Mel’niсk V. N., Karachun V.V., Levсhenkо O.I.

National Technical University of Ukraine «KPI»

THE LOSS OF ENERGY OF ACOUSTIC WAVES

The conversion LV Dnipro (fig. 1) is constructed on the base of intercontinental ballistic missile RS-20 ( SS-18 “Satana” ). Since 2003 construction works of the autonomous cosmic towboat (ACT) for LV Dnipro have been started. The modifications of Dnipro will allow to enlarge the the useful load’s mass on the one hand , to realize launchings of large-tonnage satellites of mass to high eleptic orbits on the other hand, and also to realization of flights to the Moon and primary planets.

On basis of argumentation one can claim that the construction of environmentally friendly rocket-cosmic complex Zenit of reaserch drafring department (RDD) “Pivdenne” and at production association (PA) “Pivdenmash” is the world level progress. A double-stage LV version Zenit-2, LV carries onto low circular polar orbit the useful weight up to 13,7 t. A three-stage LV version Zenit-3SL that is used in international Sea Launch project provides an orbital injection of spacecrafts up to 2,7 ton mass to geostationary orbit, spacecrafts up to 6 ton – to transfer to geostationary orbit, spacecrafts of 11-15 ton – to low earth orbit. The LV Zenit-3SL includes a double-stage launch vehicle Zenit-2S, upper-stage rocket DM-SLat the third stage, by space rocket complex (SRC) “Energiya” production and the block of useful load by company “Boing” development.

There are plans to modernize this space rocket complex to solve problems of starts: for launches near-earth orbit of satellite mass up to 12 ton (LV Zenit-2SLB), for launches to transfer to geostationary orbit of satellites up to 3,75 ton (LV Zenit-3SLB). The project is developed under the aegis of “Sea Launch”enterprise. The managment of works is perfomed by Ukrainian-Russian company “International space services”, RDD“Pivdenne”, PA “Pivdenmash”, drafting department (DD) of transport machine-building (Russia), SRC “Energiya”, the Center of earth space infrastructure operation.

Noise-protective screen. This construction refers to Mechanical engineering and can be used in aviation and rocket-cosmic technics for protection the facilities, pressure cells and biological objects from high power noise.

There is a known noise-protective screen (NPS), which includes a body with one-sided layer of sound absorbing material, and a case, in the shape of, distantly allocated under the body, perforated sheets (see, А.с. USSRР № 1582193, G10 К11/16, 1990).

The drawback of this NPS consists in the structural complexity, this sets conditions for the availability of a big amount of features in the NPS.

There is also a well-known NPS, that includes tough cylindrical case with length way apertures in side walls, placed on the protected body of a glass shape and allocated with an air gap, outside the body, and also a washer (see, e.g., Дидковский, В.В. Карачун, В.И. Заборов, Проектирование ограждающих конструкций с оптимальными звуко- и виброизоляционными свойствами. - К.: Будівельник, 1991, c. 91, рис. IV.І).

The drawback of this NPS is in deficient acoustic protection efficiency . This sets conditions for walls of the case to have a small inflexibility, because of aperture availability in the walls; the propagation of sound waves in the air gap between case and body occurs without obstructions.

Among known engineering solutions the most acceptable, by its construction, technical essence and attainable result, is the NPS, (see, the patent of France № 2652938, G10 К11/16, 1991, or its review on page 11 in the magazine "Изобретения стран мира" МКИ G10, "Музыкальные инструменты и акустика", Москва, вып.97, №1), which includes a body and an elastic hermetic casing (mattress is filled with a special gas and equipped with a facility for securing the circulation of the gas in the cavity of casing).

The drawback of this NPS consists in a small acoustic protection efficiency.

This can be explained, by two dominant causes. The smooth surface of casing, which does not secure the crossing between reflected from the surface sound waves, underlies the one reason. The other reason lies in the fact, that the casing is filled with gas. That is why the cavity is permeable for sound waves.

The other drawback of the NPS is a necessity, for its work, in the availability of gas with special features and apparatus for its admission, and the gas circulation supply in the casing. This sophisticates the construction, extends the material consumption and outer dimensions.

The third drawback of the NPS is in a low reliability; when the tightness of casing disturbs then the working-capacity of the NPS completely loses.

Underlie the proposition there is the assigned task to improve the NPS. The improvement can be reached by changing the form of casing and the shape of its cavity. Consequently the rise of the sound protection efficiency is secured at the synchronous simplification of construction, at the decline of materials consumption, outer dimensions, and the growth of reliability.

