鈥淔ORGET everything you know about normal submersibles,鈥� says Graham Hawkes, as he sits in his small workshop overlooking San Francisco Bay. On the walls hang pictures of the many submersibles he has already built and even a stamp from the Turks and Caicos Islands honouring one of them as a milestone in marine technology. Behind him are shelves groaning under the weight of engineering texts and books about shipwrecks, clues to the twin passions that have driven him to create an entirely new type of submarine with a design that has more in common with a jet fighter than anything currently in the water.
The new sub, called the Aviator, will fly underwater using inverted wings to create downward thrust. It will be easier and cheaper to use than conventional subs and it will be faster and more manoeuvrable, allowing it to follow highly mobile creatures such as dolphins and great white sharks. It will even be fun: amateur pilots will be able to explore to depths of 650 metres and even loop the loop or roll underwater. Later this year Hawkes plans to open a flight school in tropical waters where would-be adventurers can perform 鈥渁quabatics鈥� and experience 鈥渢he sheer damn thrill of going somewhere no other human has gone鈥�.
But above all, the Aviator has the potential to transform the way humans use the seas for leisure and research. Because it offers for the first time easy access to the vast unexplored depths, the Aviator could change the nature of undersea exploration.
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The new design is a far cry from the subs that researchers use today. These have changed little since 1964 when the Woods Hole Oceanographic Institution in Massachusetts launched the deep-sea submersible Alvin. A typical trek into the deep in such a sub requires a support ship to carry the sub, its maintenance crew, the researchers and a skilled pilot. The ship costs up to $20 000 a day to run. To prevent water entering the sub and shorting the sensitive onboard circuitry, the vehicle鈥檚 hatches are not normally opened while it is in the sea, which partly explains the need for a large, specialised support ship. It means that the researchers and the pilot have to climb into the sub while it is on deck. The sub is lifted into the water using a powerful crane and then sinks at an agonisingly slow pace.
Once underwater, the sub鈥檚 typical speed is about 3 kilometres per hour, so exploring far afield is out of the question, as is scientific study of any but the slowest creatures. And the vehicle creates such a commotion of electric fields, sound and light that many creatures are simply scared away. With these limitations, it is no surprise that there are only a few such subs operating today. Researchers must fight for the opportunity to use them and many simply avoid subs altogether because of the complexities and cost of running a mission.
Hawkes has his heart set on changing this. The Aviator will be designed to fly through the water using inverted wings to generate a downward force and allow rapid descent. It will be simple to use and reliable. And the sub will be entirely waterproof, inside and out. A crew of two will be able to tow the sub out to sea behind a small boat and get in and out without any fear of splashing waves creating a short circuit. This is a hugely significant difference since it eliminates the need for a support ship with a crane, one of the major costs associated with underwater exploration.
The idea of underwater flight was born when Hawkes set out to design a submersible that could take a person to the deepest place on Earth, a trench called Challenger Deep, 11 kilometres beneath the surface of the Pacific Ocean near Guam, the southernmost island of the Marianas. Flying to the bottom seemed an elegant and inexpensive way to get there (麻豆传媒, 25 February 1995, p 26). In 1996, Hawkes successfully tested a prototype, called Deep Flight, and he is still working on the concept. However, the widespread interest generated by the project showed him the broad appeal of subsea aviation and he set to work on the Aviator. 鈥淚 want to take journalists down, a poet, film-makers. I want to take Al Gore down. And then maybe we can start making a difference here,鈥� he says.
To generate the downward forces that are needed to keep the Aviator beneath the surface, the vehicle must move more than 10 kilometres per hour. Yet the thrusters Hawkes uses are no more powerful than those on conventional subs. To achieve this extra speed, Hawkes has created a design with only one-sixteenth of the drag of a conventional sub. The most important factor influencing drag is the vehicle鈥檚 cross section in the direction of motion. To keep this to a minimum, the sub鈥檚 two occupants sit one behind the other in self-contained cockpits, tandem style. With careful streamlining, this presents a cross section only one-tenth of a conventional two-person sub. He achieves the rest of the drag reduction by doing away with external lights and manipulator arms, which create significant drag as well as increasing cost and complexity.
This extra speed entirely changes the nature of undersea exploration, says Hawkes. Traditional subs change their buoyancy by taking in or offloading water, a slow process that requires large onboard tanks and lots of power. However, with the extra speed and the downward force generated by the wings, Hawkes can design the Aviator so that it has a positive buoyancy, an inherently safe design that will float to the surface should the sub lose power.
