This is a good point.
However, it's probably worth pointing out that in the past few decades -- at least here in the PNW -- carbon fiber availability to the hobbiest and small producer has been spotty.
I'd refer to Boeing and being the same 787 carbon fiber for my personal projects, but that's just because they're made from Boeing offcuts donated to a local University. At the time (ca 2006), even bare weave was hard to obtain from private suppliers.
Its feasible that Rush may have had help from Boeing sourcing his material, which puts comments like that in a different light.
6061 is more commonly used in automotives than in aircraft.
- “2024 aluminium alloy is an aluminium alloy, with copper as the primary alloying element. It is used in applications requiring high strength to weight ratio, as well as good fatigue resistance. It is weldable only through friction welding, and has average machinability.
- “7075 aluminium alloy is an aluminium alloy with zinc as the primary alloying element. It has excellent mechanical properties and exhibits good ductility, high strength, toughness, and good resistance to fatigue. It is more susceptible to embrittlement than many other aluminium alloys because of microsegregation, but has significantly better corrosion resistance than the alloys from the 2000 series.”
- “6061 is a precipitation-hardened aluminium alloy, containing magnesium and silicon as its major alloying elements. It has good mechanical properties, exhibits good weldability, and is very commonly extruded. It is one of the most common alloys of aluminium for general-purpose us.”
Materials science is a fascinating field.
It means you're using a material that's been vetted over decades in life-critical applications in harsh conditions by expert engineers all over the world. Aerospace aluminums today are derived from Japanese alloys invented in WW2 and were a major innovation in metal aircraft. It's much more expensive than steel, but we use it because of favorable characteristics. Here's an overview of different aluminums and where they're used: https://www.aircraftaluminium.com/blog
That said, I think there are times when it does mean something. I believe military grade/milspec chips/ICs are often engineered to be more resilient to environmental factors like heat and vibration, interference, etc. If I'm wrong about that, I suspect it won't be long before we learn if I'm right.
It did not guarantee anything outside of that. Soundness of design and ensuring inputs and environmental factors conformed to the spec was up to the engineers.
The problem, it is a military specification so the public may not be able get access to it.
If I start using a screwdriver to hammer in nails, it doesn't matter how many expert engineers use screwdrivers. I'm using it for a purpose it is unfit for.
Just because it's aircraft grade doesn't mean that it is (or isn't) suitable for building a submarine.
Why use novel vessels when tried and true work. Why did they have to try a carbon-fiber wrapped vessel? The bathysphere went all the way down to the Marianas trench --many decades ago. Why try something new in unforgiving environments?
Why fire an engineer after he started raising questions about safety?
It seems like there was a bit of a cavalier attitude that cost five people their lives.
- "Oxygen was supplied from high-pressure cylinders carried inside the sphere, while pans of soda lime [hn: sodium hydroxide?] and calcium chloride were mounted inside the sphere's walls to absorb exhaled CO2 and moisture.[6] Air was to be circulated past these trays by the Bathysphere's occupants using palm-leaf fans.[2]"
- "Suddenly, without the slightest warning, the bolt was torn from our hands, and the mass of heavy metal shot across the deck like the shell from a gun. The trajectory was almost straight, and the brass bolt hurtled into the steel winch thirty feet [9.1 m] away across the deck and sheared a half-inch [13 mm] notch gouged out by the harder metal. This was followed by a solid cylinder of water, which slackened after a while into a cataract, pouring out the hole in the door, some air mingled with the water, looking like hot steam, instead of compressed air shooting through ice-cold water.[6]"
- "The ocean during this dive was rougher than it had been during any of their previous dives, and as the Freedom rocked on the surface, its motion was transmitted down the steel cable, causing the Bathysphere to swing from side to side like a pendulum. As the Bathysphere descended, Barton succumbed to seasickness and vomited inside it. However, the first half of the radio transmission had already been broadcast, and neither Beebe nor Barton wished to cancel its second half, so they continued their descent.[5] ... the Bathysphere was still rocking wildly and Beebe and Barton were both bruised and bleeding from being knocked about inside it."
- "During their first test dive, they demanded to be pulled up after descending only four feet (1.2 m) because the sphere had begun to leak; they soon discovered this was because Tee-Van had neglected to fasten all of the bolts that hold the hatch shut.[2] Another problem occurred on their second test dive, during which they discovered that the lower end of the rubber hose holding the power cable and phone line had begun to deteriorate, and they spent the rest of the day reversing the hose's direction so that the end which was deteriorating would be the end above the water.[5]"
Very poor taste to say this now.
"If you're not breaking things, you're not innovating. If you're operating in a known environment as most submersible manufacturers do, they don't break things." (8:49)
"Our rule is we risk capital, we don't risk people." (9:56)
"We used the same prepreg that's used on the 787." (11:15)
And my favorite: "When you're outside the box, it's really hard to tell how far outside the box you really are." (8:30) He does seem to be far outside the box now.
But the most significant quote IMHO is the one about "the same prepreg that's used on the 787". Like they often tell you that phone holders for bikes are made of "aircraft-grade aluminium" (which usually means it's 6061, the most common alloy). It's a strong indication of bullshit -- name dropping that doesn't have anything to do with the subject matter.
In the rest of the presentation he seems nice enough, and truly passionate about deep sea exploration. So maybe he was a cool guy, I don't know. But in the end it's his hubris that killed him and his clients.