why do astronaut use special showers

Because water moves in the air.
Water doesn’t flow out of a tap, it floats in a bubble(水泡)! Astronauts used a special hose(软管)to take showers. And when they’re finished, they use a vacuum(真空的)hose to suck the dirty water off of their bodies.
Taking a shower aboard a spaceship isn’t like taking one at home. On a spaceship, you must store up water. And preparing the equipment for showers takes a long time. It is also not a simple activity. On Russian spaceships, an astronaut gets in an elastic(弹性的) cylinder(汽缸) with caps at both ends. Rubber slippers, fixed to the floor, keep the astronaut from flying upward. The astronaut puts a soft pipe into his or her mouth in order to breathe. Then the astronaut presses his or her nose to keep water out, because water doesn’t drop downward in space. When the water is turned on, it comes out of holes at the top and bottom of the cylinder. Astronauts use a soap-filled cloth to wash and then a plain cloth to clean.