This explosion has an outward resemblance to a ground-based nuclear explosion and is accompanied by the same damaging factors as a ground-based explosion. The difference is that the mushroom cloud of a surface explosion consists of dense radioactive fog or water dust.

Characteristic of this type of explosion is the formation of surface waves. The effect of light radiation is significantly weakened due to screening by a large mass of water vapor. The failure of objects is determined mainly by the action of an air shock wave. Radioactive contamination of the water area, terrain and objects occurs due to the fallout of radioactive particles from the explosion cloud. Surface nuclear explosions can be carried out to destroy large surface ships and solid structures of naval bases, ports, when severe radioactive contamination of water and coastal areas is permissible or desirable.

Underwater nuclear explosion.

An underwater nuclear explosion is an explosion carried out in water at a certain depth. With such an explosion, the flash and the luminous area are usually not visible. During an underwater explosion at a shallow depth, a hollow column of water rises above the surface of the water, reaching a height of more than a kilometer. A cloud is formed at the top of the column, consisting of splashes and water vapor. This cloud can reach several kilometers in diameter. A few seconds after the explosion, the water column begins to collapse and a cloud forms at its base, called the base wave. The base wave consists of radioactive fog; it quickly spreads in all directions from the epicenter of the explosion, simultaneously rises up and is carried by the wind. After a few minutes, the base wave mixes with the sultan cloud (sultan is a swirling cloud enveloping the upper part of the water column) and turns into stratocumulus from which radioactive rain falls. A shock wave is formed in the water, and on its surface - surface waves propagating in all directions. The height of the waves can reach tens of meters. Underwater nuclear explosions are designed to destroy ships and destroy the underwater part of structures. In addition, they can be carried out for strong radioactive contamination of ships and the coastal strip.

An underwater nuclear explosion is an explosion carried out in water at a certain depth. With such an explosion, the flash and the luminous area are usually not visible. During an underwater explosion at a shallow depth, a hollow column of water rises above the surface of the water, reaching a height of more than a kilometer. A cloud is formed at the top of the column, consisting of splashes and water vapor. This cloud can reach several kilometers in diameter. A few seconds after the explosion, the water column begins to collapse and a cloud forms at its base, called base wave. The base wave consists of radioactive fog; it quickly spreads in all directions from the epicenter of the explosion, simultaneously rises up and is carried by the wind. After a few minutes, the base wave mixes with the sultan cloud (sultan is a swirling cloud enveloping the upper part of the water column) and turns into a stratocumulus cloud, from which radioactive rain falls. A shock wave is formed in water, and surface waves form on its surface, spreading in all directions. The height of the waves can reach tens of meters. Underwater nuclear explosions are designed to destroy ships and destroy the underwater part of structures. In addition, they can be carried out for strong radioactive contamination of ships and the coastal strip.

The damaging factors of a nuclear explosion and their impact on various objects.

A nuclear explosion is accompanied by the release of a huge amount of energy and is capable of almost instantly incapacitating unprotected people, openly located equipment, structures and various materiel at a considerable distance. The main damaging factors of a nuclear explosion are: shock wave (seismic explosion waves), light radiation, penetrating radiation electromagnetic pulse, and radioactive contamination of the area.

shock wave. The shock wave is the main damaging factor nuclear explosion. It is an area of ​​strong compression of the medium (air, water), which propagates in all directions from the point of explosion at supersonic speed. At the very beginning of the explosion, the front boundary of the shock wave is the surface of the fireball. Then, as it moves away from the center of the explosion, the front boundary (front) of the shock wave breaks away from the fireball, ceases to glow and becomes invisible.

The main parameters of the shock wave are excess pressure in the front of the shock wave, the time of its action and velocity head. When a shock wave approaches any point in space, the pressure and temperature instantly increase in it, and the air begins to move in the direction of the shock wave propagation. With distance from the explosion center, the pressure in the shock wave front decreases. Then it becomes less atmospheric (a rarefaction occurs). At this time, the air begins to move in the direction opposite to the direction of shock wave propagation. After establishing atmospheric pressure air movement stops.

