Here’s a pet peeve of mine about a communications situation that comes up sometimes in certain kinds of science fiction.
The situation: Some characters are on a spaceship. They need to communicate with other characters on another spaceship nearby, but the radio isn’t working.
In most versions of this situation that I encounter, the two ships are in visual range of each other. And the ship with the broken radio has a working propulsion system that gives off visible light.
And so it seems obvious to me that they can communicate in Morse Code (or a similar system) by turning the drive on and off.
Related options include:
- Alternately cover and reveal windows to send dots and dashes.
- Go outside the ship in a spacesuit and wave your arms in Semaphore.
- Throw small objects at the other ship, in dot/dash intervals.
- Wobble your ship back and forth (or spin it clockwise and anticlockwise) to send dots and dashes.
- If the other ship has life-sign-detecting technology, then run fore and aft in your ship to send dots and dashes.
- Paint words on your ship’s hull.
- Cross over to the other ship using a shuttle or jetpack.
…And so on. If people on the other ship can see or otherwise detect something about your ship, then there are lots of ways to communicate, using binary patterns of some sort (Morse Code, ASCII, Unicode, whatever) or other visual mechanisms. Radio is a useful communications medium, but it’s not the only one.