Osa I (Project 205) craft
|Name||Osa (Project 205)|
|Preceded by||Komar-class missile boat|
|Succeeded by||Tarantul-class corvette|
|Subclasses||Osa I, Osa II|
|Type||Fast attack craft|
|Length||38.6 m (127 ft)|
|Beam||7.64 m (25.1 ft)|
|Draught||1.73 m (5.7 ft) (with M-504B - 1.84 m (6.0 ft))|
|Sensors and |
|Electronic warfare |
The Project 205 Moskit (mosquito) more commonly known by their NATO reporting name Osa, are a class of missile boats developed for the Soviet Navy in the late 1950s. Until 1962 this was classified as a large torpedo boat.
The Osa class is probably the most numerous class of missile boats ever built, with over 400 vessels constructed between 1960 and 1973 for both the Soviet Navy and for export to allied countries. "Osa" means "wasp" in Russian, but it is not an official name. The boats were designated as "large missile cutters" in the Soviet Navy.
While the earlier Komar class were cheap and efficient boats (and the first to sink a warship with guided missiles, destroying the Israeli Navy's Eilat), their endurance, sea keeping, and habitability were modest at best, and the missile box was vulnerable to damage from waves. Among their other weak points were the wooden hull, the radar set lacking a fire control unit, and an inadequate defensive armament consisting of two manually operated 25 mm guns with only a simple optical sight in a single turret.
The Komars' offensive weapons were a pair of P-15 Termit (NATO: SS-N-2 "Styx") missiles, and there was insufficient capacity to hold the more modern longer-ranged P-15Ms. The sensors were not effective enough to use the maximum range of the missiles, and the crew of 17 was not large enough to employ all the systems efficiently.
In order to remedy all these shortcomings, it was felt that bigger boats were needed to mount the necessary equipment and to provide more space for a larger crew.
The Project 205 boats are bigger than the pioneering Project 183R (NATO: Komar class) boats, with a mass four times greater, and nearly double the crew. They were still meant to be 'minimal' ships for the planned tasks.
The hull was made of steel, with a low and wide superstructure made of lighter AMG alloys, continuous deck, and a high free-board. The edges of the deck were rounded and smooth to ease washing off radioactive contamination in case of nuclear war. The hull was quite wide, but the Project 205 boats could still achieve high speeds as they had three Zvezda M503 radial diesel engines capable of a combined 12,000 hp (15,000 hp on Project 205U onward) driving three shafts.
The powerful engines allowed a maximum speed of about 40 knots together with reasonable endurance and reliability. There were also three diesel generators. Two main engines and one generator were placed in the forward engine room, the third main engine and two generators in the aft engine room. There was a control compartment between the two engine rooms.
The problem related to the weak anti-aircraft weaponry of the earlier Project 183R was partially solved with the use of two AK-230 turrets, in the fore and aft deck. An MR-104 Rys (NATO: "Drum Tilt") fire-control radar was placed in a high platform, and controlled the whole horizon, despite the superstructures that were quite wide but low. Even if placed in the aft, this radar had a good field of view all around.
The AK-230 turrets were unmanned, each armed with two 30 mm guns capable of firing 2,000 rpm (400 practical) with a 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. Truly effective anti-surface gun weaponry was not available until the introduction of the Project 12341.1 Molniya (NATO: "Tarantul") class corvettes, with 76 mm guns.
The offensive armament consisted of four P-15 Termit (NATO: SS-N-2 "Styx") missiles, each protected from bad weather conditions inside an enclosing box-shaped launcher. This doubled the available weapons compared to the Project 183R, giving greater endurance. The missiles were controlled by a MR-331 Rangout (NATO: "Square Tie") radar and a Nikhrom-RRM ESM/IFF that even allowed targeting over the horizon, if the target's radar was turned on.
With all these improvements, these ships were considerably more effective. They had one of the first, if not the first close-in weapon systems (CIWS). The survivability rating was improved to 50%, and the required volley of 12 missiles could be launched by only three ships. Sinking a destroyer was therefore regarded as 'assured' using only six ships (two squadrons of three vessels), making the Project 205 vessels easier to coordinate and even cheaper than would be the required number of Project 183R boats to achieve the same effectiveness.
As a result of these improvements, Project 205 boats were without equal in the late 1950/early 1960s. Over 400 were made in USSR, and another 120 in China. Some of the improved Project 205U (Osa II) were equipped with the 9K32 Strela-2 (NATO: SA-N-5 "Grail") surface-to-air missiles in MTU-4 quadruple launchers, 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-15U missiles. The later 205M and 205mod boats had longer tubes for the further-improved P-15M missiles.
The Project 205's hull proved to be very versatile and were used as the basis for a whole series of Soviet fast attack craft and patrol boats.
The Israeli Saar missile-boats sank a Syrian Osa class missile-boat during the Battle of Latakia and three Egyptian Osa class missile-boats in the Battle of Baltim. No Israeli ships were damaged in these battles.
In contrast, the Indian Navy Osa missile-boats were very successful against the Pakistani Navy in Operation Trident, with a total of five ships sunk, two damaged beyond repair, an oil facility destroyed and Karachi Port held under blockade for no losses.
Osas were also used in the Iran-Iraq War, with few 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 and the Iraqi Navy incurred some damage. Iraq has lost only five missile boats during the eight years of war.
The shortcomings that the export Osas had were mainly the low efficiency of their missiles against small and ECM-equipped targets, as seen in the Battle of Latakia. In this conflict, Osas and Komars fired first, thanks to the longer range of missiles and favourable radar propagation conditions, but missed the targets due to jamming, 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 and the AK-630 CIWS.
The successor was the Project 1241 Tarantul class corvette, with twice the displacement and a higher cost, but still initially armed with only four P-15s. They finally had a better electronic suite and a 76 mm gun with high rate of fire, along with newer P-270 Moskit and Kh-35 supersonic missiles, AK-630 CIWS, and 'Bass Tilt' radars. Fewer were built however, and so the Osas, after replacing the old Komars, remained widely in service up to the turn of the 21st century.
About 175 Osa I and 114 Osa II boats were built for the Soviet Navy, the last were decommissioned in about 1990 in the main Soviet fleet. Amongst the post-Soviet countries, one boat is in service with the Azerbaijan Navy and two are in service with the Latvian Navy.