Defying Gravity

Italian astronaut Luca Parmitano had a terrifying experience during a spacewalk. While working on the International Space Station (ISS), his helmet1 began filling with water. At first, Parmitano wasn't sure what it was. "My head is really wet," he told NASA flight controllers back on Earth. As the water began to accumulate, Parmitano realized there was a problem. "It's too much . . . Now it's in my eyes," he recalls saying. Concerned that he might choke2 on the water, ground control stopped the spacewalk. Back inside the ISS, Parmitano took off his helmet and discovered that it contained almost half a liter of water. Where had this water come from? NASA found out that a malfunction3 in the suit's liquid cooling system had caused water to leak. Some of the water got into Parmitano's helmet. Though NASA has taken steps to correct the problem, the experience underscores the dangers that astronauts face each time they venture outside a spacecraft.

Training for a Spacewalk

Spacewalks are safer now than they were over 50 years ago, when—in 1965— Russian Alexei Leonov carried out the first one. However, as Parmitano's experience illustrates, there are still risks involved. To ensure that missions are successful, astronauts train on Earth for hundreds of hours. They learn to deal with the lack of gravity in space, for example, by floating in a large tank4 of water, where they experience a feeling very close to the weightlessness of space. For every hour they will walk in space, astronauts practice for 10 hours in the water. They also familiarize themselves with the exact route they will take once they leave a spacecraft. They go over this path repeatedly, so they know exactly what to do on a spacewalk. Astronauts also train for emergencies that may come about during a walk. One of the most common is losing consciousness. Although spacesuits have an internal heating and cooling system, they can still get very hot, especially when astronauts are doing physically demanding work outside the spacecraft for hours. Astronauts are trained to monitor their breathing and to make sure their bodies aren't overheating, which could cause them to pass out. Another potential challenge that astronauts are trained to deal with is being separated from a spacecraft. During a walk, astronauts work in pairs and are attached to the ISS for safety reasons. Every NASA spacesuit has a mini jetpack, and astronauts are trained to use it to float back to the station if they somehow become detached from the craft.

Sunita Williams: Spacewalker

As a child, Sunita Williams believed that space travel would be routine when she grew up— something everyone did. She never thought she'd be one of the pioneers. The former pilot has now visited the International Space Station several times, and has spent dozens of hours walking in space. National Geographic: What's the most impressive thing about a spacewalk? Sunita Williams: The view—being up very high looking down and seeing the northern lights below. NG: Is it scary? SW: On my first walk in 2006, there was a problem with a solar array (a solar panel) on the station, and we needed to fix it. A long arm connects the space station to the array. As I started going up this arm to the array, I felt like I was climbing a skyscraper. I had to tell myself, "It's okay. You're not going to fall." In space, you can get really confused sometimes. You don't know if you are going up or down, left or right. During that first walk outside the ISS, I had to remind myself how we trained in the water tank. That helped me stay calm. NG: Are there things you do to keep yourself grounded5 while living in space? SW: On my first flight, I would go down to the Russian end of the space station because there was only one bathroom at the time. Astronaut Misha Tyurin would always say, "Would you like some tea?" We would sit or float in the air for five or ten minutes drinking tea and just talk about life.