What does an astronaut experience during takeoff and landing? How astronauts test the limits of the human body: Biologist Francis Ashcroft on our limits

Museum Scientific Adviser "Experimentanium" and physiologist Anton Zakharov tells what happens to the human body while he flies into space and while he is there. The online edition M24.ru gives the full text version of the lecture.

We will talk about what happens to a person on a space station a little later, but for now we need to deal with the difficulties that await a person when taking off into space. The first difficulty he encounters is what? I think you can guess?

- Weightlessness.

No, weightlessness a little later.

- Overload.

Overload, absolutely correct. Here is a small tablet, a tablet of sensations that a person has when he experiences overload. In general, what is overload, where does it come from? Do you think there are ideas? Please.

- The plane or space station begins to rise, while the person begins to deviate in the other direction, an overload occurs.

Why is it called overload?

- Probably because the person feels uncomfortable.

In fact, you and I are just very much used to living with a load. When you and I are, as now - you are sitting, I am standing - on our planet Earth, we are attracted to the Earth, and our blood is attracted to the Earth more than all other parts of our body, because it is liquid. It's like she's going to Earth. And the rest of our body is more solid, so they are slightly less attracted to the Earth, but their shape is more constant. And we are very well adapted to this load, and when we lose this load, there will be a not very pleasant feeling, which I will talk about later.

But before getting into weightlessness, where this load is absent, a person experiences overloads, that is, an excessive effect of gravity. With a double overload - an overload of 2 g - the human body is filled with heaviness, the face sags a little, it is difficult to get up, of course, you need to lift not 50-60-70 kg, which you usually weigh, but twice as much. With a triple overload, it is no longer possible for a person to stand, and the person’s digital vision is first turned off, because the cells that are responsible for digital vision consume a lot of energy. At 4.5 g, vision is completely turned off, there is already not enough blood in our retina, it is impossible to raise an arm or leg further. And at 12 g most people pass out. Everything that I am saying now concerns not instantaneous overloads, but which last for some time, at least 10-20-30 seconds, instantaneous overloads are stronger. Do you think such overloads in ordinary life can be met without going up into space?

Is it possible to experience a 4.5 g overload without taking off into space? In fact, usually somewhere around 1.5, but if you ride rides, just 3-4 g is quite possible to experience. And so, it is clear that a person standing motionless experiences 1 g; on the plane - somewhere around 1.5; the parachutist who lands is about 2 g; at the moment of opening the parachute for a very short time, he experiences 10 g, that is, almost on the verge of losing consciousness. At the same time, the astronauts who are now flying experience less - 3-4 g, they have these 8-12 - very strong overloads - no, only astronauts experienced them, when they were just building spaceships, then it was 7-8 g, it was problem. Now everything is done so that it was easier to take off.

In fact, military pilots often experience the most intense G-forces. At the moment of performing some aerobatics, it’s quite possible for 12 g, but for a short time, so they don’t lose consciousness - this is one, but two - they are very prepared, so it’s easier for them to cope. The maximum overload permissible for health, even short-term ones, is approximately 25 g. If the overload is greater, even for a short time, then the probability that a person will break his spine begins to approach 90%, and this, of course, is not very good.

We talked about ordinary overloads, the so-called positive overloads. We found out that antigravity does not exist. What do you think, negative overloads can be? (But g-force and gravity are slightly different concepts) And, indeed, there are negative g-forces, if you just stand on your head, you will experience a negative g-force of -1 g, because the blood that usually rushes to the legs and the parts of the body that usually press each other in one direction, they will press against each other in the other direction, and the blood will begin to rush to the head. This is quite a negative g-force and, of course, large negative g-forces are also unhealthy, and they can also be experienced without flying into any space. For example, they are experienced by bungee jumpers - what in English is called bungee jumping.

In fact, this bungee jumping... Firstly, I'm even scared to look at the photos, and secondly, this is a very interesting ritual. Does anyone know where he came from? The fact is that the Indians of the Vanuatu tribe in South America in this way boys were ordained into men. They climbed a tall tree, took some kind of strong vine, tied it to their feet, and the teenager had to jump from this vine of visas, not reaching the ground a meter or two. And if he calmly endured, he became a man. When Oxford students learned about this in the 1970s, they were wildly delighted and decided that this tradition should be repeated. But they decided that the first jump should be full of solemnity, and dressed up in tailcoats. Now bungee jumpers are informal people, and the first jumpers jumped in suits, it was quite beautiful.

We talked about g-forces, this is not the only problem that astronauts experience. The astronauts took off, coped with overloads, rise into space, and right there the first joys and the first problems await them.

