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[3.0] Cruise Missiles Of The 1950s & 1960s

v4.0.0 / chapter 3 of 8 / 01 jul 13 / greg goebel / public domain

* While the US JB-2 flying bomb clone and the delta-winged JB-1/10 didn't go anywhere, they led the US armed services to develop larger cruise missiles with greater payload and range for nuclear strike. Much effort was put into the development of such weapons in the 1950s, but they were made obsolete by the introduction of intercontinental ballistic missiles (ICBMs). Really effective cruise missiles would have to wait for a later decade.

Martin Matador


[3.1] AIR FORCE MATADOR / MACE
[3.2] UK RED RAPIER
[3.3] US NAVY RGM-6 REGULUS / RGM-15 REGULUS II
[3.4] AIR FORCE SNARK
[3.5] NAVAHO / TRITON
[3.6] US AIR FORCE HOUND DOG
[3.7] WESTERN LONG-RANGE ASMS: RASCAL / BLUE STEEL / SKYBOLT / SRAM
[3.8] FOOTNOTE: PROJECT PLUTO

[3.1] AIR FORCE MATADOR / MACE

* The USAAF's work on the JB-2 led to a next-generation cruise missile, the "Matador". Martin was awarded a $1.8 million USD contract in 1946 to develop this weapon under project "MX-771", and conducted initial test launches of the "XSSM-A-1" and "YSSM-A-1" prototypes at White Sands Missile Range beginning in 1949. The prototypes were redesignated "XB-61" and "YB-61" in 1951. Although the program was nearly canceled, the Korean War revitalized it, and a production contract was awarded to Martin in 1951. The "B-61A" Matador entered operational evaluation late in that year and was accepted for operational service in 1954. It was redesignated "TM-61A" in 1955.

The "Matador-A", to simplify the issue of what to call it, was a mid-sized pilotless aircraft, with a high-mounted swept wing and a tee tail. It differed from the X/YB-61 prototypes, which had mid-mounted wings on a spindle-shaped fuselage. The Matador-A was launched by a single Aerojet-General solid fuel booster with 254 kN (25,850 kgp / 57,000 lbf) thrust, the booster being discarded after launch. It was one of the first aircraft of any type to use such a "zero length launch" scheme. In cruise flight, it was propelled by an Allison J33-A-37 turbojet engine with 20.5 kN (2,090 kgp / 4,600 lbf) thrust, with the air intake set flush into the missile's belly.

   MARTIN MATADOR-A:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                8.74 meters         18 feet 8 inches
   length                  12.06 meters        39 feet 7 inches
   total weight            5,440 kilograms     12,000 pounds
   warhead weight          1,360 kilograms     3,000 pounds
   speed                   1,040 KPH           650 MPH / 560 KT
   cruise altitude:        10,700 meters       30,000 feet
   range                   1,100 kilometers    690 MI / 595 NMI
   _____________________   _________________   _______________________

The Matador-A was radio-guided by an operator tracking it on radar from a beacon carried on the missile. It was fitted with a 50 kilotonne nuclear warhead, though some sources also state that it could be fitted with a high explosive warhead. The requirement for radio guidance limited range to line of sight of the control center, and made the missile vulnerable to jamming. The Matador was launched from hardened shelters or from mobile trailer launchers.

The Air Force decided to build a considerably enhanced "Matador-B", discussed below, but development took longer than expected. As an interim measure, the USAF implemented a modestly improved version of the original Matador, designated "TM-61C". This "Matador-C" used the same airframe but had an improved "short range navigation vehicle (Shanicle)" guidance system that allowed it to plot its own course by mapping its position from a network of microwave transmitter stations. The Matador-C was introduced in 1957 and eventually replaced all Matador-As in service. It is unclear if Matador-As were converted to Matador-Cs.

About 1,200 Matadors were built, with production ending in 1957. The weapon was deployed to West Germany, Florida, and Taiwan, and remained in service until 1962. The Matador-C was retroactively redesignated "MGM-61C" in 1963.

