Summary
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New exterior flight camera housings (known here as "aeroshells") were designed and fabricated for projects Medusa and Prometheus
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Background
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(Fall 2023 - Spring 2024). The Prometheus aeroshell consists of a sleek, lightweight, and thermally insulating fiberglass shell mounted to a 3D printed PLA mounting frame. A piece of high-temp, high-strength glass is embedded into the shell to allow the camera a clear view. Compared to its predecessor from Project Phoenix, the overall design offers much-improved aerodynamic and heat-shielding capabilities. The aeroshells flew successfully at the test launch of Prometheus, with all four shells returning undamaged and high quality footage recovered from the installed flight camera.
Above are photos of several flight aeroshells taken shortly after Prometheus test launch.
Page Contents:
- Background
- Research and Preliminary Designs
Background
An initiative to redesign the aeroshells was made after the launch of Project Phoenix and the discovery of several issues with the existing aeroshells.
These were the Phoenix aeroshells in their development stages (images from 2022): 
And images from Phoenix launch, after recovery (2023):
Two designs were made in parallel, one to hold the Runcam Split flight cameras and another to hold 808 Keychain Cameras. These aeroshells were 3D printed from SLA resin and bolted onto the mission package tube. After launch, multiple issues were identified in this design:
- Many of the cameras Many of the cameras turned off on the pad, so they did not record footage. Overheating was identified to be the most likely cause.
- The cameras were turned on and the rocket left on the pad for an unexpected length of time (~1 hour).
- Since launch happened in January, the temperature outside was still chilly. The camera generates heat while operating, so the overheating most likely happened because its own heat was trapped inside the shell.
- They may have also absorbed heat from the warm sunlight.
- After recovery, some of the aeroshells were noticed to have a gummy or sticky surface texture.
- After launch, avionics placed another set of aeroshells outside in the sun, with cameras inside them. The experiment recreated the camera shutoff and sticky texture from launch.
- The stickiness could be due to improper curing of the resin print.
- Could also have been softening from in-flight heating (air friction, stagnation).
- The aeroshells required access to the inside of the tube to mount, as well as space for nuts on the interior. This can obstruct the AV bay from being inserted into the rocket, and requires the aeroshells to be integrated before anything else gets put inside.
- The shape is bulky, with many corners, flat faces, pockets, and protrusions that disrupt airflow. Phoenix had a significant (~10,000 ft) discrepancy between predicted apogee and actual apogee. The shape of these aeroshells likely exacerbated coning and increased drag on the rocket in a way that was not predicted in simulations.
- The aeroshell cracked on impact with the ground. This is fine, we don't need to design things to survive hitting the ground.
With the new design, we hope to fix the issues of the previous while improving the aerodynamic performance and thermal robustness.
Research and Preliminary Designs
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In Spring 2023, Summer Hoss '23 led aeroshell redesign sessions. The goals were to conduct research and establish a preliminary design.
- Research was conducted to narrow down a set of materials that provided sufficient thermal insulation while being reasonable to buy and fabricate with. These materials ended up being:
- Nylon 66 3D print - somewhat more heat-resistant than PLA or SLA, though still runs the risk of softening.
- carbon fiber - very heat-resistant. Pure carbon fiber may soften from heat, depending on the thickness. May be difficult to work with, given the size of the aeroshells and the team's level of experience with composite materials.
- Other composite materials - same as carbon fiber, but the team has limited experience with it.
- Some design ideas were generated:
- Using the shape of the existing but unused aeroshell CAD model made by Chad Meier '23.
- This idea was implemented, shown in the next two images below.
- Incorporating a mirror so that the camera can be oriented differently from the direction we Incorporating a mirror so that the camera can be oriented differently from the direction we want a recording of.
- In-flight vibrations were found to not interfere with this type of design.
- This idea was initially implemented, then removed due to the complexity it introduced.
- Incorporating air pockets for increased insulation
- Using aerogel
- It's expensivean expensive and unfamiliar material
- We can achieve sufficiently high performance using less complex materials
- Using honeycomb structures such as Nomex
- Adds a lot of thickness
- Using aerogel
- Relocating the onboard cameras to inside the rocket.
- People really wanted them on the exterior though.
- Using the shape of the existing but unused aeroshell CAD model made by Chad Meier '23.
- Interior flight cameras are more aerodynamic
- Consequently, it's a much more common design
- It's difficult to buy or find examples of exterior flight cameras for high-powered rockets. Most, like the Estes AstroCam, are made for small model rockets.
- People really wanted our cameras on the exterior, for the view.
- Using the shape of the existing but unused aeroshell CAD model made by Chad Meier '23.
In Fall 2023, the In Fall 2023, the design of the aeroshells became a collaborative effort between the Medusa Aerodynamics and Prometheus Structures subteams. Interested members cooperated to produce rough designs for the Medusa conceptual design review (CoDR) and preliminary design review (PDR), slides linked. These were designed for the 808 cameras, to be made with T300 standard modulus twill weave carbon fiber and withstand a maximum in-flight temperature of 1300°F . A negative mold would be (Note: this temperature requirement lowered as design changes were made to the rocket). A negative mold would be made for them using foam and a CNC router. After preparing the mold, the carbon fiber would be laid up and vacuum bagged. Ideally, the part can be left to cure in a composites oven so that it attains a higher operating temperature. We obtained access to Prof. Zachary Cordero's composites oven in his lab for this purpose. Post processing would be done to create holes for mounting these to the mission package tube.
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For the Medusa conceptual design review (CDR), the development of the aeroshells shifted to be more the responsibility of the aerodynamics subteam. Design changes were made so that the shells could be more easily fabricated and design details were further developed. Thermal simulations were attempted, but unsuccessful. The slides are attached here.
This simplified design involves two plies of carbon fiber over a 3D printed frame, with heat-resistant paint applied to the exterior as an ablative coating.
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After the cancellation of Project Medusa, the remaining members of the Medusa Aerodynamics subteam (Vealy Lai '26, Conrad M Casebolt '26, Ethan Wong '26) were absorbed into Project Prometheus and turned their primary focus to developing the aeroshells. With renewed efforts, a clearer design process was defined for this component.the aeroshells. With renewed efforts, a clearer design process was defined for this component.
Design Goals:
The new aeroshells should be able to protect the flight cameras from physical and thermal damage from the moment the rocket is powered on to the moment it hits the ground. This means that the interior of the aeroshells should stay below 50°C at all times, even with ambient temperatures as high as 100°F, stagnation temperatures up to 1000°F, and heat emitted from the operating camera itself. The aeroshells need to keep themselves and the cameras securely fixed to the rocket, so they and their connectors must be able to withstand all in-flight forces with a safety factor of at least 1.5. The shell must also provide a clear and sufficiently large viewing window so that all motor ignition, stage separation, and deployment events are visible in the camera recordings.
Design Requirements:Goals [TBD, KEEP WRITING HERE - VL 5/5/24
The aeroshells, of which there are four (4), shall be mounted to the outside of the mission package tube on each stage. Each aeroshell must contain and protect a camera which records the flight of the rocket. The upward facing aeroshells shall capture the deployments of the recovery systems. The downward facing aeroshells shall capture the ignitions and staging.
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The camera must not overheat inside the aeroshell when left on (includes pad time and flight time).
In-flight forces were determined to be negligible compared to the strength of the shell materials and connectors.
Aerodynamic Design
The aeroshell is streamlined on both ends. Its diameter is only minimally larger than the Foxeer Camera which it houses.
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