Well, the joy, of course, when a person rises into space, full pants - this is understandable. And with astronauts, as with small children, this happens - and this is confirmed biochemical research- higher "hormone of happiness" in the blood than ordinary people. And they can, in principle, be understood, a lot of cool things are happening there. Let's watch one video from the ISS. In principle, people have fun, as they can, of course. It is not necessary to carry things with your hands, you can also vilify them with your feet. Movements must be very accurately calculated, must be very accurate. This is how astronauts actually do not wash their hands, it was filmed especially for the video, for the sake of these 10 beautiful seconds, the astronauts will spend a lot of energy later, collecting these droplets one by one. It just seems - wow, how cool they scattered, but they really scattered, now they all need to be collected, the problem is quite serious.

So, we have roughly seen how astronauts live in space, now let's think about what problems await them there. The first problem is related to the fact that a person does not experience there gravity. Earth gravity is not experienced, including its balance organs. Where do we have the organs of balance, does anyone know?

- In the head, cerebellum?

In the ear No, the cerebellum is the brain center that provides balance coordination, but it is not a sensitive part, but the sensitive part is in our ear. The beautiful pebbles that are shown here are otolith crystals, these are pebbles that we have in the vestibular apparatus, its sac, and when we turn our head from side to side, they roll inside our vestibular apparatus, so we understand that our head is turned relative to the rest of the body. Here in these bags are these crystals. What happens in space, one simple thing happens in space, these pebbles, like all steel, begin to float inside the vestibular apparatus - a person fails. On the one hand, his eyes tell him that he is still standing upright, everything is fine, and on the other hand, the balance organs say: I don’t understand what happened, I’m bobbing in all directions, I don’t know what to do. There is a manifestation similar to space sickness - this is seasickness. Then the same thing happens, the vestibular apparatus sways in different directions, and the eyes sway not so much, and the body fails, and the body starts what to do?

- Feel sick.

He starts to feel sick, and in space he begins to feel sick in the same way, but since this restructuring occurs much more abruptly in space, almost all astronauts have space sickness. True, not everyone is sick, but those who are sick are a dangerous thing. Because people usually experience attacks of space sickness at the moment when they have already docked to the space station and still in spacesuits. They begin to make the first movements, leaving the space station, that is, they are in closed spacesuits and, laughing, laughing, but this is one of the serious reasons for the death of astronauts, simply because the spacesuit is closed, and you cannot fly without a spacesuit. Why, I will talk about this a little later.

Going further, another problem that awaits people in space is a decrease in the number of blood cells. There are various reasons for this, one of the reasons is this: in space, there is a decrease in bone tissue, and inside the bone tissue, blood cells are formed. Therefore, if the bones become smaller, then the cells become smaller. In general, a rather unpleasant thing, especially unpleasant when an astronaut returns to Earth and needs to go through a period of adaptation back to conditions on Earth. He, among other things, experiences a powerful lack of oxygen precisely because he lacks these blood cells that carry oxygen. Actually, more about the bones. Why do bones break in space, you know? Any ideas?

- There is no load.

There is no load, absolutely right, in order for our bones to work normally, they must constantly receive some kind of load, you and I must constantly work. But we remember that it is not easy to work in space: there is no need, there is no opportunity. Since nothing weighs there, no matter what you do, you spend a lot less effort. And despite the fact that astronauts train all the time, they still cannot experience the same level of physical activity as on Earth. Therefore, after 3-4 flights, problems with the bones begin, which, in particular, lead to osteoporosis, when the bone tissue is destroyed.

Another problem is again with blood. I said that we are very well adapted to the load on Earth. How are we adapted? We have an excess amount of blood, each of the adults has about 5 liters of blood. This is more than we need. Why do we need this excess? Because we are upright, and most of our blood remains in the legs, at the bottom of our body, and not everything reaches the head, so we need to store some excess so that there is enough blood for the head. But in space, gravity immediately disappears, and therefore this excess blood that was in the legs begins to urgently move somewhere throughout the body. In particular, it enters a person's head and brain, resulting in strokes, microstrokes, because too much blood enters, and the vessels simply burst. As a result of this, the astronauts especially often run to the toilet in the first week, just losing excess fluid, they lose about 20% of excess fluid during the first week of being in orbit.

Muscles also do not experience stress. Regardless of the size of the load, no matter how much it weighs on Earth, there will be no difficulty in moving it in space. Therefore, astronauts, as I have already said, definitely train in space. This is the next video. Naturally, there is no point in lifting weights in space, you can try to run. Indeed, a person runs, only, pay attention, he is tied to a treadmill, because if he were not tied to a treadmill, he would simply fly away. Again, you can’t lift weights, but you can unbend the springs, and astronauts spend at least 4 hours a day in physical exercises. Astronauts, as you know, are the most prepared people, the most physically strong and resistant. And all the same, when they return from space, they, firstly, never again reach the form that they had before the first flight, and secondly, even an approximate recovery after these loads takes about the same time as an astronaut was in orbit. That is, if he was there for six months, he will recover for six months, for the first few weeks they cannot even walk. That is, their leg muscles practically atrophied, they did not use them for six months.

