Table of Contents

Spacewalking

What Is a Spacewalk?

A spacewalk is no walk in the park! Imagine having to work in space where the temperatures can change from extreme heat to extreme cold. Micrometeoroids that you can’t see may be trying to penetrate your suit! And, you’re not there to have fun... you’re there to perform some very complicated and sometimes delicate work in a suit that weighs over 100 kg or 250 lbs! And how about this: you don’t actually walk with your feet and legs... you mostly use your arms and hands to pull yourself around. That’s a lot of pressure!

A spacewalk is also known as an extravehicular activity (EVA). It refers to any activity that’s taking place outside of the protection of a spacecraft. There are three types of EVAs:

1. Planned EVAs: EVA’s that are worked out prior to the mission as part of the mission objectives.
2. Unscheduled EVAs: EVA’s that are not planned but are necessary for mission success.
3. Contingency EVA’s: EVA’s that are performed as an emergency to save the spacecraft and/or its crew. (No contingency EVA’s have ever been performed but there are always two people on every mission who are trained just for this purpose.)

Within the next decade, a series of approximately 160 spacewalks will be taking place with the specific purpose of assembling and maintaining the International Space Station. Spacewalkers will be required to connect electrical cables, solar panels, and to install and move components.

The finished Space Station will feature living accommodations and science labs—all 400 km above Earth! In April 2001, astronaut Chris Hadfield was the first Canadian to step out into space.

Training for a Spacewalk

You’d think that walking in space would require a lot of strength in your legs and feet, but astronauts actually move around using arms and hands! They pull themselves around from place to place by using handholds along the shuttle or the International Space Station.

To be prepared for an EVA, the astronaut has to make sure he is physically fit. That means regular cardiovascular workouts and weight lifting.

Additional strength training exercises are included in the regimen for extra muscle power.

To get used to the feeling of floating in space, astronauts practice UNDERWATER. Because of the buoyancy or upward floating feeling that water provides, scuba diving is the closest feeling that astronauts will get to being in space!

Astronauts who are helping to construct the International Space Station train in giant water tanks—the largest being in the Johnson Space Center in Houston, Texas. This water tank is so huge that it can house a full-scale model of the International Space Station!

Tools They Can Use

Tools Used as Safety Measures

Astronauts need safety tools to keep them in place while they use a collection of EVA tools to maintain, repair, or assemble items in space.

On Earth, the force of gravity prevents us from floating away. Gravity is the force of attraction between the Earth and masses near its surface. The more mass or matter an object contains, the greater the attraction or force of gravity.

In space, the gravitational attraction in between planets and stars is very low. There is nothing to keep the astronauts "grounded." Therefore, astronauts need safety tools called tethers that will prevent them from floating away. Tethers typically link astronauts to a slide wire along the Space Station or to the shuttle.

Other means of keeping astronauts connected are handholds and foot restraints. Astronauts use handholds that have been built along the Shuttle or Space Station to pull themselves along. Once they reach their destination and want to start working, they can hook their boots into foot restraints.

If they didn’t hook into their foot restraints, they would move in the opposite direction of the item to which they were applying force—this is known as the Third Law of Motion. Let’s say an astronaut is trying to install a solar panel on the International Space Station. If he didn’t lock himself down and didn’t have a chance to bolt down the panel, pushing down on the solar panel would cause him to start floating upwards. The speed at which he would float away would depend on the mass of the solar panel. Because a solar panel has a greater mass than an astronaut, it would move away at a slower speed than the astronaut.

Handy Tools

Other EVA tools used for handiwork need to be safe and easy for the astronaut to use. These tools always feature a place on which a tether can be hooked. Sometimes, the tools are straight out of the Earth toolbox, only they’ve been adapted so it’s easier for a spacewalker to hold.

These adaptations are necessary because the gloves that the astronauts wear are very thick with insulation. (It protects them from extreme temperatures and micrometeoroids.) Plus, the pressure in the suit means that it is more comfortable for astronauts to keep their fingers stretched out while at rest. Once they try to grasp onto a tool or object, the glove folds in on itself so the pressure within the glove increases. That means holding a small tool will require greater force and the pressure will increase that much more within the glove. So, the tools are generally oversized.

Typical "Earth" items that you might see an astronaut carry include cutters, an adjustable wrench, an allen wrench, a hammer, and vise grips.

The tools shown here are representative samples of the tools available to spacewalkers. Many EVA tools are standard Earth tools that have been modified for space use. Loops, to attach tethers, are added to prevent loss in orbit. For some tools, such as the adjustable wrench and probe, the handle has been enlarged to make grasping with a spacesuit glove less tiring.

Before Stepping Out: Precautions and Preparations

Before astronauts can step out into space, they need to start preparations a day before the spacewalk. Here’s the astronaut’s general checklist:

• Check that the suits and equipment are working properly.
• Before the EVA begins, the astronaut needs to start breathing pure oxygen. This "washes out" the nitrogen dissolved in the blood. In the reduced pressure of the spacesuit, nitrogen left in the bloodstream could form little bubbles in the body. This causes a disorder called "the bends."
• Decrease the cabin pressure. This helps slowly remove nitrogen from the body to minimize the risk of "the bends" or decompression sickness.
• Put on the spacesuit which is called the Extravehicular Mobility Unit (EMU).
• Step out into the airlock. (This is an airtight chamber in which you can control the pressure. It sits between the cabin and the Shuttle’s cargo bay.) Depressurize the airlock until it matches the vacuum of space. Then step out into the cargo bay.
• Use a tether to hook the suit up to a slide wire along the Shuttle or Space Station so you don’t float away. Use more tethers to hook up tools and equipment to the suit so they don’t float away.
• As you start moving in space, always keep track of your tether. Use hand-over-hand movements to grasp onto handholds.
• If you need to start doing work and require both hands to hold an object or tool, you need to lock yourself into foot restraints.

Learn more about spacesuits.