October 10, 2014 – When rookie spacewalkers Reid Wiseman and Alexander Gerst stepped outside of the International Space Station (ISS) on Tuesday, they made it appear effortless as they replaced a failed pump module and installed backup power gear for the Canadarm2 and Mobile Transporter. The two astronauts worked outside of the Quest airlock of the ISS for 6 hours and 13 minutes and completed everything on their task list.
Gerst spent much of his time riding the station’s robotic arm, maneuvering the pump module. He later wrote, “Safe to say, this was the most amazing thing I have done in my life. The pump module I carry here has a mass of 400 kg. I could move it with my little finger.”
So how do rookie spacewalkers prepare for this kind of adventure? Walking in space is nothing like walking on Earth and there is a huge amount of risk involved. How do astronauts bring themselves to step outside of the safety of the International Space Station and work in the vacuum of space?
Astronauts Wiseman of NASA and Gerst of the European Space Agency are members of the six-person Expedition 41 crew currently living aboard the ISS and each member of the crew has spent years training for a spacewalk, also known as an extravehicular activity (EVA). Through training, they’re able to lessen those risks. It also takes a large team effort working behind the scenes.
To begin with, the robotic arm that held Gerst was maneuvered by NASA Flight Engineer Barry Wilmore, who also served as the spacewalk coordinator.
Additionally, the Mission Control Center in Houston that is responsible for monitoring and helping the spacewalkers is called the Extravehicular Activities (EVA) Operations. There are 39 engineers divided roughly in half for “EVA Systems,” which are the spacesuit and ISS airlock experts, and “EVA Task,” which focus on spacewalk tools and keeping track of the spacewalkers’ scheduled tasks.
The EVA team is busy long before the day of the spacewalk. Before astronauts leave Earth, they have to learn to use all of the gadgets and tools that they’ll use in space, and also how to use the spacesuit itself.
Helping them learn are astronaut trainers like Scott Wray. Wray is part of the EVA team at NASA’s Johnson Space Center that assists astronauts through the entire process, from their first spacewalk training, to writing the job descriptions for work that needs to be performed in space, to monitoring the work as it’s done.
“As an EVA instructor and Flight Controller, I have a responsibility to prepare astronauts to perform in a spacewalk. I have to teach them how to work in the suit, how to use tools to repair and maintain ISS, and also be able to respond to emergencies while out on EVA,” Wray said. “Performing a spacewalk is unlike anything else you have ever done. The EMU (Extra Mobility Unit) spacesuit is cumbersome to work in; mobility and dexterity are limited. Astronauts come in many shapes and sizes and from various backgrounds. My job is to make them all qualified to perform a spacewalk.”
First, the astronauts have to learn how to put on their spacesuit. It provides the air needed to breathe outside of the spacecraft, provides water, and also keeps the astronaut’s body temperature comfortable, even though outside temperatures could range from -200 degrees Fahrenheit to 200 degrees above zero. The suits are also pressurized at a significantly lower pressure than the ambient cabin pressure of the spacecraft, so astronauts must learn a lengthy protocol for putting the suit on and preparing for the spacewalk in order to avoid decompression sickness.
The suit weighs nearly 300 pounds. Current spacewalks include floating more than walking, so the design of the suit is not very flexible. Instead of walking, movement is performed by working hand-over-hand along external handrails. This puts all of the stress and fatigue on a crew member’s hands.
“The EMU spacesuit is pressurized to 4.3 pounds per square inch. It’s much like wearing a suit of armor that resists bending at the joints. Every move you make is pressing against the pressurized bladder of the suit,” said Wray. “Imagine every time you try to grip a tool or handrail, your glove is resisting. After a 6-8 hour spacewalk, translating across the space station and using hand tools to perform maintenance, your hands are pretty worn out. In addition, every item taken outside is tethered so that it doesn’t float away. Managing your tool bags and tethers while everything wants to float can be challenging.”
