There has been a number of refinements and fundamental changes to the recovery and electronics bay portions of the rocket in the past few weeks, so I've listed the main ones by category! It's going to be a monumental push to finish the project by our deadline
– which is only a week after the academic quarter ends at UCSD. With classes, internships, and occasional meals I suspect that the next month will present numerous late nights for all the brave students of SEDS who have committed themselves to this project.
While I had originally anticipated that the electronics system as a whole would be minimal, the advantage of having a large volume to work with has given us the opportunity to accommodate our own experimental parachute ejection system, which will be a custom PCB that we have designed ourselves. While I'm not an expert in electronics, one interesting aspect of this system will be it's constant communication through an antenna – mounted lengthwise in the nosecone – that will constantly relay the flight telemetry back to the ground. Additionally, the system will be recording the acceleration of the rocket, and perhaps even looking at the double integral of the acceleration to give live estimates of altitude in addition to the barometric altitude estimates that we will be recording using a commercial flight altimeter. This will be an entirely separate system, along with a separate power source for redundancy.
Each parachute compartment – The main and the drogue – will contain two ejection wells, each with two ematches installed. Each parachute ejection system will be wired to one of the ematches in every single ejection well, meaning that while one system will inevitably fire first – even if only by a fraction of a second – we have complete redundancy in both the systems and the explosive charges.
Because of the space-conservative design of the system, the wires caring the current for parachute ejection must necessarily bridge the gap between the airframe and the shoulder of the nosecone, which must separate during parachute deployment. It is such that at this junction we must have a connector which is tight enough to not experience loss of continuity due to vibrations or launch acceleration, but loose enough so that it doesn't impede the separation of the nose cone and the airframe during parachute deployment.
Because of this connection juncture, it is especially critical that the shear pins holding in the main parachute are not accidentally sheered during the deployment of the drogue parachute at apogee.
By consensus, we have also decided to omit the secondary (forward) bulkhead supporting the electronics sled tube against the inside of the nose cone that I had drawn in an earlier blog post. This additional support will instead come from two-part expansion foam which will be poured into the cavity created inside the nosecone prior to the installation of the centering bulkhead at the aft of the nose cone.