Influence of Explosion Conditions on Shock Wave Propagation

The shock wave propagation and its damaging effect are mainly influenced by meteorological conditions, terrain and forests.

Weather conditions have a significant effect only on the parameters of weak shock waves (DPav 0.1 kg/s) . As a rule, in summer, in hot weather, the parameters of the shock wave are weakened in all respects, and in winter, its strengthening, especially in the direction of the wind. As a result, the size of the affected areas, especially objects of low strength, can vary several times.

With rain and fog, a decrease in the pressure of the air shock wave is observed, especially at large distances from the explosion site. Under conditions of average rain, fog, pressure in the front of the shock wave is 5-15% less than in the absence of precipitation.

In conditions heavy rain and fog pressure in the shock wave is reduced by 15-30%.

The relief of the area can strengthen or weaken the effect of the shock wave. With a slope of 10-20°, the pressure increases by 10-50%, and with a slope of 30°, the pressure can increase by 2 times or more. In ravines, hollows, the direction of which coincides with the direction of the shock wave, the pressure is 10-20% higher than on the surface. On the opposite slopes of heights, in relation to the center of the explosion, as well as in hollows and ravines located at a large angle to the direction of propagation of the shock wave, the pressure in its front decreases. The pressure reduction ratio depends on the slope of the reverse slope. With a slope of 20°, the pressure decreases by 1.1-1.4 times, and with a slope of 30° - by 1.2-1.7 times.

Phenomena that occur during underwater explosions are associated with a very wide range of problems in which unsteady motions participate. We start by considering two quite classical problems.

Bubble collapse. One of the first questions that arise when studying an explosion under water is the question of how the gas bubble formed during the explosion, which is filled with explosive detonation products, changes over time.

In the simplest approximate formulation, the problem can be formulated as follows. Let a spherical gas bubble of variable radius be in a boundless incompressible fluid with density 1 and constant pressure. We neglect gravity, viscosity, as well as surface tension and condensation of gases in the bubble. It is required to find the law of radius change

The speed of fluid movement caused by a change in the bubble radius, in this moment time depends only on the distance of the considered point from the center of the bubble and is

where is some function of time. This relation allows us to calculate the kinetic energy of the entire mass of the liquid at the moment

We will assume that at the initial moment the liquid is at rest, even if the difference between the pressure in the liquid and the pressure of the gas inside the bubble is equal, by virtue of our proposals, this is a constant value. If surface tension is ignored, then

(the minus sign is explained by the fact that from where we find by integration

Comparing this expression with (2), we obtain a differential equation with separable variables

and its integration leads to the relation

from which you can find the required dependence

It follows from equation (4) that at , the speed R increases indefinitely as This reflects the fact that at the moment the bubble disappears, a water hammer occurs - we have an example of a global feature, which was mentioned above. The described effect is called bubble collapse.

Assuming in (5) we find the collapse time:

You can also consider a pulsating bubble, which, after collapse, expands to its initial size. The last formula allows us to determine the oscillation period of such a bubble:

Note that in the exact formulation of the problem of the motion of a gas bubble formed during an underwater explosion, the influence of the water surface and gravity should be taken into account, and the pressure in the bubble should be considered as changing according to the law:

where the volume of the bubble at time is a constant. The mass of gas inside the bubble and the forces of surface tension can be neglected. In this setting, at the initial moment, the water surface can be considered flat, and the boundary of the gas bubble can be considered a sphere; a further change in the shape of these surfaces is found from the solution of the problem.

The solution of the problem of the motion of a gas bubble in such an exact formulation for initial stage received recently by L. V. Ovsyannikov. We will speak about the further stages of the movement below when discussing the problem of the Sultan.

Bjorknes balls. Let two air or gas bubbles pulsate in an infinite fluid, which we still assume to be incompressible (with a density of 1) and weightless.

Back in the last century, the father and son Bjerknes discovered and explained an interesting phenomenon associated with this experiment - it turns out that if the bubbles pulsate in the same phase, then they are attracted to each other, and if they are in antiphase, they repel each other.

