This hardpoint is called Ghost Trail. It makes your spaceship leave behind ghost images that fade away quickly at a rate of ~10 times per second. It could come in two variants:
Plain, which uses the spaceship’s shield color on the ghost images.
Rainbow, which makes them cycle through colors like seen below.
And before you ask, yes, I did take this from A Hat in Time’s Collapsing Rifts. I even recreated the background effect :v
Idea