Note: only rockets with an active deployment system (i.e. deployment not only handled by motor) will have a parachute bulkhead.

The parachute bulkhead, also referred to as the parachute plate sometimes, is the bulkhead that seals the parachute bay from the rest of the rocket, and acts as the connection point of the recovery system to the rocket. In addition to the thrust plate and fins, the parachute bulkhead experiences some of the greatest forces of any part of the rocket.

The parachute bulkhead must be designed with two main criteria in mind; flame resistance and pullout strength.

Flame Resistance

Since deployment charges usually sit right on top of or go off near the parachute bulkhead, it needs to be flame resistant. This is a nonissue in larger rockets, since the bulkheads are usually made of aluminum, but in smaller rockets wood is often used. When wood is used, a covering of metal should be applied, either with thick aluminum foil or a thin metal sheet, which would be glued to the wood bulkhead. This metal covering may need to be replaced after multiple launches.

Pullout Strength

Heh.

Pullout strength refers to the resistance of the bulkhead to pull out under either the regular or snatch forces of the recovery system. This force is all usually concentrated in a single bolt hole with the eyebolt, which can lead to significant deformation of the parachute bulkhead, as if the parachute is trying to pull the bulkhead out. Due to the extreme symmetrical curve that this force causes, it is also sometimes referred to as "bowling," as it can form the bulkhead into the shape of a shallow bowl.

A bulkhead can be determined safe against pullout strength by calculating the snatch force and applying it to the bulkhead in an FEA software like Fusion 360. Keep in mind that you also need to consider these forces on the other components, like the epoxy between the bulkhead and the airframe.

Wire Passthroughs

Parachute bulkheads usually separate the avionics bay from the parachute bay, so wires need to run through to the deployment charges. To accomplish this without pressurizing and destroying the avionics, a sealed wire passthrough needs to be used. Although not elegant, this can be accomplished with no special equipment by drilling a small hole in the bulkhead, running a series of wires through, and then sealing the hole around the wires with epoxy. Then, a removable connector can be placed on either end of the wires, and you are set.

For a easier to use or more aesthetically pleasing approach, bulkhead connectors can be used. These are special commercially-available connectors designed to pass wires through into a sealed chamber, and can be purchased for a wide range of bulkhead thicknesses, number of wires, pressure, and current.

Browser not supported