Weightlessness
Astronauts aboard the International Space Station
Burning a candle on Earth (left) and in zero gravity (right)
Weightlessness- a state in which the force of interaction of a body with a support (body weight), arising in connection with gravitational attraction, the action of other mass forces, in particular the inertial force that arises during the accelerated movement of a body, is absent. Sometimes you can hear another name for this effect - microgravity. This name is incorrect for near-Earth flight. Gravity (force of attraction) remains the same. But when flying at large distances from celestial bodies, when their gravitational influence is negligible, microgravity actually arises.
To understand the essence of weightlessness, you can consider an airplane flying along a ballistic trajectory. Such methods are used to train astronauts in Russia and the USA. In the cockpit, a weight is suspended from a string, which usually pulls the string down (if the plane is at rest or moving uniformly and in a straight line). When the thread on which the ball hangs is not tensioned, a state of weightlessness occurs. Thus, the pilot must control the plane so that the ball hangs in the air and the string is not taut. To achieve this effect, the plane must have a constant downward acceleration g. In other words, pilots create zero g-force. Such an overload can be created for a long time (up to 40 seconds) by performing a special aerobatics maneuver (which has no name other than “failure in the air”). The pilots sharply lower the altitude; at a standard flight altitude of 11,000 meters, this gives the required 40 seconds of “weightlessness”; Inside the fuselage there is a chamber in which future cosmonauts train; it has a special soft coating on the walls to avoid injuries when climbing and dropping altitude. A person experiences a feeling similar to weightlessness when flying on civil aviation flights upon landing. However, for the sake of flight safety and the heavy load on the aircraft structure, civil aviation drops the altitude by making several long spiral turns (from a flight altitude of 11 km to an approach altitude of about 1-2 km). Those. The descent is carried out in several passes, during which the passenger feels for a few seconds that he is being lifted up from the chair. (The same feeling is familiar to motorists who are familiar with routes passing along steep hills, when the car begins to slide down from the top) The claims that the aircraft performs aerobatic maneuvers such as the “Nesterov loop” to create short-term weightlessness are nothing more than a myth. Training is carried out in slightly modified production passenger or cargo class vehicles, for which aerobatic maneuvers and similar flight modes are supercritical and can lead to destruction of the vehicle in the air or rapid fatigue failure of the supporting structures.
Peculiarities of human activity and equipment operation in zero gravity conditions
In conditions of weightlessness on board a spacecraft, many physical processes (convection, combustion, etc.) proceed differently than on Earth. The absence of gravity, in particular, requires a special design of systems such as showers, toilets, food heating systems, ventilation, etc. To avoid the formation of stagnant zones where carbon dioxide can accumulate, and to ensure uniform mixing of warm and cold air, the ISS, for example, has a large number of fans installed. Eating and drinking, personal hygiene, working with equipment and, in general, ordinary everyday activities also have their own characteristics and require the astronaut to develop habits and the necessary skills.
The effects of weightlessness are inevitably taken into account in the design of a liquid-propellant rocket engine designed to launch in zero gravity. Liquid fuel components in tanks behave exactly the same as any liquid (forming liquid spheres). For this reason, the supply of liquid components from the tanks to the fuel lines may become impossible. To compensate for this effect, a special tank design is used (with gas and liquid media separators), as well as a fuel sedimentation procedure before starting the engine. This procedure consists of turning on the ship's auxiliary engines for acceleration; the slight acceleration they create deposits the liquid fuel at the bottom of the tank, from where the supply system directs the fuel into the lines.
The effects of weightlessness on the human body
When transitioning from the conditions of earth's gravity to conditions of weightlessness (primarily when a spacecraft enters orbit), most astronauts experience an organism reaction called space adaptation syndrome.
When a person stays in space for a long time (several weeks or more), the lack of gravity begins to cause certain changes in the body that are negative.
The first and most obvious consequence of weightlessness is the rapid atrophy of muscles: the muscles are actually turned off from human activity, as a result, all the physical characteristics of the body decrease. In addition, the consequence of a sharp decrease in the activity of muscle tissue is a reduction in the body's oxygen consumption, and due to the resulting excess hemoglobin, the activity of the bone marrow that synthesizes it (hemoglobin) may decrease.
There is also reason to believe that limited mobility will disrupt phosphorus metabolism in the bones, which will lead to a decrease in their strength.
