Team Design Projects
Hermes Disk -Gap Band Gap Drogue
Materials
Porosity
There are two types of porosity related to parachutes: fabric and geometric porosity. Fabric porosity relates to the inherent permeability of the parachute material. Geometric porosity relates to what percent of the parachute's canopy is "cut out." The equivalent metric between fabric and geometric porosity measures is 27.4 ft3/ft2/min, at 1/2-inch water pressure ≈ 1% geometric porosity (Knacke, 5-71).
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| Spec ID | Title |
|---|---|
| MIl-C-7020 | Cloth, Parachute, Nylon |
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Procedures
Shroud Lines
From Knacke (6-84), "all lines and tapes are [traditionally] measured under a preload. A preload of about 1% of the ultimate material strength is required to align all fibers in the woven or braided material before the individual fibers are stretched." Furthermore, "[it] is practical to let all fabrics relax for a short period after rewinding from the storage spool before measuring the material."
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