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. These 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 official name.
Origins
These missile boats were designed to be much better fighting vessels than the previous Komar (Project 183R) class. While the Komars 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 was the wooden hull, the radar set lacking a fire control unit, and as single defenive position consisting of two manually operated 25 mm guns, (even if quite powerful themselves) with a simple optical sight. The Komars' offensive weapons were a pair of SS-N2A/P-15 missiles, and there was not enough capacity to hold the more recent longer-ranged P-15Ms. The sensors were not effective enough to utilize the maximum range of missiles, and the crew, numbering eleven, was not large enough to employ all the systems. As a result of these well recognized shortcomings, 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 only be assured 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, to assure one was successful.
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 still achieve 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 allowed a maximum 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 the use of two AK-230 turrets, in fore and aft deck (similar to the Hegu class, a Chinese improved and longer Komar, with an additional 25 mm gun). A 'Drum Tilt' radar was placed in a high platform, and controlled the whole 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. The AK-230s were unmanned, quite low and small, each armed with four 30 mm guns capable of firing 2,000 rpm (400 practical) with 2,500 m practical range. Use against surface targets was possible, but as with the previous Komar ships, once all missiles were expended it was planned to escape and not fight. Effective anti-surface weaponry was not available until the introduction of the Tarantul corvettes, with 76 mm guns.
The missile armament consisted of four hangars (protected from bad weather conditions) each with one SS-N 2/P-15 missile. This doubled the available weapons, allowing more persistent actions in the sea. The missles were controlled by a Garpun radar and ESM /IFF set Hig-Pole, that even allowed targeting over the horizon, if the target emitted radar impulses.
With all these improvements, these ships were considerably more effective. They had one of the first, if not the first Close-in weapon system (CIWS). The survivability rating was improved to 50%, and the required volley of 12 missiles could be launched by only three ships. Destroyer sinking was therefore 'assured' using only six ships (two squadrons of three vessels), making the Osas easier to coordinate and even cheaper than eighteen Komars.
As a result of these improvements, Osas were without equal in the late 1950/early 1960s. Over 400 were made in USSR, and another 120 in China. The improved 'Osa II' was equipped with the SA-N 5 'Grail' surface-to-air missile with two quad launchers and 16 missiles, in an attempt to improve air-defences. This new model also had improved, more powerful engines, and new cylindrical missile boxes, with the improved P-20M missiles.
Many developments were derived from this basic design, such as the Shersen class torpedo boat, the Matcka 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, which often replaced motor-launches to improve patrolling around Soviet shores. All these ships had Osa I or II hull, or a smaller version derived from the basic design. Overall hundreds of these were made, but they were rarely exported and were never classified as 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 their missiles against small and ECM equipped targets, as seen in Battle of Lakatia. In this conflict, Osas and Komars fired first, thanks to the longer range of missiles and favourable radar propagation conditions, but missed the targets, and were not capable of escaping due to some engine malfunctions. The lack of medium caliber gun hampered defence against gunboats, even though the USSR had 37, 45 and 57 mm guns capable of being fitted in place of one 30 mm gun, as happened in some other vessels, such as the Poti ASW corvettes. Effective anti-missile systems were never equipped even though there was no significant size or weight difference between the AK-230/Drum Tilt and the ADG-630/Bass Tilt CIWS.
The successor was the Project 1241 Tarantul class corvette, with twice the displacement and a higher cost, but still armed with only four SS-N 2s. They finally had 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. Few were built, however, and so Osas, after replacing the old Komars, remained widely in service until recent times, even though 200 ton class missile boats are really too small to be equipped with both offensive and defensive equipment.
Ships
About 175 Osa 1 and 114 Osa 2 boats were built for the Soviet Navy, the last 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
Philippines- Philippine Navy - 8 boats purchased from the USSR as a sign of peace in 1999
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
Eritrea- Eritrean Navy 5 boats
Finland- Finnish Navy - 4 boats transferred 1974-75. Known as Tuima class missile boats. Decommissioned in 2003 and 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.