Lethal overload for a person. Overloads, their effect on a person in different conditions
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. A common 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 back pressure, 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. Biochemistry is broken 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
In aviation and space medicine, overload is considered to be an indicator of the magnitude of the acceleration that affects a person when he moves. It is the ratio of the resultant moving forces to the mass of the human body.
Overload is measured in units of multiples of body weight in terrestrial conditions. For a person who is on earth's surface, the overload is equal to one. adapted to it human body so it is invisible to humans.
If an external force imparts an acceleration of 5 g to any body, then the overload will be equal to 5. This means that the weight of the body under these conditions has increased five times compared to the original.
During takeoff of a conventional airliner, passengers in the cabin experience an overload of 1.5 g. According to international standards, permissible value overload for civil aircraft is 2.5 g.
At the moment of opening the parachute, a person is subjected to the action of inertial forces, causing an overload that reaches 4 g. In this case, the overload indicator depends on the airspeed. For military paratroopers, it can range from 4.3 g at a speed of 195 kilometers per hour to 6.8 g at a speed of 275 kilometers per hour.
The response to overloads depends on their magnitude, the rate of increase and the initial state of the organism. Therefore, both minor functional shifts (feeling of heaviness in the body, difficulty in movements, etc.) and very serious conditions can occur. These include complete loss of vision, dysfunction of the cardiovascular, respiratory and nervous systems, as well as loss of consciousness and the occurrence of pronounced morphological changes in the tissues.
In order to increase the resistance of the body of pilots to accelerations in flight, anti-g and altitude-compensating suits are used, which, when overloaded, create pressure on the abdominal wall and lower limbs, which leads to a delay in the outflow of blood to the lower half of the body and improves blood supply to the brain.
To increase resistance to accelerations, training is carried out on a centrifuge, hardening of the body, breathing oxygen under high pressure.
When bailing out, rough landing of an aircraft or landing on a parachute, significant overloads occur, which can also cause organic changes in the internal organs and spine. To increase resistance to them, special chairs are used with deep headrests, and fixing the body with belts, limiters of displacement of the limbs.
Overloading is also a manifestation of gravity on board the spacecraft. If under terrestrial conditions the characteristic of gravity is the acceleration of free fall of bodies, then on board the spacecraft the overload characteristics also include free fall acceleration, which is equal in magnitude to the jet acceleration in the opposite direction. The ratio of this value to the value is called the "overload factor" or "overload".
In the acceleration section of the launch vehicle, the overload is determined by the resultant of non-gravitational forces - the thrust force and the aerodynamic drag force, which consists of the drag force directed opposite to the speed and the lift force perpendicular to it. This resultant creates a non-gravitational acceleration, which determines the overload.
Its coefficient in the acceleration section is several units.
If a space rocket in Earth conditions moves with acceleration under the action of engines or experiencing environmental resistance, then there will be an increase in pressure on the support, which will cause an overload. If the movement occurs with the engines turned off in a void, then the pressure on the support will disappear and a state of weightlessness will come.
At the launch of the spacecraft on the astronaut, the value of which varies from 1 to 7 g. According to statistics, astronauts rarely experience g-forces exceeding 4 g.
Overload capacity depends on temperature environment, the oxygen content in the inhaled air, the duration of the astronaut's stay in weightlessness before the start of acceleration, etc. There are other more complex or less perceptible factors, the influence of which is not yet fully understood.
Under the action of an acceleration exceeding 1 g, the astronaut may experience visual impairment. Acceleration of 3 g in the vertical direction, which lasts more than three seconds, may cause serious impairment of peripheral vision. Therefore, it is necessary to increase the level of illumination in the compartments of the spacecraft.
With longitudinal acceleration, the astronaut has visual illusions. It seems to him that the object he is looking at is shifting in the direction of the resulting vector of acceleration and gravity. With angular accelerations, an apparent displacement of the object of vision in the plane of rotation occurs. This illusion is called circumgyral and is a consequence of the impact of overloads on the organs of the inner ear.
Numerous experimental studies, which were started by the scientist Konstantin Tsiolkovsky, showed that the physiological effect of overload 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. Due to the increase in their weight, the internal organs are shifted downward and cause a strong tension in the ligaments.