Moving on, another problem related to what an astronaut should breathe in space. The problem is two-sided: first of all, you need to lift air or oxygen into orbit. What do you think is better to lift - air or oxygen than we breathe with you?

- Oxygen.

Oxygen, so the Americans also thought that it was better to lift pure oxygen into orbit, albeit a little rarefied. Although, in fact, pure oxygen is a pretty scary thing. Firstly, it is dangerous for the body, it is a poison - in large quantities, and secondly, it explodes very well. For the first few years, rockets filled with pure oxygen took off normally, and then at some point one spark ran, and the spaceship was gone from stone to stone. After that, they decided to do the same as they did Soviet Union, - just cylinders with liquid air. It's a heavy option, it's expensive, but it's safe.

There is a second problem: when we breathe, we emit carbon dioxide. If there is too much carbon dioxide, at first the head starts to hurt, drowsiness appears, and at some point a person may lose consciousness and die from excess carbon dioxide. We on earth emit carbon dioxide and plants take it in; in space, even if you take one or two plants with you, they will not do the job, and you cannot take many plants with you, because they are heavy and take up a lot of space. How to get rid of carbon dioxide? There is one special Chemical substance, which can absorb excess carbon dioxide, is called lithium hydroxide, it is carried into space, it just absorbs excess carbon dioxide. One very interesting, such a heroic story is connected with this substance, the story of the Apollo 13 spacecraft, I think adults remember this story.

Have the kids ever heard of the Apollo 13 spacecraft? Have you heard that they even made such a film, what happened to this ship? He had a very unsuccessful flight, there were many different things, we are interested in what happened with lithium hydroxide. The story is this: "Apollo 13" is not the first, not the second time flew to the moon, to explore the moon. Three people flew there, they had their own spacecraft and a special capsule that was supposed to land on the moon, and two people who were supposed to go out on the moon, do something there, and then return on the capsule back and fly to Earth. But somewhere on the 3rd day of the flight, an explosion suddenly occurred, and part of the main ship turned around, including damaging the life support system. In principle, not such a terrible problem, because the boat, on which it was necessary to fly up to the Moon, was intact, and it was quite possible to return to Earth on it. But there was a completely idiotic problem: the lithium hydroxide canisters that were stored on the boat and the lithium hydroxide canisters that were stored on the ship were different, they just had different inlets. And all the engineers in America who were associated with the project, and many engineers in the world, for about a day, did what people usually do in the Crazy Hands program. They figured out how to use glue, scraps of newspapers, paper clips and whatever was on the ship to remake one exit into another so that people could fly back to Earth. They succeeded, thank God, and this ship (while it was landing, there were also many different problems), thank God, landed normally.

We found out that people in space have problems when they are awake: bad blood, bad muscles, bad bones, and so on and so forth. Sleeping in space is also bad. There are two reasons: the first reason is that no one turns off the light on the space station, it must work all the time, some experiments are being carried out there all the time. The work is very stressful, so the cosmonauts sleep on shifts: first one, then the other. It’s hard, if you sleep like that for a day, sleep two, three, then it’s okay, but if you sleep like that for two or three weeks or a month, then changes in the body begin, and this is harmful. This is harmful for us too, because now there are a lot of people in major cities lives in the wrong light regime, because of this we suffer and do not even notice it. Another problem is related to the fact that since there is no attraction, and a person cannot lean on anything, and this is a very important feeling, as psychologists have found out. In order to fall asleep, a person needs to lean against something and feel confident. Therefore, astronauts put on special bandages under their knees and put on special bandages over their eyes to create at least some kind of imitation of what is pulling them somewhere. It doesn't work out very well, but it works. There is a third problem related to carbon dioxide: while we are sleeping, we breathe and release carbon dioxide, we do not move, and carbon dioxide accumulates on the surface of our face. On Earth it's not scary, why?

- He moves all the time.

