/sci/ - Science & Math

>Engineers made the pilot’s chamber spherical because the shape can be both strong and light. They also made the steel 2.5 inches (6.4 centimeters) thick to withstand the crushing pressure of the deep. If they had made the chamber a cylinder, by comparison, the hull would have needed to have been three times as thick to stand up to the pressure. The hull, complete with its hatch and viewport, was tested twice in a pressure chamber at Pennsylvania State University to an equivalent full-ocean-depth pressure of 16,500 pounds per square inch (1,138 bars). It passed both tests. Twenty-two strain gauges attached to the sphere gave data that indicated the sphere could withstand up to 140 percent of the test pressure without buckling.

>When designing the sub, James Cameron and Ron Allum kept the sphere’s internal diameter to 43 inches (109 centimeters) because, as the heaviest part of the sub, its weight dramatically impacts the overall size of the vehicle. The heavier the sphere, the more foam would be needed to float the entire structure back to the surface. And the foam itself, capable of withstanding the crushing pressures at full ocean depth, is quite dense. More weight, more foam. More foam … more weight. It adds up quickly and dramatically. To keep the sub small enough to launch and recover from a ship, as opposed to being towed to the site like the Trieste, it was critical to have as small a sphere as possible.