Where weightlessness begins. What is weightlessness from the point of view of a physicist and an astronaut? Effect on the human body

Weightlessness is the absence of force between body weight and support. More precisely, it is a state in which gravitational attraction is completely absent. In some cases, this state is called microgravity.

Sometimes different research centers conduct certain experiments in zero gravity conditions. Not everyone can go into space, where weightlessness is a natural state. For this reason, specially equipped aircraft are used to achieve weightlessness. The trajectory of the aircraft in this case is a parabola.

Such a flight begins at an altitude of 6 km. There is a sharp climb to approximately 7.5 km, which takes about 20 seconds. Passengers at this moment experience an overload of up to 1.8 g, which means a double increase in weight. The plane then reduces engine thrust to almost 0 and is sent along a parabolic trajectory.

The maximum of the parabola is reached at an altitude of 8 km, and free fall begins. Over the next 20 seconds, weightlessness occurs inside the aircraft. Next, the plane levels out. The angle between the horizontal and the direction of movement of the aircraft reaches 45 degrees. The engines turn on again and the aircraft flies horizontally again. Thus, depending on the type of aircraft, up to 30 parabolic maneuvers are performed in one flight.

The only method of creating weightlessness on Earth is called parabolic flight. In Russia, similar experiments have been conducted for 30 years. Typically, an Airbus is used.

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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 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 influence of weightlessness is inevitably taken into account in the design of a liquid-propellant rocket engine designed to be launched 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.

Impact 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 (more than a week), 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 at the International Space Station (ISS). At an altitude of 350 kilometers (the altitude of the station), the acceleration of free fall has a value of 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 cosmic speed, 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 ballistic trajectory, that is, the trajectory along which the aircraft would fly under the influence of the force of gravity alone. This trajectory at low speeds turns out to be a parabola, which is why it is sometimes mistakenly called “parabolic”. In general, the trajectory is an ellipse or hyperbola.
Such methods are used to train astronauts in Russia and the USA. In the cockpit, a ball is suspended on a string, which usually pulls the string down (if the plane is at rest or moving uniformly and in a straight line). The lack of tension in the thread on which the ball hangs indicates weightlessness. Thus, the pilot must control the plane so that the ball hangs in the air without tension on the string. To achieve this effect, the plane must have a constant acceleration equal to g and directed downward. 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 aerobatic maneuver called “failure in the air.” Pilots abruptly begin to climb, entering a “parabolic” trajectory, which ends with the same sharp drop in altitude. Inside the fuselage there is a chamber in which future cosmonauts train; it is a completely upholstered passenger cabin without seats to avoid injuries both in moments of weightlessness and in moments of overload.
A person experiences a similar feeling of (partial) weightlessness when flying on civil aviation flights during landing. However, for flight safety reasons and due to the heavy load on the aircraft structure, any scheduled aircraft drops altitude, making several long spiral turns (from a flight altitude of 11 km to an approach altitude of about 1-2 km). That is, the descent is carried out in several passes, during which the passenger feels for a few seconds that he is slightly lifted up from the seat. The same feeling is experienced by motorists who are familiar with routes passing along steep hills when the car begins to slide down from the top.
Claims that the aircraft performs aerobatic maneuvers such as “Nesterov loops” to create short-term weightlessness are nothing more than a myth. Training is carried out in slightly modified production passenger or cargo aircraft, for which aerobatic maneuvers and similar flight modes are supercritical and can lead to destruction of the aircraft in the air or rapid fatigue wear of the supporting structures.
The state of weightlessness can be felt at the initial moment

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 seat. (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 at low speeds; for a satellite it 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

Wikimedia Foundation.
2010.:
- Synonyms
- Angrboda
Pugachev, Emelyan Ivanovich
According to the law of universal gravitation, all bodies are attracted to each other, and the force of attraction is directly proportional to the masses of the bodies and inversely proportional to the square of the distance between them. That is, the expression “absence of gravity” makes no sense at all. At an altitude of several hundred kilometers above the Earth's surface - where manned spacecraft and space stations fly - the Earth's gravitational force is very strong and practically no different from the gravitational force near the surface.

If it were technically possible to drop an object from a tower 300 kilometers high, it would begin to fall vertically and with the acceleration of free fall, just as it would fall from the height of a skyscraper or from the height of a person. Thus, during orbital flights, the force of gravity is not absent or weakened to a significant extent, but is compensated. In the same way as for watercraft and balloons, the force of gravity of the earth is compensated by the Archimedean force, and for winged aircraft - by the lifting force of the wing.