He really moves all the time, why? Because there is a small breeze, but that's not even the point. When we exhale carbon dioxide, we exhale it warm, and warm gas will rise to the top because it is lighter than cold. In space, neither warm nor cold gas has weight, so the exhaled gas will accumulate above the person, and he will simply sleep in this cloud if nothing is done about it. But they are really doing something about it - and in space there are very powerful ventilation systems that disperse carbon dioxide so that we can sleep peacefully. And these same ventilation systems filter the air from various infections and pathogens. Now they have learned to cope with this more or less, and at first the astronauts were very sick, because the quarantine was not strict enough, and it is much easier to get infected in space with something. Because when we sneeze on Earth, what we sneeze falls to the ground and remains in some kind of dust, we do not directly inhale it. And if an astronaut sneezes, then everything that he sneezed remains in the air, so the probability of catching this infection is much higher, so everything is filtered there. The cosmonauts really have a lot of dust there, they still sneeze a lot, but they already get sick less because the quarantine is more stringent.

Another problem that awaits astronauts is cosmic radiation. We on Earth are protected from cosmic radiation by an atmosphere that does not transmit radiation, in particular, ozone layer well protected from it. And in space there is no ozone layer, and astronauts experience increased radiation. It is dangerous, and this was feared for a very long time, until they checked how much radiation a person experiences there. He experiences about the same as the inhabitants of those places that are located in granite rocks, for example. Granite rocks also emit a little radiation, about the same amount an astronaut receives. That is, residents of, say, Cornwall (this is in England), consider astronauts in this respect, even get a little more radiation. And quite a lot of radiation is received by pilots and stewardesses of supersonic aircraft (Concorde, for example), which fly at high altitudes.

But we hope that someday a person will not only fly to space stations, but also fly to Mars, to other planets. And in these cases, a threat awaits us, because usually space stations fly around the Earth - where the radiation field is not very strong. But there are two "donuts" of powerful radiation fields around the Earth, through which you need to fly to get to the Moon, Mars, and other planets. And the radiation is very strong there, and one of the problems of going to Mars now is exposure to radiation for several months. People may fly there, but they will fly very sick - naturally, no one wants this. Therefore, they are now figuring out how to make both a light spacesuit and light spacecraft skin, which, moreover, would protect against radiation. Because, in principle, it is not difficult to protect yourself from radiation, you can cover the ship with lead, and okay - we are protected from radiation, but lead is very heavy.

We talked about cons, cons, cons. But there are not only disadvantages when flying into space. When we fly into space (this is not really a big plus, it's just very nice) we get a little higher. Under the influence of gravity, while we walk somewhere all day, our vertebrae press on each other, and most importantly, they put pressure on the intervertebral discs. They “flatten” a little during the day, so a person is several centimeters taller in the morning than in the evening. You can check it at home if you haven't tried it. Why is it advised to always measure height at the same time, because it changes during the day. So, in space, gravity does not act, so astronauts grow a little, sometimes even too much. One cosmonaut grew by as much as 7 centimeters, he was very happy, he was already many years old at that moment, there was only one problem - the spacesuit did not grow at the same time, it was quite crowded. Now all spacesuits are made - 10 centimeters are left in case the astronaut grows up.

An interesting thing: in space, it turns out, regeneration processes go faster, wounds heal faster, and even whole parts of the body can recover. Now there will be a video with a snail. Here, of course, accelerated shooting, in fact, it has been growing for about two weeks. On the ground, snails also regenerate, but worse. Why this happens is unclear. Why am I saying all this? I said already at the beginning: before our eyes, in the near future, the number of people who will fly into space will grow, and grow, and grow. Perhaps soon this will not be a topic for a popular science lecture, but a standard lesson at school: you will need to know what happens to a person when he simply decides to fly on an excursion into space. I really believe that this will happen soon, and I hope you do too. If you have questions, please ask.

- Tell me, if there were overloads, turning off consciousness, how quickly does a person recover later, regain consciousness?

When consciousness is turned off, the system is the same as when a person faints. Someone immediately gets up, someone does not immediately, it has a strong effect on someone, less on someone. In general, it is, of course, harmful. A person loses consciousness because he does not have enough oxygen entering the blood, which means that not enough oxygen enters the brain. As a result, some brain cells may begin to die, some are more active, some are less active.

On March 22, 1995, cosmonaut Valery Polyakov returned from space after 438 days of flight. This record of duration has not been broken so far. It became possible as a result of ongoing in-orbit studies of the influence of cosmic factors on the human body.

1. G-forces during takeoff and landing

Perhaps it was Polyakov who, like no one else, was prepared to stay in orbit for a year and a half. And not because he supposedly has phenomenal health. And he was engaged in pre-flight preparation no more than others. It's just that Polyakov, being a professional doctor - candidate of medical sciences, who worked at the Institute of Biomedical Problems of the Russian Academy of Sciences, like no one else in the cosmonaut corps, knew the "human structure", the body's reactions to destabilizing factors and methods for compensating them. What are they?

