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BGM-109 (exact model unknown) Photo: U.S. Navy

The Tomahawk is the U.S. Navy's multipurpose strategic and tactical long range precision-guided cruise missile. Launched from surface ships and submarines, it was used in action in all recent major U.S. military engagements, and will remain one of the most important missiles in the U.S. inventory for quite some time.

The BGM-109 missile has been developed in several distinct variations, which are described in separate sections of this article. These variations include:

• SLCM (Sea-Launched Cruise Missile): BGM-109A/.../F, RGM/UGM-109A/.../E/H
• GLCM (Ground-Launched Cruise Missile): BGM-109G
• MRASM (Medium-Range Air-to-Surface Missile): AGM-109C/H/I/J/K/L

SLCM (Sea-Launched Cruise Missile): BGM-109A/.../F, RGM/UGM-109A/.../E/H Tomahawk

AGM-109 Photo: General Dynamics

In 1971 the U.S. Navy began to study the possibility of a submarine-launched strategic cruise missile, either a larger design for launch from UGM-27 Polaris missile tubes or a smaller one for launch from torpedo tubes. In June 1972 the torpedo-tube missile was chosen, and design contracts were let to the industry in November that year for what was then called the SLCM (Submarine-Launched Cruise Missile).

In January 1974, the two most promising designs were selected for a fly-off competition, and in 1975, the designations ZBGM-109A and ZBGM-110A were assigned to the designs of General Dynamics and LTV, respectively.

After a few test flights by the YBGM-109A and YBGM- 110A prototypes in February 1976, which included the critical transition from water to air in a subsurface launch, the BGM-109 was declared winner of the competition. At that time, it had already been decided that the SLCM should also be launched from surface ships, and therefore the acronym was changed to Sea-Launched Cruise Missile.

Flight testing of the YBGM-109A, including the TERCOM (Terrain Contour Matching) guidance system, continued during the following years.

In January 1977, the Carter administration initiated a program called JCMP (Joint Cruise Missile Project), which directed the USAF and the U.S. Navy to develop their cruise missiles using a common technology base. At that time, the Air Force was developing its AGM-86 ALCM (Air- Launched Cruise Missile). One consequence of JCMP was that only one cruise missile propulsion system (the Williams F107 turbofan of the AGM-86) and TERCOM guidance system (the McDonnell Douglas AN/DPW- 3 of the BGM-109) would be further developed. Another one was a fly-off competition for the ALCM role between the AGM-86B and the AGM-109, an air-launched derivative of the YBGM-109A. After flights between July 1979 and February 1980, the AGM- 6B was declared winner of the competition and the AGM-109 ALCM development was stopped.

From top: BGM-109C, BGM-109A, BGM-109B Image: via FAS

Development of the BGM-109 SLCM had of course continued during the ALCM evaluation. In March 1980, the first surface-ship launch of a production BGM- 09A Tomahawk occurred from the USS Merrill (DD-976). This was followed in June that year by the launch of a production missile from the submarine USS Guitarro (SSN-665). Operational evaluation continued in the following years, and the Tomahawk SLCM was finally declared ready for service in March 1983. The initial versions, both also known as Tomahawk Block I, were the strategic BGM-109A TLAM-N (Tomahawk Land-Attack Missile - Nuclear) with a thermonuclear warhead and the BGM-109B TASM (Tomahawk Anti-Ship Missile) with a conventional warhead against surface-ships. Initially, the missile variants for the different launch environment options were designated by suffix letters, BGM-109A-1 and -109B-1 being surface-launched and BGM-109A-2 and -109B-2 submarinelaunched. In 1986, this was changed to the use of R-for-Surface and U-for-Underwater launch
environment letters:

The RGM-109A is launched from MK 143 box-launchers or (in newer installations) MK 41 VLS (Vertical Launch System) cells with the help of a solid-propellant rocket booster. After the missile has cleared the launcher, the four tailfins are extended, followed by the deployment of the two straight wings. When this is completed, the ventral air intake for the Williams F107-WR-400 turbofan cruise engine extends, the spent booster is jettisoned, and the turbofan started.

The Tomahawk is guided to its target by a system called TAINS (TERCOM Assisted Inertial Navigation System) using a McDonnell Douglas AN/DPW-23 TERCOM (Terrain Contour Matching) system. In TERCOM, altitude information obtained by a radar altimeter is continuously matched to a preprogrammed radar map of the area below the missile, so that the Tomahawk can effectively follow a detailed predetermined flight path. This path can include several waypoints to change altitude and direction, e.g. for flying around hills to be concealed from detection by point-defenses around the target for as long as possible.

