BY THE TIME BRITISH-BORN ASTRONAUT Nick Patrick completed his final spacewalk in NASA’s 30-year Space Shuttle programme, his “dive-log” totalled 430 hours.
This was accumulated from some 200 sorties – 100 in open water, 100 in the Neutral Buoyancy Laboratory (NBL) and three in outer space.
That last dive spot is “a harsher environment, and a lot harder to get to,” says Nick. Spacewalking “is like wearing a scuba-diving suit while working on your roof!”
Following up on my previous article (How Scuba Helps Us in Space, May 2007), I caught Nick at the NBL at NASA’s Sonny Carter Training Facility in Houston, Texas to talk about his experience of diving in the big tank.
I wanted to know why all International Space Station (ISS) astronauts representing the USA, Europe, Canada and Japan have spent so many hours under water qualifying for EVA (extravehicular activity, or spacewalks) prior to their space flights.
Nick had been an unflown astronaut when I first met him for DIVER. Then
he flew on Shuttle mission STS-116 Discovery, and commanded a second aquanaut mission to the Aquarius NEEMO underwater facility in Florida.
He then started rehearsing three EVAs for his second Shuttle mission, STS-130 Endeavour.
Launched to the ISS in February 2010, this delivered the “Node 3 Tranquility module” and the Cupola, a seven-panelled bay window that astronauts use as a robotics workstation and Earth observation lounge.
To get the Cupola installed on the station and outfitted for operations, Nick and his spacewalking partner Bob Behnken had to practise their work under water at the NBL.
To prepare for space-dives, spacewalkers can take a scuba dive in the NBL prior to a six-hour suited run. During the underwater rehearsal “I adapt the mentality of cave-diving, a philosophy that served me well with NEEMO,” says Nick.
“I spent a lot of time during my dive upside-down, holding onto the station. Since there is no ‘up’ or ‘down’ in space, it can be disorienting when ‘left’ is ‘right,’ and ‘right’ is ‘left’. People had warned me about that.”
Once in orbit, Nick found that his scuba dives really paid off. “I never had a moment of trouble,” he says. In the pool “I had imagined where I might want handholds, and then I practised reaching for those handholds.”
Nick enjoyed comparing a spacewalk (virtual or real) to a cave dive.
“In cave-diving and in my NEEMO dives, there are multiple sources of air, a long secondary regulator hose, and you have to fix problems where you are.
“I found that to be a useful philosophy in space,” says Nick. Whether swimming in a cave or crawling across the International Space Station, “you have to go back the way you came. I was comfortable in a cave and in an EVA.”
What if the NBL were open to the public “I think a scuba diver would enjoy exploring the International Space Station like a reef or wreck. ‘What’s this protrusion, this socket, or this cable’ It’s covered in interesting artefacts.”
He felt that a typical diver could identify a camera stanchion and an antenna or two, but might encounter an archaeological mystery trying to figure out the rest. “Too bad we can’t let a diver loose in the NBL!”
Nick described the NBL on a standard workday: “There are a whole lot of divers hovering about – utility divers with tools, for example. Due to the weight, we carry a plastic drill on our tool-belt, so when we need a real one, the utility diver will swap the plastic one for a functioning PGT [pistol-grip tool].”
All NBL runs are documented, so two divers operate the video cameras recording the astronauts’ every move.
Two others move the spacewalkers around the pool when the astronauts’ umbilicals have stretched to their limit.

THERE ARE DIFFERENCES between wearing an Extravehicular Mobility Unit spacesuit under water and floating in the actual suit in orbit in real time.
“I had 25 runs in the NBL, six or seven for each EVA,” explained Nick. “We suited up topside and got lowered down to the bottom of the pool, clearing our ears gradually. Then it would take 10 minutes to weigh off.”
For his third STS-130 EVA, Nick was lead spacewalker. He and Bob entered the airlock mock-up under water to practise their exit for the real deal.
“In the pool, the aft side of the airlock has a Plexiglas surface, so the divers can see us. Bob and I set up our safety tethers, then I would egress head-down and make a forward somersault out the door. Bob followed me. Then we set up the bags we needed.”
Nick underlined the slight difference between the rehearsal and performance venues: “One is blue and wet, and the other is black and a vacuum!”
For the spacewalkers’ first task, Bob headed to Tranquility and the US lab module Destiny to open ammonia connections. Nick installed heater and data cables on a pressurised mating adaptor on the side of Tranquility so the module could keep warm in space.
Ninety minutes later, the astronauts met at the Cupola beneath Tranquility.
In space, the Cupola is on the bottom of the space station, but in the pool it’s on top. As the weight of the multi-layer insulation (MLI) covering the Cupola windows would cause it to fall towards the bottom of the pool, this important layout switch gave the astronauts more practical experience in gathering the MLI and stuffing it into trash bags.
“In orbit, the MLI had a tendency to spring up into its natural position,” explained Nick. “Imagine trying to fold a tablecloth blowing in the wind. On Earth, the weight of the towel holds the fold. Not so with crunchy, stiff MLI.”
For their next trick, Bob continued to outfit Tranquility by installing a foot restraint. Nick got to play with real power-tools on the Cupola. “I released the Cupola’s launch locks – 21 bolts, three on each of the seven windows.
I had to follow a special pattern – I couldn’t climb on the window shutters once they’d been unbolted.”
Nick then had to attend to video cabling from Node 2 Harmony to the Russian segment of the station.
What of the NBL in the future Steve Bowen took over as EVA Branch Chief in the Astronaut Office when his predecessor was assigned to NASA’s final Space Shuttle flight.
He described STS-133 Discovery in January 2011 as “a good model going forward” for the ISS. He had a month to learn how to perform two detailed spacewalks, standing in for an injured astronaut who couldn’t launch.
“Before my arrival, the STS-133 team had developed such well-constructed procedures, through their training and especially their time at the NBL over the previous year, that we would have been able to execute the procedures even with no NBL training for me,” he told me.
“This STS-133 experience gives me confidence that we can use the NBL and the EVA team to develop really good procedures that the ISS crew will be able to safely and successfully execute… for almost any ISS contingency.”

EUROPEAN SPACE AGENCY ASTRONAUT André Kuipers from Amsterdam was scheduled for a Kazakhstan launch on 21 December aboard a Russian Soyuz spacecraft, beginning a six-month mission on the ISS. What did he think of the Houston facility
“Both for moving around in weightlessness and for being in a dangerous environment, scuba-diving is very useful,” he told me.
“From a scuba point of view, this NBL is a boy’s dream. If you like wreck-diving, there’s a whole space station under water. I wish every scuba diver could have some dive time in the NBL.”

Neutral Buoyancy
Laboratory, Houston
Length: 61.5m
Width: 31.1m
Depth: 12.2m
Volume: 23.5 million litres
Water Temp: 28.9-30°C
Breathing Mix: Nitrox