At the launch of the spacecraft, the overloads lie in the range from 1g to 7g. This is extremely dangerous if the overload acts on vertical axis i.e. head to toe. In this position, even with an overload of 3g, which lasts for three seconds, serious impairment of peripheral vision occurs in a person. If these values are exceeded, the changes can become irreversible, and the person is guaranteed to lose consciousness.

Therefore, the seat in the ship is placed in such a way that the acceleration acts in the horizontal plane. The astronaut also uses a special compensation suit. This makes it possible to maintain normal cerebral circulation during long-term overloads of 10g, and short-term overloads up to 25g. The rate of increase in acceleration is also extremely important. If it exceeds a certain limit, then even minor overloads can become fatal for the astronaut.

After a long stay in orbit, a detrained organism endures the overloads that occur during landing, much harder than during launch. Therefore, a few days before landing, the astronaut prepares according to special technique involving exercise and medication. During landing, such an orientation of the ship in the dense layers of the atmosphere is of great importance so that the axis of overload is horizontal. During the first space flights, it was not possible to achieve proper stabilization of the ship, and therefore the astronauts sometimes lost consciousness during landing.

2. Weightlessness

Weightlessness is a much more difficult test for the body than overload. Because it acts for a long time and continuously, causing changes in a number of vital functions in the human body. So, weightlessness puts the central nervous system and receptors of many analyzer systems (vestibular apparatus, muscular-articular apparatus, blood vessels) in unusual conditions of functioning. As a result, blood flow slows down, blood accumulates in the upper body.

The “meanness” of weightlessness lies in the fact that adaptive processes in physiological systems, the degree of their manifestation, practically does not depend on individual features organism, but only on the duration of stay in weightlessness. That is, no matter how a person prepares for it on earth, no matter how powerful his body is, this has little effect on the adaptation process.

True, a person quickly gets used to weightlessness: dizziness and other negative phenomena stop. The astronaut “tastes” the fruits of weightlessness when he returns to earth.

If no methods of counteracting the destructive effect of weightlessness are used in orbit, then in the first few days a landed cosmonaut experiences the following changes:

1. Violation of metabolic processes, especially water-salt metabolism, which is accompanied by relative dehydration of tissues, a decrease in the volume of circulating blood, a decrease in the content of a number of elements in tissues, in particular potassium and calcium;

2. Violation of the oxygen regime of the body during physical exertion;

3. Violation of the ability to maintain a vertical posture in static and dynamic; a feeling of heaviness of body parts (surrounding objects are perceived as unusually heavy; there is a lack of training in dosing muscle efforts);

4. Violation of hemodynamics during work of medium and high intensity; pre-fainting and fainting states are possible after the transition from a horizontal to a vertical position;

5. Reduced immunity.

In orbit, a whole range of measures is used to combat the destructive effect of weightlessness on the body. Increased intake of potassium and calcium. Negative pressure applied to the lower half of the body to drain blood. Barocompensation underwear. Muscle electrical stimulation. Dosed medication. Training on a treadmill and other simulators.

3. Hypodynamia

The treadmill and various muscle simulators are also used to combat physical inactivity. In orbit, it is inevitable, since movements in weightlessness require much less effort than on the ground. And returning to earth even after daily grueling training, astronauts experience a decrease in muscle mass. In addition, physical activity has a beneficial effect on the heart, which, as you know, is also a muscle.

4. Radiation

The effect of this factor on the human body is well studied. The World Health Organization has developed standards for radiation doses, the excess of which is harmful to health. These regulations do not apply to astronauts.

It is believed that a person can undergo fluorography no more than once a year. At the same time, he receives a dose of 0.8 mSv (millisievert). An astronaut receives a daily dose of up to 3.5 mSv. However, by the standards of space medicine, such radiation background considered acceptable. Since to a certain extent it is neutralized by medication. The daily dose of radiation is not constant. Each cosmonaut has an individual dosimeter that counts the millisieverts accumulated in the body. For a year of stay in space, you can get from 100 to 300 mSv.

“Of course, this is not a gift,” says Vyacheslav Shurshakov, head of the laboratory of methods and means of space dosimetry at the Institute of Biomedical Problems of the Russian Academy of Sciences, “but such is the specificity of the cosmonaut profession.”

The annual threshold dose is 500 mSv. Which is 25 times the threshold for employees of nuclear power plants, which is 20 mSv.

Well, and the total dose, after which the astronaut is not allowed to fly, is 1000 mSv. At the same time, when Gagarin flew, this figure was 4000 mSv. Sergei Avdeev came closest to the threshold, flying 747 days in total. The dose he received is 380 mSv.