Both astronauts and cosmonauts practice spacewalks in large pools. In Houston, Wray and the EVA team instruct astronauts in the Neutral Buoyancy Laboratory (NBL). The NBL is the world’s largest indoor pool at 202 feet (62 meters) long and 102 feet (31 meters) wide. The pool is 40 feet (12 meters) deep and at the bottom of the NBL there is a full-size model of the International Space Station.
Being underwater in the NBL is similar to being in space, but not quite the same. You’re not truly weightless underwater, but what is called neutrally buoyant. This means that an object doesn’t want to float to the surface or sink to the bottom. In the NBL, weights or floats will be attached to the spacesuit and the tools to simulate weightlessness.
In this underwater world, astronauts learn to work efficiently in their spacesuits. Astronauts will begin their training in standard scuba gear, but once they’ve gotten comfortable with tools and assigned tasks, they’ll start practicing while wearing a spacesuit. Typically, an astronaut will go through 10 to 15, six-hour underwater training sessions in the spacesuit, developing the skills they’ll need to work effectively as an EVA crew member in orbit.
EVA team members in scuba gear aid astronauts during the training, helping them move around until they get used to moving in their spacesuits. They’ll also be there to protect the astronauts if anything happens with the suit. It’s the beginning of a deep trust and friendship that will continue when the astronaut takes their first step into space.
Training increasingly shifts toward providing crew members with a general suite of EVA skills. The astronauts must train for every possible contingency and maintenance EVA and concentrate a lot of time training with the tools and methods they’ll use during a spacewalk. By the time they leave Earth, astronauts are ready to fix anything that might break while they’re on the International Space Station.
“Much of my job involves developing a technique to repair and/or replace a broken component with only the tools that are onboard the ISS,” said Wray. “Sometimes we have to get pretty creative and come up with off-nominal fixes. Imagine having to maintain and repair your house over the next 15 years without ever going to the hardware store. You only have a small number of tools at your disposal and limited replacement parts.”
If there is a specific job that needs to be accomplished, members of the EVA team need to develop the procedures that allow the astronauts to accomplish the tasks associated with that mission. They also provide technical insight and guidance and respond to crew questions during the spacewalk itself.
The EVA team also ensures that every step in the procedure is completed and that nothing is left behind. EVA Systems monitors data from the spacewalkers’ suits and from the airlock. EVA Task keeps track of the spacewalkers’ timeline and any possible issues while the crew is outside of the vehicle.
On the day of the spacewalk, in addition to the Houston team, the team includes hardware designers, tool engineers, spacesuit design engineers, and safety engineers. When things are not going according to plan, the team works together to find a quick resolution. Time is always of the essence and the ability to resolve unforeseen issues means the difference between success and failure.
Wray became all too aware of this fact during a scheduled EVA on July 16, 2013 when ISS crew member Luca Parmitano had to abort his EVA due to water intrusion into his helmet.
“He was at risk of drowning in his own helmet, but performed flawlessly under-pressure as he translated back to the crewlock while the water was increasing in his helmet, covering his ears, eyes, and nose. After he was safe inside, and we (the execute shift) had handed over to the next shift, I was struck by how close we had come to losing a friend that day. I was also extremely proud of how Luca had responded to the emergency and performed exactly how we had trained him. So the responsibility is tough,” said Wray.
The EVA team comes from a wide-range of backgrounds and their knowledge of the EVA position comes from on-the-job training. They work in spacesuits in the simulated environment of the NBL until they can give astronauts the training they need. They also work closely with and rely on the experience of veteran spacewalkers.
“Together we develop a training program that can provide rookie astronauts with the skills necessary to perform a spacewalk during their expedition,” Wray said. “I can still remember Reid and Alex’s very first time working in the spacesuit at the NBL during their first year as rookie astronauts, and here they are whirling around our planet, doing it for real, and doing it well. Sometimes I’m so excited about my job that I can’t believe I get paid to do it.”
Reid Wiseman and Barry Wilmore will begin the next ISS spacewalk on Wednesday, October 15 at 6:20 am MDT.