The assigned task can be solved in consideration of such fact that the NPS includes a body and a hermetic casing, allocated on its surface. According to the invention, the casing is made of hollow hoops, allocated in alignment, gathered endwise with apertures without an air gap, where the air is removed.

The difference of the NPS is that hoops have the shape of coils, fitted to each other.

The realization of casing in shape of hoops, allocated in alignment, gathered endwise without an air gap, secures the crossing of, reflected from its surface, sound waves, and raises the level of sound energy dissipation in the air, adjoined to the hoops. Consequently, the acoustic protection efficiency grows.

The air, removed from the hoops, transforms their cavities into absolutely tight for sound areas, through the lack of any substance that will be able to relay sound waves in it.

In the issue, the hermetic casing turns, partially, or, completely, into non-transparent for sound waves, this reduces to the furtherer acoustic protection efficiency rise.

At the same time, the air removal from the hoops, eliminates the necessity of using the gas and its server, this simplifies the construction, reduces the material consumption and outer dimensions.

Therewith, the execution of casing in the shape of air-free hoops raises the reliability, because during the depressurization of one (or some), hoops continue to work.

The hoops implementation in the shape of coils reduces their amount in the casing. Such construction simplifies the manufacture and is very important for bulky objects, for example rockets. For small-size objects, coil shape secures the casing receipt, by means of coiling the block on the body of object (pipe) of a proper length.

The NPS is schematically introduced on the fig. 2, the general form; on the fig.3 – the A location on the fig. 2; the variant of the NPS fulfillment on the fig. 2; on the fig. 4 is the version of fulfillment of the NPS.

The NPS includes the body 1 of glass shape. On its surface there is the hermetic casing 2. The casing 2 is made in alignment in the shape of hollow hoops 3 that are gathered endwise without air gap, from cavities 4 of this hoops the air is removed. The hoops 3 on the surface of the body 1 can be allocated into one line 5 or into some, for example, into the lines 6 and 7 (fig.3). The allocation of the hoops 3 into two lines secures the casing 2 of total wall K thickness with C diameters of contacting hoops cavities altitude overlapping. It additionally increases the acoustic protection efficiency. The hoops 3 are made of metal or other material, which has a sufficient inflexibility and high sound reflecting ability, for example, of polyvinyl chloride. The space between hoops can be filled with the sound absorbing material 8. The hoops 3, besides plain form (fig. 2 and fig. 3), can also possess (fig.4) the shape of the coils 9, which, in addition, contact with each other, by the ends 10, during their gathering.

Such form of hoops simplifies the manufacture of bulky casings, for example, casings for cargo bays of rockets.

For using, the NPS is installed on the protected object 11, for example, a gyroscopic facility, and is fastened on the basis 12.

The principle of the NPS operation is following.

When the intensive sound field P, its waves, work on the NPS, namely, the waves 13, 14, 15, obtaining the bulging surface of the coils 3 of the casing 2, partially, reflect from it in the shape of the waves 13', 14', 15', that crosses with the waves 13-15 and, in addition, between each other. This increases the number of sound waves cross points in the acoustic field. The growth of sound waves cross point number reinforces their energy dissipation in the environment.

Other group of the sound waves 13-15 penetrates into the walls of the hoops 3 and sharply brakes, by the non-air cavities 4. And, consequently, this group, intensively, dissipates through the material of coils at the expense of the inside friction. The availability, on the way of the sound waves 13-15 of the non-sound-penetrating for them, cavities 4, especially in the casing 3 between two lines 6 and 7 of hoops (fig. 3), and the additional dissipation of sound energy, in the issue of reflected sound waves crossing, leads to the significant growth of acoustic protection efficiency. The NPS with some lines of hoops is almost non-penetrating (non-transparent) for sound waves.

Also in the NPS, besides growing of acoustic protection efficiency, the necessity of using a special gas, a device for its supply, and circulation falls away. This simplifies the construction, reduces the resistance, decreases the materials consumption and outer dimensions, by, simultaneously, the reliability raising.

The invention can be used for protection from the aerodynamic noise of chambers with useful load of carrier-rockets, pressure cells and gyroscopes in hydro equalized platforms and in integrators of lengthwise accelerations of rockets, in aerospace complexes for multiple using, in heavy planes, biological objects etc.