Photo by ITAR-TASS/Albert Pushkarev

Overload- the ratio of the absolute value of the linear acceleration caused by non-gravitational forces to the acceleration free fall on the surface of the earth. Being the ratio of two forces, g-force is a dimensionless quantity, however g-force is often expressed in units of gravitational acceleration. g. An overload of 1 unit (i.e. 1 g) is numerically equal to the weight of a body resting in the Earth's gravity field. Overload at 0 g is tested by a body in a state of free fall under the influence of only gravitational forces, that is, in a state of weightlessness.

Overload is a vector quantity. For a living organism, the direction of action of the overload is important. When overloaded, human organs tend to remain in the same state (uniform rectilinear motion or rest). With a positive overload (head - legs), the blood goes from the head to the legs, the stomach goes down. Negative G-force increases blood flow to the head. The most favorable position of the human body, in which he can perceive the greatest overloads, is lying on his back, facing the direction of acceleration of movement, the most unfavorable for transferring overloads is in the longitudinal direction with his feet to the direction of acceleration. When a car collides with a fixed obstacle, a person sitting in a car will experience back-chest overload. Such an overload is tolerated without much difficulty. An ordinary person can withstand overloads up to 15 g about 3 - 5 seconds without loss of consciousness. Overloads from 20 - 30 g and more a person can withstand without loss of consciousness no more than 1 - 2 seconds and depending on the magnitude of the overload.

Symptoms and mechanism of action of overloads
General symptoms. A person's response to overloads is determined by their magnitude, growth gradient, duration of action, direction in relation to the main vessels of the body, as well as the initial functional state of the body. Depending on the nature, magnitude and combinations of these factors, changes in subtle functional shifts may occur in the body to extremely severe conditions, accompanied by a complete loss of vision and consciousness in the presence of deep disorders of the functions of the cardiovascular, respiratory, nervous and second systems of the body.

General changes in the state of a person under the action of overloads are manifested by a feeling of heaviness in the whole body, initially with difficulty, and with an increase in the magnitude of the overload and a complete absence of movements, especially in the limbs, in some cases, pain in the muscles of the back and neck [Babushkin V.P., 1959 ; deGraef P., 1983]. There is a pronounced displacement of soft tissues and their deformation. During long-term exposure to sufficiently large positive g-forces on areas of the legs, buttocks, and scrotum that are not protected by counterpressure, skin petechial hemorrhages may appear in the form of dots or large spots, intensely colored, but painless, which spontaneously disappear within a few days. Sometimes there is swelling in these places, and with negative g-forces - swelling of the face. Visual disturbance occurs early. At high g-forces, loss of consciousness develops, which lasts 9-21 s.

The mechanism of action of positive and negative overloads is complex and is due to the primary effects caused by inertial forces. The most important of them are the following: redistribution of blood in the body to the lower (+G Z) or upper (-G z) half of the body, displacement of organs and deformation of tissues that are sources of unusual impulses in the central nervous system, impaired circulation, respiration and stress reaction. Developing hypoxemia and hypoxia entail disorders of the function of the central nervous system, heart, endocrine glands. Violated the biochemistry of life processes. Damage to cellular structures of a reversible or irreversible nature, detected by cytochemical and histological methods, may occur.

One of the main requirements for military pilots and astronauts is the ability of the body to endure overloads. Trained pilots in anti-G suits can endure G-forces from -3 to -2 g up to +12 g. Resistance to negative, upward g-forces is much lower. Usually at 7 - 8 g the eyes “blush”, vision disappears, and the person gradually loses consciousness due to a rush of blood to the head. Astronauts during takeoff endure the overload lying down. In this position, the overload acts in the direction of the chest - back, which allows you to withstand several minutes of an overload of several units of g. There are special anti-g suits, the task of which is to facilitate the action of overload. The suits are a corset with hoses that inflate from the air system and hold the outer surface of the human body, slightly preventing the outflow of blood.

Overloading increases the load on the structure of machines and can lead to their breakdown or destruction, as well as to the movement of loose or poorly secured loads. The permissible value of overloads for civil aircraft is 2.5 g

1. G-forces during takeoff and landing

At the launch of the spacecraft, the overloads lie in the range from 1g to 7g. This is extremely dangerous if the overload acts along the vertical axis, that is, from the head to the feet. In this position, even with an overload of 3g, which lasts for three seconds, serious impairment of peripheral vision occurs in a person. If these values are exceeded, the changes can become irreversible, and the person is guaranteed to lose consciousness.

After a long stay in orbit, a detrained organism endures the overloads that occur during landing, much harder than during launch. Therefore, a few days before landing, the astronaut prepares according to a special method that involves physical exercises and medications. During landing, such an orientation of the ship in the dense layers of the atmosphere is of great importance so that the axis of overload is horizontal. During the first space flights, it was not possible to achieve proper stabilization of the ship, and therefore the astronauts sometimes lost consciousness during landing.

