RIM - 7 Sea Sparrow RIM - 7 Sea Sparrow is a US ship - borne short - range anti - aircraft and anti - missile weapon system , primarily intended for defense against anti - ship missile s . The system was developed in the early 1960s from the AIM - 7 Sparrow air - to - air missile as a lightweight " point defense " weapon that could be retrofitted to existing ships as quickly as possible , often in place of existing gun - based anti - aircraft weapons . In this incarnation it was a very simple system , guided by a manually aimed radar illuminator . Since its introduction , the Sea Sparrow has undergone significant development and now resembles the AIM - 7 only in general form ; it is larger , faster and includes a new seeker and a launch system suitable for vertical launch from modern warships . Fifty years after its development , the Sea Sparrow remains an important part of a layered air defense system , providing a short / medium - range component especially useful against sea - skimming missiles . History . Background . High - speed jet aircraft approaching ships at low altitudes presented a serious threat to naval forces in the late 1950s . Approaching under the local horizon of the ships , the aircraft would suddenly appear at relatively close ranges , giving the ships only seconds to respond before the aircraft dropped their payloads and withdrew . This gave the aircraft an enormous advantage over earlier weapons such as dive bomber s or torpedo bomber s , whose low speed allowed them to be attacked with anti - aircraft gun s . The advantage was so great that when the Royal Navy was faced by the threat of the new Soviet Sverdlov class cruiser , they responded in a non - linear fashion by introducing the Blackburn Buccaneer aircraft to attack them . Further improving the capabilities of aircraft against ships were a variety of precision - guided weapons , starting with World War II manually controlled weapons such as the Fritz X , and evolving into semi - autonomous cruise missile s , such as the Raduga KS - 1 Komet , that relied on a combination of initial guidance from the launching aircraft and terminal guidance on the missile itself . These systems allowed the aircraft to launch their attacks from outside the range of shipboard weapons , in relative safety . Only the presence of defensive fighters operating at long ranges from the ships could provide cover against these attacks , by attacking the launch aircraft before they could close on the ships . US Navy doctrine stressed long - range air cover to counter both high - speed aircraft and missiles , and development of newer short range defenses had been largely ignored . While developing expensive long - range fighters like the Douglas F6D Missileer , most ships were left equipped with older weapons , typically Bofors 40 mm gun s or similar weapons . By the early 1960s their capability against modern aircraft and missiles was limited ; a lack of fast - reacting mounts , gunsight radars of limited accuracy and long settling times for the fire control system s all meant that the guns were unlikely to be able to respond effectively . The introduction of sea - skimming missiles dramatically increased the threat of ASMs against these ships . Unlike the earlier generation of ASMs , sea - skimmers approached at low level , like an attack aircraft , hiding themselves until the last moment . The missiles were relatively small and much harder to hit than an attacking aircraft . While the older defenses might be considered a credible threat to a large aircraft or a missile approaching at higher altitudes , against a sea - skimming missile they were useless . To successfully counter this threat , ships needed new weapons able to attack these targets as soon as they appeared , accurately enough to give them a high first - attempt kill probability - there would be little time for a second attempt . Point defence missile system ( PDMS ) . The US Army faced a similar problem defending against attacks by high - speed jet - powered attack aircraft . In this case the local horizon was generally even more limited , blocked by trees and hills , and engagement times could be measured in seconds . They concluded that a gun - based system was simply unusable in this role ; by the time the radar had locked - on and the gunsight calculated proper " lead " there would be no time to shoot at the target while it was within a gun ' s relatively short range . Missiles , on the other hand , could progressively tune their approach while they were flying toward the target , and their proximity fuse s meant they only needed to get " close enough " . In 1959 the Army started development of the MIM - 46 Mauler , which mounted a new high - speed missile on top of the ubiquitous M113 Armored Personnel Carrier chassis , along with a medium - range search radar and a separate tracking and illumination radar . In order to deal with the quick response times needed , the fire control system was semi - automatic ; operators would view targets on the search radar and prioritize them , the fire control system would select ones within attack range and automatically slew the missiles toward them and launch . Since the missile would be operating close to the ground in highly cluttered environments , it used a combination of beam riding along the illumination radar and an infrared seeker in the nose , which allowed tracking as long as either the path in front or in rear of the missile remained free of obstructions . These same basic engagement parameters - high - speed and the associated fleeting sighting times - applied to sea - skimming aircraft and missiles as well . The Navy intended to adapt the Mauler to shipboard use by removing its search radar and wiring it into the existing ship - borne radar systems instead . The 9 - box launcher and illuminator radar would be