To explain this phenomenon, we need the following elementary fact - a ball moving translationally in an infinite fluid can be imitated by a point dipole located in the center of the ball. Indeed, let a ball of radius R move with velocity along the x-axis. The velocity potential of this movement is a harmonic function outside the ball equal to 0 at infinity and on the surface of the ball satisfying the condition (the normal component of the velocity, and 0 are cylindrical coordinates, see Fig. 101). These conditions are obviously

satisfies the function and the solution of the problem is unique, therefore, it is the desired potential. We see that outside the ball it coincides with the velocity potential of the dipole located at the origin of coordinates: moreover

Turning to the description of the Björknes phenomenon, let us replace the bubbles with point sources of intensities located respectively at the points of the x axis, moreover, if the bubbles pulsate in the same phase, and if they pulsate in antiphase. To take into account the possibility of displacement of the centers of bubbles, we will also assume that dipoles are placed at the same points. Since the bubbles are equal, it suffices to study the motion of one of them, say, the one that pulsates in the vicinity of the origin. We will assume that the bubble radii are small in comparison with a.

If we neglect the influence of the dipole located at the point , then at the point M, close to the origin of coordinates, the potential of the velocity field will be written in the form

where I is the distance of the point M to the second source, and the moment of the dipole (Fig. 101). We have and near the origin Therefore, (9) can be approximately rewritten in the form

or, if we discard the insignificant constant (for a fixed term, in the form

Here the first term gives the potential of the source located at the origin, the second -

the potential of another source (approximately) and the third - the potential of the dipole. If we denote by the radius of the bubble pulsating in the vicinity of the origin, then the rate of its change (which is determined by the first term) and the translational velocity of the bubble is determined by the third term; the plus sign is explained by the fact that we are talking about the speed of the bubble, not the liquid).

Let us now use the fact that, by virtue of our assumption of weightlessness, the total pressure on the bubble must be equal to zero. According to the Cauchy integral, the pressure at a point close to the beginning,

When integrating over the boundary sphere and the bubble, terms that do not depend on 0 or are proportional cancel out due to symmetry, so only the terms

The condition for the total pressure to vanish therefore leads to the equality

fair at all times

It remains to take into account that for the full period of bubble pulsation, the total effects of the change are equal to zero. But then, as can be seen from (12), the total effect of a change in the value over the period and, therefore, in sign is opposite to the sign Since

translational velocity of the bubble center, and then we conclude that the increment for the period of pulsation is negative at and positive at. This explains the Björknes phenomenon.

Let's note one more variant of the same phenomenon. As is known, the influence of a solid wall on a source is exactly equivalent to the influence of another source of the same intensity on it, located mirror-symmetrically with the first source relative to the wall.

Similarly, the action on the source of the free surface can be replaced by the action of a symmetric source, the intensity of which is opposite in sign to the intensity of the first source.

Rice. 102. (see scan)

Therefore, the above analysis also explains the following experimentally observed fact: a gas bubble that pulsates in water near a solid wall is attracted to the wall, and a bubble that pulsates near the free surface is repelled from it.

Let's move on to new challenges.

Paradox in an underwater explosion. Let a hollow cylinder with thick (20-30 mm) walls and a thin (1-3 mm) bottom made of iron or copper be partially immersed in water (Fig. 102, a). At a fixed immersion depth H at a distance h from the bottom of the cylinder, an explosive charge is placed on its axis and an explosion is performed. For each h, the minimum weight of the charge is selected, at which the bottom is destroyed.

It is natural to expect that the function strictly increases, but the following paradoxical fact was observed in numerous experiments: the function F strictly increases until h reaches a certain value; after that, in a section two or three times larger, it remains practically constant; when the value of F increases again (Fig. 102, b). The nature of the destruction of the bottom also changes - when the bottom breaks through a large area, and when the break is sharply localized.

Let us give a qualitative explanation of this paradox. Experiments show that the effect of an underwater explosive explosion is divided into two stages. At the first stage, immediately after the explosion, the products of the explosion form a gas bubble. First of all, a shock wave departs from it, which carries away about half of the energy of the explosion, and then the liquid velocities increase and the diameter of the gas bubble rapidly increases.

