[weird-eye-issue]

Why is the capsule considered the only critical safety component?

If everything else fails wouldn't it just fall to the bottom of the ocean? Even if it can survive that depth that only sounds good on paper. Nobody could get to you.

[lb1lf]

The capsule itself is positively buoyant.

As long as it can jettison the ballast (and is not tangled up in something on the seabed, say, the Titanic), it will come to the surface.

[ceejayoz]

And the ballast is held on via electromagnets. Lose (or deliberately cut) power, you're going up.

[tristanb]

I don't think it is on this "sub". I believe I read they used a material that degraded over time in water.

[barelyauser]

Isn't this like a huge waste of energy?

[andruby]

I don't think weight is a huge issue for submarines (unlike say airplanes), so taking a few batteries along should be fine.

(I don't know anything about subs) you could even store a few batteries in the ballast.

[ceejayoz]

Between "waste some power on a magnet" and "we're permanently stuck on the bottom of the ocean about to run out of air", I know which one I'd pick.

[HeyLaughingBoy]

There's a difference between a "waste of energy" and a failsafe emergency system that happens to use a lot of energy.

[adql]

It's nothing compared to amount of power to the engines, you don't need kilowatts to "just" hold a ballast

[nvusuvu]

Clear tradeoff for safety.

[RC_ITR]

Sure, but they can also incorrectly steer themselves into wreckage that causes them to be stuck...

[weird-eye-issue]

Right, so you need the ballast. Which is not inherently part of the capsule. Which proves my point.

[lb1lf]

Well, you need to be able to change the weight of the capsule somehow, otherwise you'd be stuck bobbing at the surface. (Or at the seabed).

The puzzling bit, from what I have gathered, is that the ballast is not fail safe.

[Out_of_Characte]

Because an implosion is a single point of failure leading to instant death. Anything else can be salvaged by staying calm and using one of multiple ways to resurface.

[cheekibreeki2]

Subs will always have 1000 ways to kill you and most of them are catastrophic. You're pretty much boned if anything goes wrong especially with so few crew members, lack of compartments, backup propulsion, etc.

[weird-eye-issue]

Really? Anything else can just be magically salvaged? I'm not sure there is that much room for error 2 miles below the surface

[RC_ITR]

They are visiting a debris field. There is a much more than zero chance they are stuck on something.