The deep sea environment is as challenging as outer space in many ways. The pressure on a submerged vessel mounts as it goes deeper, due to water above and around it. This places a limitation on divers with aqualungs or diving suits. The depth record with a suit is about 600 metres.
Deep diving vessels carrying air-breathing humans must be constructed sturdily, and internal atmospheric pressures kept high to prevent them being crushed. At the bottom of Challenger Deep, at nearly 11,000 metres below sea-level, the pressure is over 1,070 times normal pressure at sea-level. A gradual increase in atmospheric pressure can be handled by the body. But there are also dangers if pressure reduces quickly. Air bubbles form in the bloodstream causing pain and literally bending the body, with potentially fatal effects. So decompression must take place gradually too.
Oceanographic exploration started systematically in the 19th century. The Challenger Deep is named in honour of HMS Challenger, a British naval vessel which carried out a exploration and mapping assignment between 1872-76. Challenger discovered over 4,000 new species in that voyage.
The creation of a global telegraphic system triggered more exploration as cables had to be laid underwater to span oceans. The World Wars led to further exploration since combatants wanted to deploy submarines. But even nuclear subs of the 21st century don’t dive deeper than 400-500 metres normally.
Specialised vessels go much deeper. In the 1930s, the Bathysphere was designed and constructed by William Beebe and Oscar Barton. It went down to 900-plus metres. It was anchored with a cable that allowed it to be pulled up, as well as offering telephonic communication.
In the 1950s, the father-son pair of Auguste and Jacques Piccard designed the Trieste. In 1960, Piccard junior reached a depth of 10,911 metres at Challenger Deep in that vessel. But it was severely damaged and lucky to resurface after a ten-hour dive.
Human fascination with deep diving continues to draw adventurers. In 2012, the filmmaker James Cameron took Deepsea Challenger to Challenger Deep and landed at 10,908 metres. This technologically advanced vehicle spent three hours on the bottom, exploring and gathering data. The 7-metre vessel uses a light foam of small hollow glass balls suspended in epoxy resin. This foam, Isofloat can float and also resist terrific pressures. The vessel had thruster motors instead of ballast tanks like the earlier National Geographic and Rolex.
The US navy has its Alvin class of deep submergence vehicles, which are reusable. The 17-tonne Alvins have dived below 2400 metres at least 5,000 times, collecting scientific data. It carries a 3-person crew. At least 2,000 papers have been written citing Alvin data.
Vescovo, who is successful private equity investor has a not-so-friendly rivalry with Cameron. The Limiting Factor, which Vescovo helped to fund is one of the few such vessels which is capable of being reused repeatedly.
The costs of such expeditions is daunting. Quite apart from building expensive vessels, with expensive equipment, it’s necessary to hire mother-ships with skilled crews. The costs could reduce if unmanned AI autonomous vehicles are used instead and there’s lots of research into this.
Much exploration is “blue sky research” done to add to our knowledge about marine environments. But there’s solid commercial justification. Apart from mapping ocean floors and discovering new species and strange physical phenomena such as underwater volcanos and warm currents, there are potential commercial payoffs.
The seabed could be a rich source of minerals including many metals and rare earths. Medicine and biology has benefited from studying marine species. We understand weather systems better as we understand the oceans and this will be vital for Climate Change mitigation.