AIM-7 Sparrow
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The AIM-7 Sparrow is a medium-range semi-active radar homing air-to-air missile operated by the United States Air Force, US Navy, and USMC as well as various allied air forces. Sparrow and its derivatives were the West's principal beyond visual range (BVR) air-to-air missile from the late 1950s until the 1990s. It remains in service, although it is being phased out in aviation applications in favor of the more advanced AIM-120 AMRAAM. When a sparrow missile is being launched, NATO pilots use the brevity code Fox One in radio communication, signifying the launch of a Semi-Active Radar Homing missile (SARH). The armed forces of Japan employ the sparrow missile, though it is being phased out and replaced by the Mitsubishi AAM-4.
The Sparrow was used as the basis for a surface-to-air missile, the RIM-7 Sea Sparrow, which is used by the US Navy for air defense of its ships.
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[edit] Development
[edit] Sparrow I
The Sparrow emerged from a late-1940s US Navy program to develop a guided rocket weapon for air-to-air use. In 1947 the Navy contracted Sperry to build a beam riding version of a standard 5-inch (127 mm) HVAR, the standard unguided aerial rocket, under Project Hotshot. The weapon was initially dubbed KAS-1, then AAM-2, and, from 1948 on, AAM-N-2. The airframe was developed by Douglas Aircraft Company. The diameter of the HVAR proved to be inadequate for the electronics, leading Douglas to expand the missile's airframe to 8 in (203 mm) diameter. The prototype weapon made its first aerial interception in 1952.
After a protracted development cycle the initial AAM-N-2 Sparrow entered service in 1956, carried by the F3H-2M Demon and F7U Cutlass fighter aircraft. Compared to the modern versions, the Sparrow I was more streamlined and featured a bullet-shaped airframe with a long pointed nose.
Sparrow I was a limited and rather primitive weapon. The limitations of beam-riding guidance (which was slaved to an optical sight, requiring visual identification of the target) restricted the missile to visual-range attacks and made it essentially useless against a maneuvering target. Only about 2,000 rounds were produced to this standard.
[edit] Sparrow II
As early as 1950 Douglas examined equipping the Sparrow with an active radar seeker, initially known as XAAM-N-2a Sparrow II, the original retroactively becoming Sparrow I. In 1952 it was given the new code AAM-N-3.
By 1955 Douglas proposed going ahead with development, intending it to be the primary weapon for the F5D Skylancer interceptor, and ten years later an advanced active radar similar to the modern AMRAAM the Avro Arrow to be built under license by Canadair this is discussed later. However the small size of the missile forebody and the K-band AN/APQ-64 radar limited performance, and it was never able to work in testing.
The program was cancelled in 1958, and although there was some discussion of Canadair taking over the work, when the Arrow was cancelled all work ended.
[edit] Sparrow 2D
In the 1960s as part with the Avro Arrow project an advanced version of the Sparrow II missile equipped with its own radar was considered. In that day it was thought that it was not modern and had little potential. Another note about it is that because of the potential high power of the CF-105's and the missile's radar it may have had longer range. Sadly it was not put into production and it is unknown if it was produced and if it was how many. If developed it may have had similar capability's to the modern AMRAAM
[edit] Sparrow X
A subvariant of the Sparrow 2D that carries the same nuclear warhead as the MD-2 Genie but was cancelled due to that when it was proposed was slightly before the CF-105 was cancelled.
[edit] Sparrow III
Concurrently, in 1951, Raytheon began work on the semi-active radar homing version of Sparrow family of missiles, the AAM-N-6 Sparrow III. The first of these weapons entered US Navy service in 1958.
The AAM-N-6a was similar to the -6, but used a new Thiokol liquid-fuel rocket engine for improved performance. It also included changes to the guidance electronics to make it effective at higher closing speeds. The -6a was also selected to arm the Air Force's F-110A Spectre (F-4 Phantom) fighters in 1962, known to them as the AIM-101. It entered production in 1959, eventually being built to about 7500 examples.
Another upgrade switched back to a Rocketdyne solid-fuel motor for the AAM-N-6b, which started production in 1963. The new motor significantly increased range, which was up to 35 km for head-on attacks.
During this year the Navy and Air Force agreed on a standardized naming for their missiles, the Sparrows becoming the AIM-7 series. The original Sparrow I and aborted Sparrow II became the AIM-7A and AIM-7B, even though both were long gone from the inventory. The -6, -6a and -6B became the AIM-7C, AIM-7D and AIM-7E respectively.
25,000 AIM-7E's were produced, and saw extensive use during the Vietnam War, where its performance was generally considered disappointing. The mixed results were a combination of reliability problems (exacerbated by the tropical climate), limited pilot training in fighter-to-fighter combat, and restrictive rules of engagement that generally prohibited BVR (beyond visual range) engagements. The Pk (kill probability) of the AIM-7E was less than 10%; US fighter pilots shot down a grand total of 55 aircraft using the Sparrow.
