New exterior flight camera housings (known here as "aeroshells") were designed and fabricated for projects Medusa and Prometheus (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, as well as eliminating the need for separate upward- and downward-facing shells. 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.
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- Background
- Research and Preliminary Designs
- Design Development
- PMTS Design
- Overview
- Manufacturing Process
- Results
- Future Plans
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:
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- Sand down the inside of the mold to get rid of any burrs and smooth out surfaces. A few minutes of sanding will suffice.
- Remove all the dust from the inside by washing and drying or wiping with acetone.
- Rub down the inside and top planar surface of the mold with wax until glossy and smooth. A pea-sized portion of wax should be sufficient.
- The wax is toxic if ingested, so wash your hands after use.
- Put gloves on (and optionally a mask) and move to a well-ventilated area, preferably outside. Apply a coat of PVA release film by gently rubbing it in a layer over the wax. A bottle cap of PVA should suffice.
- Recommended to do this outside and stand upwind because plastic fumes are not good to breathe in.
- Visually, the layer should appear shiny.
- Optionally: If you want multiple coats, wait until the first coat dries (drying time listed on the bottle).
Vacuum Bag Preparation Steps **@Vealy can you describe this process?**Steps
Materials: Vacuum bag plastic, vacuum bag double-sided tape *Vealy what are these actually called?*
- Vacuum Bag Prep (with pleats)
- Vacuum Pump Tube Prep
- Leaving one side open
Epoxy & Fiber Glass Layups
bagging film, vacuum seal tape
- Cut out some vacuum bagging film the size of your part(s), leaving generous margins.
- If a clean glass surface is available, apply mold release to it and then use the glass as the bottom side of the bag.
- Doing this can help eliminate the sideways compression that can be introduced by a full bag. This can affect the quality of some layups, depending on how the compression should (and shouldn't) be applied.
- Otherwise, cut a big piece of film and fold it in half to form the two sides of the bag.
- Use vacuum seal tape to seal two sides of the bag together. Make sure the seal is smooth and free of wrinkles and leaks. The remaining side will be sealed once the part is inside.
- If the part to be vacuumed is not flat, make the top layer of the bag longer and fold some pleats into it before sealing. This will ensure the film has enough slack to conform to the geometry of the part.
- Look up video demonstrations of this! There are many techniques for good vacuum bag preparation that can be learned that way.
- If a thru-hole connector is available for the vacuum pump, cut a hole in the top of the bag for it. Attach the pump that way.
- Otherwise, attach a hose to the pump and tape some breather around the end to prevent epoxy from getting inside (just in case). Use vacuum seal tape to seal the hose into one side of the bag.
- Make sure the hose is not blocked when the bag is fully sealed.
- If a clean glass surface is available, apply mold release to it and then use the glass as the bottom side of the bag.
- Cut out some vacuum bagging film the size of your part(s), leaving generous margins.
Epoxy & Fiber Glass Layups
Do in well-ventilated area.
Materials: Vacuum Pump, thin-woven fiber glass sheet, Materials: Vacuum Pump, thin-woven fiber glass sheet, thick-woven fiber glass sheet, 2-part Epoxy Resin, peel ply, breather, gloves, mask (optional)/respirator
- Cut one rectangle of thin-woven and two rectangles of regular-woven fiber glass (per Aeroshell) in a sufficient size to fit inside the negative mold cavity.
- Cut a layer of peel ply slightly larger than the fiber glass rectangles.
- Cut a rectangular layer of breather roughly equal in size to the upper planar face of the negative mold.
- Put on gloves.
- the fiber glass rectangles.
- Cut a rectangular layer of breather roughly equal in size to the upper planar face of the negative mold.
- Put on gloves.
- Weigh the fiberglass fabric on a scale. Measure out an amount of epoxy and hardener in the appropriate mixing ratio, with a total weight equal to that of the fabric to be laminated.
- West Systems 105 Epoxy and 206 (slow) Hardener were used.
- When ready, slowly mix the resin and hardener together until uniform. Try to avoid introducing bubbles.
- Be conscious of time. This epoxy has a pot life of about half an hour, meaning that at that point it can become too viscous to apply. Note that working time is a different specification that indicates when the epoxy will start curing, typically well past its pot life.
- It can help to mix batches of epoxy and layup one aeroshell at a time, though you will want to vacuum bag them before the epoxy begins curing. Having multiple people working in parallel is ideal
- Once they are mixed, there is a limited time window in which this process can be successfully completed. We have found that after about half of the listed epoxy working time, it becomes stickier and difficult to work with
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- Be conscious of time. This epoxy has a pot life of about half an hour, meaning that at that point it can become too viscous to apply. Note that working time is a different specification that indicates when the epoxy will start curing, typically well past its pot life.