Fast and flexible
The speed through the water also allows greater manoeuvrability. Each of the two crew will have a joystick linked to flaps on the wings to control movement up and down, and a rudder control linked to flaps on the craft鈥檚 tailfins. Hawkes claims that the vehicle will be flexible enough to perform aquabatics. 鈥淭here is no scientific or industrial reason for that. We鈥檙e just exploring underwater aviation to see what the hell we can do,鈥� he says.
Each cockpit is a self-contained aluminium pressure hull rated to a depth of roughly 650 metres. This limit is always a trade-off, he says. But 650 metres is more than enough, Hawkes says, to take people into the realm of 鈥渟hipwrecks and weird animals鈥�.
As well as the flight controls, each cockpit will have its own life-support system and will be topped with a transparent hemispherical hatch. One of the problems with underwater observation is that the water-glass-air interfaces severely refract light passing through at any angle other than 90 degrees to the glass. Although people can cope quite well with these distortions, Hawkes hopes to minimise them. The hulls are designed so that the occupants鈥� eyes will be at the very centre of the hemispheric hatches. So any light reaching them will have passed through the domes at almost exactly 90 degrees, keeping distortions to a minimum. In addition, the refractive index of the domes will match that of seawater, so that they will seem to disappear. The result should be a near perfect panorama.
To introduce his design to the world, Hawkes plans to fly a prototype of the Aviator under the Golden Gate Bridge later this year. He is the first to admit this is a publicity stunt, but says the feat will also test some new ideas. During Deep Flight鈥檚 first outing, Hawkes found himself spiralling through the water when he thought he was flying straight. He feared a problem with the design, but later found that in clear water when he could see the bottom the problems disappeared. It turned out to be the same problem pilots sometimes have when the horizon is not visible and they are unable to orient themselves. Conventional submersibles do not experience this because they usually remain horizontal in the water.
To combat this, the Aviators will use positioning technology already proven on remotely operated subs. The plan is to create an artificial horizon for the pilot using chip-based magnetometers that determine the orientation of the sub relative to the Earth鈥檚 magnetic field.
Bruce Robison, a deep-sea biologist at the Monterey Bay Aquarium Research Institute in California, who has worked extensively with submersibles and robotic vehicles, says Aviators could have 鈥減rofound scientific value鈥�. But, he adds, 鈥渋t鈥檚 unrealistic to imagine that a vehicle this different, this innovative, is immediately going to have research applications. But if it works we鈥檒l figure out how to use it.鈥�
Conventional subs cannot keep up with animals such as dolphins or great white sharks, so the new subs could prove invaluable for observing them. The Aviators鈥� speed and manoeuvrability will make it possible to follow these creatures in motion, if not at their full speed. Other mobile creatures in the mysterious middle depths of the ocean are also poorly studied because current vehicles are usually confined to the bottom. 鈥淭he animals are laughing at us,鈥� says Robison.
Another goal could be to track down the giant squid. To date, no one has seen one of these leviathans alive, though dead ones have been washed up on beaches. 鈥淚t illustrates how incredibly backward we are with subsea access,鈥� Hawkes says. 鈥淢aybe they鈥檙e just really smart and we鈥檙e really dumb.鈥� He compares the light, sound and electric fields emitted by current submersibles to walking through the forest with a brass band. 鈥淵ou鈥檇 come back and say, `No tigers. There are snails and slugs, but nothing interesting.鈥� Laughing, he recalls a cartoon where Jacques Cousteau is looking at a few small creatures illuminated by the light of his sub while a host of monsters lurks beyond his view.
Hawkes has eliminated as much of this 鈥渘oise鈥� as possible. He plans to minimise light at times and use cameras that amplify what little ambient light penetrates the depths. And while Aviators will fly into the oceans using electric thrusters-which are common on submersibles-positive buoyancy means they can glide back up in silence, bar the occasional sound of steering controls.
To finance his work, Hawkes has formed a company with Californian investors called The Spirit of Adventure. Their aim is to tap into the growing adventure tourism business. Hawkes also hopes to sell Aviators to wealthy individuals. Initially they will cost about $800 000 each but this price should fall if the subs can be built in large numbers.
Whatever the commercial or scientific future of Aviators, Hawkes is optimistic. As he points out, there鈥檚 a whole world out there waiting to be discovered.