In 1969 an improved version, the E-2, was introduced with clipped wings and various changes to the fusing. Considered a "dogfight Sparrow", the AIM-7E-2 was intended to be used at shorter ranges where the missile was still travelling at high speeds, and in the head-on aspect, making it much more useful in the visual limitations imposed on the engagements. Even so, its kill rate was only 13% in actual combat in 1972, leading to a practice of ripple-firing all four at once in hopes of increasing kill probability. (Michel 232) Its worst tendency was that of detonating prematurely, approximately a thousand feet in front of the launching aircraft, but it also had many motor failures, erratic flights, and fusing problems. (Michel 228) An E-3 version included additional changes to the fusing, and an E-4 featured a modified seeker for use with the F-14 Tomcat.
Improved versions of the AIM-7 were developed in the 1970s in an attempt to address the weapon's limitations. The AIM-7F, which entered service in 1976, had a dual-stage rocket motor for longer range, solid-state electronics for greatly improved reliability, and a larger warhead. Even this version had room for improvement, leading British Aerospace and the Italian firm Selenia to develop advanced versions of Sparrow with better performance and improved electronics as the Skyflash and Selenia Aspide, respectively.
The most common version of the Sparrow today, the AIM-7M, entered service in 1982 and featured a new inverse monopulse seeker (matching the capabilities of Skyflash), active radar fuse, digital controls, improved ECM resistance, and better low-altitude performance. It was used to good advantage in the 1991 Gulf War, where it scored many USAF air-to-air kills; however it's kill probability, overall, is still less than 40%.
The AIM-7P is similar in most ways to the M versions, and was primarily an upgrade program for existing M-series missiles. The main changes were to the software, improving low-level performance. A follow-on Block II upgrade added a new rear receiver allowing the missile to receive mid-course correction from the launching aircraft. Plans initially called for all M versions to be upgraded, but currently P's are being issued as required to replace M's lost or removed from the inventory.
The final version of the missile was to have been the AIM-7R, which added an infrared seeker to an otherwise unchanged AIM-7P Block II. A general wind-down of the budget led to it being cancelled in 1997.
Sparrow is now being phased out with the availability of the active-radar AIM-120 AMRAAM, but is likely to remain in service for a number of years.
[edit] Sea Sparrow
Sea Sparrow was developed as a lightweight "point defense" weapon that could be retrofitted to existing ships, often in place of existing gun-based anti-aircraft weapons. The primary development issues were changes to the seekers to allow them to operate with shipboard radars, and the new Mark 25 trainable launcher system, based on the ASROC launcher, to align the seeker head with the target before launch. Combined with a Mark 115 manned fire control director it was know as the Basic Point Defense Surface Missile System (BPDSMS) or just BPDMS.
As a surface-to-air system, the Sparrow has a number of disadvantages. For one, the missile steers with its mid-mounted wings, which initially made them unfoldable. For this reason the missile takes up much more room than it would have to if the wings could be folded. Additionally the engine is optimized for flight time, as opposed to fast acceleration, which makes sense when launched from an aircraft moving at high speed at a target at long range. In the surface-to-air role, however, one would rather have very high acceleration in order to allow it to intercept sea-skimming targets as soon as possible. Furthermore, the Sea Sparrow possesses a shorter range. Some estimates indicate that it may be effective only to 10 nm, about one quarter of the range of an air-to-air AIM-7 Sparrow.
As part of the NATO Sea Sparrow Missile system (NSSM) the launcher size was reduced by folding the mid-mounted wings, resulting in the Mark 29 NSSM launcher. The older manned directors were replaced by unmanned AN/SPS-65 radars, part of the Mark 91 Fire control system. NSSM replaced BPDMS on Aircraft Carriers and was used on other ships such as Spruance class destroyers.
In order to address these issues, a consortium of many Sea Sparrow users joined together to create the Evolved Sea Sparrow Missile (ESSM). The new design uses the tail-fins for steering, allowing the wings to fold. This allows the missile body to increase in size while still fitting into the same launchers, growing to 10 inches in diameter and offering far higher performance. Additionally the wing-based maneuvering of the older design is designed to save energy during the long gliding period of the missile, while the tail-fin based steering of the ESSM uses up more energy but offers considerably higher maneuverability while the engine is still firing.
Another recent development is the Jet Vane Control (JVC) unit, which can be added to the base of the missile to allow it to be vertically launched. After being "popped" from the launch cell the JVC rotates the missile to bring the seeker onto the target and level the flightpath in that direction. It is then jettisoned. Vertical launching allows a single cell to cover the entire area around the ship, because the seeker can be pointed in any direction by the JVC after launch. Additionally the time needed to point the launcher is eliminated. Another major advantage of the ESSM is that it uses a Mk 25 quad-pack canister allowing four missiles to be loaded into a Vertical Launch System (VLS), instead of just one, quadrupling capacity.[1]
Though initially employed by the United States Navy and other NATO countries, there are now numerous navies that use variants of the Sea Sparrow.
