The convention in ‘day to day’ diving is that it’s wet – the diver is exposed to the watery outside environment, and all of the resulting stressors that this wet environment places on the human body. That stress is cause for the various limitations we divers face with every immersion. The most critical element causing this stress is pressure.
A basic lesson in dive physics – here on land, we are subject to the weight of our atmosphere. A one-inch square column extending from sea-level to space weights 14.7 pounds. This is because the gasses in our atmosphere are very light and exist at a low density. Once we take the plunge into the dense fluid medium of water, we are subject to far greater atmospheric pressures. That same square inch column [of water] weighs in at 14.7 pounds at about 33 feet/10 meters of depth. So, for every 33 feet that we dive, we are subject to one additional atmosphere of pressure. At the edge of the continental shelf, with depths approaching 1000 feet, the diver has the weight of the world times thirty resting on every square inch of his body.
With our bodies acclimated here on the surface [at one atmosphere], putting us under pressure (depth), and more specifically breathing gasses under pressure, is cause for our body’s tissues to absorb elements of our breathing gas to re-acclimate, or trend towards equilibrium [this would be full tissue saturation]. This process, or ‘on-gassing’, and the reciprocal ‘off-gassing’ when ascending and surfacing, is the fundamental process behind decompression theory. A ‘wet’ diver cannot defy these laws of physics and human physiology, and therefore must be mindful of rates at which we on-gas and off-gas, with the latter being cause for decompression sickness or ‘the bends’.
As a benchmark, consider the US Navy’s ’60 for 60 rule’, where a diver can descend to 60 feet and stay for 60 minutes and then ascend directly with no (theoretically) ill effects suffered from decompression. The longer and/or deeper the dive, the diver is then required to ascend slowly, even making intentional ‘decompression stops’ before surfacing – allowing the body to slowly reacclimate to pressure back here on land. Much below 130 feet, it becomes very difficult to spend any meaningful amount of time at work without incurring any decompression. And then at depths that are my target of study – 200 to 500 feet – all dives require staged decompression, and lots of it. For instance, a 35 minute working dive could require as much as 3 hours of decompression. This is ‘idle time’ or potentially ‘wasted time’, and many would argue that it is a highly inefficient mode of work, offering little reward considering the time investment required.
During a recent field project, I sought to buffer that idle time by introducing a portable habitat technology. The idea being that we spend our work time at depth, then make use of our idle time while resting in reasonable comfort. While this has been successful at some scale, it warrants continued development, and evaluation of its applicability in enabling more routine deep scientific diving.
The best case scenario is to eliminate this need to decompress altogether – effectively eliminating idle time, and vastly enhancing the ratio of time invested versus time well spent. There are two logical solutions where;
1. We alter human physiology such that the body is no longer subject to the effects of pressure – at this writing this is science fiction, though surely has been considered with Cousteau’s description of ‘manfish’. Many of us recall another concept – when we sat on the edge of our seats with Bud’s epic dive in James Cameron’s film ‘the Abyss’, where he breathed an oxygen enriched fluid inside of a suit. Both of these are fictitious at this point in time, though should not be discounted as we consider our own evolutionary paths here on the Blue Planet.
2. We need to eliminate the source of the problem – that is, eliminate the diver’s exposure to pressure. Pressure is the one element that has kept our species here in a terrestrial status quo, with long-duration, meaningful, working manned-undersea exploits remaining perhaps more challenging than placing humans in space. This is very much a non-fiction approach, with very real enabling technologies in place today.
Atmospheric Diving Systems (ADS) are one such enabling technology that solves the pressure problem. By keeping the diver at surface pressure in a hard suit of armor, the human body is not exposed to outside pressure, does not absorb breathing gas, and hence has no need to decompress. The premise is that the diver is effectively wearing a submarine! While all technology has its place, the advantage of an ADS system over a submersible is that it provides for some degree of mobility – allowing the diver to function like a human – and articulate to a reasonable degree to operate tools and carry out work tasks.
By eliminating the effects of pressure and the resulting human limitations of depth and time, we can dive to virtually any depth with nearly one hundred percent of in-water time spent working. This of course comes with some compromise by way of the logistical footprint to set up and use the equipment, initial technology investment to some degree [as opposed to wet/autonomous surface to surface mixed-gas dives for example], and only time will tell if the rewards present themselves with this technology as a tool for scientists.
As I sit here somewhat awestruck as I take a closer look at the new Exosuit ADS, the opportunities for scientific exploration scream out to me. An entirely new frontier is out there for the taking, and now may very well be within reach.
Follow this project here: http://newswatch.nationalgeographic.com/tag/exosuit-project/
This Blog mini-series chronicles the author’s journey through depth, time, and space with the latest generation Atmospheric Diving System (ADS) Exosuit, designed and constructed by Dr. Phil Nuytten of Nuytco Research Ltd. in Vancouver, British Columbia. The first production suit is owned and operated by the Diving Division at the J. F. White Contracting Company located in Massachusetts – who has generously reached out to the science community to afford new opportunities for discovery with this technology.