If at the end of this stage the breakthrough of the bottom and the release of gases into the atmosphere does not occur, then the second stage begins.

The gas bubble under the action of atmospheric pressure will begin to shrink, moving away from the bottom of the cylinder. We considered the problem of compression of a gas bubble in water above; it should only be borne in mind that in practice its shape is not spherical, but pear-shaped with an extension downwards. Over time, the bubble flattens, forming a cap with a notch at the bottom, and therefore the collapse of the bubble occurs on its lower surface. The hydraulic shock that occurs at the moment of collapse leads to a jet that goes back to the bottom of the cylinder (Fig. 103). This jet has a cumulative character, the energy in it is comparable to the energy of a bubble on

the first stage. At a certain weight F of the charge, the jet pierces a small hole in the bottom of the cylinder.

Breakthrough at the first stage of the process is characterized by a strict increase in the function at the second stage, the breakdown force little depends on the distance. Thus, the qualitative picture of the phenomenon can be considered sufficiently clear, but a somewhat complete quantitative calculation has not yet been carried out.

Spherical cumulation. In the previous chapter, we considered the motion of cumulative jets as steady. Meanwhile big interest represents also the process of jet formation, which is essentially non-stationary.

For simplicity, let us consider the case of spherical cumulation, where it is assumed that at the initial moment the liquid occupies the lower half-space with a recess in the shape of a hemisphere. In addition, it is assumed that at , the liquid instantly becomes heavy, and the potential function and the particle velocity on the free surface are equal to zero.

The problem is reduced to finding a function harmonic in spatial coordinates in the variable region equal to 0 at infinity, and on the boundary (free surface of the liquid) satisfying the condition

which, taking into account the ratio

can be rewritten as

An approximate solution of this problem in the plane version can be obtained by the method

electrohydrodynamic analogies (EGDA) using electrically conductive paper. For this, it is necessary to write down the difference analog of condition (13); if we denote by the index the points on the free surface of the liquid and by the index of the time step, then we will have

At the initial moment, we obtain the distribution Ф on the known free surface:

By implementing these boundary conditions on electrically conductive paper, we can construct lines of equal potential, and then streamlines for selected points of the free surface. Next, you can find the fluid velocity at these points, construct a free surface at a time with an index, and use (14) to find a new potential distribution on this surface. This distribution is again realized on the electrically conductive paper and the process continues.

On fig. 104 shows a consistent picture of the formation of a cumulative jet under the action of gravity for the moments of time

The results were obtained by V. Kedrinsky by the method described above.

On fig. 105 shows film footage of the repetition of Pokrovsky's experiment (§ 29). A test tube with water, the free surface of which is given a spherical shape with the help of a glass meniscus (visible in the first frame), is thrown vertically onto the table. At the moment of impact, the liquid instantly becomes heavy, so that this experience can be considered in connection with

(click to view scan)

with the above calculations for spherical cumulation. Under the frames in Fig. 105 indicates the time elapsed since the impact.

Sultan's problem Under certain conditions, as a result of an underwater explosion, an interesting phenomenon is observed, which is called the “sultan” - water is ejected to a great height above the free surface in the form of a narrow cone (Fig. 106). It is noted that

this phenomenon is characteristic of a liquid medium and is not observed in underground explosions.

Let us point out some features of an underwater explosion. In the previous section, we already spoke about two stages in the development of such an explosion. The first, very short stage is characterized by the creation of a shock wave, which takes about half of the total energy of the explosion. In the problem considered here, the wave reaches the free surface and breaks off a certain mass of water. The chipped off mass breaks up into a large number of small splashes, each with a small energy, and a funnel in the form of a depression is formed on the free surface.

The second stage is associated with the evolution of the gas bubble formed during the explosion, which also carries about half of the energy. This evolution, as we have said, leads to collapse and the formation of a jet, which (under the proper conditions of explosion, i.e., the depth of the charge and its weight) comes out to the free surface at the moment when a funnel has formed there. At this stage, you can use the model of the potential flow of an incompressible fluid - we come to the problem of determining the velocity field orthogonal to the surface of the funnel (the problem of spherical cumulation, which was just mentioned). As a result, the funnel escapes

a cumulative jet, which gives the sultan - a burst with quite a lot of energy.

