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Harpoon


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BB-61 Iowa375kHarpoon was the U.S. Navy's answer to the massive Soviet force of anti-ship missile ships.

Begun under the FY68 program as a 50nm anti-ship missile, suitable for air platforms but by 1970 extended to ship launch, to increase US anti-ship missile firepower to make up for the declining strength of the carrier force.
As procured it did not require a dedicated launcher although in many cases one was provided.
It did not materially reduce shipboard resources already provided for major naval missions such as antiair and antisubmarine warfare.
The canister launcher avoids intrusion into AAW and ASW weapon capacity at a relatively low cost in ship space and weight.

Requests for quotation were issued in January 1971, a prime contractor (McDonnell Douglas) being selected that June, without flyoff, given the cost and urgency of the program.
The first missile flew in February 1972. Technical evaluation was completed in June 1975, delayed by some extent by small system problems; however, Harpoon was operationally evaluated in 1977, production beginning that year.
It was envisaged at first as an air and surface-ship weapon, but also replaced the proposed submarine missile, STAM studies of an encapsulated version for torpedo tube launch began in 1972.
During her reactivation, Iowa received the RGM-84 Harpoon cruise missile system that gave the ship a long-range strike capability against surface targets.

Two complete Harpoon systems, consisting of four Mk.141 launchers with sixteen RGM-84 missiles were fitted to the ship, each Mk.141 launcher holding a cluster of four All-Up-Round (AURs) in ceramic armoured canister launchers.
The missiles were stored and fired from the canisters at a fixed angle. The ship evaluated contacts, Naval Tactical Data System (NTDS) tracked and used electronic support measures (ESM) data to decide whether to fire.

ESM supported defensive threat warning, long-range situation awareness and over-the-horizon targeting (OTH-T) for cruise missiles and tactical air strikes.
Microwave ESM looked at the external characteristics of foreign radar signals such as radio frequency and pulse-repetition frequency intercepts and were an extremely important source for identifying hostile activity and were likely to be the first and often only means to classify an enemy unit such as a submarine beyond sonar range.
Microwave ESM could detect foreign surface radar signals at 45-60 miles and some air search radar signals at 80 nautical miles.

Planning a fight through displays of combat information is essential to victory.
NTDS was vital for keeping accurate tracks of contacts to avoid "blue-on-blue" disasters.
It enabled the ship to manage combat more effectively.
It had automatic input of navigation (LORAN) fixes, the pit log (for speed), gyrocompass and anemometer.
The ship's CIC used Command and Decision System (CDS) computers' contact data to prioritized contacts by threat and designated weapons systems to specific targets.
NTDS-equipped ships in the operation passed these contacts data to each other over the Link-11 radio data link network.

Each NTDS ship transmitted contact data as computer display symbols showing the target type (surface, air, submarine), target identity if known and identity of the ship or aircraft tracking it.
One ship, the network controller, polled the other NTDS ships in turn.
A polled ship's NTDS computer automatically broadcasted updated contact data on all tracks for which that ship was responsible.
All NTDS ships in the network recorded the track data broadcasts.
ASW and radar sentry AWACS) aircraft participated in the NTDS data network.
The SH-2F Seasprite helicopter proved highly useful for antiship surveillance and targeting missions but could report sightings only by UHF voice radio.
The newer SH-6oB Seahawk helicopters transmitted contact data as NTDS computer symbols over a point-to-point pencil beam data link to the ship.
The ship broadcasted this information to the rest of the force in her Link-11 broadcasts.
NTDS ships relayed track data over radio-teletype circuits to non-NTDS ships to help them find targets. (Link-14)
The ship programmed the missile from the Harpoon control console in the CIC to fly out on a given bearing toward a target and optionally gave the missile a minimum or expected range to the target.

Early Harpoon missiles had a range of about 60 miles and made an almost straight-in approach to the target with an optional pop-up-and-dive maneuver to dodge target defenses.
Harpoon could be fired at an ESM contact when the ship had her radar off for stealth or when the target was over the radar horizon.
The Harpoon missile seeker would attack the first target it found on the assigned bearing beyond the seeker turn-on range.
Harpoon was an offensive weapon in coastal operations.
Strike warfare missions were national strategic tasks.
An important side effect of this strategic capability was the institutional rise of the surface warfare officer community within the Navy.
The surface launched RGM-84 used the same airframe body as the air launched version plus a booster.

The Harpoon has five component sections in all:
Guidance Section - used active guidance.
Warhead Section - was composed of 510 pounds including 215 pounds Destex HE.
Propulsion Section - was composed of a liquid fuelled turbojet engine for cruise and attack flights.
Bobtail Section - housed actuator fins which controlled the flight after booster separation.
Booster Section - solid propellant propelled missile away from ship.