- Coat fully the inside of the negative mold with a layer of epoxy, using about 1/3 of the total epoxy allotted for one Aeroshell.
- Lay the thin-woven layer of fiber glass into the negative mold cavity. Gently press/move the layer until it contacts the surface of the cavity and nearly every point.
- This process is difficult and requires practice. Tips:
- Start from the deepest point in the mold.
- Provide excess material at first and flatten it out later.
- Don't overstretch the material.
- Use nails to lightly fit the sheet into sharp corners.
- This process is difficult and requires practice. Tips:
- Repeat the above process two more times but using the regular-woven sheets of fiber glass cut out earlier and 1/3 of the remaining epoxy each time.
- Press the precut sheet of peel ply into the mold covering all of the fiber glass.
- Place the breather on top of everything else.
- When this is done proceed quickly to the following section.
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- Convert the CAD file into a .STL file. Material as PLA and 0.2mm thickness are sufficient.
- When slicing the file, change the following settings:
- The side which touches the MPT should be normal to the print bed (even though it is not flat).
- Infill should be >70%
- Supports set to ON EVERYWHERE.
- Brim set to ON.
- Make sure to remove all the excess material from the screw holes and supports after printing.
Cutting the Aeroshell to the Proper Size *Conrad return to this 5/16/2024
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- set to ON EVERYWHERE.
- Brim set to ON.
- Make sure to remove all the excess material from the screw holes and supports after printing.
Cutting the Aeroshell to the Proper Size
Materials: Skeleton, four (4) M2 screws, Dremel with cutting and sanding wheels
- Place the fiberglass shells over the 3D printed part.
- Mark the locations of the screw holes and drill through the fiberglass.
- Screw the fiberglass onto the 3D printed part, then and trace around the edge and trim it to size with a Dremel cutting wheel. A sanding wheel can be used to even out a rough cut.
- Note that the fiberglass can deform slightly after being screwed in, so the edge may be uneven if the shell is trimmed based on how it sits without the screws it.
- Stay safe! Wear proper PPE to avoid breathing in the dust.
Glass Pane
Materials: 1x1" square of heat resistant glass, marker, glass scorer, glass-breaking pliers, sandpaper
- Break the 1x1" square in half into two pieces.
- Use a marker to draw a line divided the glass into two equal rectangles. Score along the midline on both sides of the glass.
- Carefully break the glass in two using the glass breaking pliers. A useful technique is to hang the excess glass corner over an edge and repeatedly hit (rather softly) the overhanging piece using the glass-breaking pliers.
- In theory, each glass panel should yield two useful glass pieces.
- Cut the glass into the correct shape to fit into the aeroshell.
- Use a marker and ruler to trace the correct five-sided shape on the 0.5x1" glass panel
- Score the glass along the lines using a glass scorer on both sides.
- Carefully break off the excess glass using the glass-breaking pliers.
- Sand down the edges until the desired dimensions are achieved.
- Caution: Don't scratch up the glass surface through which the camera is viewing.
- Break the 1x1" square in half into two pieces.
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- Mix some epoxy and apply it to the edges of the aeroshell where the glass should sit. Lay the glass down flat, and let dry.
Results
These Aeroshells flew on the Prometheus test flight in April 2024. All four remained intact through subsonic flight speeds and an estimated apogee of 5,000 feet (**double check this CC 5/16/2024). Only one Aeroshell carried a live camera, and the footage captured was deemed sufficient documentation which captured valuable footage of the booster recovery system deployment. The camera did not overheat during flight or on the pad.
A whistling sound was recorded on the camera audio as the rocket ascended. It is unknown whether this sound is produced by air flowing past the aeroshell or another part of the rocket.
Integration
The two-piece approach necessitates the following integration steps:
- Mount the skeleton to the mission package tube using four (4) M3 or 1/8" screws and corresponding nuts, with the nuts inside **or outside? CC 5/16/2024** the MPT.
- Attach the camera to the skeleton and connect the camera to the avionics bay.
- Mount the shell to the skeleton using four (4) M2 screws.
Future Plans
Future Design Improvement Ideas (as of May 2024)
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- The skeleton could be printed in two parts to get rid of the roughness on the face bordering the MPT.
- ** Link to AUR Aeroshell page