Now we need to understand whether it is possible to defend against it, and how. Often there are statements that it is enough to cover the rocket with a mirror coating or to polish the projectile, but unfortunately, everything is not so simple.
A conventional aluminum-coated mirror reflects approximately 95% of the incident radiation, and its efficiency depends strongly on the wavelength.
Spectral reflectance of mirrors with various metal coatings
Of all the materials shown in the graph, aluminum has the highest reflectivity, which is by no means a refractory material. If the mirror heats up slightly when irradiated with low-power radiation, then when a powerful radiation hits, the material of the mirror coating will quickly become unusable, which will lead to a deterioration of its reflective properties and further avalanche-like heating and destruction.
At a wavelength of less than 200 nm, the efficiency of the mirrors drops sharply, i.e. against ultraviolet or x-ray radiation (free electron laser) such protection will not work at all.
Mirror coating damaged by laser CO2 laser
There are experimental artificial materials with 100% reflection, but they only work for a specific wavelength. Also, mirrors can be covered with special multi-layer coatings that increase their reflectivity to 99.999%. But this method also works only for a single wavelength, and incident at a certain angle.
Do not forget that the operating conditions of weapons are far from laboratory, i.e. mirror rocket or projectile will need to be stored in a container filled with inert gas. The slightest turbidity or stain, for example, from handprints, immediately worsen the reflectivity of the mirror.
The exit from the container immediately exposes the mirror surface to the environment - the atmosphere and heat exposure. If the mirror surface is not covered with a protective film, it will immediately lead to a deterioration of its reflective properties, and if it is covered with a protective coating, it will itself deteriorate the reflective properties of the surface.
Comparative reflection spectra of films of reinforced aluminum, standard aluminum and aluminum without protection
Summarizing the above, we note: mirror protection is not very well suited for protection against laser weapons. Then what is suitable?
To some extent, the method of “smearing” the thermal energy of the laser beam along the body will help by ensuring the rotational movement of the aircraft (LA) around its own longitudinal axis. But this method is only suitable for ammunition and to a limited extent for unmanned aerial vehicles (UAVs), to a lesser extent it will be effective when irradiated with a laser in the front of the case.
On some types of protected objects, for example, on planning bombs, cruise missiles (KR), or anti-tank guided missiles (ATGM) attacking a target when flying from above, this method also cannot be applied. Non-rotating, for the most part, are mortar mines. It is difficult to collect data on all non-rotating aircraft, but I am sure that there are a lot of them.
SDB-39 and JSOW planning bombs
JASSM and 3M-14 cruise missiles
ATGM TOW2B attacking target when flying over it
In any case, the rotation of the aircraft will only slightly reduce the effect of laser radiation on the target, since the heat transferred by the powerful laser radiation to the hull will be transferred to the internal structures and further along all the components of the aircraft.
The use of fumes and aerosols as countermeasures against laser weapons also has limited capabilities. As already mentioned in the articles of the series, the use of lasers against ground-based armored vehicles or ships is possible only when used against surveillance equipment, which we will return to protection. Burn the BMP case /tank or surface ship with a laser beam in the foreseeable future is unrealistic.
Of course, it is impossible to apply smoke or aerosol protection against aircraft. Due to the high speed of the aircraft, the smoke or aerosol will always be blown back by the oncoming air pressure, for helicopters they will be blown away by the air flow from the propeller.
Thus, protection against laser weapons in the form of sprayed fumes and aerosols may be required only on lightly armored vehicles. On the other hand, tanks and other armored vehicles are often equipped with standard smoke screen systems to disrupt the enemy’s weapons systems, and in this case, when developing appropriate fillers, they can also be used to counteract laser weapons.
Elements of the complex of active protection (KAZ) "Afganit", intended for the production of protective curtains, promising tank T-14 based on the platform "Armata"
Returning to the protection of optical and thermal imaging intelligence, we can assume that the installation of optical filters that prevent the passage of laser radiation of a certain wavelength, suitable only at the initial stage to protect against low-power laser weapons, for the following reasons:
- in service will be a large range of lasers from different manufacturers operating at different wavelengths;
- a filter designed to absorb or reflect a certain wavelength when exposed to high-power radiation is likely to fail, which will either lead to laser radiation on sensitive elements, or failure of the optics itself (clouding, distortion of the image);
- Some lasers, in particular, a free electron laser, can change the working wavelength in a wide range.
Optical and thermal imaging reconnaissance can be protected for ground equipment, ships and aviation equipment by installing high-speed shields. If laser radiation is detected, the protective screen should close the lenses in fractions of a second, but even this does not guarantee the absence of damage to sensitive elements. It is possible that the widespread use of laser weapons over time will require at least duplication of intelligence in the optical range.