Weight and gravity
Quite often, the disappearance of weight is confused with the disappearance of gravitational attraction. This is wrong. An example is the situation on the International Space Station (ISS). At an altitude of 350 kilometers (the altitude of the station), the acceleration due to gravity is 8.8/², which is only 10% less than on the surface of the Earth. The state of weightlessness on the ISS does not arise due to the “lack of gravity,” but due to movement in a circular orbit at the first escape velocity, that is, the cosmonauts seem to constantly “fall forward” at a speed of 7.9 km/s.
Weightlessness on Earth
On Earth, for experimental purposes, a short-term state of weightlessness (up to 40 s) is created when an aircraft flies along a parabolic plane (and in fact, ballistic, that is, the one along which the aircraft would fly under the influence of the force of gravity alone; this trajectory is a parabola only if low speeds of movement; for a satellite this is an ellipse, circle or hyperbola) trajectory. The state of weightlessness can be felt at the initial moment of free fall of a body in the atmosphere, when air resistance is still small.
Links
- Astronomical Dictionary Sanko N. F.
- Zero gravity parabola Video from Roscosmos television studio
Notes
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Synonyms:See what “Weightlessness” is in other dictionaries:
Weightlessness... Spelling dictionary-reference book
Lightness, ethereality, weakness, hydro-weightlessness, insignificance, airiness Dictionary of Russian synonyms. weightlessness see lightness 1 Dictionary of synonyms of the Russian language. Practical guide. M.: Russian language. Z. E. Alexandrova ... Synonym dictionary
A condition in which external forces acting on a body do not cause mutual pressure of its particles on each other. In the Earth's gravitational field, the human body perceives such pressures as a feeling of weight. Weightlessness occurs when... Big Encyclopedic Dictionary
Modern encyclopedia
Weightlessness, a state experienced by an object in which the effect of weight does not manifest itself. Weightlessness can be experienced in space or during free fall, although the gravitational attraction of a “weighty” body is present. Astronauts... ... Scientific and technical encyclopedic dictionary
The state of a material body moving in a gravitational field, in which the forces of gravity acting on it or the movement it makes do not cause pressure on the bodies on each other. If a body is at rest in the Earth's gravitational field on a horizontal plane,... ... Physical encyclopedia
Weightlessness- WEIGHTLESSITY, a state in which external forces acting on a body do not cause mutual pressure of its particles on each other. Weightlessness occurs when a body moves freely in a gravitational field (for example, during a vertical fall, movement along... ... Illustrated Encyclopedic Dictionary
WEIGHTLESSNESS- a state in which there is a material body moving freely in the gravitational field of the Earth (or any other celestial body) under the influence only of gravitational forces. Will distinguish. The peculiarity of the H. state is that during H. the external forces acting on the particles of the body. forces (gravitational forces) do not cause mutual pressure of body particles on each other.
When a body is at rest in the Earth's gravitational field on a horizontal plane, it is also acted upon by a numerically equal but oppositely directed force - the reaction of the plane. As a result, internal fluids arise in the body. forces in the form of mutual pressure of body particles on each other. The human body perceives such internal. effort as a familiar state of weightiness for him. These internal ones appear. forces due to the reaction of the plane. The reaction is a surface force, that is, a force directly acting on some part of the surface of the body; The action of this force is transmitted to other particles of the body by the pressure of neighboring particles on them, which causes the corresponding internal forces in the body. efforts. Similar internal forces arise when any other surface forces act on the body: traction force, environmental resistance force, etc. If the surface force is numerically greater than the force of gravity, then the internal force is correspondingly greater. effort, which causes the phenomenon of overload and occurs, for example, during rocket launch.
The gravitational force is a mass force and, unlike surface forces, acts directly on each of the particles of the body. Therefore, when only gravitational forces act on a body, they directly impart to each of the particles of the body the same acceleration and these particles move as free, without exerting mutual pressure on each other; the body is in state H.
In general, the state of H. occurs when: a) external forces acting on the body. forces are only mass (gravitational forces); b) the field of these mass forces is locally homogeneous, that is, the field forces impart to all particles of the body in each of its positions accelerations that are identical in magnitude and direction, which, when moving in the gravitational field of the Earth, practically occurs if the dimensions of the body are small compared to the radius of the Earth ; in the beginning. the velocities of all particles of the body are identical in magnitude and direction (the body moves translationally).