A very similar phenomenon (but, of course, with much less energy) is observed when a bullet is fired into the water in a direction perpendicular to the free surface (Fig. 107). Another manifestation of the same effect can be observed when a rare direct rain falls on still water - the surface of the water is then covered with small fountains that rise to meet the rain.

A qualitative explanation of these phenomena is clear from Fig.

108, which shows three successive phases of the entry of a bullet (or a raindrop): first, the water surface slightly bends down (phase a), then the falling body sinks into the water and a cavity forms behind it (phase b) and, finally, the kinetic energy of the body goes to the collapse of the cavity. As a result of this collapse, a counter jet appears, which has a cumulative character (phase c).

This explanation is confirmed by a modification of the experiment - if you shoot a bullet into the water not perpendicular to the surface, but at a certain angle, then after the shot an inclined plume is formed in the direction opposite to the movement of the bullet (Fig. 109). Here, the deflection of the water surface in phase a will be asymmetrical, the cavity in the phase will move in the direction of the bullet flight, and the cumulative jet in the final phase will not go perpendicular to the water surface, but towards the movement of the cavity!

Explosion in the air. The characteristic difference between an explosion in air and an explosion in water is that here the main part of the energy is converted into a shock wave. Research on the propagation of shock waves in air is of primary importance. Until now, when carrying out large-scale blasting, engineers are faced with incomprehensible phenomena - sometimes the effect of a shock wave is many times greater, and sometimes many times less than that which was calculated using well-tested formulas. As a rule, such deviations are caused by anomalies in the atmosphere, because both the speed of the acoustic and the speed of the shock wave depend on the state of the atmosphere (density, temperature, humidity). The inhomogeneity of the atmosphere changes the front of the shock wave - it. can go up, or maybe cling to the ground.

As in water, peculiar “waveguides” can be created in air, when in some direction the attenuation of waves turns out to be significantly less than usual (we will talk about this phenomenon below, in § 34).

About a year ago there were sharp disputes among hydrodynamicists on the following question. Let a spherical explosive charge without a shell at the moment of explosion (in air) have a speed V such that the kinetic energy is commensurate with the potential energy E of the charge or is significantly greater than it; the question is, how will the speed change the effect of the explosion?

Two extreme points of view were expressed in the dispute: according to one, the speed of the charge at the time of the explosion should practically not affect the effect, the parameters of the shock wave can change only by a few percent. According to others, the speed can increase the effect of the explosion by about ten times.

The solution to this dispute turned out to be quite simple. It is necessary to divide the phenomenon into two stages - the release of explosion energy and the formation of a shock wave. At the first stage, in accordance with the point of view of one of the disputing groups, the charge speed has no practical effect, the entire potential energy of the explosive is converted into the kinetic energy of the flying particles of the explosion products. At the second stage, it is necessary to consider a gas cloud whose particle velocities are composed of the radial velocity (from the center of the charge) and the translational velocity of the charge itself.

Calculations and experiments have shown that the effect of a moving charge (at a sufficiently large distance from the place of explosion) is equivalent to the effect of a stationary charge with a potential energy equal to the sum of the potential energy of the explosive and the kinetic energy of the charge at the time of the explosion. In this case, it must also be assumed that the reduced center of the explosion is spaced from the actual center of the explosion in the direction of charge movement by a distance determined by the kinetic energy and potential energy E.

American physicist Robert Oppenheimer (Robert Oppenheimer), who is also the "father of the atomic bomb", was born in New York in 1904 in a family of wealthy and educated Jews. During World War II, he led the development of American nuclear scientists to create the first atomic bomb in the history of mankind.

Trial Name: Trinity
Date: July 16, 1945
Location: Test site in Alamogordo, New Mexico.