The accuracy of the TAINS guidance is around 80 m (260 ft) CEP, which is good enough for the RGM-109A's variable-yield (5 kT - 200 kT) W-80-0 thermonuclear warhead.

In an UGM-109 underwater launch, the missile remains enclosed in its transport canister until it has cleared the torpedo tube. The canister is then ejected, and the booster ignites to propel the missile to the surface. After it is fully airborne, some protective covers are jettisoned, and the flight procedes as in a surface launch. Newer SSNs also have vertical launch tubes for the UGM-109 missile.

UGM-109 (exact model unknown) Photo: U.S. Navy

The BGM-109B (later RGM/UGM-109B) TASM was developed concurrently with the BGM-109A TLAM-N, and was actually the first variant to be deployed in operational status. Instead of TERCOM (which is obviously useless over water), the TASM uses a radar guidance system very similar to that of the AGM/RGM/UGM-84 Harpoon anti-ship missile, including the latter's strapdown three-axis attitude/heading reference system and AN/DSQ-28 J-band active radar seeker.

The missile is launched in the general direction of the target and at some distance from the expected target position, it enters a serpentine flight pattern to search for it using both passive radar to scan enemy emissions and active radar to lock on a detected target. Once the seeker has locked on a target, the RGM/UGM- 109B proceeds towards it at very low altitude (sea-skimming). Manoeuvers after lock-on can include short pop-ups to get a better fix on the target position and/or course changes to strike the target from an unexpected direction. The missile is armed with a 450 kg (1000 lb) WDU-25/B high-explosive blast-fragmentation warhead, and can hit the target either from the side or from the top after a terminal pop-up manoeuver.

The BGM-109C (initially BGM-109C-1 and -2, but changed in 1986 to RGM-109C and UGM-109C) TLAM-C (Tomahawk Land-Attack Missile - Conventional) is a conventionally-armed (same WDU-25/B warhead as -109B TASM) missile for long-range strikes against high-value targets. It entered U.S. Navy operational service in 1986. The TLAM-C (also known as Tomahawk Block II) uses the same INS/TERCOM suite as the -109A TLAM-N for mid-course guidance.

For higher accuracy in the terminal phase of the flight, it uses an AN/DXQ-1 DSMAC (Digital Scene Matching Area Correlation) system, because the conventional warhead requires higher precision to be effective. DSMAC is an electro-optical sensor system which takes images from the ground below the missile and compares these to reference images stored in the on-board computer. Any deviations lead to a course correction of the Tomahawk missile, and the system's accuracy is about 10 m (30 ft) CEP. The original TLAM-C Block II had only one mode of final approach, it always flew straight into the side of the target. Early in the development program, however, the BGM-109C software was upgraded to Block IIA. This allows pre-launch selection of two additional attack modes. The first of these is a pop-up/terminal-dive manoeuver, and the second is known as PWD (Programmed Warhead Detonation). Using PWD, the WDU-25/B warhead is detonated while the missile is flying directly over the target, making it especially effective against targets behind a protective shielding like a revetment.

RGM-109C Photo: U.S. Navy

The Tomahawk Block IIB is designated BGM-109D (intially BGM-109D-1 and -2, but changed to RGM-109D and UGM-109D before it entered service) TLAM-D (Tomahawk Land-Attack Missile - Dispenser). It is similar to the TLAM-C (also using the TAINS/DSMAC guidance package), but in place of the unitary WDU-25/B warhead, it uses a warhead section with 166 BLU-97/B CEB (Combined Effects Bomblet) submunitions. The BLU-97/Bs can be dispensed in partial packages to attack several targets in one mission. The RGM/UGM-109D entered service with the U.S. Navy in 1988.

The BGM-109E was a proposed improvement of the BGM-109B anti-ship missile, and the BGM-109F was to be a TLAM variant with an anti-airfield warhead (possibly using BLU-106/B submunitions). The BGM-109E/F versions were both cancelled in the mid-1980s, but the -109E suffix was later reused for the Block IV program and then again for the Tactical Tomahawk missile (q.v. below)

Operation Desert Storm in 1991 saw the first combat use of the Tomahawk missile, with 261 TLAMCs and 27 TLAM-Ds fired against Iraqi targets. The overall hit rate was reported as 85%. During the 1990s, Tomahawks were used whenever the United States needed to strike tactical and strategic targets at long range. Major operations included Operation Desert Fox (Iraq, December 1998) and Operation Allied Force (Serbia, April/May 1999), when several hundred Tomahawks were launched.

