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Ground testing has shown that the cup does not buckle under normal piston operating loads, even those as high as 3500 lbs (an order of magnitude greater than normal operating loads) as we predict we saw in Ground Test November 10, 2017 Hermes Ground Test.
v2.0: Hermes Dimensions
Development
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| Thickness (t) | 0.125" |
|---|---|
| Inner Radius (ri) | 2.675" |
| Outer Radius (ro) | 2.8" |
| Length | 15" |
| Useable Packing Volume | ~340 in3 |
Mass Saving Cut Options
We ultimately chose to pursue the column design due largely to the simplicity of fabrication and decreased likelihood of line entrapment.
Optimized Cup Cuts for Column Design
Here are the spreadsheet calculations for the optimized cup cuts given the column design: Calculations for CADs (Cup and Diaphragm).xlsx
Ultimately, to increase the safety factor, we chose to increase reduce the cut width by a factor of 2. Simulation results are below.
Flight 1
Due to manufacturing constraints, only 4 of the mass saving cuts were implemented. This design did not fair well in shipping, future teams are suggested to place the diaphragm and a similar feature in the cup for travel.
