A crew lives on a station in a hostile environment. Leaving that environment requires oxygen tanks and specialized gear to deal with pressure differentials. A space station? Nah. A base built on the ocean floor. The US Navy was interested in such a base in the 1960s, and bases like this are a staple of science fiction. But today, we see more space stations than underwater bases. Have you ever wondered why?
Diving deep underwater is a tricky business. At a certain depth, the pressure forces gas like nitrogen to dissolve into your body. By itself, this isn’t a problem, but when you ascend, it is a big problem. If the gas all comes out at the same time, you get bubbles, which can cause decompression sickness, commonly called the bends. The exact problems vary, but the bends often cause extreme joint pain, fatigue, or a rash. Sometimes people die.
While you think of the bends as a deep-sea diver’s problem, it can also happen in airplanes and outer space. Any time you go from high pressure to low pressure quickly, you are subject to decompression sickness. Depending on what you are doing, there are different ways to mitigate the problem. For diving, traditionally, you simply don’t surface too quickly.
You dive, do your work, and then head towards the surface, stopping at preset stops to let the pressure equalize gradually. Physics is a bear, though. The longer you stay at a given depth, the longer you have to decompress.
That means you rapidly reach a point of diminishing returns. Suppose you dive to the ocean floor. You spend an hour working. Then you have to spend, say, eight hours gradually rising to the surface. That makes extended operations at significant depth impractical.
George Bond was thinking about all this and had an interesting idea. It is true that, in general, the longer you stay down, the more gas your body absorbs. But it is also true that, eventually, your tissues saturate, and then you don’t absorb any more.
Saturation Diving
So the counterintuitive insight was not to send a diver down and then back up repetitively. Instead, you keep the diver under pressure for the entire job. Then, once, at the end, you decompress. This is known today as saturation diving.
This leads to a new problem: If you plan to send a diver down to the ocean floor for a week, they can’t just hang out in a wetsuit the whole time. They need somewhere to eat, rest, and all the other things you need to do when you aren’t working. They need a base.
It still isn’t as simple as it might seem. There are problems with oxygen toxicity, the effort to breathe under pressure, and other issues. But these are largely solvable.
George Bond did experiments under the project name “Genesis,” where animals and, eventually, people were subjected to high pressures for extended durations. At roughly the same time, Edwin Link (a familiar name if you know about flight simulators) and famed diver Jacques Cousteau were experimenting with long-term saturation diving as well.
As part of a larger plan, Link experimented with placing one person at a modest depth for a day, and Cousteau had a two-person team at greater depths.
The Navy decided to run some experiments to see if Bond’s ideas would work in reality. They started the “man in the sea” experiments that deployed three prototype “sealabs” that were far more ambitious than previous commercial projects.
Sealab I
Sealab 1 (Public Domain)
In 1964, off the coast of Bermuda, the Navy placed an ambient-pressure cylinder 192 feet down. An umbilical connected the habitat to the surface. You’d think the station would be full of air, but high pressures of nitrogen can cause other health problems, so, instead, the divers had a helium and oxygen mix.
The crew of four was supposed to stay submerged for several weeks. However, an approaching storm cut their stay to only 11 days. Still, the experiment was a success.
It also brought up several problems. If you’ve taken a hit of helium, you know it makes your voice squeaky, which can make it difficult to communicate with other people. More importantly, though, is that helium is a good conductor of heat. Divers get cold fast hanging out in a helium-rich atmosphere.
You can see a video from the Navy in 1965 describing the program below.
As a side note, former astronaut Scott Carpenter was set to be the fifth person in Sealab I, but a scooter accident in Bermuda bumped him from the roster.
Sealab II
In 1965, the Navy tried again with Sealab II off the coast of La Jolla in California at a depth of around 200 feet. This time, Scott Carpenter made the trip.
Sealab II (Public Domain)
Sealab II was more complex with demonstration tasks and a planned mission length of up to 30 days. For a long trip like this, the same problems arise as you’d have in a space station. Carbon dioxide needs scrubbing, and oxygen levels need control. Humidity and corrosion are constant problems. Equipment noise affects people over the long term.
The new habitat was twice as large as Sealab I. There were heaters, hot showers, and refrigeration. The idea was to have a crew that rotated every 15 days, but Carpenter spent 30 days inside.
The Navy also tried to train a bottlenose dolphin — Tuffy — to act as a helper to the crew with mixed results. While the mission, overall, was a success, there were issues with the crew feeling isolated and confined, along with sleep problems due to noise and lights.
Famously, President Lyndon Johnson was to speak to Carpenter after his 30-day stay and called while Carpenter was in a decompression chamber full of helium. The resulting confusion among telephone operators is pretty funny, as you can see in the video below.
Sealab III
The next and final attempt to submerge a crew was Sealab III in 1969. At a depth of about 600 feet — 200 feet beyond the normal planned operation depth — the Sealab III mission reused the Sealab II module, refurbished and upgraded. Five teams of nine divers were scheduled to spend 12 days each in the habitat.
At such a depth, problems magnify and margins for error all but disappear. The Navy was already stretched thin in Vietnam, and Sealab III had a difficult time getting not just off the ground, but under the sea. The project was late and overbudget. Work got sloppy, and corners got cut. When the habitat developed a helium leak, four divers volunteered to repair it in place, but failed on their first attempt.
A second attempt had the divers taking amphetamines to stay awake, which went predictably wrong. A diver, Berry Cannon, died. At the time, it was chalked up to improper setup of his rebreather, although a more modern investigation speculates that he may have been electrocuted. Either way, it was enough to end the program. The Navy gave up on the program and focused on other undersea programs, such as submarines. If there are any undersea bases, they are too secret for us to know about them.
You can see a Navy video showing the progress of Sealab III before the accident below. Unfortunately, the audio track isn’t present, so it isn’t always clear what the message is.
The End?
You might wonder why someone didn’t continue this work. We don’t have underwater bases, farms, mines, or hotels. Why not? It is true, of course, that the Navy continued to use limited saturation diving for certain, sometimes clandestine, purposes.
Well, the answer is complicated. The Navy’s work on Sealab directly created the tech and techniques used every day by saturation divers around the world, many of whom maintain underwater petroleum production equipment. However, that’s very specialized, and even then, a modern remote vehicle is a better choice for many tasks. Just like space is a harsh place to live, so is the ocean floor. Everything corrodes and leaks.
Now, we build space stations, and the day of the station on the ocean floor will either never come or will be in the future. But regardless, the technology developed by these pioneers will inform human undersea operations for the foreseeable future. Meanwhile, robots are cheaper and more effective for nearly any task. Still, there are times when only a human will do.