ripcord

noun

1. a cord on a parachute that, when pulled, opens the parachute for descent.
2. a cord fastened in the bag of a passenger balloon or dirigible so that a sharp pull upon it will rip or open the bag and let the gas escape, causing the balloon to descend rapidly.

noun

1. a cord that when pulled opens a parachute from its pack
2. a cord on the gas bag of a balloon that when pulled opens a panel, enabling gas to escape and the balloon to descend