The crew of NASA's NEEMO 14 surfaces Sunday, after spending two weeks in the Aquarius marine lab off the coast of Florida, over 60 feet under water.
The six-man crew has done 52 simulated space walks under several different gravities -- the moon, Mars and an asteroid. They've conducted experiments on the weights and masses and gravities of space suits so that NASA can try to make them more comfortable to wear, had their physiology and bodily fluids monitored, and experienced the same enforced closeness that they would if they were on a space mission.
Tomorrow (Saturday) they'll start the 18-hour process of depressurizing their bodies to prepare for the long trip to the surface. The pressure at that depth is so high that you can't whistle, says Chris Hadfield, the crew's leader, who spoke to me and a few other reporters today. A pot of water won't boil until it's 260 degrees F, and when you drop a teabag, it floats for awhile before it lands.
NASA's NEEMO missions are a way to test human and mechanical endurance in extreme environments on Earth to prepare both humans and machines for extended stays in space.
Underwater space walks are remarkably similar to the real thing, Hadfield says, and he's been on two -- he was the first Canadian to float in space. The discontinuity of working while an angelfish, or the continent of Africa, passes by is the same, and "You step outside and there's a lander and a rover and a huge tank farm for oxygen to keep us alive. Every science fiction book and movie you've ever seen has drawn the same thing, and here it is, in full 3-D, for us to use. It mentally evokes the feeling of being on another planet."
Living in Aquarius feels like the space station, too -- it's noisy. "You have to have fans working all the time to keep the air fresh, and there's a lot of electrical equipment and pumps running -- it's like you're in the belly of the machine. It smells a bit like a machine. Space stations are not tranquil places -- you're living in a whirling machine, and you get used to the new hubbub of noise."
And, just like on all space flights, some of the hardest challenges are social. The crew's communication with NASA has been deliberately delayed at times by 20 minutes, so NASA and the crew exchange e-mails for factual communications and videos to greet each other. "They say hi and talk about how they're feeling to the video camera -- to get a human feeling."
Conversations with the American and Russian crews on the International Space Station have bolstered everyone's spirits, and Hadfield brought his guitar on the mission so the crew can sing together at night. "You have to think about what's the right balance, what stimulation is needed mentally and physically to stay healthy and productive in an environment like this."
This is the first time an Atlantis crew has used social media from underwater, and that has been a pleasant surprise. It's forced the crew to express what they're thinking and seeing, Hadfield says, and now they have thousands of followers, from all over the world, on Facebook, Twitter and Flickr.
What he has missed most, though, is the sun. "Here it's always mottled pastel blue or black. You know if it's day or night, but you can never feel the sun -- you only know it's daytime somewhere else."
Still, the inconveniences of being underwater are small compared to the thrill of being able to participate in things that seem "almost magical," Hadfield says. "We're just now at the point (in the human race) where we're starting to permanently leave our planet. We're forging our first steps away from Earth. It's a natural continuation since the very first person stepped over the first hill in Africa millions of years ago.
"It's easy to get distracted from this and not see that it's happening, but with every step we take to make the space station more capable, it opens the possibility of human understanding of where we are in the universe."
Here's a NASA video of Hadfield on an underwater space walk taken a couple of days ago. He's explaining what the crew is doing to the students, teachers and staff at Chris Hadfield High School.