Watching a few episodes of the new Mars-mission show Away only reinforces for me why future interplanetary missions need to have submariners on board, not necessarily pilots. https://www.latimes.com/entertainment-arts/tv/story/2020-09-04/netflix-away-space-travel-mars-explainer

Away ship crew: hey look, a flammable chemical is leaking out, how about I, a hand-selected professional trained for years, take an action that accidentally sets it on fire, while everyone else mills around and afterward no one can agree on what actually happened.

Submarine crew: random 19 yr old E-3 on board for 6 mos smells something funny, knows exactly the right thing to say on an emergency reporting system to warn the whole crew. Another 22-yr old electrician knows by memory where to go to turn power off...

...2 hose teams fully outfitted in firefighting gear are in place on two different levels within in minutes, with thermal imaging. 30 minutes later the entire event has been debriefed and the crew provided lessons learned for next time.

Away ship crew: appears to spend half of their time on their space-iPhones, devoting most of their attention on the trip to Mars obsessing over personal issues back home.

Submarine crew: woah, I can get 3-day old email (which will never contain bad news) while I’m out? Nice!

Submarine crew, w/in minutes of learning there is even the hint of a problem with the ship’s freshwater supply: turns off showers, laundry; shifts to paper plates, minimizes propulsion plant water consumption, immediately starts up secondary water maker, starts planning repairs.

Away spaceship crew:

Disclaimer: this is tongue in cheek, understand that these are TV astronauts, and this is fiction.

My point about submariners stands. Why not have a crew w/ marrow-deep expertise on complex propulsion, comms, and nav systems; radiation and atmosphere control, firefighting, etc.?