In the late 1980s, McDonnell Douglas (now Boeing) received a contract to develop the Block III upgrade for the TLAM-C/D. Block III had a significantly upgraded guidance unit, incorporating a GPS receiver to assist the TAINS system, and the improved DSMAC 2A which uses a wider imagery range and more scenes for the final fix. The Block III missiles were also upgraded with an improved F107-WR-402 engine with higher thrust and lower fuel consumption. The RGM/UGM-109C Block III also uses an improved WDU-36/B warhead which is smaller (thereby increasing fuel space) and lighter than the WDU-25/B but offers the same effect. The new warhead significantly increases the range of the Block III TLAM-C missile. The first launch of a Block III Tomahawk occurred in January 1991, and IOC was achieved in May 1993. All Block IIA/IIB missiles will be upgraded to Block III standard when they are due for scheduled maintenance (every 3 to 4 years).

BGM-109D Photo: Raytheon

In 1994, Hughes (now Raytheon) started to develop the Block IV upgrade, also known as TBIP (Tomahawk Baseline Improvement Program), which had the goal to develop a single all-purpose missile, the RGM/UGM-109E TMMM (Tomahawk Multi-Mode Missile) for use against ships and land targets. For this purpose an imaging seeker (either a FLIR or a mm-wave radar) was to be installed, so that the computer could be fed with images of either ships or land targets. Other options under consideration for Block IV were autonomous target acquisition by the seeker and a datalink for retargeting in flight. The planned warhead was the WDU-36/B of the TLAM-C Block III, but the latter's F107 engine was to be replaced by the much cheaper Teledyne CAE J402-CA-401 turbojet. The RGM/UGM-109H THTP (Tomahawk Hard Target Penetrator) was a proposed Block IV missile with a penetrating warhead. However, the TBIP proved to be too expensive, and was cancelled in May 1996. The program was eventually replaced by the Tactical Tomahawk (q.v. below). The designations of the Block IV missiles (RGM/UGM-109E and RGM/UGM-109H) were also "transferred" to the Tactical Tomahawk program.

The latest development of the Tomahawk SLCM is the RGM-109E/UGM-109E Tactical Tomahawk (a.k.a. "TacTom") variant (the -109E designations were carried over from the Block IV). It was first proposed in 1998 as a low-cost replacement for the cancelled Block IV TBIP program. Tactical Tomahawk was originally known as Block V, but has now been renumbered as Block IV. The major TacTom program goal was a missile which would cost significantly less (about one half) per production round than an up-to-date TLAM-C/D. Therefore a cheaper engine is used and the structure is lighter. The originally planned engine was the TBIP's J402-CA-401 turbojet, but this was changed during development to a Williams F415-WR-400/402 turbofan, causing a significant delay in the time schedule. Because of the lighter structure (which includes reducing the number of tailfins from four to three), the UGM-109E is unsuitable for launch from torpedo tubes, but can still be used from SSNs equipped with vertical launch systems. The RGM/UGM-109E also features a number of significant operational improvements. The missile can be reprogrammed in flight via an UHF satellite link to divert to any one of 15 pre-programmed alternate targets or to an arbitrary location defined by GPS coordinates. It can also loiter over the target area for some time while transmitting imagery from its on-board TV camera via the satellite link. The image can be used to assess battle damage and/or to retarget the missile.

RGM-109E Photo: U.S. Navy

The first flight of a TacTom test vehicle occurred in August 2002, and the first underwater launch of a UGM-109E succeeded in November 2002. The first LRIP (Low-Rate Initial Production) contract was awarded to Raytheon in October 2002. IOC (Initial Operational Capability) was officially reached in May 2004, when RGM-109E missiles were installed on USS Stethem (DDG-63). In August that year, Raytheon received a five-year contract for full-scale production of Tomahawk Block IV rounds to replenish the Navy's cruise missile arsenal. The initial RGM/UGM-109E Tactical Tomahawk version will be armed with the WDU-36/B blast-fragmentation warhead of the TLAM-C Block III.