For example, space fly. the apparatus (or satellite) and all the bodies located in it, having received the appropriate beginning. speed, move under the influence of gravitational forces along their orbits with almost identical accelerations, like free ones, and neither the bodies themselves nor their particles exert mutual pressure on each other, i.e., they are in state H. At the same time, relative to the cabin, they fly . apparatus, the body located in it can remain at rest anywhere (freely “hang” in space). Although gravitational forces under N. act on all particles of the body, there is no external force. surface forces, which could cause mutual pressure of particles on each other. Please note that internal efforts of a different nature, not caused by external forces. influences, for example molecular forces, temperature, and muscular forces in the human body can also occur in the H.
H. can significantly influence a number of physical. phenomena. For example, in a liquid poured into a vessel, the forces of intermolecular interaction, which are small under “terrestrial” conditions compared to the pressure forces caused by weight, only affect the shape of the meniscus. With H., the action of these forces leads to the fact that the wetting liquid placed in a closed vessel is evenly distributed over the walls of the vessel, and air, if there is any, occupies the middle part of the vessel, while the non-wetting liquid takes the shape of a ball in the vessel. Drops of liquid poured out of the vessel are also drawn into balls.
As a result it means. differences between H. conditions and “terrestrial” conditions, in which instruments and assemblies of satellites and space satellites are created and debugged. fly. spacecraft and their launch vehicles, the problem of H. occupies an important place among other problems of astronautics. Thus, in conditions of H., instruments and devices in which physical ones are used are unsuitable. pendulums or free supply of liquid, etc. Taking into account H. becomes especially important for systems with containers partially filled with liquid, which, for example, occurs in an engine. installations with liquid-jet engines, designed for repeated activation in space. flight. A number of other technologies are also emerging. problems.
It is especially important to take into account the unique conditions of H. during the flight of habitable spacecraft. ships, because the living conditions of a person under H. differ significantly from the usual, “earthly” conditions, which causes changes in a number of his life functions. However, a preliminary training and preventive measures allow a person to stay and work successfully in H.
It is also assumed that for a very long time. Flights on orbital (near-Earth) or interplanetary stations can create art. "gravity", locating, for example, work areas in cabins rotating around the center. parts of the station. The bodies in these cabins will be pressed against the side surface of the cabin, the edges will play the role of a “floor”, and the reaction of this “floor” applied to the bodies will create art. "heaviness".
Weightlessness - more precisely, microgravity - is a special state outside of Earth's (or any other) gravity, when it is practically not felt, and the astronaut's body is in a state of continuous free fall. Weightlessness can be experienced, for example, in a free-falling elevator or airplane (such acrobat aircraft are used for training in artificial weightlessness), or in Earth orbit, on the International Space Station. Prolonged exposure to weightlessness is detrimental to the physical condition of astronauts, so scientists are studying how to reduce the rate of muscle and bone loss in microgravity to protect future travelers to Mars and beyond. Literally six months spent in orbit cause irreversible changes in the human body.
Prolonged stay in conditions of weightlessness leads to health problems - this is a fact. For example, people already know that astronauts will experience a wide range of medical problems during their flight, including muscle atrophy, calcium deficiency, poor cardiopulmonary function, visual impairment, and even weakened immunity. Researchers from Michigan's Henry Ford Hospital have added another problem to this list - it has been proven that weightlessness destroys joints that do not recover even after returning to Earth.
Weight as the force with which any body acts on a surface, support or suspension. Weight arises due to the gravitational attraction of the Earth. Numerically, the weight is equal to the force of gravity, but the latter is applied to the center of mass of the body, while the weight is applied to the support.
Weightlessness - zero weight, can occur if there is no gravitational force, that is, the body is sufficiently away from massive objects that can attract it.
The International Space Station is located 350 km from Earth. At this distance, the acceleration of gravity (g) is 8.8 m/s2, which is only 10% less than on the surface of the planet.
This is rarely seen in practice - gravitational influence always exists. Astronauts on the ISS are still affected by the Earth, but there is weightlessness there.
Another case of weightlessness occurs when gravity is compensated by other forces. For example, the ISS is subject to gravity, slightly reduced due to distance, but the station also moves in a circular orbit at escape velocity and centrifugal force compensates for gravity.
Weightlessness on Earth
The phenomenon of weightlessness is also possible on Earth. Under the influence of acceleration, body weight can decrease and even become negative. The classic example given by physicists is a falling elevator.
