First, neither Buck Rogers nor Flash Gordon were naval aviators. Buck Rogers was in the Army Air Service and Flash Gordon was a polo player Yale graduate.
Second, I would offer up Major Matt Mason
Third the US army has over 300 vessles and they have no problem with rank structure
Fourth, Even the Air Force has boaty things.
Fifth, since the US does not have any spacecraft assigned to Space Force, nor will there be in the foreseeable future, the question on what to call the boss is moot.