DISCLAIMER: some mod silos may not work. Only somewhat tested Lignumis' silo.

Concerning the launch_wait_time and rocket_rising_delay properties:

The minimum value is 1 and 255 seems to disable launches (they take forever).

The API docs do not specify the minimum value for these properties, but a value of 0, which should disable the wait times,
causes a failure to load the game. I assume Wube wanted to add these delays so the engine could keep up with dozens of rockets launching at a time.