Yes, but the plane flies and does not fall, and the passenger inside the cabin does not fly like astronauts on the ISS. During a normal flight, the passenger feels his weight perfectly, and what keeps him from falling to the ground is not the direct lifting force, but the ground reaction force. Only during an emergency or artificially caused sharp decline does a person suddenly feel that he stops putting pressure on the support. Weightlessness arises. Why? But because if the loss of height occurs with an acceleration close to the acceleration of free fall, then the support no longer prevents the passenger from falling - she herself falls.

spaceref.com It is clear that when the plane stops sharply descending, or, unfortunately, falls to the ground, then it will become clear that gravity has not gone away. For in terrestrial and near-Earth conditions, the effect of weightlessness is possible only during a fall. Actually, a long fall is an orbital flight. A spacecraft moving in orbit at escape velocity is prevented from falling to Earth by the force of inertia. The interaction of gravity and inertia is called “centrifugal force,” although in reality such a force does not exist, it is in some way a fiction. The device tends to move in a straight line (tangentially to the near-Earth orbit), but the Earth's gravity constantly “spins” the trajectory of movement. Here, the equivalent of gravitational acceleration is the so-called centripetal acceleration, as a result of which it is not the value of the speed that changes, but its vector. And therefore the speed of the ship remains unchanged, but the direction of movement is constantly changing. Since both the spacecraft and the astronaut are moving at the same speed and with the same centripetal acceleration, the spacecraft cannot act as a support on which the weight of a person presses. Weight is the force of a body acting on a support that arises in the field of gravity and prevents it from falling. But a ship, like a sharply descending airplane, does not prevent it from falling.

That is why it is completely wrong to talk about the absence of Earth’s gravity or the presence of “microgravity” (as is customary in English-language sources) in orbit. On the contrary, the gravity of the earth is one of the main factors in the phenomenon of weightlessness that occurs on board.

We can talk about true microgravity only when applied to flights in interplanetary and interstellar space. Far from a large celestial body, the gravitational forces of distant stars and planets will be so weak that the effect of weightlessness will arise. We have read more than once in science fiction novels about how to deal with this. Space stations in the form of a torus (wheel) will spin around a central axis and create an imitation of gravity using centrifugal force. True, in order to create the equivalent of gravity, you will have to give the torus a diameter of more than 200 m. There are other problems associated with artificial gravity. So all this is a matter of the distant future.

— Is it true that there is no gravity in space?

- NO, it’s not true: the law of universal gravitation operates everywhere.

Why then do astronauts “fly” inside their ship, strap themselves to their beds while they sleep, and catch “flying chips” throughout the cabin?

They experience weightlessness because move in a circle(around the Earth) at enormous speed (7.9 kilometers per second); This can be roughly demonstrated by pouring water into a small bucket and swirling it vigorously. The water will not pour out, it will be pressed to the bottom by “centrifugal force”, or rather by the force of inertia: since inertia acts rectilinearly, and the “rounding” of the trajectory of movement constantly changes the direction of movement.

It is the inertia of motion in a circular orbit around the Earth that compensates for the force of gravity. If the spaceship had not been flying at this speed - but had been motionless - it would have immediately crashed to Earth - it does not matter that it is located at a distance of several hundred kilometers from the Earth: its gravitational force is enormous and extends to a very large (theoretically - infinite) distance. If there was a huge tower sticking out of the ground, 500 kilometers high (at about this height the ISS constantly moves), and we stood on top of this tower, we would not experience any weightlessness, but the usual gravity of the Earth (perhaps a little less than on a surface).

Therefore, Space, in this regard, is no different; but only in space, where there is no atmosphere, can you move at such a tremendous speed that you can compensate for earth’s gravity. Is it possible to somehow “get” weightlessness on Earth? This is a rather pleasant feeling when nothing forces the muscles to tense. When you can float without touching objects, push off with your feet once - and fly a huge distance - and quickly, faster than a running person! It would probably be great to visit some special salon that provides “zero gravity” services!

But on Earth, this is a problem. The water disappears: although a person in the water may not “fall to the bottom”, and in principle may not float up - but as if “hovering” in place - this is still not weightlessness at all. If you stay upside down under water for a long time, blood will rush to the brain just like on land. The muscles will be just as tense as anywhere else on Earth: the same force of gravity acts on them, and the body’s organs, including internal ones, will have their usual weight. Zero gravity is something completely different!

Perhaps the only possible way creating total weight loss is being on boardfastdeclining airplane. And then, the duration of this effect is no more than a couple of minutes. You can, of course, just jump - but then the body will be in weightlessness for less than a second. During a skydive, although weightlessness will last longer, it will not be complete, due to the greatly increased friction with the air, which to some extent will become “solid”, like support and the body will feel some weight.

