Scattered across the ship, there are 4 radios that can be activated that don't play a message from Dr. Richtofen, these are where they are and the order to be pressed:
1st Radio: In the room below the power room, on top of file cabinets to the right when coming in from the Flinger side.
2nd radio: In the Stamin-Up room, as you are entering, turn right and it's on a barrel in the corner.
3rd radio: Go the bottom of the zipline that is on the ship, there should be a large cargo container a little bit ahead of you. At the bottom of the cargo container on the right, the radio will be in a vertical position.
4th radio: Underneath the stairs from PhD Flopper to the characters.
After they have been pressed, a yellow flashing light should appear in the sky.