To reduce the effect of high accelerations, the astronaut is placed in the spacecraft in such a way that the g-forces are directed along the horizontal axis, from the back to the chest. This position provides an effective blood supply to the cosmonaut's brain at accelerations up to 10 g, and for a short time even up to 25 g.
When the spacecraft returns to Earth, when it enters the dense layers of the atmosphere, the astronaut experiences deceleration overloads, that is, negative acceleration. In terms of integral value, deceleration corresponds to acceleration at start.
A spacecraft entering the dense layers of the atmosphere is oriented so that the deceleration g-forces have a horizontal direction. Thus, their impact on the astronaut is minimized, just as during the launch of the spacecraft.
The material was prepared on the basis of information from RIA Novosti and open sources
As children, we all dreamed of becoming astronauts, policemen and doctors. And someone dreamed of driving a car. And not just drive, but become a real professional and ride a super car. This is how rich and desperate guys come to Formula 1, who are not afraid of speed and overload. Speaking of g-forces, the pressure that pilots experience is comparable only to that of astronauts. And today we will find out what kind of overloads the pilots of fireballs experience and who has the strongest head.
8th place: So. Let's start with an ordinary person who is standing. Even in this position, you and I experience overloads with a force of 1 g. And this is not the limit. An ordinary person can withstand overloads up to 5 g. For example, a passenger in an airplane during takeoff experiences an overload force of 1.5, and a parachutist will experience 1.8 ji when descending at a speed of 6 m / s.
7th place: and again - a parachutist, though when opening a parachute. Here it is more difficult. At this moment, as much as 5 ji are pressed on him. And the speed at the same time changes from 60 to 5 meters per second.
6th place: The next heroes of the rating who are familiar with overloads are cosmonauts during their descent in the Soyuz spacecraft. Up to 4 ji. And here you will not envy them, because only a few can withstand long-term overloads.
So, with a positive overload (head-legs), blood goes from the head to the legs. The stomach goes down. When negative, the blood rises to the head. The stomach can turn out along with the contents. But, astronauts are trained people and they are not afraid of overload)))
5th place: and we can already hear the sound of racing cars. Yes, we are in Formula 1.
Just imagine: during the races, the pilot experiences about 1000 g-forces up to 6G. This is braking, speeding up, entering a long turn. Especially g-loads put pressure on the pilot's neck. To avoid a neck fracture, pilots wear a special "frame" around the neck. By the way, the helmet also weighs a lot, about 4 kg. But on the hottest tracks, such as Malaysia or Bahrain, the temperature in the cockpit of the car can reach 60 ° C, and the humidity is 80%, and this is just a sauna. During the race, the pilot can lose up to 3 liters of water. Therefore, before the start, pilots always drink a lot. This is either plain water, or water with lemon or some additives, but they should not drink juices. When it is hot and there is nothing to breathe and constant physical overload affects the pilot, it is not at all easy for him to drive a car.
4th place: we rightfully give it to the pilots of sports aircraft, because it is they who have the range of overloads ranging from -3 ... -2 to +12. It is very difficult and one cannot do without an anti-g suit. By the way, for reference: resistance to negative, upward g-forces is much lower. Usually, at -2 ... -3, it “turns red” in the eyes and the person loses consciousness due to a rush of blood to the head. But the astronauts during takeoff alone are so strong that they can withstand only a few minutes.
3rd place. And it is occupied by one of the smallest birds in the world - Anna's Hummingbird.
Imagine: shaking off water from its head, a hummingbird experiences 6 times more g-forces than Formula 1 racers, and at the same time continues to calmly flutter in the air. Anna's hummingbird takes just 0.1 seconds to turn its miniature head 180°. You can watch it in very slow motion here. At the same time, the head of a bird experiences overloads of 34g: for comparison, in a Formula 1 car, the driver receives an average of 6g.
In addition, during flights, the males of this species of hummingbirds dive sharply. And it is at this moment that the birds experience overloads of up to 10 g, that is, acceleration at some points of the trajectory is 10 times higher than the acceleration of free fall. In this case, birds can be under the influence of strong overloads for more than one and a half seconds. For comparison, overloads of 7 g lasting more than a second in pilots can lead to loss of consciousness.
