Osa-class missile boat
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 Osa I (Project 205) craft
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| Class overview | |
|---|---|
| Name | Osa I |
| Succeeded by | Osa II class missile boat |
| Completed | 400+ |
| General characteristics | |
| Type | fast attack craft |
| Displacement | 172 tons standard, 210 tons full load |
| Length | 37.5 m |
| Beam | 7.64 m |
| Draught | 3.8 m |
| Propulsion | 3× M504 B2 waterjets; 12,500 hp |
| Speed | 38 knots |
| Range | 500 nm at 35 knots |
| Armament | list error: <br /> list (help) 2× AK-230 30 mm/65 1× 12.7 mm machine gun 4× SS-N-2A Styx |
The Osa class is the NATO reporting name for a group of fast attack craft developed for the Soviet Navy in the early 1960s. The Soviet designations are Project 205 (Проект 205) and Project 205U (Проект 205У) Tsunami. The craft are probably the most numerous class of missile boats ever built, with over 400 vessels constructed for both the Soviets and for export to allied countries. Two main variants were built: the Osa 1 (Project 205) which had box-shaped missile containers and the Osa 2 (205U) which had cylindrical missile containers. "Osa" means "wasp" in Russian, but it is not an original name.
Origins
These missile boats were designed to be much better fighting vessels than the previous Komar class. While these were cheap and efficient (and the first to sink a warship, destroying the Israeli Navy's Eilat), their endurance, sea keeping and habitability were modest and the missile box was vulnerable to damage from waves. Among their weak points there was the wooden hull, the radar set lacing a fire control unit, the only defence position with two 25 mm guns, (even if quite powerful themselves), only manual powered, with optical simple sighting unit. The offensive weapons were only a pair of SS-N2A/P-15 missiles, but there was not enough capability to hold the more recent P-15Ms, with longer range. Moreover, the sensors were not effective enough to utilize the maximum range of missiles, and the crew, numbering eleven, was not enough to employ all the systems. The overall problems were so recognized that Komars were organized in squadrons of six units, because it was expected that every NATO destroyer needed two missile hit to be sunk and this could be assured only with 12 missiles. Since 'Komar's were rated with a rather low capability to survive, it was necessary to use three squadrons for every target destroyed, to assure that one had success.
Project
Osa ships were bigger than 'Komar' class, with a mass four times greater, and thirty crew. They still were meant as 'minimal' ships for the planned tasks.
The hull was metallic (steel), with low and wide superstructure, continuous deck and a high free-board. The hull was quite wide, but OSAs could achieve still high speeds as they had three diesel engines capable of 12,000 hp, on three axis (to simplify the design, paradoxically, all engines were linked to one propeller). The powerful engines granted a high speed of 40 knots (with 60 hp/ton, three times that of a 'fast tank' like Leopard 1) and reasonable endurance and reliability.
The problem related to the weak anti-aircraft weaponry was partially solved with two AK-230 turrets, armed with four 30x213 mm guns, in fore and aft deck (as Hegu class, Chinese improved and longer Komar, with an additional 25 mm gun). A 'Drum Tilt' radar was placed in a high platform, and controlled all the horizon, despite the superstructures that were quite wide but low. So, even if placed in the aft, this radar had a quite good field of view all around. AK-230 were unmanned, quite low and small, armed with 30 mm guns capable of 2,000 rpm (400 practical) and with 2,500 m practical range. Use against surface targets was possible, but as with the previous Komar ships, when enemy vessels approached it was planned to escape and not fight, once ended missiles. For an effective anti-surface weaponry, it was needed to wait Tarantul corvettes, with 76 mm guns.
The missile armament was based on four hangars (protected from bad weather conditions) with one SS-N 2/P-15 missile aech. This doubled the available weapons, allowing more persistent actions in the sea. The use of them was granted by Garpun radar and ESM /IFF set Hig-Pole, that allowed even targeting over the horizon, if the targeted ship was emitting radar impulses.
With all these improvements, these ships were way more effective. They had one of the first, if not the first CIWS. The surviving capabilities were improved to 50%, as rated, and the whole amount of 12 missiles can be launched by only three ships. So the destroyer sinking was 'assured' by only six ships (two squadrons of three vessels), a way better coordinable and even cheaper than eighteen Komars.
Being small enough to obtain all these improvements, Osas were without equals in the late 1950/early 1960s and were over 400 were made in USSR, while in China another 120 were built. The improved 'Osa II' had SA-N 5 'Grail' with two quad launchers and 16 missiles, in an attempt to improve the air-defences, one of the problems showed by such small ships. This new model had also improved and more powerful engines, and new cylindrical missile boxes, with P-20M missiles, a very improved weapon compared to the early ones.
