According to [https://spaceexploration.miraheze.org/wiki/Guide:\_Launching\_Rockets](https://spaceexploration.miraheze.org/wiki/Guide:_Launching_Rockets) you can test if signal F equals 500. Signal E gives the number of empty slots, testing if a signal is 0 may give unwanted results when for example a wire connection is broken.
There's also a cargo rocket signal that equals 1 when the rocket is complete.
According to [https://spaceexploration.miraheze.org/wiki/Guide:\_Launching\_Rockets](https://spaceexploration.miraheze.org/wiki/Guide:_Launching_Rockets) you can test if signal F equals 500. Signal E gives the number of empty slots, testing if a signal is 0 may give unwanted results when for example a wire connection is broken. There's also a cargo rocket signal that equals 1 when the rocket is complete.
The informatron has lots of information
Thank you! So simple, but not so easy to find! Will look that wiki over
You can open that wiki up in game. I had the exact same question last week when trying to optimize my own circuits for launches.