After the Titan tragedy, Russ Swan calls for more science, less reckless conjecture.
The Titan episode revealed that nowadays, for some, it is never ‘too soon’ to make jokes in bad taste out of other people’s tragedies.
The more I read about this vessel, and the people behind it, the more the whole thing seems as ill-informed as some of the coverage in both mainstream and social media. From animations of what the implosion might have looked like to poorly-informed pundits making armchair adjudications, the story has seen more speculation than substance.
In particular, the pronunciations of a rent-a-quote expert on US news who described how the hull would have been crushed ‘like a soda can’. My fault for expecting any meaningful content.
For my part, my first job (between school and college) was in a materials testing laboratory, and obviously this makes me a world expert and fully qualified to pontificate.
The main part of the hull was thick carbon fibre, which certainly doesn’t crumple like thin aluminium. Among the many disturbing reports that began to circulate was even the suggestion that the material used was past its use-by date.
The stress in a composite is carried largely by the resin matrix rather than the fibre filaments
Carbon fibre is a wonder material of our age, famously strong and lightweight and the mainstay of racing vehicles of all kinds. It’s practically indestructible, isn’t it?
I recall that it was the carbon/carbon leading edge panels on the wings of the space shuttle Columbia that shattered, after being struck by some foam insulation from the external fuel tank.
In the aftermath of that disaster, it was almost the last thing to be tested because it was thought impossible for it to fail. Huh.
That proved about as accurate as the ‘unsinkable’ tag applied to Titanic, eleventy-one years ago, until the moment it actually sank.
Speaking of tags, the name Titan demonstrates some of that same hubris. This tiny and, as events have shown, fragile vehicle had none of the qualities of a Greek deity. The cause of the failure will eventually be deduced by people cleverer than me, and lessons will be available for any that choose to learn them. Perhaps the carbon delaminated, or perhaps it was the great acrylic window that shattered.
Another possibility is failure at the interface between carbon and the titanium end caps – dissimilar materials behaving in dissimilar ways under great load.
The sub had completed previous dives, not without incident but also without killing anyone, so the finger of suspicion must point to a fatigue failure.
What hasn’t been discussed much is that composite materials are strong in tension, not so much in compression. Pressure vessels are mostly designed to contain high pressures, less often to hold high pressures out. In compression, the stress in a composite is carried largely by the resin matrix rather than the fibre filaments.
How strong is a piece of string? Quite strong when pulled, not so much when pushed.
- In late June, the US and Canadian authorities launched an investigation into the Titan incident, together with assistance from the UK Marine Accident Investigation Branch and its French counterpart the BEAmer. Their report will be submitted to the International Maritime Organisation.