When fired, the booster propelled the missile away from the ship approximately 5 miles and was discarded. The dropoff zone for the discarded booster section was about 1 miles.
The turbojet engine propelled the missile from the booster separation to the target.
The stabilizing and actuator fins were stored folded in the canister and sprang out into position after launching.
During the flight the actuator fins received inputs from the guidance system directing the missile to target.
The firing weight of the RGM-84 Harpoon was 1,530 pounds, which includes a booster weight of about 362 pounds. It had a cruising speed of 0.87 Mach.
The maximum range was 64.5 nm in Range and Bearing Launch (RBL) mode and 85.5 nm in Bearing Only Launch (BOL) mode.
Photographs courtesy of Pieter Bakels.
TOMAHAWK549kAt left, the Wisconsin (BB-64) launching a Tomahawk missle.

In 1985, BB-61 class battleships were, like the Spruance class destroyers and Ticonderoga class cruisers, the Navy's predominant surface ship Tomahawk platforms, weapons for long-range offensive action against high-value ships and targets ashore.

The Tomahawk system had three components: the missile, the weapons control system and the launcher.
There were several models of each component.
There was no special shipboard sensor for Tomahawk.
Instead, the shipboard Tomahawk weapons control system correlated real-time intelligence data and narrowed the target ship's location into an area that the Tomahawk anti-ship missile could search.

The armoured box launcher (ABL) a deck-mounted casing for four elevating tubes for Tomahawk, replaced earlier open racks such as used for Harpoon after fire nearly destroyed the cruiser Belknap (CG-26) in 1975.
A prototype deck-mounted armoured box launcher went aboard Merrill (DD-976) as test ship for Tomahawk in 1979.
Diversion of ABL's to the recommisioned battleships left most of the destroyers available to mount higher-capacity vertical launch systems.

In 1970 Chief of naval Operations Admiral Elmo Zumwald started research for a cruise missile with longer range than Harpoon for shipboard launch to disperse naval strike capability beyond aircraft carriers.
He revived the Regulis nuclear land-attack cruise missile concept.
He called the cancellation of Regulis in 1958 "the single worst decision about weapons that the Navy made during my years of service".
In 1971 the Navy suggested that a new land-attack cruise missile could exploit advances in small jet engines and microprocessors for precision guidance.
In June 1972 the Office of the Secretary of Defense (OSD) authorized designing a sea-launched cruise missile for land attack.
It could carry either conventional or nuclear warheads.
The nuclear version generated little enthusiasm in the navy.
Nuclear weapons required awkward security and restricted ship's operations.
Officers doubted that the nuclear cruise missiles would ever be used and expected them to be sacrificed in arms talks anyway.

(TLAM-N)

The nuclear-warhead sea-launched cruise missile was the Tomahawk land-attack missile-nuclear.
Unlike other naval nuclear weapons, Tomahawk incorporated a permissive action link (PAL) to prevent launch without political authorization.
It was not assigned to SIOP (single integrated operational plan) targets; instead, it was reserved to retaliate against Soviet bases in the event that Soviet forces attacked U.S.naval forces with nuclear weapons.
The ship programmed the over-water flight path for the missile to a designated landfall, where the missile would orient itself by matching actual terrain contours (TERCOM) with a stored digital map.
From the landfall the missile flew a course at very low altitude around enemy defenses and terrain obstacles.
It updated its position en route by TERCOM - the initial contour-matching fields were larger so that the missile could better orient itself.
When the on-board guidance system computed that the missile had arrived at the target, the warhead detonated.
Tomahawk Mission Planning Centers ashore programmed nuclear-warhead Tomahawk missions.
Before launch, the ship could reassign the aim point under a flexible target option (FLEX) to attack an updated target position, such as a target that was discovered to have relocated or to have survived an earlier attack.

(TLAM-C)

The best-known Tomahawk version is the conventional-warhead land-attack missile.
Early TERCOM-guided block II-A TLAM-C missiles were used against Iraq in 1991 and 1993.
Each carried a 1,000-pound high-explosive semi-armor-piercing conventional warhead.
It became operational in March 1986.
Its warhead was taken from the old Bullpup air-to-ground missile.
The weight of this warhead reduced the fuel load for the conventional-warhead Tomahawk, so that its range was about half that of the nuclear-warhead version (700 vs. 1,300 nautical miles).
Strike route planning was the same as for the nuclear version, except that the conventional version used digital scene-matching area correlation (DSMAC) for terminal guidance.
On approach to the target, the missile photographed the area and matched the scene with a stored digital image for final course adjustment toward the specific target.
Strike planners choose landmarks that were not themselves targets, since these would be less likely to be demolished during early strikes.
Tomahawk flew straight into the target (point detonating fuze), exploded at a programmed point over it, or popped up and dove on it to evade terminal defenses.
In 1993 Iraqi air defense forces observed that Tomahawk rolled over before diving on targets.
Tomahawk TLAM-D carried 166 bomblets to scatter over airfields, buildings or other soft targets during its flight.
It could attack multiple targets during one mission and detonated at the last target.

Since the success of the Tomahawk strikes on Iraq, national military commanders have kept Tomahawk-equipped ships foreward-deployed for contingencies.
The presence of Tomahawk-equipped ships enables aircraft carriers to depart an area without leaving potential aggressors uncovered.

Block III and IV Tomahawk had a Global positioning System (GPS) receiver and a time-of-arrival control to synchronize strikes with each other and with air strikes. They all had a land-attack capability and their missions could be planned quickly in theatre aboard aircraft carriers and command ships. Since they could be aimed quickly, they could strike time-urgent targets.