Many developments were extrapolated from this basic design: Shersen class returned to the torpedoing task, while Matckas were on the contrary missile hydrofoils with better speed (and Osa II hulls). Mols were an export-model Shersen, and Turyas were the hydrofoil equivalent of Shersen. Finally there were Stenka patrol boats, with ASW sensors and torpedoes, these were often replaced with motor-launches to improve patrolling around Soviet shores. All these ships had Osa I or II hull, or a smaller one but still derived from the basic design. Overall there were hundreds made, but they saw little export and so, they were never as known as the Osas.
Combat service
These missile boats saw action during the Six Day War, Yom Kippur War, and Indo-Pakistani War of 1971. The Israelis sank an Osa class Syrian boat during the Battle of Latakia, while the Indian Navy had more success against the Pakistanis - see Operation Trident (Indo-Pakistani War). Osas were also used in the Iraq-Iran War, with many losses, especially in a single battle in 1980 when several were destroyed by F-4s with AGM-65s. This battle occurred on 29 November 1980[1] and the Iraqi Navy incurred heavy damage.
The shortcomings that Osas had were mainly the low efficiency of missiles against small and ECM equipped targets, as showed in Battle of Lakatia. In this, Osas and Komars fired first, thanks to the longer range of missiles and favourable radar propagation conditions, but missed the targets, and then were not capable of escaping due to some engine malfunctions. The lack of medium caliber gun hampered defence against gunboats, even if the USSR had 37, 45 and 57 mm guns, well capable to be fitted in place of one 30 mm gun, just like happened in some other vessels, like Poti ASW corvettes. Real CIWS (meant as anti-missile systems) were never used even if there was not a real mass or dimension difference between AK-230/Drum Tilt and ADG-630/Bass Tilt.
The successors were Project 1241 Tarantul class corvettes , with twice the displacement but also a higher cost, and still with only four SS-N 2s. They had finally a better electronic suite and a 76 mm gun with high rate of fire. CIWS and 'Bass Tilt' radar were fitted, and at one time they were equipped with Moskit supersonic missiles. Not many of them were built, however, and so Osas, after replacing the old Komars, remained until today widely used, even though 200 ton class missile boats are really too small to be equipped with both offensive and defence equipment.
Ships
About 175 Osa 1 and 114 Osa 2 boats were built for the Soviet Navy, the last boats were decommissioned in about 1990 in the main Soviet fleet. Amongst the post-Soviet countries 1 boat is in service with the Azerbaijan Navy and two are in service with the Latvian Navy
Osa I
Benin- 2 boats in 1979
Bulgaria- Bulgarian Navy - 3 boats 1970-71
China- People's Liberation Army Navy - 4 boats in early 1960's plus over 120 license-produced.
Egypt- Egyptian Navy - 10 boats 1966 (4 sunk by Israeli Navy in Yom Kippur War)
East Germany- East German Navy - 15 boats transferred 1962-1971 - decommissioned 1981-1990
India- Indian Navy - 8 boats transferred in 1971 - decommissioned 1982-1990
Latvia- Latvian Navy - 6 ex-East German boats
North Korea- North Korean Navy - 12 boats transferred 1968-73
Poland- Polish Navy - 13 boats transferred 1964-1975 - decommissioned 1984-2006
Romania- Romanian Navy - 6 boats
Syria- Syrian Navy - 8 boats
Yugoslavia- Yugoslav Navy - 10 boats
Soviet Union
Osa II
Algeria- Algerian Navy - 8 boats transferred 1978
Angola- Angola Navy - 6 boats transferred 1982-83
- Bulgaria
- Bulgarian Navy - 6 boats
Cuba- Cuban Navy - 13 boats
Ethiopia- Ethiopian Navy 4 boats (1 is in service with Eritrea)
Finland- Finnish Navy - 4 boats transferred 1974-75. Known as Tuima class missile boats. Decommissioned in 2003. Sold to Egyptian Navy.
- India
- Indian Navy - 8 boats transferred 1976-77 , decommissioned 1999-2003
Libya- Libyan Navy - 12 boats
Somalia- Somalia - 2 boats
- Syria
- Syrian Navy- 12 boats
Vietnam- Vietnamese Navy - 8 boats
South Yemen- South Yemen - 8 boats
- Soviet Union
References
- Conway's All the World's Fighting Ships 1946-1995
- Page on Osa 2 from Indian Navy history
- Page on Osa 1 from Indian Navy history
- Trident and other operations in 1971 Indo-Pakistan war
- Slade, Stuart, The true history of Soviet anti-ship missiles, RID magazine, may 1994.
- Shikavthecenko, V, 'Lightings in the sea: the Russian FACs developments' RID September 1995.