* Even as the Matador was being deployed, there were concerns that it was simply too troublesome to move around and launch, and that its radio guidance system was too easy to jam or spoof. This led to an improved version, originally designated "TM-61B", with initial test flights of "YTM-61B" prototypes in 1956. The new missile was clearly derived from the Matador, but it had a shorter wingspan and a longer blunt nose, and it was judged different enough to be redesignated "TM-76 Mace" in early 1958. It entered operational service as the "TM-76A Mace-A" in 1959.

Martin TM-76 Mace

The Mace-A had an advanced terrain matching guidance system, with the designation of "Automatic Terrain Navigation And Navigation (ATRAN)", developed by Goodyear Aircraft. ATRAN used a downward-looking radar sensor to map the ground track of the missile, and compared the observed track with a map stored on film. Unlike the Matador, the Mace-A could be transported in a fully assembled state, except for its solid-rocket booster.

The problem with ATRAN was that it required the missile to fly at low altitude, limiting range. It also required radar maps of the route to the target area, which were hard to make in the days before reconnaissance satellites. As a result, the Air Force quickly moved to the "TM-76B Mace-B", which replaced ATRAN with an inertial navigation system (INS) developed by AC Spark Plug. First launch was in 1960. The trouble with fitting the Mace with an INS was that it had to be launched from a precisely known position, which was difficult to determine from a mobile launcher in the days before navigation satellites. For this reason, the Mace-B was usually fired from a fixed hardened shelter.

The Mace-B was launched by a single solid-rocket booster with 445 kN (45,350 kgp / 100,000 lbf) thrust, and powered by an uprated Allison J33-A-41 expendable turbojet engine with 23.2 kN (2,360 kgp / 5,200 lbf) thrust in cruise flight. The Mace-B had extended range and was fitted with a 1.1 megatonne fusion warhead.

   TM-76B / MGM-13B MACE B:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                7 meters            22 feet 11 inches
   length                  13.4 meters         44 feet
   total weight            8,160 kilograms     18,000 pounds

   speed                   1,040 KPH           650 MPH / 560 KT
   cruise altitude:        10,700 meters       30,000 feet
   range                   2,200 kilometers    1,380 MI / 1,200 NMI
   _____________________   _________________   _______________________

The Mace was deployed to West Germany and Okinawa. In 1964, the Mace-A was redesignated "CGM-13A" and the Mace-B was similarly redesignated "CGM-13B". The Mace-A was phased out in 1966, followed by the Mace-B in 1971, when it was thoroughly obsolete. Some were converted into targets, with the designations "MQM-13A" and "MQM-13B".

The potential effectiveness of the Matador and Mace is hard to judge. They were very cheap and reliable weapons as far as their airframes went, and provided a degree of backup for tactical air strikes into Eastern Europe in the middle parts of the Cold War. However, their guidance systems were very crude. Since none of them were ever used in combat, the issue is academic.

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[3.2] UK RED RAPIER

* While the Americans were working on Matador, the British also worked on comparable cruise missile systems. Investigations began at the end of the war, with a recommendation put forth by the working committee in September 1950 for development of a radio-controlled cruise missile. A request for design concepts was issued at the end of the year under "Operational Requirement 1097 (OR.1097)", also known as "Unmanned Bomber 109T (UB.109T)".

The general specifications for the "Short Range Expendable Bomber", as it was known, defined a machine with a range of 740 kilometers (460 miles), a radio-control distance of 465 kilometers (290 miles), a speed of 925 KPH (575 MPH / 500 KT), and a warload of 2,270 kilograms (5,000 pounds). The warload was seen as conventional, British nuclear weapons being too big at the time, but a nuclear warhead was obviously an option for the future once the boffins managed to get the weight down. The missile would be rail-launched with a RATO booster or compressed-air charge, and would have an accuracy of 225 meters (350 yards), with the radio control system capable of handling 60 missiles per hour.

Following inspection of proposals, the program was approved for further development in November 1951, with contracts awarded to Bristol and Vickers for the "Red Rapier", as it had been named, in March 1952. The government project team also considered the Martin Matador, but it did not meet their requirements.

The Bristol Red Rapier was known as the "Type 182" and envisioned a missile with a sleek fuselage, like a stretched drop tank; a variable-incidence swept wing perched on top; a swept tee tail; and a ventral fin mounting a single Bristol BE.19 expendable turbojet, with a thrust of 16.7 kN ( kgp / 3,750 lbf) thrust. It would have a length of 10.3 meters (33 feet 10 inches), a span of 6.3 meters (20 feet 10 inches), and a launch weight of 4,240 kilograms (9,350 pounds). Construction was to be of a composite material known as "Durestos", made of asbestos mixed with phenol / formaldehyde resin, then in use for drop tanks.