TASM

In November 1972 design began for the Tomahawk anti-ship missile.
It carried the same 1,000-pound high-explosive semi-armor-piercing warhead as the conventional land-attack Tomahawk.
It could penetrate a submarine's pressure hull or a large warship's hull plating.
Originally it was planned for a range of 140 nautical miles, which was adequate for underwater launch, since submarines find targets by sonar and are invulnerable to hostile cruise missiles during approach to target.
Surface warships needed a longer-range weapon to attack Soviet warships, which could fire their anti-ship missiles from 250 nautical miles.
Surface search radars cannot be used for long-range anti-ship targeting (over-the-horizon targeting) because of their inherent horizon-limited range, about 250 miles.
The challenge was not to build a 250-nautical-mile-range missile but to plan a targeting system for it.
Critics doubted that a task group would fire weapons over the horizon at targets that task group sensors could not locate, since the probability of missing the targets would seem to be high, making an over-the-horizon attack an act of unilateral disarmament.
The same critics accepted that the large Soviet anti-ship cruise missiles were threats from 250 nautical miles' range. Rear Admiral Walter Locke, the cruise missile project officer, asked the John Hopkins University Applied Physics Laboratory and the Harpoon seeker contractor, McDonnell Douglas, to investigate whether a Tomahawk could search for a target inside an area of uncertainty.
Replacing the Tomahawk anti-ship missile turbojet with the costlier land-attack Tomahawk turbofan engine could increase TASM range to over 300 nautical miles to allow the missile to fly search patterns. In 1975 the applied Physics Laboratory developed search patterns so that the Tomahawk anti-ship missile was capable of autonomous scouting and strike missions.

The next problem was how to get surveillance information to the launching ship for over-the-horizon targeting.
Opponents within OSD refused to authorize funds for research into over-the-horizon targeting, but the Naval Electronics Systems Command funded an experiment called Outlaw Shark.
For this experiment, a computer database was set up at the Submarine Operational Command Center in Naples, Italy and another computer was installed aboard a submarine.
The Naples Outlaw Shark system copied operational intelligence data being collected for later transmission to a Sixth Fleet aircraft carrier, condensed the data and relayed it without delay to the submarine over a computer-to-computer encrypted radio data link.
Sometimes the submarine received intelligence data only six minutes after the occurrence of the event being described. The submarine's computer correlated the intelligence data with its own contact data and prepared search patterns adequate for an immediate Tomahawk anti-ship attack.
In December 1976 the submarine used this system to generate search patterns for actual ships not held by its own sensors.
Analyses showed that the search patterns would result in Tomahawk hits on those ships.
The first test of a Tomahawk anti-ship missile was a launch at a target hulk 224 nautical miles away.
The Tomahawk flew 175 nautical miles to the target and began searching.
It then flew 173 nautical miles in search patterns and found the target.
This was the first long-range anti-ship cruise missile flight not to use a data link between the missile and a controller.
Tomahawk anti-ship missiles became operational in 1982.
In contrast to the procedure for early Tomahawk land-attack missiles, for the anti-ship mission the ship controlled all targeting and planned the entire strike mission.
Tomahawk weapons control systems were SWG-2 for armoured box launchers and SWG-3 for vertical launch systems.
Each provided track and launch control functions.
The ship used the launch-control group to track the status of the Tomahawk missiles and to fire them.
The Tomahawk anti-ship missile used the Harpoon active radar guidance section with a passive seeker for identification and direction finding.
The missile classified and prioritized targets to attack the most valuable target.

As with Harpoon, Tomahawk anti-ship missiles could fly dogleg courses so that they could attack from unexpected directions and in such a way that missiles from one or more ships arrived on target simultaneously.
The ship kept a database of surface ships in her assigned patrol area on the track-control group computer.
In the initial Tomahawk weapons control system, each ship kept her own track database.
With newer versions, one ship was the force over-the-horizon track coordinator (FOTC) for a task group.
Track data came from the ship's own sensors, NTDS data links and intelligence sources.
General surveillance information came from surveillance satellites and aircraft, from SOSUS and from shore-based (Outboard) radio direction finding.
Each ship's Tomahawk weapon control system was linked to tactical information exchange satellite radio broadcasts (TADIXS and OTCIXS) over the ship's radios.

A newer system, JOTS, recorded data from OTCIXS and TADIXS broadcasts and maintained a local picture as seen by off-ship sensors.
JOTS used commercial computers and was entirely passive.
The ship could get into Tomahawk range without revealing her presence to the target.
A Tomahawk anti-ship missile could be fired as a "wake-up call" or "screaming meemie" towards a radio-silent enemy battle group.
It the enemy ships would switch on their radars to target the actively searching Tomahawk, a follow-on strike could exploit the newly available locating information.
Spruance class destroyers and Ticonderoga class cruisers can use their long-range passive towed-array sonar to locate targets over the horizon.
Submarines have long used the same tactic.
Photographs & text courtesy of Pieter Bakels.

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