What is Astronaut Training Underwater and Why it is Needed

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Learning to Take the Weight off your Feet

In dreams we sometimes fly above imaginary landscapes, floating as if weightless in a sleepy sea. Is this what it’s like to be in space?

Nearly 500 or so people have been into space, not including the 150 or so who have been buried in orbit, their ashes released from a rocket. So, unless you count the Vomit Comet or bad turbulence at 35,000 feet during a long-haul flight, there’s not many people alive who can truly tell you what its like to be weightless. And that’s a problem if you are training astronauts for mission critical spacewalks and you need to have them experience weightlessness for extended periods of time.

The solution, quite literally, is water. The nearest approximation to being weightless in space is to float with what’s called neutral buoyancy, a state of perfect balance where you add weights to your diving or space suit so that you neither sink nor float. With a little practice you can tune your buoyancy so perfectly that you can go up or down just by breathing in and out. The change in the volume of your lungs is enough to disturb the equilibrium of floatation and the minute effort of breathing is all you need to control your underwater flight.

Once I was lucky enough to scuba dive in the Gulf of Mexico, with two miles of water below. Usually, unless someone spills a lot of oil, the Gulf has the crystal waters of the open ocean. Such clarity completes the illusion of being in space and there’s a uniform quality of light. Often I had to check my depth gauge and the direction my bubbles to determine which way was up. These are just the conditions created in a giant training pool for astronauts such as the one in the Neutral Buoyancy Laboratory (NBL) in the Johnson Space Center, Houston, Texas.

The NBL pool contains over six million gallons of water. That’s a mini lake and it took a month to fill (presumably from a normal sized tap!) when it was made. It’s big enough to fit simulations of the cargo bay of space shuttles or the Hubbel telescope so that the aquanauts can try out the same maintenance and repair work they will do as astronauts in space. The giant pool is also filtered so well that it cycles its entire volume through the filters in just 19 hours, hence it has the clarity to trick the mind that you really are floating in the abyss. It’s not exactly like space because there’s some drag from the water and Earth’s relentless gravity will still accentuate downward movement compared to zero-G. But the astronauts say that its about as good as it gets to the real thing.

By the way, if you want to give it a try you can pay for a trip to a similar facility in Star City, Russia. Or if that’s not practical, James Cameron’s film, The Abyss, gives a feel for the giant pool environment too. It was made in the seven million gallon containment tank of an unfinished nuclear power station.

The Unbearable Lightness of Being

People who work in space need to be able to control both their bodies and their minds. Learning to walk in the weightlessness of space is one thing, but learning not to go stark starring mad inside a space suit or a space ship is quite another. Perhaps that’s why there is yet another kind of underwater training facility for astronauts where they can stay in a spaceship-like capsule for days at a time. At the Aquarius facility in the waters off Key Largo, Florida, NASA rents space from a NOAA (National Oceanic and Atmospheric Administration) sub sea station. Here, nearly 20 metres beneath the sea, astronaut crew live for three weeks or so at a time, carrying out routine diving operations both inside and outside the underwater spaceship.

I’ve been lucky enough to dive into Aquarius while making a TV documentary. It looks like a creation from H.G. Wells' War of the Worlds: a long yellow cylinder, with giant rivets, raised off the seabed with sleeping, dining, bathroom and research facilities for six or so people. At one end there is a water dock where divers swim into the accommodation. Through the round glass portholes the outside reefs can be seen and sometimes shoals of barracuda, tarpon and mahi mahi pass by. Of course there are no fish in space but then again the wonders of the stars and the Earth through a space ship port would provide similar distractions.

There has been much study of the mental health of astronaut crews. Some of the most interesting findings are that mixed sex crews get on better whereas the stress levels of bullish alpha male types increase when confined together. Isolation causes introversion and we start to live more in our minds. Facilities like Aquarius help us understand the effects of long term isolation. It’s a field that has close alliance with the study of prison incarceration, and even industrial deep sea divers cooped up in much deeper chambers under oil rigs. For potential space travelers it’s a big issue if they are to mentally survive a long spell spent on the International Space Station or even, in the foreseeable future, a two year flight to Mars.

In floatation tank experiments that started in the 50s and 60s, subjects were immersed in warm salt water, blindfolded and given ear plugs. With no external sensation there were reports of the imagination playing overtime to the point of hallucination (although in some cases that may have been helped by a hearty dose of L.S.D.). While there is no such extreme isolation for space crews it’s certain that those who travel far into the abyss of space will have to be strong of mind. So the best astronauts have to be able to cope with floating and be well-grounded at the same time!


Training tanks for Astronauts and Cosmonauts:





Aquarius, long term stays underwater and the NEMO project:



Psychological effects of isolation:

1. In floatation tanks:



2. On mission to Mars:



Vomit Comet:


Number of people who’ve been to space dead and alive:



The Abyss, feature film: