Firstly FCP is not a good audio tool. If you have no other option, use Sound Track Pro which has better EQ and dynamics.
The five attribute that you need are EQ, dynamics compression, distortion, phasing, noise.
Firstly EQ the sound to roll off a lot of low frequencies. Secondly parametric boost around 1-2 Khz. Roll off all hi frequencies above about 6Khz.
Compress the dynamics savagely. Distort the signal. This can be done with various overdrive plugins. If you have access to a VST capable device, there are free plugins like Ruby Tube that can distort plus something that can phase or flange the sound. Finally you need crackle and noise as a background to help sell the effect.
If it is astronaut, then the classic NASA beep can be probably found online. Listen here to get an idea of what the elements are –
https://history.nasa.gov/alsj/a11/video11.html#Step