retained in a relatively compact mount . Development started in 1960 under the " Point Defense Missile System " ( PDMS ) , the naval version to be known as the " RIM - 46A Sea Mauler " . The Navy was so confident in the Sea Mauler that they modified the design of their latest frigates , the " Knox " class , to incorporate a space on the rear deck for the Sea Mauler launcher . The Navy ' s confidence in Mauler proved misplaced ; by 1963 the program had been downgraded to a pure technology development effort due to continued problems , and was canceled outright in 1965 . All three of the stakeholders , the US Army , US Navy and British Army , started looking for a replacement . While the British took a longer - term approach and developed the new Rapier missile , the US Army and Navy scrambled to find a system that could be deployed as quickly as possible . Facing the problem of guidance in a cluttered environment , the Army decided to adapt the infrared AIM - 9 Sidewinder missile into the MIM - 72 Chaparral . This was based on the AIM - 9D , a tail - chaser , and would be useless for the Navy where its targets would be approaching head on . They required a radar - guided system , and this naturally led to the AIM - 7 Sparrow . They also considered Chaparral for smaller ships due to its much smaller size , but no such fits were ever attempted . Basic point defence missile system ( BPDMS ) . Quickly organizing the " Basic Point Defense Missile System " , BPDMS , the then - current AIM - 7E from the F - 4 Phantom was adapted to shipboard use with surprising speed . The main developments were the new Mark 25 trainable launcher developed from the ASROC launcher , and the Mark 115 manually aimed radar illuminator that looked like two large searchlights . Operation was extremely simple ; the operator would be cued to targets via voice commands from the search radar operators , and he then slewed the illuminator onto the target . The relatively wide beam of the radar only needed to be in the general direction of the target , the continuous wave signal being Doppler shift ed by the moving target and showing up strongly even if it was not centered in the beam . The launcher would automatically follow the motions of the illuminator , so that when the missile was fired it would immediately see the signal being reflected off the target . In this form the Sea Sparrow was tested on the USS " Bradley " starting in February 1967 , but this installation was removed when the " Bradley " was sent to Vietnam later that year . Testing continued , and between 1971 and 1975 Sea Sparrow was fitted to 31 ships , DE - 1052 to 1069 and DE - 1071 to 1083 . The " missing ship " in the series , USS " Downes " ( DE - 1070 ) was instead used to test an upgraded version ( see below ) . The Sea Sparrow was far from an ideal weapon . Its rocket engine was designed with the assumption that it would be launched at high speed from an aircraft , and therefore is optimized for a long cruise at relatively low power . In the surface - to - air role one would rather have very high acceleration in order to allow it to intercept sea - skimming targets as soon as possible . The power profile is also suitable for cruising in thin air at high altitudes , but at low altitudes it does not produce enough power to overcome drag and dramatically decreases range ; some estimates indicate that the Sea Sparrow may be effective only to , about one quarter of the range of the air - launched Sparrow . An engine of much higher power would greatly improve performance , in spite of a shorter burning time . Another problem is that the Sparrow is steered with its mid - mounted maneuvering wings . These were used on the Sparrow because they required less energy for basic maneuvers during cruise , but this made the missile less maneuverable overall , which was not well suited to the quick - reaction weapon . Additionally , the powered wings meant that they could not easily be adapted to fold , and therefore the launcher cells were sized to the wings instead of the missile body , taking up much more room than required . Although the Sea Sparrow was meant as a small missile system that could be fit to a wide variety of ships , the launcher was relatively large and was deployed only to larger frigates , destroyers and aircraft carriers . Finally , the manually aimed illuminator was of limited use at night or in bad weather , which was hardly encouraging for a ship - borne weapon where fog was a common occurrence . Improved basic point defense missile system ( IBPDMS ) . In 1968 , Denmark , Italy , and Norway signed an agreement with the US Navy to use the Sea Sparrow on their ships , and collaborate on improved versions . Over the next few years a number of other countries joined the NATO SEASPARROW Project Office ( NSPO ) , and today it includes 12 member nations . Under this umbrella group , the " Improved Basic Point Defense Missile System " ( IBPDMS ) program started even while the original version was being deployed . IBPDMS emerged as the RIM - 7H , which was essentially the RIM - 7A with the mid - mounted wings modified to be able to fold . This was done in a fashion similar to carrier - based aircraft ; the wings were hinged at a point about 50 % along the span , with the outer portions rotated back toward the body of the missile . This allowed them to be stored in tighter container tubes in the new Mark 29 launcher , and flip open automatically when they were released from the tube . The seeker was modified to work with a variety of guidance radars , including those being used with existing European missile systems . Production of the RIM - 7H began in 1973 as NATO Sea Sparrow Missile System ( NSSMS ) Block I . For the US Navy ' s use the new MK - 95 illuminator system was also introduced , similar to the original Mark 115 but with automatic