If on large carriers the installation of protective screens and duplicating means of optical and thermal imaging intelligence is quite realizable, then on high-precision weapons, especially compact sizes, it is much more difficult to do. First, the weight and size requirements for protection are significantly tightened, and secondly, exposure to high-power laser radiation, even with the shutter closed, can cause the optical system components to overheat due to dense layout, which will lead to partial or complete disruption of its operation.
American ATGM “Javelin”, Russian “Verba” MANPADS and a short-range missile RVV-MD are the most vulnerable targets for laser weapons
What are the ways to effectively protect equipment and weapons from laser weapons? There are two main methods - ablation protection and structural heat insulation protection.
The ablative protection (from the Latin ablatio - removal, mass carryover) is based on the substance carried off from the surface of the protected object by a flow of hot gas and / or on the rearrangement of the boundary layer, which in total significantly reduces heat transfer to the protected surface. In other words, the incoming energy is spent on heating, melt, and evaporation of the protecting material.
At the moment, ablative protection is actively used in the launching modules of spacecraft (SC) and in the nozzles of jet engines. The most widely used are plastic materials based on phenolic, silicone, and other synthetic resins containing carbon (including graphite), silica (silica, quartz), and nylon as fillers.
Ablative Protection Scheme
Ablative protection is one-time, heavy and bulky, so it makes no sense to use it on reusable aircraft (read not all manned, and most of the unmanned aircraft). Its only use is on guided and unguided projectiles. And here the main question is what thickness should be the protection for a laser power, for example, 100 kW, 300 kW, etc.
On the Apollo spacecraft, the protection thickness ranges from 8 to 44 mm for temperatures from several hundred to several thousand degrees. Somewhere in this range will lie the required thickness of the ablative protection against combat lasers. It is easy to imagine how it will affect the weight and size characteristics, and, consequently, the range, maneuverability, weight of the warhead (CU) and other parameters of the ammunition. The ablative thermal protection must also withstand overloads during launch and maneuvering, and must comply with the norms of terms and conditions of storage of ammunition.
Ablation protection of the Buran spacecraft in the context
Uncontrolled ammunition is under question, since the uneven destruction of the ablative protection from laser radiation can change the external ballistics, as a result of which the ammunition deviates from the target. If the ablative protection is already used somewhere, for example, in hypersonic ammunition, then its thickness will have to be increased.
Another method of protection is constructive coating or housing design with several protective layers of refractory materials that are resistant to external influences.
If we draw an analogy with spacecraft, then we can consider the thermal protection of the reusable Buran spacecraft. In areas where the surface temperature is 371 - 1260 degrees Celsius, a coating was applied consisting of amorphous silica fiber 99,7% purity, to which is added a binder - colloidal silicon dioxide. The coating is made in the form of tiles of two sizes with thickness from 5 to 64 mm.
Borosilicate glass containing a special pigment (white coating based on silicon oxide and shiny alumina) is applied to the outer surface of the tiles in order to obtain a small absorption coefficient of solar radiation and a high emission coefficient. Ablation protection was used on the nose fairing and the toes of the wing of the apparatus, where temperatures exceed 1260 degrees.
It should be borne in mind that during long-term operation, the protection of tiles against moisture may be impaired, which will lead to the loss of thermal protection of their properties, so it cannot be directly used as an anti-laser protection on reusable aircrafts.
Spaceship "Buran". White and black tiles - reusable heat protection, black elements of the nose and wing edges - ablative heat protection
The thickness of the thermal protection of the spacecraft "Buran" depending on temperature
At the moment, a promising ablative thermal protection is being developed with minimal surface wear, which protects aircraft from temperature to 3000 degrees.
A group of scientists from the Royce Institute at the University of Manchester (UK) and the Central Southern University (China) developed a new material with improved characteristics that can withstand temperatures up to 3000 ° C without structural changes. This is a Zr0.8Ti0.2C0.74B0.26 ceramic coating that is superimposed on the carbon-carbon composite matrix. According to its characteristics, the new coating significantly exceeds the best high-temperature ceramics.
The chemical structure of heat-resistant ceramics itself plays the role of a protective mechanism. At temperature 2000 ° C, Zr0.8Ti0.2C0.74B0.26 and SiC materials oxidize and turn into Zr0.80T0.20O2, B2O3 and SiO2, respectively. Zr0.80Ti0.20O2 partially melts and forms a relatively dense layer, and oxides with a low melting point of SiO2 and B2O3 evaporate. At a higher temperature 2500 ° C, Zr0.80Ti0.20O2 crystals melt into larger formations. At 3000 ° C, an almost completely dense outer layer is formed, mainly consisting of Zr0.80Ti0.20O2, zirconium titanate and SiO2.
