beyond a certain depth, if a submersible fails, you just die
it's like a space ship in that regard
worse than a helicopter imo
at least there's a tiny chance you land on something soft and don't get bisected by debris
but if your sub goes bad, you are definitely getting the bends if you don't just get crushed/drown
It's way, way worse than a spaceship. On a spaceship you've generally got enough water and oxygen via the fuel cells to last a week or two, you'll probably die of overheating or CO2 (CO2 is also the issue with a large sub disaster like the Kursk). On a sub like this...you'll freeze or die of lack of O2.
Also, loss of pressure on a spaceship is bad but survivable. 1 atm to zero. The Byford Dolphin was 450 meters down and that was 9 atm to zero. The Titanic is 3800 meters down (0 to 380 atm, the other way round, explosive compression.).
If Apollo 13 had happened on a sub it's arguable there'd not be enough left of the craft to show up on sonar.
Wait what difference are you trying to describe between lack of O2 and overabundance of CO2? Both of these go hand in hand in these situations right? There isn't a CO2 scrubber on a submarine that doesn't work either. That seems like a terrible way to go because CO2 hurts when it's built up in your blood
As awesome as it was in concept, that thing was a safety nightmare from the very beginning. With every other manned spacecraft if something goes wrong during launch you can blast off and land the capsule safely in the ocean, but with the shuttle there were large portions of the ascent and descent profiles where, if something went wrong, you were going too fast to turn around but too slow to make it to space so you were just hosed.