Have you ever seen people building houses? To build a house, you need workers. They use their hands, tools (工具) and machines to put things together. Building the International Space Station (国际空间站) is the same. The difference is that the workers are astronauts. They walk in space and use robots' arms and hands to do the work.

In the space station, astronauts are comfortable. The temperature there is about 21℃. But outside of the station, it can be too hot or cold for people. In the sunlight, it's about 120℃. In the shadow (暗处) of the station, it's about -85℃. So when astronauts walk in space, they have to wear heavy clothes—spacesuits.

These suits also keep astronauts safe from flying rubbish in space. Each time people go into space, they leave rubbish there. So astronauts should be careful because there's a lot of rubbish, and some rubbish goes many times as fast as a plane!

Space walking is not easy, and it can be dangerous. So getting ready for it takes a lot of time to learn. Astronauts will need to do 160 space walks to finish their work in the space station. That will take about 1,900 man-hour work.