Is there, at least theoretically, a way to achieve weightlessness without

the need to move or fall, in a stationary laboratory, whenthan indefinitely?

Yes, but purely theoretically: to build such an establishment incenter of the earth! Yes, in its very center (center of mass), in the bowels, in the core: the entire mass of the globe will be outside and exert a gravitational influence on the visitor of such a “club” from all sides simultaneously and with equal force. The resulting direction of gravity will be ZERO - man(or any object) will freeze and will not fall anywhere. In fact, this is of course not possible (in the next couple of billion years) - due to the enormous pacerature and colossal pressure in the bowels of the Earth, but on some other celestial body, in principle, probably.

Well, what if it’s still on Earth, and in a slightly more realistic way than in the earth’s core?

Perhaps it is possible, but other earthly inhabitants will not like it much: disperse planet rotation speed approximately 17 times! A day on Earth will last about an hour and a half (40 minutes during the day and about the same at night). But anywhere on the equator there will be real weightlessness! The surface of the Earth, in the equatorial part, will move at the same speed with which the satellites rotate, that is, with the first cosmic speed; the force of inertia at this latitude completely compensates for gravity and it will be possible to fly! But not only people will fly, and this is a problem...

All objects: keys, lighters, hats, chairs, suitcases, bicycles, cars - everything will not be on the ground - but where they “please”. Small stones, medium stones, huge cobblestones will float in the air, collide, fly apart, fly up to the ground, hit, then jump off, rise very high, come back - in general, this is such a commotion... The whole earth, in general, is not a monolithic rock, but stones, grains of sand, specks of dust and all that, superimposed on one another. All this will no longer be pressed to the ground and will begin to move randomly. Nothing will be visible from the dust. Buildings, to

which stand on a foundation are 90 percent supported by the gravity of the Earth, which will cease to take place. Entire mountains that are supported from below by the earth's mantle will becomebreak away and fly away. What about water? Well, of course, the water will also curl into small drops or large balls and fly around, covered in dust. Moreover, there will be a lot of water - all the oceans will instantly rush to where the force of weight is less. Together with the oceans, everything from all over the planet that can come off will arrive.me: everything will end up at the equator or in the air near it. The entire planet will “inflate” at the equator - and it will turn from a ball into a highly oblate ellipsoid. The fiery liquid mantle from the depths will also rise, following everything else. What about the air? The air will be thrown out in a huge fountain in the equatorial plane far into space, some will then return to the poles - then again flow to the equator and burst out. The hurricane will be continuous, continuous and brutally strong. Combined with all the light, medium and heavy objects flying in the air, it will probably be pure hell...

Yes, in such a scenario it is better to dig towards the core... Maybe there is still a “normal” way to “produce” weightlessness? In order not to touch the whole planet, but to dig a bunker under some mountain: the mountain is on top, close: it attracts upward. And the center of the Earth is far away - it pulls down. Is it possible to achieve “balance”?

Then you will have to “burrow” to a third of the radius of the Earth, and the mountain must be the size of the Moon... Although... The mountain must be made of such material that it will be a hundred thousand timesdenser than gold! An ordinary mountain, weighing a billion tons, was several meters in size. Place such a “blank” on the roof of the bunker - and there will be the world’s first boarding house that offers entertainment in zero gravity! It is only necessary to strengthen the ceiling structure well, because such a heavy body of such small dimensions will crush everything in the world, and will gradually sink into the very depths of the earth... And yet... We need to somehow break off a billion tons of such substance from the nearest extinct White Dwarf and bring it...

And yet, more seriously: is there really no real way? use anti-gravity, or shield the attraction from below a little, or turn on artificial gravity from above? You only need to lift a human body, several tens of kilograms, because you don’t need enormous energy for this? The elevator lifts you up, and your legs lift you to such a height every day... You can increase your own weight many times over in a centrifuge, or even on a simple carousel. Maybe you can just as easily reduce it somehow? This, in principle, will not contradict the law of conservation of energy? Anti-matter has been obtained a long time ago, maybe it can be used somehow?

Anti-matter does not provide anti-gravity: by and large, it is the same matter, only with the opposite electrical charge. On a carousel swing you can get weightlessness - but only for a short time; in general, the same effect as from a regular “jump”: half a second of weight loss, and then the same amount of overload. Method for creating long-term weightlessness on Earth not yet known. Although, most likely there should be a possibility.

Maybe someone has already figured it out? Write a comment or ask your friends on social media. networks: