Have you installed the latest version of HotRockets properly? Are you able to test SDHI + all dependencies on a stripped-down KSP installation? (i.e. no other add-ons) I am having the same issue. I have tested SDHI + all dependencies on an otherwise clean install and am still having issues. I do NOT have hot rockets installed as it is not listed as a dependency. The engine bell glows red but no particle effects occur. The engine produces thrust, and the sound plays. I've looked at the part.cfg for yours and the stock LV-909 and cannot see any differences in the FX that might be causing it.