The launch codes are necessary to access the elevator to the spaceship's landing pad. They are acquired from Hornfels, located up at the Observatory.
After the first death, the player retains knowledge of the codes. The first time the player dies in the loop, Slate will remind the player to the codes, then assume they have been inhaling too many fumes when the player says they already have them.
The codes, when translated from morse code spell M D N .