wiki/ Lv2UmbilicalCord

LV2 Umbilical Cord

Overview: The umbilical cord attaches the rocket to the launch tower electronics box. The cord has only two wires; usually it acts as shore power (providing the rocket with power while on the launch tower) but right before launch the umbilical switches functions and is used to let the rocket control a launch interlock relay (the "rocketready" relay).

This way if something goes wrong onbaord the rocket, the flight computer can abort the launch without relying on the wireless communications being up and running.

The switch of functions and the rocketready relay are on the rocket ready relay (RRR) board.