Vickers 725 Red Rapier

The Vickers Red Rapier was the "Type 725" or "SP.2" and it was simple to the point of crude in its appearance, the design concept being to make it as easy to produce and cheap as possible. The Vickers 725 Red Rapier featured a spikelike fuselage; a rectangular wing perched on top of the fuselage; and a swept tail assembly, with a small turbojet mounted on the tip of the tailfin and on the ends of the tailplane, for a total of three engines. The planned powerplant was the Rolls-Royce Soar turbojet with 7.8 kN (795 kgp / 1,750 lbf) thrust. Length of the Type 725 was 13.8 meters (45 feet 5 inches), span was 9.75 meters (32 feet), and the launch weight was 5,445 kilograms (12,000 pounds). Construction was to be of cheap soft steel, mostly in the form of sheet metal.

The nature of the radio control system appears to have been something of a puzzle for the project. Direct radio control was of course the main option, just at it was for Matador and other missiles like it, but some sources claim that Red Rapier might also have used a standard radio navigation system, such as Decca Navigator or LORAN. In fact, it seems that the uncertainties over the Red Rapier project were piling up even as Bristol and Vickers pursued development. A supersonic missile was considered in the summer of 1954; major redefinitions in a defense program are often a hint that it's about to fall over and die, and the Red Rapier was axed at the end of September 1954. The project was killed because manned bombers with stand-off weapons were seen as more accurate and practical.

By that time, Bristol was close to flying a prototype "Type 182R", where the "R" meant "Recoverable", built out of aircraft aluminum and fitted with retractable landing gear from a de Havilland Venom fighter. Vickers had been drop-testing aerodynamic models of the Type 725 and had put together a full-scale mockup. No full-scale Red Rapier prototype ever flew.

Late in the program, a "Blue Rapier" was also considered, this being a decoy drone based on the Red Rapier. The Blue Rapier has caused confusion in some sources, which state that the Bristol 182 was the Blue Rapier while the Vickers 725 was the Red Rapier, but both were actually Red Rapiers.

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[3.3] US NAVY RGM-6 REGULUS / RGM-15 REGULUS II

* While the US Air Force developed the Matador as their logical follow-on to the JB-2, the US Navy developed their own cruise missiles, the "Regulus I" and the "Regulus II", as a follow-on to their Loon experiments.

Work on the Regulus I was begun by Vought in 1946, with initial flight in 1951 from Edwards Air Force Base in California, using prototypes with retractable tricycle landing gear. The missile was intended to provide the Navy with a nuclear strike capability. Although the original concept was to launch the Regulus I only from submarines, the scope of the program was expanded to include launches from surface vessels and land sites. First launch from a ship was in 1952, followed by a launch from a submarine in 1953, the same year production began. The Regulus I was declared operational in 1954.

Vought Regulus I

The Regulus I was originally designated "SSM-N-8" and later redesignated "RGM-6", with incremental "RGM-6A" and "RGM-6B" variants. It was cigar-shaped, with an air intake in the nose and swept-back wings in the middle of the fuselage. It had a tailfin but no tailplane, and used rudder and elevons for flight control. The wings folded for storage.

The Regulus I was launched by a pair of solid-fuel booster rockets from a simple launch rail, and was powered in cruise flight by an Allison J33-A-18A engine with 20.5 kN (2,090 kgp / 4,600 lbf) thrust. The missile was radio controlled and fitted with a nuclear warhead, either a W-5 fission warhead with a yield of about 40 kilotonnes or, from 1958, a W-27 fusion warhead with a yield in the megatonne range.