The dark gray surface of the material before testing, as well as the surface after two minutes of testing at 2000 ° C and 2500 ° C. In the center of the right sample is the area where the flame temperature reached 3000 ° C
The world is developing and special coatings designed to protect against laser radiation.
A representative of the People’s Liberation Army of China, back in 2014, said that American lasers do not pose a particular danger to Chinese military equipment sheathed with a special protective layer. There are only questions left: what kind of power, from lasers, does this coating protect, and which has thickness and mass.
Of greatest interest is the coating developed by American researchers from the National Institute of Standards and Technology and the University of Kansas - an aerosol composition based on a mixture of carbon nanotubes and special ceramics that can effectively absorb laser light. Nanotubes of the new material uniformly absorb light and transfer heat to nearby areas, reducing the temperature at the point of contact with the laser beam. Ceramic high-temperature joints provide the protective coating with high mechanical strength and resistance to high temperature damage.
During the tests, a thin layer of material was deposited on the copper surface and, after drying, focused a beam of a long-wave infrared laser, a laser used for cutting metal and other hard materials, on the material surface.
Analysis of the collected data showed that the coating successfully absorbed 97.5 percent of the laser beam energy and without failure sustained the energy level in 15 kW per square centimeter of surface.
On this coating, the question arises: in testing, the protective coating was applied to the copper surface, which itself is one of the most difficult materials to be treated with a laser, because of its high thermal conductivity, it is unclear how it will behave such a protective coating with other materials. Also, there are questions about its maximum temperature resistance, resistance to vibration and shock loads, exposure to atmospheric conditions and ultraviolet radiation (sun). Not specified time during which the exposure was carried out.
Another interesting point: if the aircraft engines are also covered with a substance with high thermal conductivity, then the whole body will be uniformly heated from them, which unmasks the aircraft in the thermal spectrum to the maximum.
The cutting speed of copper is the smallest of all metals in the table due to the high thermal conductivity; perhaps, the developers of the protective material did not accidentally choose this material as a substrate for testing, trying to inflate the characteristics of their design
In any case, the characteristics of the above aerosol protection will be in direct proportion to the size of the protected object. The larger the protected object and the coverage area, the more energy can be scattered over the area and given in the form of thermal radiation and cooling by the oncoming air flow. The smaller the protected object, the thicker you will have to do protection, because a small area will not allow enough heat to be diverted and the internal structural elements will be overheated.
The use of protection from laser radiation, whether ablative or constructive insulating, can reverse the tendency to reduce the size of guided ammunition, significantly reducing the effectiveness of both guided and non-guided munitions.
All bearing surfaces and controls - wings, stabilizers, steering wheels, have to be made from expensive and difficult to process refractory materials.
Separately, the question arises on the protection of radar detection equipment. On the experimental spacecraft "BOR-5" radio transparent thermal protection was tested - fiberglass with silica filler, but I could not find its thermal protection and weight and size characteristics.
It is still unclear whether, as a result of irradiation of radomes of reconnaissance radar tools with high-power laser radiation, even with protection from thermal radiation, a high-temperature plasma formation can appear that interferes with the passage of radio waves, as a result of which the target may be lost.
To protect the case, it will be possible to use a combination of several protective layers - heat-resistant, low heat-conducting from the inside and reflective-heat-resistant-high heat-conducting from the outside. It is also possible that materials will be applied on top of the protection from laser radiation to ensure stealth, which cannot withstand laser radiation, and will have to be restored after receiving damage from a laser weapon if the aircraft itself has survived.
It can be assumed that the improvement and widespread use of laser weapons will require the provision of laser protection against all available ammunition, both guided and unguided, as well as manned and unmanned aerial vehicles.
The introduction of laser-free protection will inevitably lead to an increase in the cost and weight and size characteristics of guided and unguided munitions, as well as manned and unmanned aerial vehicles.
In conclusion, we can mention one of the developed methods of active counteraction to a laser attack. The company Adsys Controls, located in California, is developing a protective system Helios, which should bring down the enemy's laser guidance.
When you hover the enemy's combat laser on the protected Helios device, it determines its parameters: power, wavelength, pulse frequency, direction and distance to the source. In the future, Helios prevents the enemy's laser beam from focusing on the target, presumably by aiming the oncoming low-energy laser beam, which confuses the enemy's guidance system. Detailed characteristics of the Helios system, the stage of its development and its practical performance are still unknown.