Spacewalks

Artist’s impression of astronauts working on the outside of the ISS

When a new part for the ISS arrives with a launcher, it has to be connected to the Space Station. Some parts plug in automatically, others are manoeuvered into place with the help of a robotic arm. But sometimes the connection has to be done by hand – this is a job for astronauts.

Often these connections have to be made on the outside of the ISS. In this case the astronauts have to perform a so-called “Extra Vehicular Activity” (EVA) or “spacewalk”.

Space is a very harsh environment. In the vacuum of space it is impossible for humans to breathe, and there are extreme temperature conditions. High-energy rays from the Sun and small particles can also hurt the astronauts. Therefore astronauts need very special gear to protect themselves.

EVA training in the swimming pool

Spacesuits are designed to protect astronauts against such dangers. The suits are airtight and cover the whole body in several layers. The inner layers are made to control the temperature, the outer layers to protect the astronauts against the high-energy rays. Tanks are attached to the back of the spacesuits with enough oxygen for several hours.

A spacesuit is big and cumbersome, making it difficult to move. Also, the weightless conditions make it hard for astronauts to control their movements. Moving around in space is very different from moving around on Earth. To make sure that everything goes well, the astronauts undergo a lot of training on Earth long before the actual spacewalk is performed. Typically, spacewalks are practised in big underwater tanks – the best place to simulate and experience a sensation of weightless conditions on Earth.

German ESA astronaut Thomas Reiter during a spacewalk

In space astronauts have to be very careful to attach themselves to the ISS in order not to float away from it. In order to avoid this, the astronauts hook themselves to hand-rails on the outside of the ISS. Naturally, the tools the astronauts use also have to be securely fastened at all times. These tools are similar to the powered screwdrivers and wrenches you can buy in any do-it-yourself shop on Earth, and are used to tighten bolts and lock pieces of the ISS firmly together.