“WE GOT a telegram. It said: ‘Return to port. Unload all goddamn geophysicists and geochemists. Biologists coming’,” recalls Jerry van Andel, a researcher on board the US submersible ALVIN in February 1977 when a telegram arrived from the Woods Hole Oceanographic Institution in Massachusetts. It was the confirmation he had been waiting for. Van Andel and his team of geologists were in the Galapagos Islands cruising the Pacific Ocean floor. On the first of several planned dives, they stumbled upon a major geological discovery that would turn marine biology on its head.
What they found were hydrothermal vents – seeps of hot, mineral-rich water that support whole communities of strange creatures way down in the depths. “At some point the pilot pointed out lots of oval, white stones,” van Andel recalls. “We took a closer look and they turned out to be clam shells, about a foot across – the biggest clams I’d ever seen.” Alongside were huge golden shrimp and exotic-looking fish, all living in total darkness more than 2000 metres below the surface. The discovery showed these regions are far more than just dark, lifeless deserts, and completely changed the way scientists view the deep.
ALVIN went on to become the most successful manned submersible ever. Now, 40 years after its launch, it is finally being retired. Its replacement is due to start work in 2009. But while the design team is already busy, US dominance of the deep might be coming to an end. The China Ocean Mineral Resources R & D Association (COMRA) based in Beijing has almost finished its own sub, designed to go deeper than any other manned vessel in operation, including ALVIN’s replacement. If all goes to plan it will be cruising the sea floor around China by the end of 2006. Meanwhile, the private designers of a radical new sub called Deep Flight claim it will supersede all of the world’s submersibles in a few years. The race to explore the deep has just started to hot up.
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Underwater exploration began in the 1930s when William Beebe and Otis Barton from the New York Zoological Society descended 1000 metres inside a steel ball less than 2 metres across. The pair reported all manner of exotic creatures, but since the sub was suspended below a ship, real exploration was difficult. In 1960, the Swiss inventor Auguste Piccard took things a good deal further with Trieste, his bathyscaphe in which his son Jacques descended 11,000 metres into the Marianas Trench near Guam, the deepest spot on Earth. Despite the disappointing view out of the window – just one flatfish – the dive set a world record and proved that life exists even in the deepest parts of the ocean.
Since then, no one has returned to the abyss. Deterred by Trieste’s uninspiring observations, the technical challenges of building a manoeuvrable vessel able to withstand pressures exceeding 1000 atmospheres and the fact that just 1 per cent of the ocean floor lies below 6500 metres, scientists have focused their efforts in shallower seas.
However, there are plenty of good reasons to study the ocean depths. So six years ago, scientists in the US started to think about a replacement for ALVIN. The team that had used ALVIN drew up a technology wish-list that included better batteries, more windows, improved depth rating, the latest scientific instruments and greater comfort for the crew. In 2004 the US National Science Foundation agreed to fund the project with $21.6 million, while Woods Hole provided additional funding for instruments, lighting and sensors. The result was a submarine simply called a “replacement human operated vehicle”, unofficially billed as the most advanced vessel beneath the sea (see Diagram).
The new sub looks much like its predecessor but will be far more capable. Six thrusters will help it remain stable when taking samples, and a new ballast system will allow it to travel to the depths faster, giving it more time on the seabed, says Bob Brown, manager of the project at Woods Hole. It will also carry more sensors and survey equipment, giving scientists more tools to study the deep ocean.
At heart, all deep-sea subs are the same – they are built around a spherical pressure hull that provides maximum strength for its size and weight. Most vessels diving today use spheres constructed from 7.5-centimetre-thick titanium and are roomy enough for a crew of three. The new sub’s sphere will be bigger, with a volume of 5 cubic metres giving 20 per cent more space than ALVIN’s hull.
The large metal sphere makes the craft very heavy. To prevent it sinking like a stone, most of the rest of the sub will be built of a special buoyant material called syntactic foam. Using the right amount of foam will make its overall weight in the water zero – the craft will be neutrally buoyant. A variable ballast system that can take on or pump out water will allow the vessel to descend or rise and maintain trim.
The foam itself is composed of tiny glass spheres encased in epoxy resin. The material’s ability to resist any change in volume as the sub descends makes it difficult to manufacture and it is typically only made in pieces of just 0.02 cubic metres at a cost of $2,250 each. Every piece must be carefully shaped and glued onto the hull of the craft.