The second variant of the Tactical Tomahawk will be the TTPV (Tactical Tomahawk Penetrator Variant), armed with a new WDU-43/B penetrating warhead for use against hardened and/or underground targets, like storage bunkers for weapons of mass destruction. The first test flight of the TTPV, designated RGM-109H and UGM-109H (reusing the -109H suffix of the cancelled THTP  penetrator version), was successfully conducted on 21 March 2003, and IOC is currently planned for 2005.

UGM-109E Photo: U.S. Navy

The Tomahawk versions currently in the U.S. Navy operational inventory are the RGM/UGM-109C/D TLAM-C/D, and the RGM/UGM-109E Block IV. The original RGM/UGM-109A TLAM-N and RGM/UGM-109B TASM variants have been retired in the early 1990s. Including the groundlaunched BGM-109G Gryphon, more than 4000 xGM-109 missiles of all variants have been built so far.

Specifications

Note: Data given by several sources show slight variations. Figures given below may therefore be inaccurate!

Data for RGM/UGM-109A/B/C/D:

GLCM (Ground-Launched Cruise Missile): BGM-109G Gryphon

As early as 1971 the U.S. Air Force had tentative plans to replace the retired MGM-13 Mace with a modern GLCM (Ground-Launched Cruise Missile) with TERCOM precision guidance and a small fuel-efficient turbofan engine. The plans became more firm in 1976, and in January 1977 the USAF was allowed to develop and field a GLCM derivative of the Navy's BGM-109 Tomahawk SLCM. The first launch of the BGM-109G Gryphon (sometimes spelled Griffin) GLCM from its mobile TEL (Transporter/Erector/Launcher) occurred in May 1980, and operational testing began in May 1982. The GLCM was operationally deployed in Europe from 1983 to counter (together with the U.S. Army's MGM-31C Pershing II) the Soviet RSD-10 Pioner (SS- 0 Saber) mobile IRBM system.

The BGM-109G was very similar to the Navy's nuclear-armed BGM-109A except that a different W-84 thermonuclear warhead was used. The Gryphon was launched from a mobile TEL, which could hold four missiles. Like the BGM-109A, it used an INS/TERCOM guidance system with an accuracy of about 80 m (260 ft) CEP.

BGM-109G Photo: USAF

In December 1987, the USA and the USSR signed the Intermediate Range Nuclear Forces (INF) Treaty, which abolished all medium- and intermediate-range nuclear armed missiles.

Withdrawal of the GLCM began in 1988 and was completed in May 1991. A total of about 500 BGM-109G missiles had been built.

Specifications

Note: Data given by several sources show slight variations. Figures given below may therefore be inaccurate!

Data for BGM-109G:

MRASM (Medium-Range Air-to-Surface Missile): AGM-109C/H/I/J/K/L

In the late 1970s both the U.S. Navy and the USAF had plans for a tactical air-launched mediumrange cruise missile. By 1978 it had become clear that Navy and Air Force would have to agree on a common missile, and in March 1980 General Dynamics was awarded a development contract for a MRASM (Medium-Range Air-To-Surface Missile) based on the AGM-109 Tomahawk, which had lost shortly before against the AGM-86B in the USAF's ALCM (Air-Launched Cruise Missile) competition.

The MRASM was planned in several different versions for both Navy and USAF. The Air Force variants were very similar in general arrangement to the BGM-109 SLCM missile family, except that the F107 turbofan engine was replaced by a much cheaper Teledyne CAE J402-CA-401 turbojet. Due to size and weight restrictions imposed by ammunition elevators on U.S. aircraft carriers and the maximum safe return weight of the A-6E aircraft, the Navy MRASM variants were significantly shorter and lighter than the USAF MRASMs. The shorter nose also necessitated the use of a slight sweep-back on the wings.

The initial MRASM version for the Navy was to be the AGM-109C, a conventional land-attack missile similar to the BGM-109C with a unitary warhead (most probably the TLAM-C's WDU-25/B). The AGM-109H was a USAF version also known as TAAM (Tactical Anti-Airfield Missile), and was to carry 28 BLU-106/B BKEP (Boosted Kinetic-Energy Penetrator) runway-cratering submunitions. The Navy's AGM-109J was either a low-cost derivative of the AGM-109C or a variant armed with a submunition dispenser. In any case, the -109J was cancelled very early in the MRASM program. The AGM-109C/H/J were all planned to use TERCOM/DSMAC guidance like the BGM-109C/D TLAM-C/D missiles. The designation AGM-109I was unofficially used by the U.S. Navy for a generic MRASM equipped with a low-cost TERCOM system and an IIR (Imaging Infrared) terminal seeker. This MRASM could serve both as land-attack and anti-ship missile. Planned versions with an IIR seeker were the USAF's AGM- 09K with a WDU-25/B warhead, and the Navy's AGM-109L with a WDU-7/B warhead.

