Issue link: https://www.e-digitaleditions.com/i/1520252
SPORT ROCKETRY MAY/JUNE 2024 39 JonRocket.com Model Rocket Kits, Parts, Supplies, and Accessories Traditional rear ejection is when a para- chute is wrapped around the motor mount and the motor mount is ejected out of the rocket. Some rocket designs vector the ejection charge backward to deploy a para- chute. In my opinion this isn't rear ejection; it's just normal ejection pointed backwards. Rear ejection has a poor reputation within the model rocketry community for being unreliable. Here's my list of reasons why rear ejection is unreliable in practice: 1) Rocketeers don't have much room to pack a chute. 2) Rocketeers typically don't have much experience packing a rear ejection chute. 3) e hot motor can melt a plastic para- chute and, as a result, what was supposed to be your recovery device turns into a melted chunk of plastic attached to the ejected motor mount while the Range Safety Officer yells "head's up" and then decides it's necessary to remind you to fly all of your "experiments" out on the high-power range. I resolved item three on this list of po- tential pitfalls by wrapping my parachute around a non-minimum diameter body tube. is reduced the likelihood of my 18-inch plastic parachute melting due to the hot motor, as it added an air gap be- tween the parachute and motor. Flight test- ing would later prove the parachute reliably deploys without melting. Flight Simulation With the basic design complete I used a one-degree of freedom simulation code I've written in Excel, and calculated that a D12-0 staged to a B6-2 would make a safe flight. When construction was complete, I verified the final measured weight was not greater than what I had assumed for the simulation. If my actual rocket weight had been greater than the assumed simulation weight, I would've needed to rerun the sim- ulation with the correct weight. Construction Aer analyzing the stability of the nose cone, coming up with a design, and per- Figure 3. An artist's representation of the flight of the upper stage nose cone rocket.