   CHANCE-VOUGHT SSM-N-8 / RGM-6 REGULUS I:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                6.4 meters          21 feet 
   length                  10.5 meters         34 feet 4 inches
   total weight            6,000 kilograms     14,520 pounds
   speed                   subsonic
   range                   800 kilometers      500 MI / 435 NMI
   _____________________   _________________   _______________________

Four diesel submarines, including the GRAYBACK, GROWLER, TUNNY, and BARBERO, were built to launch the Regulus I, and ten aircraft carriers and four cruisers were equipped with the missile as well. The GRAYBACK and GROWLER were built from scratch and could carry four missiles in a foredeck hangar, while the other three submarines were converted WWII boats and could only carry two missiles. The submarines surfaced for missile assembly and launch off a pivoting rail. Instead of booster rockets, carriers used a special trolley to launch the Regulus I off their aircraft catapults. The missile could be accompanied by a manned controller aircraft up to the target area.

A total of 514 Regulus I missiles was built. Some of those with landing gear were used as targets, with the original designation of "KDU-1" and later "BQM-6C". Regulus I remained in service until 1964.

* The Navy attempted to build a ramjet-powered successor to the Regulus I, the Grumman "Rigel", but the development program was a fiasco and Rigel was canceled in August 1953. The Navy turned back to Vought to develop the supersonic "Regulus II".

Vought SSM-N-9 / RGM-15 Regulus II

The Regulus II, designated "SSM-N-9" and later "RGM-15", was a sleek, pretty dart of a missile, with swept wings and no tailplane like the Regulus I, but with the air intake under the belly ahead of the wings and small canard fins on the nose. The wings and tailfin folded for storage. Preliminary design work began in 1951, with Vought submitting a proposal to the Navy in late 1952, and the Navy awarding the company a development contract in April 1954, specifying construction of prototypes.

The initial prototypes were fitted with retractable tricycle landing gear and a drag parachute, allowing them to take off and land from an airstrip, and were powered in cruise flight by a Curtiss-Wright J65 turbojet, an American copy of the British Sapphire engine. The Sapphire was strictly an interim fit, however, since it could not support sustained supersonic flight, and production missiles were fitted with a General Electric J79 afterburning turbojet engine with 66.7 kN (6,800 kgp / 15,000 lbf) thrust.

Production missiles were launched off a rail by a solid-fuel booster rocket with 512 kN (52,160 kgp / 115,000 lbf) thrust. The Regulus II flew in continuous afterburner, operating at high altitude in supersonic cruise at Mach 2 plus. It had a large fuel supply to provide the required range and featured an automatic fuel trim system. The Regulus II was guided by an INS. The warhead separated during terminal dive to target. This made interception more difficult, and also eliminated the need to stress the airframe to tolerate a dive.

   CHANCE-VOUGHT SSM-N-9 / RGM-15 REGULUS II:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                6.12 meters         20 feet 1 inches
   length                  17.5 meters         57 feet 6 inches
   total weight            11,000 kilograms    24,250 pounds
   speed                   Mach 2
   range                   2,220 kilometers    1,380 MI / 1,200 NMI
   _____________________   _________________   _______________________

Initial flight of a prototype was on 29 May 1956, at Edwards Air Force Base in California. The first rocket-boosted launch was on 13 November 1957, also from Edwards. First launch from a submarine was on 16 September 1958, with the GRAYBACK doing the honors. The older TUNNY and BARBERO couldn't handle the Regulus II, but the GRAYBACK and GROWLER could carry two. A nuclear-powered boat, the HALIBUT, was designed specifically for Regulus II launch, carrying four missiles. Some sources claim that a terrain-following navigation system was considered for the missile late in the development cycle.

However, the Navy's move towards submarine-launched ballistic missiles led to the cancellation of the Regulus contract in December 1958. The HALIBUT would become the only one of her class, ending up being modified as a one-of-a-kind "special mission" submarine, with special missions including spy operations. The Vought development team was very disappointed, since the missile was flying very well at the time, but the Polaris was simply a much more effective weapon in every sense. Only 54 Regulus IIs were built. The survivors were converted into high-speed targets. They were originally designated "KD2U-1" and later redesignated "MQM-15A". Their high performance made them very well suited to this role, and remained in service up to the end of 1965.

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[3.4] AIR FORCE SNARK

* The Air Force "Snark" cruise missile was intended for intercontinental nuclear attack, and was much more ambitious than the Matador/Mace or Regulus I. After a study program initiated in late 1945, in March 1946 the Army Air Forces awarded Northrop a contract for "MX-755" program, which specified development of two weapons, the subsonic "MX-755A Snark" and the supersonic "MX-755B Boojum". The odd and entirely unmilitary names were derived from Lewis Carroll's nonsense verse "The Hunting Of The Snark".

