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Articles

Signature Management

Sub Title : Signature management is imperative for survival on the battlefield; a scientific comparison between 2D and 3D camouflage nets

Issues Details : Vol 18 Issue 1 Mar – Apr 2024

Author : Col Ashwani K Sharma, Editor-in-Chief

Page No. : 44

Category : Military Technology

: March 22, 2024

In modern warfare, safeguarding military assets is paramount for battlefield success. Strategic assets like missile batteries, communication nodes, and command posts require state-of-the-art signature management to counter sophisticated surveillance and targeting technologies across various electromagnetic spectrum. Traditional visual camouflage is insufficient; protection in NIR, SWIR, TIR, and Radar bands is crucial. While reversible 2D camouflage nets offer logistical convenience, 3D nets provide superior multispectral camouflage, ensuring optimal protection for critical military assets.

The most effective survival strategy on the battlefield is to evade detection. If the enemy cannot detect you, they won’t be able to target you.

Today, the battlefield has expanded to include the rear areas with UAVs, satellites, reconnaissance. aircraft, Special Forces and even non-state players operating in depth areas, all hunting for strategic assets.

And, once detected and identified, it is easy to be targeted by multiple means today, no matter how much in depth.

Thus, all military assets, including in depth areas, must be protected by all possible means, to ensure success on the battlefield. This is all the more applicable for strategic assets that are of critical importance. Missile batteries, rocket artillery regiments, communication nodes, strategic command posts etc. are some critical assets of strategic importance whose compromise can have large-scale anddisproportionately large repercussions. The most cost effective means to enhance survivability is by using state-of-the art signature management to avoid/delay detection and to degrade surveillance and targeting capabilities of the enemy. Today, the sensors and seekers available to even non-state actors are sophisticated and are only set to improve as time goes by. It is necessary that a modern camouflage net caters to the present, and evolving, threats in the entire electro-magnetic spectra used for surveillance or targeting.

Traditionally, armies only considered visual camouflage important. However, today, visual is only a small region in the electro-magnetic spectra exploited for surveillance. Due to the proliferation of both sensors and seekers in the Near Infra-Red (NIR), Short Wave Infra-Red (SWIR), Thermal Infra-Red (TIR) and Radar bands, it is necessary that an asset is protected in these bands too. Thus, protection in all these bands is critical and a modern camouflage net needs stringent specifications, in each band, to counter available and fast emerging sensors and seekers. Poor specification in even one band would result in easy detection of the asset being protected.

There are two types of camouflage nets on the market. The reversible 2D camouflage net with different colours and pattern on either side, and the single sided, 3D camouflage net with a leaf like natural garnish quilted on a non-snagging base textile layer.

Let us discuss the current state-of-the-art specifications achievable (and specified globally) in each of the electro-magnetic bands and the pros and cons of the two types of nets.

Electro-Magnetic Spectrum of Importance to Camouflage

The Electro-Magnetic spectrum, is a continuous spectrum, from a few hertz (Hz) to many Terra Hz. Out of this, the following bands are of importance to camouflage and to enhance survivability.

  1. Ultra Violet (UV) Band–200 nm to 380 nm
  2. Visual (VIS) Band–380 nm to 780 nm
  3. Near Infra-Red (NIR) Band–780 nm to 1500 nm
  4. Short Wave Infra-Red (SWIR) Band–900 nm to 3000 nm
  5. Thermal Infra-Red (TIR) Band–3 to 5 μm and 8 to 12 μm
  6. Radar (RR)–1 GHz to 100 GHz

Pattern

For effective camouflage, the camouflage pattern is important. A short repetitive pattern, for example, usually screen printed with a typical 60 cm roll-screen, is very unnatural and at close range the repeating pattern is very noticeable. Simultaneously, at long ranges, the same short repetitive pattern of different colours, visually merge into a homogenous unified colour, adversely affecting camouflage. It is therefore important to have long pattern lengths. From experience in multiple terrains, it is found that the optimal pattern repetition should be at least 15 m.

