If you are writing about the pads that fall off the side of the missile when it leaves the Launch Tube then you are describing the Peacekeeper ICBM. That missile was deactivated years ago. The only active ICBMs in our inventory are the Minuteman IIIs and they are a 'hot launch" missile. The engines fire while the missile is still in the Launch Tube and bolted to the Thrust Mount. When a Minuteman III leaves the hole that hole is basically destroyed, except out at Vandenberg AFB where the silos are configured to allow for refurbishment.
Yeah, somebody caught my mistake earlier. I was thinking of the LGM-118 test launches.