Webbing lengths must be selected carefully to satisfy several constraints such that parachutes enter the airstream (and do not remain confined within the vehicle). For Project Hermes, the webbing constraints and resulting calculations are summarized below:
...
| Webbing Length Variable | Length (in) | Factor of Safety | Reasoning |
|---|---|---|---|
| WA,H | 295.4 | 4 | The absolute minimum factor of safety required for the constraints is a little above 3.6 so that was rounded up to 4. |
| WA,E,F,G | 189.8 | 1 | The 5DD in the constraint equation was determined arbitrarily so the factor of safety is redundant. |
| WA,B | 473.8 | 1 | The 4DM in the constraint equation was determined arbitrarily so the factor of safety is redundant. |
| WA,E,F | 17.8 | 1 | A factor of safety is not desirable here because the exact length is desired. |
| WC,D | 270 | 10 | In subsonic flow, upstream disturbances could disrupt the airflow using minimal length on this webbing. |
| WC,D,F | 12 | 1 | There's no clear constraint on this length, so an arbitrary small length was chosen. |
Resources
T.W. Knacke, Parachute Recovery Systems: Design Manual