Deep Flight II (DFII), which has been designed and is awaiting funding, will be built with acrylic crew hulls for 3,000 feet or with titanium hulls with conventional viewports for 20,000 feet. Ceramic-carbon fibre hull will enable 37,500 feet dives. Hawkes has recently resolved all engineering design issues for Deep Flight II and is actively pushing this program forward.
Wikipedia on maximum depth for military submarines: World War II German U-boats generally had collapse depths in the range of 200 to 280 meters (660 to 920 feet). Modern nuclear attack submarines like the American Seawolf class are estimated to have a test depth of 1,600 feet (490 m), which would imply a collapse depth of 2,400 feet (730 m).
2. Defense Advanced Research Projects Agency, which commissions research for the Defense Department, has given Electric Boat $26 million (and another $12 million is expected) to design a vehicle that could potentially transport high-value cargo or small groups of people at 100 knots (about 115 miles an hour) in a program known as “Underwater Express”. Electric Boat is part of General Dynamics.
The technology, if developed, could revolutionize ocean transportation if it could be adapted to cargo and passenger ships.
The vehicle would travel inside a large gas bubble created in the water, a process known as supercavitation. The bubble reduces drag, since the drag is much lower in air than in water, allowing the vehicle to travel at high speeds.
Supercavitation has been applied to torpedoes, but never to transport vehicles, according to DARPA.
Electric Boat (EB) has come up with a secret way to dramatically increase the endurance and maneuverability of a body in supercavitating flight.
Ships would be much more fuel-efficient, or could use the same amount of fuel and instead of taking two weeks to get across the Pacific, they could get across in a matter of days.
EB initially pitted its design against one from Northrop Grumman Electronic Systems in Maryland. EB was chosen to build a quarter-scale unmanned vehicle, based on the concept of a full-scale size of 8 feet in diameter and 100 feet in length, for a demonstration in spring 2010 in the waters off Rhode Island.
The demonstration will include a 10-minute run at speeds of up to 100 knots with maneuvers, including depth control, to show the controllability of the vehicle, according to a DARPA statement.
At that point, the program will conclude and the technology will be available to the Navy for use in future systems as desired