Not only will the sub be more spacious, it will give the scientists a better view. Unlike other subs that tend to have three windows – one at the front for the pilot and one on each side for two scientists – the new vessel will have five, providing overlapping fields of view. However, to cope with the crushing pressures at depth the acrylic plastic in the windows is so thick that it magnifies the view: “Everything looks enormous,” says van Andel.
The thick plastic can also distort the view – particularly when viewing objects through the edges of the windows – so the designers are consulting optics specialists to see if they can reduce this effect. There have even been suggestions that the sub could use augmented or virtual reality. The sub will be equipped with the latest digital cameras capable of very-low-light imaging, including high-definition colour still and video cameras, and multi-beam sonar to provide detailed pictures of the bottom. Images will be beamed back to the ship in real time through a fibre-optic tether so that scientists on board can share in the discoveries.
“The Trieste’s dive proved that life exists even in the deepest parts of the ocean”
But it might also be possible to take images from these externally mounted sensors, digitally enhance them and project the undistorted images in front of the crew in real time. This could overcome any problems with the thick windows and improve the view when the lighting is poor, for example. It would also help the crew to use the sub’s manipulator arms, which will have at least seven degrees of freedom and use force feedback so that operators can carry out the most delicate sampling tasks.
“Glass may be the material of choice for subs designed to go all the way to the deepest trenches”
With extra sensors and computing power the new vehicle will be power-hungry. Time on the ocean floor is limited by battery capacity, so the new vessel will need a more powerful energy source. ALVIN uses lead-acid batteries like those on forklift trucks but the design team is investigating lithium polymer batteries similar to those found in cellphones. With enough of these batteries, the sub would have sufficient power to stay at maximum depth for five-and-a-half hours. And unlike any other design, the batteries could be moulded to fit perfectly within the hull.
Lithium polymer batteries would be a major step forward for deep-sea subs. The Russian MIR I and II craft use nickel-cadmium batteries which provide a huge amount of power but are very heavy. Japanese sub designers have tried purpose-built silver-zinc batteries that give adequate power but which have a limited lifespan and cost $35,000 per dive, a thousand times that of ALVIN’s lead-acid batteries. Now the Japanese researchers have switched to lithium-ion batteries, the precursor of the lithium polymer units that Brown hopes to use.
Meanwhile, there are similar debates over a new sub in China. After decades of borrowing craft from abroad, they have decided to take the plunge and build their own. “To rent a submersible to do research is so expensive,” says Liu Feng, director-general of COMRA. “We need to do ocean science and so it is more economical for us to build our own.” Planned for launch in 2006, the new vessel will be able to descend 7 kilometres and promises to give the Chinese scientific community the most capable submersible in the world.
Like the Chinese space programme, their bid for the depths is shrouded in secrecy. However, Feng says that unlike the massive investment that put a taikonaut into space, the funds behind the Chinese sub are relatively small. Scientists that have seen a mock-up of the craft say that many of its components can be bought off the shelf, which keeps the costs down. Additionally, China seems to be collaborating with former colleagues in Russia who can offer their experience at a fraction of the price of western designers. The titanium pressure sphere is already under construction in St Petersburg and will be finished in time for the sub’s final assembly in December.
Off the shelf
The sub will be about a third larger than the ALVIN replacement, and slightly bigger than Japan’s Shinkai 6500. To be capable of descending to 7000 metres, the pressure sphere has to be thicker, and additional syntactic foam must be added to the body to keep the vessel buoyant. Foam that is rated for greater depths must be denser to maintain buoyancy. However, US export restrictions may mean that China will struggle to get hold of the highest density foam, so to compensate designers will have to add more foam and hence more weight to the vehicle, a difficulty that has led some to speculate that China has decided to go for 7000 metres only as a kind of scientific one-upmanship. Feng disagrees. “This is a real proposal from our scientists,” he says, though he won’t reveal details. Some think that since COMRA has taken the lead, the vehicle will be used for commercial mineral prospecting rather than for scientific research.
Whatever their reason, a launch date in 2006 would pip the US by a full three years. Feng admits that a launch in March 2006 is looking unlikely, as it will have to go through a series of tests in a tank before being allowed anywhere near the open ocean. But once the craft has proved itself, and a new support ship is constructed, COMRA hopes that the global scientific community will take advantage of the world’s deepest-diving manned sub.
However, both the Chinese and the US designs may look like relics of a distant age if one man’s dream becomes a reality. Graham Hawkes is an engineer and founder of Hawkes Ocean Technologies (New Scientist, 12 February 2000, p 36). He plans to shake up the world of deep-sea exploration with a totally new concept for a deep-sea submersible. “The new ALVIN is essentially the same as the last,” he says. “It’s a big mistake. The next 40 years are very unlikely to be a rerun of the past.”
