DK Science: Astronauts
Since Yuri Gagarin became the first spaceman in 1961, hundreds of space travellers, or astronauts (called cosmonauts if Russian), have ventured into space. Experience has shown that humans can work well in space both on board their spacecraft and outside on EVAs. In space, astronauts? bodies are constantly monitored, both to check their health, and as part of the study of SPACE MEDICINE ? research into how the body is affected by weightless conditions.
On Earth, an astronaut practises for spacewalking in a water tank. He wears a suit like a spacesuit, which is weighted so that it neither rises nor sinks. Such neutral buoyancy (floating) conditions are similar to the state of weightlessness that astronauts experience, and have to work in, while in space.
Astronauts on today?s space flights eat a variety of foods. Some are in their natural state, such as nuts and biscuits, and some are canned or frozen. Other foods are dehydrated and need to be mixed with water before eating. In the early days of space flight, astronauts ate nutritious but unappetizing food pastes out of toothpaste-type tubes.
Up in orbit, astronauts sometimes have to work outside their spacecraft. This extravehicular activity, or EVA, is popularly called spacewalking. Russian cosmonaut Alexei Leonov and US astronaut Edward White pioneered spacewalking in 1965. Today, astronauts go on EVAs to recover and repair satellites and carry out construction work on the International Space Station.
On shuttle mission STS-112 in October 2002, astronaut David Wolf worked for over six hours to install equipment on the International Space Station (ISS). He was helped by astronaut Piers J. Sellers. The main purpose of this mission was to take up a new truss (beam) for the framework of the ISS. It was then installed by the astronauts.
On the shuttle STS-109 servicing mission in March 2002, astronauts installed a new power unit, a new camera, and new solar arrays on the Hubble Space Telescope. On this mission, the astronauts clocked up a record 36 hours spacewalking in five separate EVAs. This was the fourth shuttle mission dedicated to servicing the Hubble telescope.
Because of the weightless environment, space flight affects the human body in a number of ways. Muscles begin to waste away and bones tend to lose mass and become more brittle. Exercise and a suitable diet helps to combat these conditions on long space flights.