The probability of tank kill (P_kill) by any type of weapon can be represented as a product of probabilities of the following events:

P_kill= P_acquis. x P_hit x P_kill/hit;

where P_acquis. is the probability of tank acquisition and identification by the enemy;

P_hit is the acquired tank hit probability;

P_kill/hit is the tank kill probability in case of hit.

Only recently the hit probability (P_hit) and kill probability in case of hit (P_kill/hit) by standard AP ammunition were estimated as a few per cent. In that case the acquisition probability (P_acquis.) had little effect on the final result.

Nowadays the situation has radically changed with precision-guided weapons coming into existence.

P_hit, P_kill/hit factors immediately approximated a hundred per cent and P_acquis. which characterizes the tank signature has become a critical factor which determines the tank survivability.

It can be seen from the diagram which shows the trends in using conventional and precision-guided weapons in the latest local conflicts

If in 1991 it took fifty-seven projectiles to kill one target, in 2003 the figure was only 1.5!

Some analysts equate the precision-guided weapon to tactical nuclear weapon by its efficiency. Moreover, precision-guided weapon is considered as a perfect weapon which cannot be defeated. Indeed, the precision-guided weapon is quite versatile and from the very beginning was designed to hit thin-armor tank surfaces and other targets; it is really a challenge for protection designers to defeat the complete range of such systems.

However, the situation is not as hopeless as it seems. And the solution is in reduction of P_acquis.

The point is that precision-guided weapon is very expensive and is used only in cases when the target acquisition probability is minimum 80%. If we manage to reduce this probability value, the precision-guided weapons ceases to be economically feasible.

Are there any ways to reduce the acquisition probability?

Yes, there are, and they can be defined as the principles of design of low-signature ground equipment, which are well-known today and which have already been partially realized in some items. As for animate nature, we can see the examples of such principles at every step.

These principles can be defined as follows:

• Minimization of the contrast between the item and the background in all wavelength ranges which can be used in acquisition systems;
  
• Continuous application of signature reduction measures and adaptability to any background changes;
  
• Priority of signature reduction requirements from R&D through full-scale production and whole life-cycle of new equipment.
  

There are several ways to realize these principles, they are well-known and described in military periodicals (see SuT 1/2004, Armada International 4/1995, MT 11/2003, Armada International 6/2003 etc.).

Some of these principles are as follows:

• Formation of the item appearance of the minimal number of simple-shape components to make a uniform surface without any gaps and salient components;
  
• Application of special materials and coatings with advanced physical and performance data including those which can change their colour and transmissivity ("chameleon");
  
• Generation of ionized air layers over the item to prevent acquisition by the systems operating in the radar frequency band;
  
• Application of aerosols non-transparent to 0.4-16 m, 0.2-0.8mm and 1.2-16mm wavelengths;
  
• Development of structures and patterns which maximal coverage of item surfaces by special materials and coatings;
  
• Minimization of the number of radiating devices;
  
• Development of lighting and vision devices, different kinds of radiating systems and secondary armament which can be retracted behind armor when idle and shifted outwards to combat position;
  
• Usage of only thermal imaging night vision systems;
  
• Screening, thermal insulation and air blowing of engine and propulsion compartments.

Below there are some examples of successful and unsuccessful realization of these principles.

Stalker armored assault vehicle (Minotor-Service, Byelorussia) is one of the first combat vehicles initially designed with priority of signature reduction.	Combat vehicles shown at VTTV-Omsk-1999" international exhibition feature camouflage painting; however, the rollers' painting pattern just intensifies the vehicle signature on the move.
The camouflage designer for T-80U MBT shown at VTTV-Omsk-2002 international exhibition (on the photo: front) became a prizewinner; though in terms of signature reduction the painting pattern does not fit with actual backgrounds, even the desert one.	Bright headgear makes the whole camouflage useless.

NII STALI JSC has been dealing with signature reduction of combat equipment and personnel for a long time and has good expertise in this field.

One of our company's products is Nakidka signature reduction material which actually makes any tank invisible for acquisition and guidance systems. The operational principle and efficiency of the material in different wavelength ranges are shown in a clip (mpg 43 Mb, download). Specifications: see "Nakidka kit for protection against surveillance and precision-guided systems"

As for personnel camouflage, the main principles and approaches to personal camouflage are stated in the article by A.P.Antipov and A.I.Egorov "Problems of Personal Protection and How to Solve Them". You can read the article here (in Russian).