Blog #4

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 Over the work period of Nov. 12 - Nov. 26, progress has been made for heat transfer and force calculations, and the analysis is complete. The team is confident that the final design will sustain an internal temperature within the desired range of 32°F to 77°F for 40 minutes, and withstand the forces from the rocket’s flight. Using the temperature equation found from the previous analysis, the team was able to calculate the total energy from heat transfer to the design after 40 minutes and compared it to the energy required to melt the phase change material. Figure 1 shows the equations used to calculate the energy. The projected energy to be transferred into the case was found to be 3581 kJ/m^2 while the energy required to melt the PCM is 3690 kJ/m^2. If perfectly designed, this would mean the internal temperature of the insulating case will remain at a constant 35°F for 40 minutes. The 3D model for the final design is complete and was used for FEA on the forces experienced during flight. A static finite element analysis was used to prove that the camera cooling system (CCS) is strong enough to withstand the forces from flight. The ends of each of the four threaded rods were assumed to be fixed while the force was assumed to be distributed across the thickness of each of the eight washers. Figure 2 displays the results of said analysis. From the FEA results and Space City Rocketry’s usage of the same rod design for past rockets, the team is confident the CCS will be secure throughout flight. Team 7 has also been in contact with Alex Blick during this work period for consultation on how to manufacture the final design.

Figure 1: Equations for calculating energy

Figure 2: Static FEA of CCS Assembly

Team 7’s final camera cooling system design consists of a square aluminum housing lined with an interior layer of aerogel. This aerogel layer will act to insulate the GoPro Hero 5 Session contained within the housing from external heat transfer. The GoPro will sit on the base of the housing pointed downwards through a layer of clear acrylic. This base will be removable from the rest of the housing and secured in place with threaded rods at each corner. This allows for the camera to be replaced as needed and will enable the interior space, between the aerogel lining and the camera, to be filled with a gel PCM. The PCM will act to absorb the internal heat generated by the camera during operation and will keep the temperature of the camera near that of the PCM (roughly 35°F) until all of the PCM has changed state. This will act to keep the camera cooler for a longer period of time while contained within the device. Additionally, a layer of Gore Sealant will be employed around the camera above the removable base to provide an airtight seal. The heat transfer calculations described above show that the energy required to completely melt the PCM within the case will not be reached in 40 minutes.

Shown below, Figure 3 displays an animation of the final assembly of Team 7’s Camera Cooling System (CCS). The design consists of two ¼” lids made of aluminum. The bottom lid will be welded shut to the main body tube, also made of aluminum. The main body tube will be 5.5” in length. The top lid will provide an airtight seal with the use of GORE sealant, an aerospace-grade adhesive material. The GoPro will be positioned such that its lens is looking through an acrylic section of the bottom lid, measuring 1.5” x 1.5”. Threaded rods will be utilized to best constrain the CCS to Space City Rocketry’s payload housing. This is a design that has been utilized in all past competition rockets and is flight proven. In order to fix the threaded rods to the CCS, ¼-20 nuts will be used alongside ¼” washers. 

 

Figure 3: Assembly of CCS

Looking forward, Team 7 plans to use the time allotted for winter break (December 14 through January 17) to continue designing detailed components of the CCS and receive input from the team's machinist. Team 7 also plans to continue sourcing raw materials to prepare for execution. The current design needs to factor in a case for the gel PCM as well as grooves to contain the camera and prevent any movement in the recording. The case for the gel PCM must be tightly sealed to prevent leakage, but needs to have high thermal conductivity so that it can absorb internal heat. Grooves or some other design to hold down the GoPro will be located internally at the base of the design. After designing the two mechanisms, Team 7 will update Alex Blick, the team advisor who will be aiding in the manufacturing process. Alex Blick and Iron Ring Technologies will be able to provide Team 7 with feedback and ideas for the solution, as well as provide input on how the machinist will be able to construct the design. After winter is over, Team 7 will finalize sourcing materials and components, as well as purchase the items. Milestone 3, completing and manufacturing the final design, will be completed by March 26th, so preparing for this during winter will put the team ahead of schedule. 

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