PSP: NASA Student Launch

Role on Team

NASA Student Launch is one of the teams within the Purdue Space Program club. Every year, NASA creates a new payload challenge and teams are expected to design, build, and test a rocket and payload.

My major contributions on the team was in the Construction Sub-team. Construction was tasked with designing and manufacturing the rocket including the air-frame, motor-thrust plate, nose cone, fins, and overall rocket structure. Within the sub-team, I was tasked with redesigning the fins. The previous year, the team utilized 3D printed fins, however, the thin design caused the fins to flutter during flight. This was a point of concern for NASA and the team so a fin redesign was a priority.

In my first meeting with the team, I proposed a new manufacturing process that initially was met with skepticism. However, after producing a prototype fin, the team leadership gained confidence in my design and made me lead for fin development.

Design & Manufacturing Methodology

The fin design was created in SolidWorks and optimized using OpenRocket. The fins featured a thin symmetrical airfoil shape. The fin size was limited by the build volume of the team's 3D printer.

The manufacturing process ideology I utilized was making a mold of the fin and using a stiff resin to create the fin around a fiberglass core. The prototype mold was a sandwich design meant to form a leak-proof seal using several bolts to provide adequate pressure to create the seal. However, the 3D printed mold's surface roughness caused small gaps to remain causing some resin to leak making fin removal extremely difficult. After removing the prototype fin from the mold, it was sanded and heat-treated. Then, the fin was overlaid with fiberglass.

Prototype Fin Manufacturing Images

Following the manufacturing of the prototype fin, it's properties needed to be characterized. One of the main concerns of the previous fins was that they fluttered during flight. To demonstrate that the fin will not flutter in the flight regime the full-scale rocket will fly in, a simple bi-modal flutter analysis was conducted (link to the analysis used). This analysis modeled the fin as a bending spring and a torsion spring. The fin was fixed to a bench and loaded with a set mass. Video was taken as the mass caused fin displacement and a computer program was used to measure the bending and angular displacement. A flutter speed was determined using these displacements and dimensional properties of the fin. The analysis showed that the flutter speed was well above the speeds the rocket would experience.

Prototype Fin Characterization Testing

fin loading - Made with Clipchamp.mp4

Learning from the findings from the prototype fin, the fin mold needed to be upgraded. To avoid leakage from the mold, a silicone mold was made. To make the silicone mold, a full-size positive of the fin assembly (fiberglass core + mounts and resin outer shell) was 3D printed. A mold casing with guide rails was also 3D printed. The 3D-printed positive was mounted in the mold casing and liquid silicone was poured into the casing. Once cured, the 3D-printed positive was removed. The outer casing included rails to ensure the fiberglass core was positioned correctly. This method allowed for all the fins produced to be identical. After all of the fins were de-molded, they were sanded, heat-treated, wrapped in fiberglass, and painted.

Performance & Legacy

The fins manufactured utilizing my methodology proved to be very durable. A single set of fins were used for all 3 full-scale flights of which two included high kinetic energy landings due to parachute malfunctions. The fins also impressed the NASA officials tasked with verifying the air-worthiness of the rocket because they could not get them to bend. At the end of the year, I chose to leave the team to focus on more propulsion related projects, however, I remained as an advisor for the Student Launch construction team. The team still uses the same manufacturing process and some of the same mold designs.

Page updated

Google Sites

Report abuse