From left: AGM-109H, AGM-109L

The MRASM program was in trouble almost from the beginning, because the U.S. Navy was not very enthusiastic about it. They feared to get a very expensive missile, which would not be an ideal fit for their mission requirements. The USAF reportedly also wanted to kill the joint program, and therefore the whole MRASM effort was cancelled in 1984, without any versions having been built.

Specifications

Note: Data given y several sources show slight variations. Figures given below may therefore be inaccurate!

Data for AGM-109H/K/L: 

Main Sources

[1] James N. Gibson: "Nuclear Weapons of the United States", Schiffer Publishing Ltd, 1996[2] Norman Friedman: "World Naval Weapons Systems, 1997/98", Naval Institute Press, 1997
[3] Bill Gunston: "The Illustrated Encyclopedia of Rockets and Missiles", Salamander Books Ltd, 1979
[4] Hajime Ozu: "Missile 2000 - Reference Guide to World Missile Systems", Shinkigensha, 2000
[5] Kenneth P. Werrell: "The Evolution fo the Cruise Missile", Air University Press, 1985
[6] Nigel Macknight: "Tomahawk Cruise Missile", Motorbooks, 1995
[7] Norman Friedman: "US Naval Weapons", Conway Maritime Press, 1983
[8] Navy NewsStand Website
[9] Raytheon Co. Website

The MGM-31 Pershing was the first and only solid-fueled MRBM (Medium Range Ballistic Missile) deployed by the U.S. Army. It has been in service for almost 30 years until all nuclear MRBMs were phased out and destroyed according to arms reduction treaties.

XM14 (XMGM-31A) - Photo: U.S. Army
 

Studies for a solid-fueled missile with a maximum range in the 900-1400 km (500-750 nm) area were begun by the U.S. Army in 1956. In 1957, the studies had shown that the proposed missile was feasible, and in the same year a temporary DOD restriction which limited the Army's missiles to a range of less than 320 km (200 miles) had been cancelled. In January 1958, the name Pershing was officially assigned to the new missile program, and in March that year Martin's Orlando division was awarded a full scale development contract.

The Pershing was designed as a two-stage solid-fueled rocket with an all-inertial guidance system, to be fired from a mobile launcher. Development was quick, and in February 1960, the first Pershing I, designated Guided Missile XM14, was launched. The first test flights used only the first stage, but by the end of 1960, full range two stage flights had been successful. The first launch from the tactical missile launcher occurred in January 1962, and in June 1962 the first Pershing I unit received its first missiles. By 1964, the first battalions were deployed to their operating area in West Germany. The Pershing I quickly replaced all PGM-11 Redstone MRBMs.

The Pershing I was powered by two soild-fueled rochet stages by Thiokol (a TX-174 and a TX- 175), and could carry its 400 kT W-50 thermonuclear warhead to a maximum range of 740 km (460 miles). It was guided by an inertial navigation system by Eclipse-Pioneer, and featured a high-speed ablative reentry vehicle. A single Pershing I launch platoon consisted of only 4 vehicles, compared to about 20 for the PGM- 1 Redstone. Coupled with the solid-propellant rockets, this led to a much higher mobility and shorter reaction time than the Redstone it replaced. For training there was an inert Pershing I missile designated XM19. In June 1963, the XM14 and XM19 Pershing missiles were redesignated as XMGM-31A and XMTM-31B, respectively. The production version of the tactical missile was subsequently designated as MGM-31A, and the XMTM-31B designation was apparently not used and eventually dropped form the list. The -31B suffix was later reused.

MGM-31A - Photo: U.S. Army
 

In early 1965, the DOD issued a requirement for a QRA (Quick Reaction Alert) Pershing missile system, with the intention to replace the USAF's CGM//MGM-13 Mace missiles by the MGM-31. In January 1966, Martin Marietta was awarded a contract to develop the Pershing Ia system to meet this requirement.

The Pershing Ia system consisted of faster ground support vehicles, a faster erector/launcher, and new solid-state electronics. The missiles compatible with the new system were designated MGM-31B. Production of the Pershing Ia began in 1967, and by 1970 it had replaced all original Pershing I systems in U.S. Army service.