Northrop XSSM-A-3 Snark

The Boojum would never be built and details of the effort are unclear. The Snark had the company designation of "N-25" and was assigned the military designation of "XSSM-A-3" in 1947. Development was somewhat protracted, with the first successful flight of the Snark in April 1951. The Snark was also powered by an Allison J33 turbojet. It had swept wings mounted forward, and had a tailfin but no tailplane, using "elevons" on the wings for flight control. The air intake was under the belly. The XSSM-A-3 Snark was launched off rails on a sled and remotely controlled by radio.

   NORTHROP XSSM-A-3 SNARK:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                19 meters           42 feet
   length                  15.9 meters         52 feet
   total weight            12,700 kilograms    28,000 pounds
   speed                   subsonic
   range                   2,480 kilometers    1,550 MI / 1,340 NMI
   _____________________   _________________   _______________________

Northrop worked on an INS with stellar navigation backup for the XSSM-A-3, but did not complete full development of that variant. The Air Force significantly raised range and payload requirements, and so Northrop had to redesign the missile substantially. The new variant had the company designation of "N-69". It originally had the Air Force designation of "B-62", which evolved through a short series of prototype subvariants, to eventually result in the "XSM-62A". It was referred to as the "Super Snark". A reconnaissance drone version was considered but not proceeded with.

Northrop SM-62A Super Snark

The SM-62A had a similar configuration to the SSM-A-3 but was substantially bigger. The wing was swept back 45 degrees; had a "dogtooth" on the leading edge; and like its predecessor had a tailfin with no tailplane and used elevons for flight control. The wings could be detached with relative ease to allow the missile to be transported by air. The SM-62A was boosted into the air by a pair of solid-propellant RATO boosters, each providing 580 kN (59,000 kgp / 130,000 lbf) thrust for four seconds. The missile was powered in cruise flight by a single Pratt & Whitney J57 turbojet engine with 46.8 kN (4,770 kgp / 10,500 lbf) thrust. The missile carried fuel in a large external tank under each wing, which were discarded when empty, and had a large volume of internal fuel storage.

The Snark was guided by a star-tracking INS developed by Northrop. Like the Regulus II, it was to be armed with a nuclear warhead that separated from the missile during the terminal attack phase of the mission.

   NORTHROP SM-62A SUPER SNARK:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                12.9 meters         42 feet 4 inches
   length                  21 meters           68 feet 10 inches
   weight                  22,700 kilograms    50,000 pounds
   speed                   subsonic
   range                   9,660 kilometers    6,000 MI / 5,220 NMI
   _____________________   _________________   _______________________

Flights of early test prototypes began in 1953, leading up to test flights of preproduction prototypes in 1957. Development of the Snark was unusually troublesome. The ocean off its Florida test site became known as "Snark-infested waters", and in 1956 one Snark decided to head south on its own and vanished from sight, only to be discovered in the Brazilian jungle by a farmer in 1982.

The Snark was put into service for operational evaluation in 1959, but it was never very satisfactory, being both vulnerable to enemy air defenses and much too inaccurate even with a large fusion warhead. It was eventually eclipsed by the development of ICBMs such as Titan and Atlas. The Snark reached full operational status in late March 1961, only to be almost immediately withdrawn from service in June by US President Kennedy, who correctly declared the big cruise missile "obsolete and of marginal military value".

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[3.5] NAVAHO / TRITON

* One of the most interesting of the 1950s cruise missiles was the North American "Navaho", the product of one of the most ambitious and "snakebitten" weapons development programs of all time. Initial studies began in 1947 under project "MX-770", leading to award of a development contract for what was then designated the "SSM-A-2 Navaho". As defined at this stage, the missile was to have cruciform fins, with a ramjet mounted on the tip of two of the fins, and a built-in rocket booster. It was to have a range of 1,600 kilometers (1,000 miles).

