Rebuilding the training potential of the ZOP in the MW RP

As part of the ongoing delivery process of Saab's autonomous AUV62-AT training system, there was an important stage in the sea trials. These trials were attended by the vessels of MW RP: a ship securing the launching and taking of the vehicle AUV and a rocket frigate.

The aim of the entire project is to restore the potential and ability of the MW to conduct advanced training of the ZOP (Battle of submarines) which significantly decreased after the withdrawal from service of submarines t. Kobben. AUV62-AT system allow for realistic training regardless of the availability of a submarine.

The issue of the availability of a submarine for the training of the ZOP also concerns sea states with extensive, active submarine forces. The reason for this condition is the operational loads, the growth of which (seen in recent years) causes the ZOP forces to lack the training of the "partner" for realistic training.

Mobile acoustic training goal ZOP

Autonomous underwater vehicles which are the main element of the ZOP training systems are divided into two main categories: one-off and recovered. The representative of the first group is the NATO system Mk-39 EMATT (Expendable Mobile Acoustic Training Target). The main advantages of this device are: small size and simplicity of use. The device does not require either adaptation of the platform or additional infrastructure. After simple programming, it is launched "from hand" and after completion of its mission it sinks.

^{Mk-39 EMATT next to containers for radio-hydroacoustic buoys}

The second mentioned category (recovered AUV) currently represents a quite wide range of solutions: from those of similar sizes to the EMATT described, to constructions based on 533 mm heavy torpedoes. Described in this Article The system belongs to the latter group, while taking a leading position in terms of training potential.

^{AUV62-AT stormed aboard the MW ship of the Republic of Poland during naval trials}

This comparison does not serve to indicate a better solution. Given the advantages and limitations, one solution does not exclude the other and each has its place in the activity of forces. For this reason, most marine forces with the capabilities of the ZOP use both solutions (EMATT and the recovery system).

Development genesis AUV62-AT

The development of the AUV62-AT system has been up to 25 years, with the first 10 years covering work on the platform itself (autonomic vehicle). The base for the construction of the platform was a heavy 533 mm torpedo, which was linked to the potential for future directions of use of vehicles by submarines (from torpedo launchers). The use of torpedo as a base, contrary to appearances, was not easy for design work. The main difference is the kinetic characteristics of both platforms. In place of capacity to achieve high speed approx. 50 knots, the designed AUV62 was designed to be characterized by long-lasting operations and precision of low-speed immersion control (approx. 5 knots). As a result, the AUV62 in fact only resembles a torpedo, because it has a completely different energy section and drive, as well as an absent in torpedoes section of immersion control with ballast system to regulate neutral buoyancy.

AUV62 System Development Calendar

1999 – AV62-F prototype is created

2005 – Development of SAPPHIRES demonstrators

2008 – SAPPHIRES achieves operational readiness

2010 – an acoustic module (section and towed converter line) for AUV62-AT is created

The result of the first stage of development was the SAPPHIRES demonstrator (Synthetic APerture Processing HI-REsolution Sensor), which reached operational readiness in 2008. Since 2010, in agreement with the Ministry of Foreign Affairs of Sweden, an initiative has been taken to adapt the vehicle to the role of a mobile acoustic training goal for training the ZOP.

The idea of taking this direction was due to increasing training needs and to securing tests of marine R & D programmes (among other things to develop new types of torpedoes). The main element of this project was an acoustic section, serving as a signature generator to simulate the target for active and passive detection. In addition, in order to achieve simulated echoes with realistic submarine-like characteristics, the acoustic section works with drivers on towed cablo-line.

This section is responsible for simulating an acoustic field without which the vehicle itself would not be able to fulfil its role. The reason is the physical characteristics of the vehicle, which is too small an object to be detected as a typical sonar to search for submarines, operating in the range of medium or low frequencies. For the purpose of active detection, the system functions as a so-called acoustic transponder, responding to an incoming pulse (active sonar) signal with appropriate parameters. However, for passive detection target simulation, the noise generator is responsible for issuing signals mimicking the desired target.

The following parameters and functionalities are of the level of advanced training systems:

• the frequency range of the acoustic transponder, including the ability to interact with low frequency LFAS (Low Frequency Active Sonar)
• frequency range of the noise generator and configuration of signature elements
• Erythema profiling ability
• long-term

The last of these functions is a key capability for using the system as a target for training torpedo shooting, which also sets the highest ceiling among these devices. Thanks to the long line of towed transducers, the AUV62-AT generates a realistic echo, creating a target with the required characteristics for modern, light torpedoes of the ZOP (such as the MW equipment of the RP MU-90 torpedo). In this respect, Saab's product until recently was one of the few which had this function, verified and confirmed by numerous naval trials using exercise torpedoes.

The described capacity is often declared in promotional materials of other lighter systems, but a substantial understatement must be taken into account. In the case of modern light ZOP torpedoes, it will not be possible to implement a full cycle of attack by the torpedo guidance system (at some stage of the torpedo run, the target will be rejected by the USN).

The achievement of these functionalities (especially the low-frequency emission capacity, in addition to the long-term mission) involves, among other things, significant energy needs, which influences the platform, the AUV vehicle. At the time of selection AUV62-AT was the largest and most advanced training system among all systems recovered. The system is also an object of interest of the US Navy planning to replace the Mk-30 operated since 1974, also based on heavy torpedo.

Currently, this group is expanding with a similar size Seagent M-T system, a French Naval Group company, whose design also uses elements of 533 mm heavy torpedoes. The French solution is an equivalent which, like the AUV62-AT, also has the ability to profile echoes (thanks to the towed line of acoustic transponders) and to interact with low frequency sonars. An interesting functionality is the ability to achieve higher speeds (over 20 knots) for simulation of nuclear-powered submarines.

The consequence of the described capabilities is the weight of the AUV vehicle, which in the case of AUV62-AT reaches about 800 kg (1 tonnes in the case of Seagent M-T) and the extended service set (transport system etc.), which limits the freedom to provide training, which in turn provides lighter equipment, especially compared to the aforementioned Mk-39 EMATT.

On the other hand, Mk-39 EMATT as well as other similar size solutions will never be able to match their larger counterparts in terms of simulation realism or provide anything above the basic level of training for hydroacoustics and limited tactical training.

^{AUV62-AT in the process of taking after mission. Visible towed cable-line with transducers}

There are several ways of compromise between the size of the vehicle and the possibility of simulation among systems with similar purpose available on the market. We are talking about intermediate solutions between EMATT and heavy ones such as AUV62 or Seagent M-T (e.g. on the basis of vehicles of the AV family Gavia or Osprey). When selecting, first questions need to be answered: how important it is for us to develop the capabilities of the ZOP and how often a submarine will be available for training. Another issue is the range of simulations that must take into account the characteristics of the ZOP sensors. In this case, consideration taken were currently operated, but most of all also sensors obtained from SZ development programs (AW-101 helicopters, multipurpose frigates of the Sword).

The AUV62-AT system will provide the Polish maritime forces, present and future highest training potential that can be offered today in the simulation conditions of the ZOP exercises. Given the difficult situation in which the underwater forces of the MW of Poland are currently located, reaching after the solution described is a logical and right decision.

Written by Kamil Sadowski

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