Porosity

Definitions

• A condition of the envelope fabric that allows hot air to escape. Excessive porosity requires increased fuel use and results in higher envelope temperatures.
• The ratio of void or interstitial area to total area of a cloth expressed in percent. The ratio of open space to covered area of a drag surface. Used for ring slot, ribbon, ring sail, and rotafoil canopies. Not to be confused with permeability.

References

• Balloon Flying Handbook, Federal Aviation Administration, 2024
• Parachute Rigger Handbook, Federal Aviation Administration, 2015