Work on prototypes was underway in 1950 when the program was drastically redefined to produce a strategic weapon with a range of 8,000 kilometers (5,000 miles). The missile would be powered by twin ramjets, in this case fitted into the fuselage, and launched by a large liquid-fuel rocket booster. The effort was given the designation of "Weapons System 104A (WS-104A)". Prototype missiles were to be designated "XSSM-A-4 Navaho II" and production weapons were to be designated "XSSM-A-6 Navaho III". The designations would prove a moving target, becoming "XB-64" and "XB-64A" respectively in 1951, and "XSM-64" and "XSM-64A" in 1956, with both variants simply called "Navaho" without a numeric suffix.

North American X-10

The Navaho would cruise at Mach 3. Since such speeds were at the leading edge of the technology of the time, eleven prototypes of the cruise missile portion of the Navaho were built with retractable tricycle landing gear and radio control to investigate such high-speed flight. These prototypes, originally designated "RTV-A-5" but known as "X-10" in service, had a rear-mounted delta wing, a vee tail, and canard fins on the nose. They were powered by twin Westinghouse J40-WE-1 turbojets, had a length of 21 meters (70 feet), and a wingspan of 8.5 meters (70 feet). The initial flight of the X-10 was in October 1953. One of them attained a maximum speed of Mach 2.05 during the flight test program, which was a world's speed record for jet-powered aircraft at the time.

The cruise missile component of the XSM-64 was very similar to the X-10, was but powered by a pair of Wright RJ-47 ramjet engines, each providing up to 176 kN (18,000 kgp / 40,000 lbf) thrust. It was launched vertically in a piggyback configuration by a large liquid-fuel booster 23 meters (76 feet 3 inches) long, and cruised to target at an altitude of 27.5 kilometers (90,000 feet) under guidance of an INS that also permitted the missile to maneuver around defenses. The XSM-64A was to have been larger and of somewhat modified configuration. It was to carry a four-megatonne warhead.

XSM-64 Navaho

The Navaho was just too much technology too soon. The first flight, in November 1956, simply shook itself to pieces 26 seconds after launch. It wasn't until the fifth flight in August 1957 that the missile lasted long enough for the cruise missile stage to start up its ramjets, and it didn't last much longer than that. The cruise missile stage for the XSM-64 had retractable landing gear for trials purposes, but not one lasted through an entire flight and not one was recovered. The program had actually been axed in July 1957 after the expenditure of $800 million USD, partly because of escalating costs, and partly because ICBMs were clearly the way of the future. No XSM-64As were ever built.

The fifth flight was simply for experimental purposes, using airframes that had already been built. There would be six more such experimental flights and not one would be completely successful, though some useful data on high-mach flight was apparently obtained. The missile is remembered by the nickname of "Never-Go Navaho". The work on the Navaho did prove highly significant for ICBM development. The rocket engine developed for the booster stage was the basis for the rocket engines for the Atlas and Thor missiles, which were never much as weapons but proved to be outstanding space launch vehicles, and the work on the Navaho's INS led to operational INS systems for both missiles and submarines.

* The US Navy attempted to build a ramjet-powered cruise missile designated the "XSSM-N-2 Triton" that had speed and range exceeding that of the Navaho and was to be launched from ships and submarines. Initial studies were conducted in 1946, but the development program was characterized by a zigzag path of changing specifications as successive goalsets were judged too ambitious. The specifications were finally lowered to the level where the Triton hardly seemed to be much of an improvement over the Regulus II, and so the Triton was canceled in 1957. No prototypes were ever flown, and in fact it is unclear that any serious hardware was ever built.

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[3.6] US AIR FORCE HOUND DOG

* Arguably the most successful US cruise missile of the 1950s and 1960s was the North American "AGM-28 (originally GAM-77) Hound Dog", which was said to have been named for some obscure reason after the Elvis Presley hit pop tune, "You Ain't Nothin' But A Hound Dog".

Development of the Hound Dog began in 1957 as "Weapon System 131B", with initial flights in April 1959 and first operational deployment in late 1959. Development was quick because the design leveraged as much as possible off an existing technology, for example, using an airframe configuration heavily influenced by the Navaho and a guidance system derived from Navaho work, as well as using an existing engine design and nuclear warhead.

