Project Overview

The Highly-Optimized Data-Gathering Explorer, or HODGE, is the Tufts Rocketry Team’s 2024-25 project, designed as the team’s second entry into the Spaceport America Cup. It will carry a student-developed scientific payload to 10,000 feet in altitude on a commercial solid rocket motor. The HODGE project takes minimal inspiration from the previous year’s CARM rocket, but is otherwise a blank-slate design intended to further hone the team’s engineering skills and improve on past problem areas.

[For ESRA] Progress Report 1 Additional Materials:

Below is the file with the additional stability analysis information, as referenced in the first progress update.

Rail Departure Velocity Analysis.pdf

Key Focus Areas and Upgrades

Although CARM was highly successful, a year of working on the project helped the team identify several key areas that required significant improvement. We have taken these considerations and put them at the forefront of HODGE’s design.

• Design Efficiency: Risk tolerance on CARM was very low, and poorly balanced across the vehicle, varying between 1.5 and 16.4. HODGE will use a single safety factor of 1.5 across the board.
• Engineering Quality: The team is adopting a first-principles-based design approach; hand calculations, then simulations, then testing will validate designs. If components do not fail at the intended load * safety factor, they will be redesigned.
• Weight: As a consequence of being overdesigned, CARM was very heavy (87 lbs). With HODGE, removing weight will be a key consideration at every single component and subsystem level. Early models and simulations show a reduction in 19 lbs so far, with hopefully more to come.
• Space Efficiency: CARM had several major areas of unused space inside the airframe. HODGE aims to cut down on these by downsizing compartments where possible and utilizing former “dead space” in the upper airframe and nosecone.
• Ease of Use and Accessibility: The CARM avionics bay was an infamous source of frustration and effort within the team. HODGE will drastically improve on this by designing with accessibility in mind from the beginning, both during integration and while at the pad. Hatches will allow for access to batteries, SD cards, and flight computer connections, hopefully minimizing the risks posed by a full de-integration of the rocket. Additionally, flight computer and camera switches will be designed to be more ergonomic and reliable, while buzzers and LEDs on the new custom flight computers will provide a better indication of healthy and continuity.
• Tooling and Fixturing: Many of CARM’s components were custom-made and required intense manual care to ensure good finish and fit. The team is hard at work developing tooling that will streamline various fabrication processes, making them more efficient and repeatable.
• Composite Build Quality: CARM was the first large-scale composite airframe built by the team, and it was a great learning opportunity. With HODGE, the team aims to produce higher-strength parts through better process control, including precise curing temperature control and improved layup techniques. Vacuum bagging and degassing are being explored as potential ways to reduce or eliminate voids.
• Flight Simulation Quality: In addition to the standard openrocket simulation, the Avionics and Mechanical teams are collaborating to set up rocketpy-based flight simulations, and to update the previous year’s segments of MATLAB simulation code.
• Fin Flutter Analysis & Simulation: Fin flutter is a complicated and dangerous failure method. The Mechanical team is hard at work researching fin flutter, developing flow and structural setups and testing materials to accurately characterize fin flutter velocity. This fin flutter analysis is the driving criteria behind HODGE’s fin design.
• Split Fin Design: HODGE will incorporate two sets of fins, one permanent and one removable. The latter is designed to break in case of a hard impact, protecting the rest of the booster (aft) section, and allowing the fixed fins to be lighter.
• Apogee Control: CARM’s only method of controlling its target apogee (aside from the motor) was via the launch angle. HODGE’s swappable fins and potential aerodynamic attachments will allow the team to make last-minute adjustments for the optimal flight profile, improving the vehicle’s chances of hitting 10,000 ft on the mark.