Camouflage and Sensors in the Radar (RR) Range

Today, the radar band has gained considerable importance in both surveillance and targeting. Air-borne radar sensors operating against ground targets, surveillance radars, fire control radars and missiles are, like thermal sensors, becoming smaller and more widespread. This is largely due to the development of UAVs. Till a few years ago, these complex systems were limited to a handful of countries and were not expected to be encountered on international missions. However, today most armies possess both aircraft pods and even UAV based radars. There is also a radar revolution in space. Commercial companies are launching radar satellites covering the earth’s surface day and night, 24/7, and in bad weather.  Thus, it is now possible to buy almost real time radar imagery by anyone with money.

Radar Range for Effective Camouflage

Due to the atmospheric attenuation, there are three “windows” that are relevant to radar transmission for camouflage purposes. They are called the X-band (8-12 GHz), Ka-band (32-37 GHz) and W-band (92-96 GHz). These are the most important frequency bands to protect. Thus, for effective camouflage, it is necessary to specify the radar range from 2-100 GHz.

Ultra Violet (UV) Band

Snow may be the most complex environment to design good camouflage due to its conflicting requirements.

2D Nets. The typical 2D net structure is an open polyester fabric, i.e. it contains holes making up between 15-25% of the area of the net. Winter camouflage requires a very high reflectance, up to 90%. This is not possible to accomplish with a fabric with 15-25% black to start with (the holes). To achieve 90% reflectance with a fabric with 15-25% holes would require pigments with more than 100% reflectance, which obviously, do not exist.

The traditional white pigment TiO2 is dark in the UV range and cannot be used. UV-pigments on the other hand have very poor coverage in the visual range and are not suitable either. The answer is a multilayer product with a TiO2 base and top layer of UV-pigments. This is a compromise, heavy and with poor performance from a camouflage perspective. Thus, one is forced to use a near white pattern on the reverse side also negating any logistic advantage.

3D Nets. The 3D nets have substantially better performance in snow than the knitted 2D nets since a closed fabric is chosen for the garnish. Though the problem is similar, as in the case of 2D, however, the solution with TiO2 and UV-pigments in two layers is a better solution, as the compromises that need to be made are far less serious and fewer. Thus, 3D nets easily outperform 2D nets in snow.

Visual Band

2D nets. In the visual band, both 2D and 3D nets are similar in performance and adequate. It is difficult to distinguish a 2D net from a 3D net at longer ranges, however, at closer ranges, or with more powerful optical surveillance equipment, a 3D net is better. There are rarely any large plain, 2D surfaces in nature, thus, a 3D net blends better with the background as compared to a 2D net due to its 3-dimensional surface where the incising pattern mimics natural foliage.

In addition, it is more difficult to fulfil the colour specifications in a 2D net, particularly if the colours on the two sides are highly contrasting. Dark colours tend to affect the light colours on the other side.

3D nets. The 3D nets avoid the visual problems that are present in the 2D nets. Incision provides a more natural look as it mimics nature better. Their gloss is better, especially when wet and it is less complicated to fulfil material specifications since the focus is on one side.

Another advantage is that 3D nets, especially at close ranges, better handles straight lines formed at junctions of two different colours, due to the incision. This also makes a 3D net more forgiving when it comes to internal shadows due to wrinkles and poor camouflage setups.

Near Infrared (NIR) Band

2D nets. The same reasoning applies in the NIR region for 2D nets as in the Visual region. The performance is adequate at long range and poor at short range due to sharp pattern changes. This actually matters more in NIR since observation ranges for NVD and NVG are generally short, especially compared to visual observation ranges. Also, colours with different NIR reflectance on opposite sides affect each other and this is cumbersome to solve.

3D nets. The NIR performance of 3D nets are superior to the 2D nets especially at the typical operating distances of NVD and NVG devices. The structure of the garnish breaks up the pattern element giving the nets a natural look.

It is also easier to fulfil a material specification since focus is on one side.

Short Wave Infrared (SWIR) Band

2D nets. For a 2D net the difficulties are the same as in the NIR range. Paints and patterns on respective side disturb each other. A colour on one side that has a low SWIR reflection would influence a paint with a high SWIR reflection on the other side.

