Movement in outer space

An object in outer space does not have to orbit the Earth, but it can move through space in general. In such a case, a state of weightlessness occurs in the reference frame connected to the subject, if the object moves only under the influence of gravitational forces, i.e. with acceleration equal to the gravitational acceleration at the given location. In no case is it necessary for the gravitational force acting on the object to be zero. Most cosmic objects move in this way, i.e. by the action of gravitational forces. The only exceptions are sections of flight when the artificial space object is accelerated or decelerated by the thrust of the engines or changes the direction of flight. In these sections of the flight, no weightlessness will arise.

Simulation of weightlessness

In connection with spaceflights, the study of weightlessness and training in being in it is very important. As mentioned, a state of weightlessness on the Earth's surface can only be achieved for a very short time. For some purposes, it is not necessary to use a state of weightlessness directly, but only to simulate a stay in it.

For these purposes, a stay in spacesuits in a pool with water is often used. The spacesuit is balanced so that the buoyancy force on it is as great as the gravity force. Then a person in a spacesuit floats in the water as in a state of weightlessness. This simulation has two shortcomings. The resistance of the aquatic environment is significantly greater than the resistance of the air, so that some movements are inhibited in the water and thus facilitated. The buoyancy force acts only on the surface of the spacesuit and the spacesuit lifts the person with force acting on the skin. A completely normal gravity force acts on the internal organs of a person inside, so it is not possible to achieve the effects of a balance disorder or nausea caused by real weightlessness.

The second way to simulate weightlessness is to stay in a wind tunnel. In it, a person is floated in a vertical tunnel vertically upwards by flowing air. The speed of the air can be used to regulate the acting force and the degree of effect. The disadvantages of this simulation are similar to those of a swimming pool, only the place of greater water resistance is affected by the flow of air along overalls.

Problems with movement in state of weightlessness

Staying in a state of weightlessness has more side effects on humans (and other higher organisms). For a short time, for several hours or days, when you stay in a state of weightlessness, a seasickness associated with stomach upset and feelings of pressure in the head appears. This is caused by non-standard stimulation of the balance system in the inner ear, which normally determines the direction of the gravity of the body.

The longer-term effect is the redistribution of fluids in the body. On the surface of the Earth, the heart pushes the blood upwards against the action of gravity, in the state of weightlessness the blood flows into the upper half of the body much more easily. Cosmonauts show redness and sometimes swelling of the face. The different nature of movements in the state of weightlessness, when it is not necessary to overcome the action of gravity and overall physical exertion is less, gradually leads to muscle atrophy. Furthermore, hormonal changes, calcium leaching from the bones and also signs of liver damage were observed in experimental animals. Some consequences of weightlessness can be eliminated, for example, by regular exercise, while others must be subjected to further thorough research in the future.

Problems with staying in weightlessness include a complete change in motor habits when performing normal activities in orbit. Weightless personal hygiene, food, excretion must be subordinated, but of course also work activities such as assembly work inside and outside the space station. Much of the common events on the Earth's surface account for the ubiquitous gravity force that "provides support”.