Hawkes’s design does away with the usual stubby submarine shape in favour of one more like a racing car or a fighter jet. Deep Flight II has two short wings, powerful thrusters and a huge viewing port at the front. It is designed to “fly” underwater. The wings are inverted to provide “negative” lift, pulling the sub down as it moves forward and negating its natural buoyancy. This allows it to descend to the ocean depths much more rapidly than a conventional sub so it can spend considerably longer down there.
The craft will be lightweight, low-cost and able to travel quickly through the sea and to dive to the deepest trenches on Earth, says Hawkes. He claims the difference between his design and others is as fundamental as the difference between a balloon and an aircraft. “We know that dirigibles did not have the performance to master the skies. We simply need to make the same natural progression underwater, from conventional subs to underwater flight.”
However, Hawkes has plenty of critics. Many in the oceanographic community say that his design will be useless for conventional science. They point out that since it will be positively buoyant, it will be unable to stop or to move slowly for detailed sampling without starting to rise towards the surface. Nor will his design have standard collection tools such as manipulator arms. But Hawkes is not put off, saying that the vehicle could carry most kinds of sampling equipment.
Not surprisingly, Hawkes also has an unconventional approach to construction. He thinks that glass may be the material of choice for subs designed to go all the way to the deepest trenches. Glass can take far higher compressive stresses than metals. He is also looking at ceramics and exotic composites such as those made from concrete (New Scientist, 9 March 2002, p 37). “There is no silver bullet,” he says. “It’s tough to make any new material practical.”
Hawkes’s ideas could be gaining favour in some circles. He has recently completed a scholarship at Woods Hole, and NASA has stumped up cash to push his ideas further. In particular the agency is funding his Spider Optic concept – an ultra-lightweight optical fibre that could be used to control a remotely operated vehicle (ROV) at depth. Most unmanned subs cannot dive to the very bottom of the sea since the vessels that launch them must pay out kilometres of heavy tether and this is extremely difficult. The Japanese ROV, Kaiko, was lost on a deep dive in 2003 when its tether snapped. So NASA hopes that a lightweight optical fibre will make launch easier and allow these subs to travel further down. NASA hopes to use this technology on ROVs that will hunt down new creatures by collecting DNA samples in deep trenches. And if that wasn’t enough, Hawkes is also embarking on his most ambitious venture to date. He has started to gather funds for what he calls the Ocean Everest Expedition – a trip that will take him to the depths only ever visited by the crew of the Trieste.
Does Hawkes think submersibles like those being built by the US and China will soon be redundant? “The one thing I am sure of is that the mindset that says we need a single craft to do all things all of the time is going to die a sudden death,” he says. “The subs of the future will be doing work we have not yet imagined.”
Send in the machines
No one has returned to the deepest parts of the ocean since the Trieste in 1960. For now, scientists can only probe the deepest and most dangerous areas of the ocean using an armada of unmanned vehicles.
Two kinds are used: autonomous underwater vehicles (AUVs) that follow a programmed course before returning to ship, and remotely operated vehicles (ROVs) that are controlled by an operator aboard a support vessel via cameras and fibre-optic cables.
Until it was lost off Shikoku Island in Japan in 2003, the Japanese ROV Kaiko regularly dived to 11 kilometres to collect sediments and sea creatures. Now a team at Woods Hole Oceanographic Institution in Massachusetts and Johns Hopkins University in Baltimore, Maryland, is preparing to launch a new type of unmanned sub – a hybrid craft that will offer new opportunities to study the deep.
The new sub will be the first to operate both as a free-swimming vehicle to survey large areas and as a tethered vehicle for more delicate sampling.
Advances in battery technology, thanks in part to cellphones, mean that the HROV sub will be able to stay under the sea surface for up to 36 hours. It is also smaller than other ROVs, and at just $5 million it will cost a fraction of ALVIN’s replacement.
So when it is cheaper and safer to send robots to the deep, why bother sending humans at all? Deep-sea researchers argue that there is no replacement for actually being there, reacting to what you see and examining the sea floor. “ROVs are fine when you have an idea of what you are going to see,” says deep-sea geologist Jerry van Andel. “But if you only see it from a camera, the sea floor never really comes to life. That’s a bad thing because it means you’re not looking for extraordinary things.”