2. Weightlessness

Weightlessness is a much more difficult test for the body than overload. Because it acts for a long time and continuously, causing changes in a number of vital functions in the human body. Thus, weightlessness puts the central nervous system and receptors of many analyzer systems (vestibular apparatus, muscular-articular apparatus, blood vessels) in unusual conditions of functioning. As a result, blood flow slows down, blood accumulates in the upper body.

The “meanness” of weightlessness lies in the fact that adaptive processes in physiological systems, the degree of their manifestation practically does not depend on the individual characteristics of the organism, but only on the duration of stay in weightlessness. That is, no matter how a person prepares for it on earth, no matter how powerful his body is, this has little effect on the adaptation process.

True, a person quickly gets used to weightlessness: dizziness and other negative phenomena stop. The astronaut “tastes” the fruits of weightlessness when he returns to earth.

If no methods of counteracting the destructive effect of weightlessness are used in orbit, then in the first few days a landed cosmonaut experiences the following changes:

2. Violation of the oxygen regime of the body during physical exertion;

4. Violation of hemodynamics during work of medium and high intensity; pre-fainting and fainting states are possible after the transition from a horizontal to a vertical position;

5. Reduced immunity.

3. Hypodynamia

4. Radiation

It is believed that a person can undergo fluorography no more than once a year. At the same time, he receives a dose of 0.8 mSv (millisievert). An astronaut receives a daily dose of up to 3.5 mSv. However, by the standards of space medicine, such background radiation is considered acceptable. Since to a certain extent it is neutralized by medication. The daily dose of radiation is not constant. Each cosmonaut has an individual dosimeter that counts the millisieverts accumulated in the body. For a year of stay in space, you can get from 100 to 300 mSv.

The annual threshold dose is 500 mSv. Which is 25 times the threshold for employees of nuclear power plants, which is 20 mSv.

Photo by ITAR-TASS/Albert Pushkarev

Any major achievement of science ultimately somehow changes the life of each of us. So it was with the discovery of electricity and electromagnetic waves, with the invention aircraft heavier than air, with the creation of semiconductors ... Now rockets and spaceships are entering the life of mankind.

There is no doubt that several decades will pass and people will use rocket transport for intercontinental communications with the same calmness and equanimity with which they now board a passenger jet liner. Space communications between the Earth and the Moon will also become commonplace. People will live and work on space stations, professions of space welders, fitters, etc. will appear.

But perhaps for the first time, thanks to scientific and technological achievements in space exploration, a person will find himself in fundamentally new conditions, where the usual physical laws manifest themselves in a different way. Something like this can happen only with the development of the deep sea.

Of course, the basic laws of physics and, in particular, mechanics are the same on Earth, and under water, and in space. But they manifest themselves differently depending on the conditions. And these conditions on Earth and in space are far from the same. On our planet, they are characterized by two main circumstances. Firstly, there are no noticeable changes in speed - accelerations in the movement of points earth's surface. And secondly, our planet attracts all objects to itself and forces them to put pressure on their supports.

The absence of perceptible accelerations is associated with the peculiarities of the Earth's motion in the world space. Together with our planet, we participate in its two main movements: daily rotation around its own axis and annual revolution around the Sun. And although we rush along with the Earth around the Sun at a speed of 30 km / s, and together with solar system around the center of the Galaxy at a monstrous speed of about 230 km / s, we do not feel this, since the human body is completely insensitive to the speed of uniform movement.

However, according to one of the fundamental provisions of mechanics, it is generally impossible to detect uniform and rectilinear motion by any internal physical experiments and measurements.

Well, what if some system, for example, space rocket, will move with acceleration under the action of engines or experiencing the resistance of the environment? With such a movement, an overload occurs, i.e. an increase in pressure on the support. On the contrary, if the movement occurs with the engines turned off in a vacuum, the pressure on the support disappears, and a state of weightlessness sets in.

Under the conditions of the Earth, the pressure on the support is associated with the action of the gravitational force. But some people think that the force of pressure on the support is the force with which the body is attracted by the Earth. If this were the case, then, for example, spaceship moving towards the Moon, there would be no weightlessness, since at any point in the orbit, the force of gravity would act on the ship. And in general, it is hardly possible to find a place in space where the resultant of the gravitational forces would be equal to zero.

Note that the pressure on the support can be caused not only by the action of gravity, but also by other factors, such as acceleration. For a motionless body resting on the earth's surface, the force of attraction actually coincides with the force of pressure on the support. But that's only special case. On Earth, a person with some force presses on its surface. In turn, according to the third law of mechanics, the surface of the Earth presses on a person from the bottom up with exactly the same force. This "opposing" force is called the support reaction. Forces of action and reaction are always applied to different bodies. In particular, in the case under consideration, the pressure force on the support is applied to the support, and the reaction of the support is applied to the body itself.

