A complete Mach 2 sounding rocket targeting 24,000 ft, designed and built entirely by me as my Tripoli Level 3 certification vehicle.
Structural adequacy was established through a combination of hand calculations and flight experience, overbuilt based on learnings from previous ARES projects. The critical load case is fin flutter during boost, where I required the flutter velocity to be 50% greater than the predicted max velocity. Calculations were performed on the bulkheads for epoxy tearout, yielding, and bolt shear to ensure all primary structures and recovery attachment points are safe to support flight.
Given this rocket has no apogee target, unlike the ARES Project rockets I have made, the safety factors could be considerably higher to ensure no component fails despite the inherent weight gain. This meant many safety factors are around 2-3, with components tested to their limits on the ground before they go near a flight vehicle
Fins to suvive Mach 2
Testing U-Bolts on Instron Machine
The recovery system was designed to functionally work everytime, as I have seen too many recovery failures in high-powered rocketry. As such, a dual-separation, dual-deploy system is used, with energetics responsible for the recovery events. Two chutes, a 24" drogue and a 72" main, will be deployed at apogee and 1,200 ft AGL respectively.
I decided to go with a recovery harness that maintains line strength and ensures repeatable deployment at any altitude. The lines are SK-75 Dyneema, 4mm, fingertrapped with 8cm loops in either end. I tested these on an Instron machine, with the chosen line yielding at 27kN of force - well above anything I'd expect! The ejection charges are kept in nylon tubing, allowing the energetic to fully combust and build pressure before bursting the tube and seperating the rocket.
Lines Diagram
Instron Tested Dyneema Samples
Completed Lines
There are two avionics bays in the airframe, the GPS bay in the nosecone for RF transparancy, and the main bay connecting the two halves of the airframe. I am using a Blue Raven as primary FC, RRC3+ as secondary FC, and a Featherweight GPS. The avionics bay also has a GoPro for video logging, and an ARES Hermes v2 flight computer for data logging. The entire bay and sleds have been printed out of ABS-GF to survive Mach 2 flight conditions.
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View from GoPro inside the Airframe
The composite airframe followed a tight manufacturing schedule, completing all structures in two weeks. I decided to machine all the metallic components myself, with the avionics bulkheads machined on a 3-axis CNC. This process solidifyed my understanding of toolpathing, fixturing, and setup, finishing two bulkheads in one day.
Completed Avionics Bulkheads