Grating Bonding

While it has the exact optical properties we need, the grating is ultimately a fragile piece of glass, and it's destined to go on a rocket flight at 10+ g's. We need to attach it to the payload in a way that keeps it safe, secure, and stable, while also allowing us to adjust its position and remove it as necessary.

Fortunately, procedures and designs have been refined that securely hold the grating while keeping it safe from vibration and outside contact. This typically involves using epoxy or glue to secure the grating inside a metal harness that then can be incorporated into the payload. In its final state, the grating touches only this glue, in as few places as possible, and these strong bonds hold it in place and allow for its positioning inside the payload.

At CU, a process has been created that has been used to successfully epoxy a large number of flight gratings for rockets. This usually involved having a grating 'jig' machined-- a stand that can precisely and securely hold the grating during the multi-day bonding process. The flight mount is placed in the jig, and then the grating is placed over top so that it just barely doesn't touch the flight mount. Teflon spacers are inserted between the mount and the optic to maintain a precise spacing, and an initial epoxy application seals the perimeter around the appropriately spaced bonding points. Once this epoxy has set, two of the spacers are removed, and the structural epoxy is injected into the cavity that they leave behind. A central teflon spacer remains, in order to ensure two different bond areas in case of any single-bond failure. After the epoxy has cured, the remaining teflon spacer is removed and the grating flight mount is installed into the payload. The entire procedure is done under constant nitrogen purge, as the epoxy fumes would react with our grating coating and tank the grating efficiency. The procedure is also practiced multiple times with both test setups and grating mass models to ensure a smooth run during the real thing.

I personally bonded the grating in June of 2017 with the support of 3-4 members of my team. After multiple practice runs and tests, we had a great bonding run that has survived multiple launches and over ten vibration tests to this day, which I'm very proud of. See below for pictures!