3D nets. The 3D camouflage net does not have to be concerned about what colours are on the reverse side. 3D nets are optimized for being invisible and match the background.

Thermal Infrared (TIR) Band

2D nets. In the thermal range the 2D nets are a compromise.

In the desert scenario it is important to have an apparent temperature similar to the sandy ground which gets heated. This can be solved with a dense 2D net, where the sun heats the material giving it a high temperature. However, the problem is that a dense net is poor at dissipating the heat generated inside the net. Connected problems that arise from using a dense material are due to the desert winds, which can be very strong, causing the camouflage nets to billow and act like a sail. A dense net also degrades the operation of sensors deployed under the net (visual, NIR, SWIR, TIR and radar) due to its construction.

On the other hand, in the Jungle scenario, it is important to have an open fabric to permit airflow since the vegetation usually has temperatures close to the ambient air temperature and a too dense fabric will heat up the net. With an open fabric, you will easily detect (in visual, NIR, SWIR, TIR and radar) what is under the net – humans, weapon and equipment hot spots etc.

3D nets. In the thermal wavelengths, the 3D nets are clearly superior. In the desert scenario, a closed garnish fabric is used to build heat in the material equal to the sandy ground, thus minimizing the contrast. At the same time sensors are permitted to be used through the open backing material. The

“sail-effect” due to high speed winds is minimized.

In contrast, in the Jungle scenario an open garnish is chosen to permit airflow which follows the temperature of the air and reducing solar loading, thus minimizing the contrast.

Radar Band

2D nets. 2D nets are more complex to produce than 3D nets since there is often only one layer that needs to hold all the properties for different bands- UV, Visual, NIR, SWIR, TIR and Radar. The simplest and most common approach to incorporate radar properties in a 2D fabric is to use yarn with stainless steel fibre. However, this simple solution produces poor results and has a very reflective net for low frequencies and a very transmissive net for high frequencies.

2D nets have a degraded performance in Radar band. This is why, usually they only specify performance in a restricted range of 2 – 18 GHz instead of the entire range of 2 – 100 GHz.

3D nets. In a 3D net, by using two separate layers, the performance of the signature properties in each band is more accurate than using a single layer as in 2D nets. The garnish and backing, each is tailor made for high performance in specific bands, making it superior to the 2D nets in composite performance. The top layer, the garnish, is fully devoted to UV, colour, pattern and NIR and SWIR performance. The backing is optimized for radar absorption. And the combination of the two gives the net its TIR performance.

Weight

The weight of the two different types of nets, 2D and 3D, depends on material specification such as strength, colour values etc.

Lightweight 2D materials often have problems with strength, withstanding flexing, colours affecting each other on respective side etc. It is thus necessary to use more paints and this increases both weight and stiffness.

Strength

The strength of a 3D net and 2D net depends on the material specification and can be adjusted. However, fabrics containing steel fibre are inherently weak.

Flame Retardancy

2D nets usually include steel fibres to incorporate radar performance. Steel fibres will burn under any circumstances, even wet, and it requires skill to protect the material from burning. Conductive polymers, in 3D nets, are much more easy to flame protection using environmentally friendly flame retarders.

Colour

The key problem is that in reversible nets of the 2D type, colours on one side affect the colours on the other side. 2D reversible nets are therefore constrained to choose combinations with less contrast for both sides. This is a compromise as dissimilar colours on one side effect the colour on the other side. Two dimensional nets are a more complex product than three dimensional nets. All the camouflage properties have to be included into a single flat layer. The advantage of the 2D nets is more a point regarding its logistics.

The 2D net is advantageous only if low value assets are to be camouflaged and moderate camouflage performance is acceptable.

A 3D net is advantageous if camouflage performance is the highest priority.

In Conclusion

As it emerges, the 3D camouflage nets offer superior camouflage properties compared to the 2D camouflage nets. The only advantage the 2D nets have is logistical, due to a different colour combination on each side of the net, however, this is at the cost of a compromised camouflage. For strategic military assets, a 3D camouflage net, with stringent specifications, is a far superior solution to ensure full multispectral camouflage and optimum protection.