It was the test of the world's first atomic bomb. In a section 1.6 kilometers in diameter, a giant purple-green-orange fireball shot up into the sky. The earth shuddered from the explosion, a white column of smoke rose to the sky and began to gradually expand, taking on an awesome mushroom shape at an altitude of about 11 kilometers.

Trial Name: Baker
Date: July 24, 1946
Location: Bikini Atoll Lagoon
Explosion type: Underwater, depth 27.5 meters
Power: 23 kilotons

The purpose of the test was to investigate the effects nuclear weapons to naval vessels and their personnel. 71 ships were turned into floating targets. This was the fifth test of a nuclear weapon. The explosion lifted several million tons of water into the air.

Challenge Name: Able (as part of Operation Ranger)
Date: January 27, 1951
Location: Nevada Proving Ground

Trial Name: George
Date: 1951

Test Name: Dog
Date: 1951
Location: Nevada Nuclear Test Site

Challenge Name: Mike
Date: October 31, 1952
Location: Elugelab ("Flora") Island, Eneweita Atoll
Power: 10.4 megatons

The device detonated in Mike's test, dubbed the "sausage", was the first true megaton-class "hydrogen" bomb. The mushroom cloud reached a height of 41 km with a diameter of 96 km.

Trial Name: Annie (As part of Operation Upshot Knothole)
Date: March 17, 1953
Location: Nevada Nuclear Test Site
Power: 16 kilotons

Test name: Grable (as part of Operation Upshot Knothole)
Date: 25 May 1953
Location: Nevada Nuclear Test Site
Power: 15 kilotons

Challenge Name: Castle Bravo
Date: March 1, 1954
Location: Bikini Atoll
Explosion type: on the surface
Capacity: 15 megatons

Explosion hydrogen bomb Castle Bravo was the most powerful explosion ever conducted by the US. The power of the explosion turned out to be much higher than the initial forecasts of 4-6 megatons.

Challenge Name: Castle Romeo
Date: March 26, 1954
Location: On a barge in Bravo Crater, Bikini Atoll
Explosion type: on the surface
Capacity: 11 megatons

The power of the explosion turned out to be 3 times more than the initial forecasts. Romeo was the first test made on a barge.

Test Name: Seminole
Date: June 6, 1956

Power: 13.7 kilotons

Trial Name: Priscilla (as part of the Plumbbob trial series)
Date: 1957
Location: Nevada Nuclear Test Site
Power: 37 kilotons

Challenge Name: Umbrella
Date: June 8, 1958
Location: Eniwetok Lagoon in the Pacific Ocean
Power: 8 kilotons

An underwater nuclear explosion was carried out during Operation Hardtack. Decommissioned ships were used as targets.

Test Name: Oak
Date: June 28, 1958
Location: Eniwetok Lagoon in the Pacific Ocean
Capacity: 8.9 megatons

Test name: AN602 (aka "Tsar Bomba" and "Kuzkin's mother")
Date: October 30, 1961
Location: Novaya Zemlya test site
Capacity: more than 50 megatons

Test name: AZTEC (under the Dominic project)
Date: April 27, 1962
Location: Christmas Island
Power: 410 kilotons

Test name: Chama (as part of the Dominic project)
Date: October 18, 1962
Location: Johnston Island
Capacity: 1.59 megatons

Test name: Truckee (as part of the Dominic project)
Date: June 9, 1962
Location: Christmas Island
Power: more than 210 kilotons

Test Name: YESO
Date: June 10, 1962
Location: Christmas Island
Power: 3 megatons

Test name: "Unicorn" (fr. Licorne)
Date: July 3, 1970
Location: atoll in French Polynesia
Power: 914 kilotons

Trial Name: Rhea
Date: June 14, 1971
Location: French Polynesia
Power: 1 megaton

During the atomic bombing of Hiroshima atomic bomb"Kid", August 6, 1945) the total number of deaths ranged from 90 to 166 thousand people

During the atomic bombing of Nagasaki (atomic bomb "Fat Man", August 9, 1945), the total number of deaths was from 60 to 80 thousand people. These 2 bombings became the only example in the history of mankind combat use nuclear weapons.