In 1976, further improvements of the Pershing Ia system were fielded, the sequential launch adapter (SLA) and the automatic reference system (ARS). The SLA allowed a Pershing Ia platoon to fire its three missiles in quick succession, and the ARS (essentially a ground based inertial unit) eliminated the need to survey the launch site before firing, making on-the-spot launches possible.

Production of the Pershing Ia was originally completed in 1975, but the line had to be reopened from 1977 to 1979 to replace missiles expended in training exercises. A total of about 750 Pershing I/Ia missiles were built, with an operational deployment level of 108 missiles in Europe.

MGM-31B - Photo: U.S. Army
 

In the early 1970s, the 400 kT warhead of the Pershing Ia had become a problem, because it effectively excluded the use of the MGM-31 in its intended role of a tactical missile (except for the few LGM-25C Titan IIs, all strategic missiles of the time had less powerful warheads!).

Therefore it was decided to develop a new warhead section for Pershing, with a lower yield warhead and a high-accuracy manoeuvering reentry vehicle (MARV) with active radar terminal guidance. The new missile was named Pershing II, and in May 1978, flight tests of the new RV on existing Pershing Ia rocket stages took place. However, by that time requirements had changed significantly. The Soviet Union had deployed its RSD-10 Pioner (designated SS-20 Saber in the West) IRBM system, featuring high mobility, long range, and a MIRV capability (SS-20 Mod.2). Pershing II was now intended as a counter to the SS-20, and its range requirement was more than doubled, to 1600+ km (1000+ miles).

To achive this, completely new rocket motors were developed by Hercules, using high-energy fuels andlight-weight casings made of Kevlar. This  effectively made the Pershing II a completely new missile, and it was designated as MGM-31C. However, the Pershing II missile was fully compatible with existing Pershing Ia ground equipment, and even the launchers could be modified to handle the new missile. The first flight test of an MGM-31C in July 1982 was a failure, but the next attempt in November that year succeeded. In December 1983, the first Pershing II battery became operational, and by December 1985 all 108 Pershing Ia missiles of the U.S. Army in Europe had been replaced by Pershing II.

MGM-31C-Photo: U.S. Army
 

The MGM-31C reentry vehicle housed a single variable yield (5-50 kT) W-85 thermonuclear warhead. With its Singer Kearfott inertial guidance system, and the Goodyear Aerospace active radar terminal guidance unit in the warhead, the MGM-31C achieved an accuracy of about 30 m (100 ft) CEP at a range of up to 1770 km (1100 miles).

In December 1987, the USA and the USSR signed the Intermediate Range Nuclear Forces (INF) Treaty, which abolished all medium- and intermediate-range nuclear armed ballistic missiles. Withdrawal of the Pershing II began in October 1988 and was completed in July 1989. All MGM- 31C and the remaining stored MGM-31B missiles were destroyed by static firing of the rocket motors, and the last Pershing II rocket motor was destroyed that way in May 1991. The W-85 warheads could be reused, however, and were modified into MK-61 Mod 11 (B61-11) free-fall bombs (the W-85 itself was a derivative of the MK-61 Mod 3/4). A total of about 380 Pershing II missiles were built.

Note: I have found no 100% convincing evidence that the Pershing Ia and Pershing II missiles were indeed designated MGM-31B and MGM-31C, respectively. While a few sources call them as such, there are also sources which attribute the designation MGM-31B to the Pershing II.Unfortunately all my main sources, including official Department of Defense missile nomenclature records, neglect to quote any MGM-31 designation for both of the missiles. Nevertheless I think the two designations are valid, because they would concur with standard U.S. Army practice for designating guided missiles: While the Army doesn't use formal missile designators in its published documents and announcements (preferring the names instead), these designations are nevertheless assigned, as is evidenced by several better-documented missile families. It is also usual Army practice to assign new designation suffix letters to missiles with relatively few changes (like Pershing I to Pershing Ia), if these missiles are part of an improved missile system. Therefore I think the -31B suffix was indeed already applied to the Pershing Ia.

Specifications Note: Data given by several sources show slight variations. Figures given below may therefore be inaccurate!

Data for MGM-31A/B/C:

Main Sources
[1] James N. Gibson: "Nuclear Weapons of the United States", Schiffer Publishing Ltd, 1996
[2] Bill Gunston: "The Illustrated Encyclopedia of Rockets and Missiles", Salamander Books Ltd, 1979
[3] Redstone Arsenal Historical Information Website