For nearly 50 years, conventional manned deep submersibles have operated on the principle of a free balloon or blimp (powered balloon). Buoyancy is normally provided by a plastic matrix material
filled with glass microspheres, each containing a bubble of air. This cast syntactic foam is easily formed to give needed lift and a streamlined configuration to the vehicle. Small propulsion and thruster motors provide limited maneuverability while submerged and precise control while hovering. Various ballasting systems give positive, neutral, or negative buoyancy during underwater operations.
While seemingly an arcane way of operating, the balloon/blimp design is just right for the slow "flight" requirements for most submerged operations, especially scientific research. The human observers inside the vehicle do not need speed as much as the ability to hover or stop at a desired work site.
Another design direction is submersibles that actually "fly" underwater. The dynamic flow of water across wings, rudders, and elevators is used to maneuver these vehicles. The pilot's controls are quite similar to those of an aircraft with rudder pedals and joystick, with a throttle control on the left side of the cockpit. Relatively large propulsion motors provide high-speed and agile maneuvering capabilities. And like an airplane, once slowed too much, the vehicle will stall as lift is lost.
Graham Hawkes, a British-born inventor and engineer, built the first practical flying submersibles. He began with his one-person Deep Flight 1 that first flew in 1995. Its designed maximum operating depth was 3,300 feet with speeds up to five knots. Hawkes built two prototypes, but only one became operational. The pilot lay in a prone position behind a bullet-shaped plastic window. Theoretically the Deep Flight could do "hydrobatics," but this was not fully tested because of limitations of the batteries.
Since retiring the prototype Deep Flight 1, Hawkes has developed three subsequent generations of flying submersibles. The next was the Deep Flight Aviator, launched in 2003. It carries a two-person crew seated in tandem pressure hulls and is designed to dive to 1,500 feet. Sub Aviator Systems (SAS) acquired the Aviator in 2005. Significantly modified in 2007 by Nuytco in Canada, the vehicle was renamed Super Aviator. The company now offers pilot training, tourist dives, and commercial services.
The next Hawkes design was a very special one, Deep Flight Challenger, capable of diving to the deepest place in the ocean. It was being built for famous adventurer Steve Fossett, who was to use it for a dive into the Challenger Deep in the Marianas Trench, a depth of about seven miles. The sub's high-speed capabilities would have greatly reduced the time needed to make the round trip. Sadly, Fossett died in an aircraft accident in 2007. Now in storage, the more than 90 percent complete Deep Flight Challenger is for sale.
The fourth-generation design is the $1.5 million Deep Flight Falcon. Two have been built so far with the first delivered to the owner of the world's largest sailboat. The second is being retained by California-based Hawkes Ocean Technologies (HOT) for its underwater flight school and commercial services. The submersible debuted on May 2009 at the California Academy of Sciences.
Meanwhile, SAS operations with the Super Aviator have involved underwater flight schools in Grand Cayman, the Bahamas, Cabo San Lucas, Mexico, and Lake Tahoe, California. The two-person sub has made more than 200 dives. Now, SAS and Nuytco are planning to build a new-design underwater flyer, Orca.
What benefits does a 4-to-6 knot, 1,500-foot dive capability submersible give an operator? While their use in underwater tourism is a great thrill ride, ticket costs for the average person are too high. Instead, this submersible can be best employed where the ability to quickly inspect over large distances is advantageous. Examples would be seafloor pipeline surveys, inspection of large underwater structures, and covert military/law enforcement operations. The HOT Deep Flight Falcon's first mission will be underwater surveys in the Gulf of Farallones National Marine Sanctuary.
Underwater hydrobatics may be fun and impressive, however, these underwater flyers primarily offer unique capabilities to efficiently conduct underwater work.