start()
        pSystem = Particles.GetComponent<ParticleSystem>();
        velocityModule = pSystem.velocityOverLifetime;

    private void LateUpdate()
        Vector3 dir = (transform.position - prevPos);

        prevPos = transform.position;

        velocityModule.x = -dir.x;
        velocityModule.y = -dir.y;
        velocityModule.z = -dir.z;

Change the simulation space from local to world.