2nd place: and again Formula 1. This case entered the history of world motorsport as the most unique and incredible. In 2003, IndyCar formula driver Kenny Bräck survived a short g-force of 214 g (almost 2100 m/s²). Thus, he broke the previous "record" set by the driver of Formula 1 David Purley (David Purley) in 1977 (179.8g).
1 line rating goes to… Not even a human. And ... an ordinary woodpecker. It is his brain that is the most perfect and most unique in structure and is able to withstand overloads when chiselling wood up to 1000g. The formula would have such a head.)))
Earth Overloads
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.
Overloads in relation to a person:
1 - 1 g .
3 - 15 g within 0.6 sec.
5 - 22 g .
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 ... -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.
Space overload
During the launch, the astronaut is subjected to acceleration, the value of which varies from 1 to 7 g.
Overloads associated with acceleration cause a significant deterioration in the functional state of the human body: blood flow in the circulatory system slows down, visual acuity and muscle activity decrease.
With the onset of weightlessness, an astronaut may experience vestibular disorders, and a feeling of heaviness in the head region persists for a long time (due to increased blood flow to it). At the same time, adaptation to weightlessness occurs, as a rule, without serious complications: a person retains his ability to work and successfully performs various work operations, including those that require fine coordination or large expenditures of energy. Motor activity in a state of weightlessness requires much less energy than similar movements in weightlessness.
With longitudinal acceleration, the astronaut has visual illusions. It seems to him that the object he is looking at is shifting in the direction of the resulting vector of acceleration and gravity.
With angular accelerations, an apparent displacement of the object of vision in the plane of rotation occurs. This so-called near-gyral illusion is a consequence of the effect of g-forces on the semicircular canals (organs of the inner ear).
Conclusion:
If the blood flow in a state of weightlessness is an order of magnitude greater than on Earth, then the loss of consciousness due to excessive blood flow to the head will be both for a smaller g and for the sum of seconds that an astronaut can withstand .. But there is one + Since we are in in the distant future, our anti-g suits, for example, which, complete with 350r, will be an order of magnitude better to help maintain consciousness during strong and prolonged overloads + artificial gravity should save, which should create a counterbalance to overloads in 2-5 seconds.
According to doctors, the human brain can withstand overloads of about 150 g if they act on the brain for no more than 1–2 ms; with a decrease in overloads, the time during which a person can experience them increases, and an overload of 40 g, even with prolonged exposure, is considered relatively safe for the head.
An overload of up to 72 g is considered safe, overloads from 72 to 88 g fall into the intermediate “red” zone, and if 88 g is exceeded, a head injury is considered highly probable. Also important in the EuroNCAP methodology is the assessment of the pressure acting on the human chest: chest compression of 22 mm is considered safe, compression of 50 mm is considered limiting.
Aircraft. Overload is a dimensionless quantity, however, it is commonly identified with the acceleration of free fall g. Normal overload 1 g means horizontal straight flight. If an aircraft makes a horizontal coordinated turn with a bank of 60 degrees, its structure experiences a normal g-force of 2 units (or 2g).
The permissible value of overloads for civil aircraft is 4.33 zhi. An ordinary person can withstand overloads up to 5 g. Trained pilots in anti-g suits can endure g-forces up to 9 g. Resistance to negative, upward g-forces is much lower. Usually at 2-3 g in the eyes "turns red" and the person loses consciousness due to a rush of blood to the head.
Man standing still | 1 g |
Passenger on an airplane taking off | 1,5 g |
Skydiver landing at 6 m/s | 1,8 g |
Skydiver when opening a parachute (when changing speed from 60 to 5 m/s) | 5,0 g |
Cosmonauts during descent in the Soyuz spacecraft | up to 3.0-4.0 g |
Pilot performing aerobatics | up to 5 g |
Pilot taking the plane out of a dive | 8,0-9 g |
Overload (long-term), corresponding to the limit of human physiological capabilities | 8,0-10,0 g |
The greatest (short-term) overload of the car, in which a person managed to survive | 179,8 g |
Notes
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