The big one is designing the sub to travel to 95% of the expected maximum depth, leaving a 5% margin of safety. I was taught to aim for a margin of safety of (I think it was) 50% back in the day. Operating so close to the safe limit for the sub is appalling. That doesn't even include all the other warning signs about the design that were brought up.
The missing beacon on the sub, in case of loss of radio contact, is another standout. No consideration given for loss of power or anything. Consideration of contingency plans is so important.
A minor one that is really indicative of the overall attitude is drilling screws into the carbon fiber hull, possibly exposing the hull to stress fractures from both the screws and the constant weight of holding a monitor. It's... just a silly thing that could have been avoided. I'm not saying those screws are why it failed, but if you can use an adhesive to hold your monitor in place, wouldn't you rather do that then by drilling directly into the hull keeping ~100 atm of ocean out of your face?
It just makes me so sad for so many reasons. It definitely could have been avoided...
Wouldn't a a 5% margin of safety mean the sub was designed to survive at 105% of the trip's expected maximum depth? 95% sounds like the opposite of a margin of safety.
Sorry, but this does not follow. I believe you are confused about the fact that the Titan was designed to go down to 4,000 meters, and the Titanic lays at 3,840 meters.
And because 3,840 is so close to 4,000 you believe they had no safety margin. Do I understand you well?
But the thing is when you design a submarine which can go down to 4,000m you don’t design a hull which instantly implodes at that precise depth. You add a safety margin on top of your design requirement and that is what you design for. And then using calculations, simulations and tests you convince yourself that your submersible is still safe even at that extra safety padded depth.
I’m not saying that this is how they designed it. After all it seems their engineering culture was deficient in several ways. But you simply can’t conclude that they had no safety margin because they dove close to their design limit.
Some ballpark typical numbers for safety factor: spacecraft ~1.2, airplanes ~1.5, automobiles ~3
How do you know they were operating close to their safety margin?
My understanding of safety margins, as I was taught, is that one should design such that you have a safety margin of 1.5x the intended use case. In other words, for 3800m expected frequent usage, it should be able to reach a depth of 5700m.
Alvin, for example, can reach a depth of 6500m.
But you’re right, we don’t know what that 4000m means, really. I’m just assuming it means safe depth without damage.