By I.V. Kozhemyakin, Head of Defence R&D Agency of St. Petersburg State Marine Technical University
By V.Yu. Zanin, commercial representative, OCEANOS JSC
Background
In 2013 the State Marine Technical University of St. Petersburg (SMTU) in cooperation with OCEANOS JSC worked on modernization of the diving breathing apparatus DA-21 as a proactive development. In late 2013 a test cycle of the second-generatio
The back-worn rebreather DA-21Mk1 has successfully replaced the first generation DA-21 and enjoys demand in serial production. In 2015 the manufacture, for the Navy, of the first production batch of front-worn rebreather DA-21Mk2 was started. Up to this point Russia had imported the front-worn units from abroad, both as ready-to-go rebreathers and as parts and components for subsequent assembly. The appearance of a new Russian unit, DA-21Mk2, in the range of diving breathing apparatuses used by the Navy suggests that Navy officials are very serious about the issue of import substitution of Special Forces equipment. This is quite timely too, considering the ban on rebreather export to Russia from the world’s leading diving equipment manufacturers. Even back in 2012, two years prior to the introduction of sectoral sanctions against the Russian Federation, the competent authorities of the Federal Republic of Germany imposed export restrictions on such equipment.
Along with the overall impetus towards upgrade and improvement of the armed forces, the process of improving the DA-21 rebreather model range has also gained a noticeable momentum. Based on the front-worn DA-21Mk2, SMTU and OCEANOS JSC are working to create a new line of breathing apparatus, not only for military use, but also for various other purposes, from diving to medical. In the next 2–3 years DA-21 breathing apparatuses will allow us to provide modern diving equipment to various Russian customers and respond quickly to emerging needs and challenges.
The design-engineers and manufacturers of the newest Russian diving breathing apparatus, DA-21 Mk2, will remember March 2016, when the Russian Minister of Defense visited the Ryazan Higher Airborne Command School named after V.F. Margelov (RVVDKU).
Back then, in the course of studying the samples of Navy diving equipment being considered for use in the Airborne Forces, Army General Sergey Shoigu estimated it as “a tad heavy” for the “winged special forces” and commissioned the creation of a “paratroop” version of diving breathing apparatus DA-21 Mk2. The rebreather had to maintain the basic self-sufficiency specifications, be half (!) as heavy and provide interface with the sail wing-type parachute systems used by the Russian Ministry of Defence1. Thus, a new vector has been set to further improve and expand the use of breathing apparatuses.
Rebreather upgrade was carried out in two directions, –device weight reduction and interfacing with a parachute system. Due to the modernization potential of the unit and the technological capabilities of manufacturing, solutions to reduce the weight of the apparatus were produced immediately.
It should be noted that out of around 400 parts used in the breathing apparatus, 250 are made of pure polymer, about 50 of metal composite (the oxygen cylinder for example) and only about 100 parts are made of metal, the majority of which are fastening elements (screws, nuts and strips), and such important items as high pressure tank valves.
The cartridge of carbon dioxide chemical adsorbent has undergone major changes; it has been equipped with new parts made of polymeric materials. The unit housing has also been strengthened by simplifying its design and eliminating switches and communications redundant in the paratroop variant.
The modernization results were not long in coming:
weight of the Russian Navy diving rebreather DA-21 Mk2 basic set - 21 kg;
weight of the modernized diving breathing apparatus DA-21 Mk2D for airborne forces – 10.5 kg.
But the search for solutions for interfacing with the sail wing-type parachute system took much longer, even despite the participation of a team of top-notch experts, who had previously served in the relevant departments of the Navy and who had a rich and varied experience of diving descents and parachute jumps, and in spite of their deep knowledge of modern foreign analogues. It took several full-scale experiments to make the basic decisions that would take into account the complexity of the task. It should be noted that both computer 3D modeling and static fitting of diving and parachute equipment, as well as elements of the combat equipment of a paratrooper, followed by test runs on the ground parachute simulator could provide answers only for a limited range of issues, albeit setting the direction for the correct way ahead.
The real way out of this situation was the practical exercise of combining the diving equipment, parachuting equipment and elements of combat gear in a vertical wind tunnel. The fact is that the location and the mutual influence of gear elements of fully equipped paratroopers in a static state, and under the influence of an incoming flow at a speed of over 170 km/h, vary considerably. Mathematical modeling gives only an averaged picture due to individual characteristics of not only the paratrooper's body type, but also his preferences in the selection of equipment and its fitting.
In this regard, most of the flight time in the wind tunnel has been dedicated to exercising different combinations of elements of diving equipment (mask, fins, hydro acoustic communication station of the diver, breathing apparatus, cargo system) – elements of parachute equipment (parachute system, cargo containers of various types) – elements of combat equipment (weapons). The results formed the basis of recommendations for both changing the structural elements of the diving breathing apparatus and refitting of the parachute equipment.
It is necessary to acknowledge the contribution of the RVVDKU team, which took a fair share of the load, both on the issue and the provision of the required technical specifications of a paratrooper's diving equipment, and on combining the equipment and paratrooper's means of combat.
The result of these common efforts was the paratrooper diving breathing apparatus DA-21 Mk2D, which not only retained all the advantages of the basic diving breathing apparatus DA-21 Mk2 often highlighted by users (a partial list of its characteristics is given below), but also achieved a considerably more lightweight design, and, of course, without detriment to its strength and durability.
Work on the unit and its integration with the parachute systems and combat equipment, has not, of course, been finished completely, but six months after the inspection by the Minister of Defense, significant practical results have been achieved. The updated prototype model of the paratrooper diving breathing apparatus DA-21 Mk2D has been presented at the International Military Technical Forum “Army 2016” at the booth of the Ryazan Higher Airborne Command School named after V.F. Margelov, where it received positive feedback from relevant experts2.
Advantages of the basic diving breathing apparatus DA-21 Mk2:
- simplicity of design an ease of operation;
- optimal combination of inhalation and exhalation resistance in all positions regardless of the diver's breathing bag filling;
- optimal location and design of the bypass valve of the lung machine, reliably protecting it from the hydrodynamic effects of any incoming flow or mechanical damage, as well as providing ease of access and activation;
- no change in geometrical dimensions of the apparatus in the process of diving;
- reliable protection from possible damage (bumps and abrasions) of the diving apparatus breathing bag;
- reliable protection of the oxygen cylinder of the apparatus and its valve against inadvertent closing/opening, impact or entanglement in marine vegetation or halyards and ropes;
- comfort of the harness system and its integration into the cargo system and autonomous buoyancy compensator of the diving equipment.
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