Meanwhile, the force of attraction is applied not to the support, but to the body. Thus, the force of pressure on the support and the force of attraction are completely different forces.

If the space rocket moves with acceleration, the pressure on the body increases by the same factor as the jet acceleration of the rocket exceeds the acceleration of free fall, equal to 9.81 m/s2. In other words, the reaction of the support increases in the accelerated section of motion. But at the same time, in accordance with the third law of mechanics, the pressure on the support increases by the same amount.

The ratio of the actual pressure on the support to its pressure on the support under Earth conditions is called overload. For a person on the earth's surface, the overload is thus equal to one. The human body has adapted to the action of this constant overload, and we simply do not notice it.

The physical essence of the phenomenon of overload is that not all points of the body receive acceleration at the same time. The force acting on the body, for example, the traction force rocket engine, is applied in this case to a relatively small part of its surface. The rest material points bodies receive acceleration with some delay through deformation. In other words, the body seems to be flattened, pressed against the support.

Numerous experimental studies, which were started by K. E. Tsiolkovsky, showed that the physiological effect of overload significantly depends not only on its duration, but also on the position of the body. When a person is in a vertical position, a significant part of the blood is shifted to the lower half of the body, which leads to disruption of the blood supply to the brain. The internal organs, as a result of an increase in their weight, also shift down, causing a strong tension in the ligaments.

In order to avoid overloads dangerous for the body in areas of accelerated movement, it is necessary to position yourself in such a way that the overload action is directed from the back to the chest. This position allows you to transfer about three times the large overload.

By the way, it is for this reason that lying down is better than standing ...

If the inhabitants of the Earth, although not often, still have to meet with the effect of overload, then they are practically not familiar with weightlessness ..

This amazing state occurs after the rocket engines are turned off, when both the pressure on the support and the reaction of the support completely disappear. The directions of top and bottom habitual for a person also disappear, and loose objects float freely in the air.

There are a number of misconceptions about weightlessness. Some think that this state occurs when the spacecraft is in airless space, "outside the sphere of gravity." Others believe that weightlessness in the Earth's satellite is obtained due to the action of "centrifugal forces" on it.

All this, however, is completely false.

Under what conditions does weightlessness arise and the pressure on the support vanishes? This phenomenon is due to the fact that free movement in outer space, both the rocket itself and all objects in it move with the same acceleration under the influence of gravitational forces. The support all the time, as it were, leaves from under the body, and the body does not have time to put pressure on it.

However, both the movement in active areas under the action of a rocket engine and the movement under the action of gravitational forces are accelerated movements. Both of them are performed under the action of forces. Why does overload occur in one case, and weightlessness in the other?

This paradox is apparent. It has already been noted above that when overloads occur, accelerations are communicated to various points of the body through deformation. Another thing is when the rocket moves in the gravitational field. Within the dimensions of the rocket, the gravitational field is almost uniform, which means that all particles of the rocket are simultaneously affected by equal forces. After all, the forces of gravity belong to the so-called mass forces, that is, the forces that are applied simultaneously to all points of the system under consideration.

Due to this, all points of the rocket simultaneously receive the same accelerations and any interaction between them disappears. The reaction of the support disappears, the pressure on the support disappears. A state of complete weightlessness sets in.

It is not quite usual to proceed in zero gravity and some physical processes. Even A. Einstein, long before space flights, raised a curious question: will a candle burn in the cockpit of a spaceship?

The great scientist answered in the negative - he believed that due to weightlessness, hot gases would not leave the flame zone. Thus, the access of oxygen to the wick will be blocked, and the flame will go out.

However, meticulous modern experimenters nevertheless decided to test Einstein's statement by experiment. In one of the laboratories the following rather elementary experiment was carried out. A burning candle placed in a closed glass jar was dropped from a height of about 70 m. The falling object was in a state of weightlessness (if air resistance is not taken into account). However, the candle did not go out at all, only the shape of the flame tongue changed - it became more spherical, and the light emitted by it became less bright.

Apparently, the whole point is diffusion, due to which oxygen from the surrounding space nevertheless enters the flame zone. After all, the process of diffusion does not depend on the action of gravitational forces.

Still, the conditions of combustion in weightlessness are different than on Earth. This circumstance had to be taken into account by Soviet designers who created a unique welding machine for welding in zero gravity.

As is known, this apparatus was tested in 1969 on the Soviet Soyuz-8 spacecraft and worked successfully.

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