Joshua Harvey

As team lead and founder of the Tufts rocketry project team, I actively participated in and managed the development of the University’s first rocket, christened “Space Bo I.” Designed as a NAR Level 1 Certification Rocket, the vehicle was powered by a commercial I-class solid rocket motor. The rocket served not only as a qualification vehicle for team members to become licensed high powered rocket users, but as an introduction to basic aerospace engineering principles for the inexperienced members of the team.

Throughout the development process, I worked with groups of members organized into subteams, such as fins or propulsion structures, as well as individual members on smaller projects, like producing a detailed CAD model of the nose cone from the equation-driven geometry. Thus, I was involved in all levels of the project, from behind the scenes work like securing funding and working with faculty mentors, to collaborating one-on-one with project team members. I’ve detailed several such work sessions below.

• Nose Cone: After performing research on nose cone geometry and considering our application, I decided on a Von Karman curve. With the goal set, I pulled in two junior members of the build team and walked them through the concept. Next, we modified the equation with our relevant measurements and moved on to CAD modeling. We found that the software we had been using did not easily support equation driven geometry. Consequently, we switched to a more advanced software and adjusted our equation to match the syntax and format of the program. This file was then further polished and sent to HP Labs for high quality additive manufacturing.

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• Avionics Bay: Controlling the deployment of the parachutes throughout flight is crucial to flight success. A commercial flight computer controls these the deployment events, mounted in the avionics bay. The avionics bay had several key technical requirements: secure mounting for the flight computer and power source, ease of removal, and pressure isolation from the parachute bay (to ensure that the pressure measured by the flight computer is not influenced by the deployment charges). After outlining these requirements, I brainstormed with build team members and produced concept drawings. Concepts were followed up with CAD models and Masonite prototypes.

• Parachute Deployment Mechanism: Deployment events are controlled by the avionics bay, but the mechanism of release is separate. The main chute is very large and produces considerable friction with the body walls when being pulled from the rocket during deployment. Due to the friction generated, a prohibitive amount of force was needed to deploy the parachute. In response, I worked with my core team to design a specialized, constricting ejection bag for the parachute, which kept the cross-sectional profile of the packed parachute small enough to allow for easy deployment.

• Motor-Fin Assembly: The rear internal structure of the rocket consists of a cylindrical frame that serves two essential functions: securing the motor and fins to the body as well as transferring the thrust of the motor to the airframe. I developed the requirements for the structure on my own and then handed them over to the subteam. I ensured that the team had the software tools and resources to complete the design. The fin geometry was iteratively created based on simulation in OpenRocket. I continued to work with the team regularly as they talked through the design, created each component in CAD and then combined the pieces, and finally produced Masonite prototypes in the machine shop.

Overall, the rocket performed well during flight. The parachute deployment mechanism of the vehicle had to be rebuilt on site due to complications, but the rocket flew and achieved a height of 2496 ft (safely under the altitude ceiling set by the launch site). The parachutes failed to deploy due to faulty placement of the ejection charge, however the flight was still considered a success as the ascent was flawless and the vehicle was recovered. In the future, a new avionics bay will be designed which will allow for optimum placement of the ejection charge to ensure proper chute ejection.