[edit] Foreign version
[edit] Italy
The Italian company Finmeccanica, Alenia Difesa licensed the AIM-7E Sparrow technology from US, and produced its own improved version called Aspide.
[edit] People's Republic of China
In the mid 1980s, China imported a small batch of the Aspide Mk.1 from Italy, then signed an agreement with Alenia to produce the missile locally under license. In 1989, China produced its first batch of Aspide Mk.1 missiles using imported parts from Italy. However, due to the EU arms embargo imposed after the June 1989 Tienanmen Square incident, China was unable to purchase additional Aspide kits. [2]
In the early 1990s, the Shanghai 2nd Mechanical-Electronics Bureau was tasked to produce a better medium-range AAM. They succeeded by merging the domestic HQ-61C missile with the Aspide's mono-pulse semi-active radar-homing seeker. The new missile was given the designation PL-11. Some western observers mistakenly confuse the PL-10, which is based on the older HQ-61 technology. [3]
Known versions of the PL-11 include:
- PL-11 - MRAAM based on HQ-61C & Aspide (AIM-7M) technology. First tested from a J-8B fighter in 1992, limited service in mid-1990s for testing and evaluation. Promoted for export as the FD-60. [4]
- PL-11A - Improved PL-11 with better range, warhead, and seeker. The new seeker only requires fire-control radar guidance during the terminal stage.
- PL-11B - Also known as PL-11 AMR, improved PL-11 with AMR-1 active radar-homing seeker developed by the 607 Institute. Did not enter service as PLAAF opted for other missiles (PL-12/SD-10).
- LY-60 - "Chinese Sea Sparrow", PL-11 adopted for navy ships for air-defense. Sold to Pakistan but did not enter service with the PLAN. VLS-launch version is rumored to be under development. [5]
[edit] UK
British Aerospace (BAe) licensed the AIM-7E2 technology in the 1970s, producing the Skyflash missile. Skyflash used a Marconi XJ521 monopulse Semi-Active seeker together with improvements to the electronics. It was powered by the Aerojet Mk52 mod 2 rocket engine (later by the Rocketdyne Mk38 mod 4). Skyflash entered service with the Royal Air Force (RAF) on their Phantom F3 in 1976, and later on the RAF Tornado F3 ADV. The Skyflash was also exported to Sweden for use on their Viggen fighters.
An upgraded version with active radar seeker, called Active Sky Flash was proposed by BAe and Thomson-CSF, but did not receive funding because the RAF opted for other missiles. [6]
[edit] Description
The Sparrow has four major sections: guidance section, warhead, control, and rocket motor (currently the Hercules MK-58 solid-propellant rocket motor). It has a cylindrical body with four wings at mid-body and four tail fins. Although the external dimensions of the Sparrow remained relatively unchanged from model to model, the internal components of newer missiles represent major improvements, with vastly increased capabilities. The warhead is of the continuous-rod type.
As with other semi-active radar guided missiles, the missile does not generate radar signals, but instead homes in on reflected continuous-wave signals from the launch platform's radar. The receiver also senses the guidance radar to enable comparisons that enhance the missile's resistance to passive jamming.
[edit] Principle of guidance (semi-active version)
The launching aircraft will illuminate the target with its radar. In radars of the 1950's these were single target tracking devices using a nutating horn as part of its antenna. This caused the beam to be swept in a small cone. Signal processing would be applied to determine the direction of maximum illumination and so develop a signal to steer the antenna toward the target. The missile detects the reflected signal from the target with a high gain antenna in a similar fashion and steers the entire missile toward closure with the target. The missile guidance also samples a portion of the illuminating signal via rearward pointing waveguides. The comparison of these two signals enabled logic circuits to determine the true target reflection signal, even if the target were to eject radar-reflecting chaff.
[edit] Specifications (AIM-7M)
- Length: 12 ft (3600 mm)
- Diameter: 8 in (203 mm)
- Wingspan: 2 ft 8 in (813 mm)
- Launch weight: 510 lb (231 kg)
- Speed: Mach 4
- Range: 44 mi (70 km)
- Guidance: semi-active radar homing
- Warhead: 88 lb (40 kg) blast fragmentation
[edit] Specifications (RIM-7M/P Sea Sparrow)
- Length: 12 ft (3640 mm)
- Diameter: 8 in (203 mm)
- Wingspan: 3 ft 4 in (1030 mm)
- Launch weight: 510 lb (231 kg)
- Speed: greater than 2,660 mph (4,256 km/h) (Mach 4)
- Range: 10 nautical miles (19 km)
- Guidance: semi-active radar homing
- Warhead: 88 lb (40 kg) blast fragmentation
[edit] See also
[edit] References
- Michel, Marshall L. (2004). Clashes: Air Combat Over North Vietnam 1965-1972, Naval Institute Press, ISBN 1557505853
[edit] External links
- [7]
- GlobalSecurity.org
- Designation-Systems.Net
- YouTube: F-15As fires live fire Sparrows at QF-4s.
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