guidance that could be used in any weather . The MK - 95 formed the basis of the highly automated Mark 91 fire control system . Missile upgrades . In 1972 Raytheon started a Sparrow upgrade program to arm the upcoming F - 15 Eagle , producing the AIM - 7F . The F model replaced the older analog guidance system with a solid state version that could operate with the F - 15 ' s new pulse - doppler radar . The guidance system was much smaller , which allowed the warhead to be moved from its former rear - mounted position to one in front of the mid - mounted wings , and increased in weight to 86 lbs ( 39 kg ) . Moving it forward also allowed the rocket engine to be enlarged , so it was replaced by a new dual - thrust engine that quickly accelerated the missile to higher speeds , and then settled to a lower thrust for cruise . The new missiles were quickly adapted for the naval role in a fashion similar to the RIM - 7H , producing the RIM - 7F . The new missile used the lower model designation in spite of the newer technology than the H model . Another major upgrade to the AIM - 7 followed , the AIM - 7M . The M included a new monopulse radar seeker that allowed it to be shot downward from a higher - altitude aircraft at a target otherwise masked by the ground . The new model also included a completely computerized guidance system that could be updated in the field , as well as further reducing weight for yet another warhead upgrade . The computerized guidance system also included a simple autopilot that allowed the missile to continue flying toward the last known target location even with the loss of a signal , allowing the launch platform to break lock for short periods while the missile was in flight . All of these modifications also improved performance against low - altitude sea - skimming targets as well . The M model entered US operational service in 1983 . While the M model was being worked on , the US Navy also introduced an upgrade for the Mark 91 fire control system , the " Mark 23 Target Acquisition System " ( TAS ) . TAS included a medium - range 2D radar and IFF system that fed information to a new console in the ship ' s combat information center . The Mark 23 automatically detected , prioritized and displayed potential targets , greatly improving reaction times of the system as a whole . The Mark 23 is also used to select targets for most other weapons systems , including gunfire and other missile systems . TAS started entering the fleet in 1980 . The NSPO also used the M series upgrade as an opportunity to upgrade the system to allow it to be launched from a Vertical Launching System ( VLS ) . This modification uses the " Jet Vane Control " ( JVC ) package that is added to the bottom of the missile . On launch , a small engine in the JVC boosts the missile up above the launching ship , then uses vanes positioned in its own exhaust to quickly slew the missile into the proper alignment with the target , which is fed to the JVC during launch . As far as the Sea Sparrow is concerned , there is no difference between being launched directly from a trainable launcher or using JVC , in both cases the missile becomes active looking directly at the target . A final upgrade to the Sparrow was the AIM - 7P , which replaced the M ' s guidance system with an improved model that allowed mid - course upgrades to be sent from the launching platform via new rear - mounted antennas . For air - to - air use this allowed the missile to be " lofted " above the target and then be directed down towards it as it approached ; this gives the missile greater range as it spends more time in thinner high - altitude air . This meant that the new version could also be directly guided against surface targets that would otherwise not show up well on radar ( which is a function of relative speed ) , allowing the ship ' s more powerful search radars to provide guidance until the missile approached the target and the reflected signal grew stronger . This also gave the Sea Sparrow a very useful secondary anti - shipping role that allows it to attack smaller boats . On 1 October 1992 during NATO exercises in the Aegean Sea the USS " Saratoga " accidentally launched two Sea Sparrow missiles . These hit the Turkish destroyer TCG " Muavenet " in the bridge and CIC , killing five of the ship ' s officers and injuring twenty - two men . The " Muavenet " was written off as a result , and the US presented them with the Knox class frigate USS " Capodanno " as reparations . Evolved Sea Sparrow missile ( ESSM ) . Although the Navy and Air Force initially planned additional upgrades for the Sparrow , notably the AIM - 7R with a combination radar / infrared seeker , these were canceled in favor of the much more advanced AIM - 120 AMRAAM in December 1996 . With the link between the airborne and shipborne versions of the Sparrow severed , Raytheon proposed a much more extensive set of upgrades to the Sea Sparrow , the RIM - 7R Evolved Sea Sparrow Missile ( ESSM ) . The changes were so extensive that the project was renamed , becoming the RIM - 162 ESSM . The ESSM takes the existing guidance section from the RIM - 7P and fits it to an entirely new rear - section . The new missile is 10 inches in diameter instead of the previous 8 inches , which allows for a much more powerful motor . It also eliminates the mid - mounted wings entirely , replacing them with long fins similar to those on the Standard missile ( and practically every other Navy missile since the 1950s ) and moves guidance control to the rear fins . The tail - fin based steering of the ESSM uses up more energy but offers considerably higher maneuverability while the engine is still firing . A new Mark 25 quad - missile pack was developed to fit four ESSMs into a single Mark 41 VLS cell . For VLS use , ESSMs are fitted with the same JVC system as the earlier versions .