If the elevator moves downward with acceleration, then the pressure on the elevator floor, and therefore the weight, will decrease. Moreover, if the acceleration is equal to the acceleration of gravity, that is, the elevator falls, the weight of the bodies will become zero.
Negative weight is observed if the acceleration of the elevator movement exceeds the acceleration of gravity - the bodies inside will “stick” to the ceiling of the cabin.
This effect is widely used to simulate weightlessness in astronaut training. The aircraft, equipped with a training chamber, rises to a considerable height. After which it dives down along a ballistic trajectory, in fact, the machine levels off at the surface of the earth. When diving from 11 thousand meters, you can get 40 seconds of weightlessness, which is used for training.
There is a misconception that such people perform complex figures, like the “Nesterov loop,” to achieve weightlessness. In fact, modified production passenger aircraft, which are incapable of complex maneuvers, are used for training.
Physical Expression
The physical formula for weight (P) during accelerated movement of a support, be it a falling bodice or a diving aircraft, is as follows:
where m is body mass,
g – free fall acceleration,
a is the acceleration of the support.
When g and a are equal, P=0, that is, weightlessness is achieved.
What is weightlessness? Floating cups, the ability to fly and walk on the ceiling, and move even the most massive objects with ease - such is the romantic idea of this physical concept.
If you ask an astronaut what weightlessness is, he will tell you how difficult it is during the first week on board the station and how long it takes to recover after returning, getting used to the conditions of gravity. A physicist, most likely, will omit such nuances and reveal the concept with mathematical precision using formulas and numbers.
Definition
Let's begin our acquaintance with the phenomenon by revealing the scientific essence of the issue. Physicists define weightlessness as a state of a body when its movement or external forces acting on it do not lead to mutual pressure of particles on each other. The latter always occurs on our planet when any object moves or is at rest: it is pressed by gravity and the oppositely directed reaction of the surface on which the object is located.
An exception to this rule is cases of falling at the speed that gravity imparts to the body. In such a process, there is no pressure of particles on each other, weightlessness appears. Physics says that the condition that occurs in spaceships and sometimes in airplanes is based on the same principle. Weightlessness appears in these devices when they move at a constant speed in any direction and are in a state of free fall. An artificial satellite or delivered into orbit using a launch vehicle. It gives them a certain speed, which is maintained after the device turns off its own engines. In this case, the ship begins to move only under the influence of gravity and weightlessness occurs.
At home
The consequences of flights for astronauts do not stop there. After returning to Earth, they have to adapt back to gravity for some time. What is weightlessness for an astronaut who has completed his flight? First of all, it's a habit. Consciousness for some period still refuses to accept the fact of the presence of gravity. As a result, there are often cases when an astronaut, instead of putting a cup on the table, simply let it go and realized the mistake only after hearing the sound of dishes breaking on the floor.
Nutrition
One of the difficult and at the same time interesting tasks for the organizers of manned flights is to provide astronauts with food that is easily digestible by the body under the influence of weightlessness in a convenient form. The first experiments did not arouse much enthusiasm among the crew members. An indicative case in this regard is when the American astronaut John Young, contrary to strict prohibitions, brought a sandwich on board, which, however, they did not eat, so as not to violate the regulations even more.
Today there are no problems with diversity. The list of dishes available to Russian cosmonauts includes 250 items. Sometimes a cargo ship departing for the station will deliver a fresh meal ordered by one of the crew.
The basis of the diet is All liquid dishes, drinks, and purees are packaged in aluminum tubes. The packaging and packaging of products is designed in such a way as to avoid the appearance of crumbs that float in weightlessness and could get into someone’s eye. For example, cookies are made quite small and covered with a shell that melts in your mouth.
Familiar surroundings
At stations like the ISS, they try to bring all conditions to those familiar on Earth. These include national dishes on the menu, air movement necessary both for the functioning of the body and for the normal operation of equipment, and even the designation of the floor and ceiling. The latter has, rather, psychological significance. An astronaut in zero gravity does not care in what position to work, however, the allocation of a conditional floor and ceiling reduces the risk of loss of orientation and promotes faster adaptation.
Weightlessness is one of the reasons why not everyone is accepted as an astronaut. Adaptation upon arrival at the station and after returning to Earth is comparable to acclimatization, enhanced several times. A person with poor health may not be able to withstand such a load.