The Hound Dog was a tidy sleek dart of a missile, with a canard configuration and a big jet engine slung beneath the rear fuselage. It was powered by a single Pratt & Whitney J52-P-3 turbojet engine with 33.35 kN (3,400 kgp / 7,500 lbf) thrust. The J52 had been developed under Navy patronage and was used on the Douglas Skyhawk attack aircraft. Some sources claim the J52 was a ramjet, a confusion that probably arose because the engine intake on the Hound Dog featured a large inlet cone much like that of a ramjet.

   NORTH AMERICAN GAM-77 / AGM-28 HOUND DOG:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                3.65 meters         12 feet
   length                  12.8 meters         42 feet
   height                  2.75 meters         9 feet
   total weight            4,600 kilograms     10,150 pounds
   speed                   Mach 2.1
   range at altitude       1,300 kilometers    805 MI / 700 NMI
   _____________________   _________________   _______________________

The Hound Dog carried a W-28 nuclear warhead with a yield reported of at least a megatonne, and probably several times that. The missile was guided by an INS, backed up with a star tracker that was mounted on the B-52's launch pylon. The INS was not particularly accurate, though with such a big warhead it really didn't have to be. The Hound Dog was capable of a degree of simple preprogrammed maneuvering. It was intended to be used disrupt Soviet defenses and clear a path for its B-52 mothership to allow the bomber to make precision strikes on its assigned targets.

GAM-77 / AGM-28 Hound Dog

There were two versions of the Hound Dog, the "AGM-28A (GAM-77)" and "AGM-28B (GAM-77A)", with the AGM-28B featuring an improved INS and star trackers built into the missile, a radar altimeter, and a slightly increased fuel supply. The B-52 carried a Hound Dog on a pylon under each wing, for a total of two missiles. The engines of the two missiles could be used to augment the B-52's own turbojets when boost power was required, with the fuel supply of the missiles replenished by fuel from the B-52's own tanks. By 1963, when Hound Dog production ceased, the US Air Force's Strategic Air Command (SAC) had about 600 Hound Dogs on inventory.

A terrain-following system for the Hound Dog was flight-tested in 1971. Bendix was awarded a contract in 1972 to develop a passive radar seeker for the Hound Dog, with this scheme flight-tested in 1973. Neither of these features were put into production. The Hound Dog was completely out of service by 1976.

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[3.7] WESTERN LONG-RANGE ASMS: RASCAL / BLUE STEEL / SKYBOLT / SRAM

* Although long-range rocket-propelled air to surface missiles (ASMs) can't be really categorized as cruise missiles, they are closely related to air-launched strategic cruise missiles and so it is useful to describe such "standoff weapons" in this document.

The first long-range ASM developed by the USAF was the Bell Aircraft "Rascal" nuclear armed stand-off weapon, which was originally designated "XB-63" and later redesignated "XGAM-63". The name was an acronym for "Radar Scanning Link", referring to the missile's guidance system. Development of the Rascal began in 1946, with the first guided but unpowered flights in 1952.

XB-63 / XGAM-63 Rascal

The Rascal was a neat dart of a missile, with small cruciform nose fins and large cruciform tail fins, though it appears that the horizontal fins had a wider span than the vertical fins in both front and back. It was liquid-fueled with "storable" propellants, probably kerosene and a room-temperature oxidizer like concentrated ("high test") hydrogen peroxide, since a missile using cooled liquid oxygen is not very portable. It was guided by an INS, with a radio control backup, and was launched in tests by a specially-configured DB-47E bomber featuring the radio control link.

   BELL XB-63 / XGAM-63 RASCAL:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                5.1 meters          16 feet 8 inches
   length                  9.8 meters          32 feet
   height                  3.8 meters          12 feet 6 inches
   total weight            8,250 kilograms     18,200 pounds
   speed                   Mach 2.5
   range                   160 kilometers      100 MI / 85 NMI
   _____________________   _________________   _______________________

The Rascal came very close to production, with at least 135 built, but it was canceled in late 1958 since the Hound Dog seemed far more promising. The USAF also experimented during the mid-1950s with using the Radioplane Crossbow drone as a long-range anti-radar cruise missile, but did not proceed to operational use. The Crossbow is discussed in a companion document on unmanned aerial vehicles.

* The British developed and deployed an air-launched missile with a resemblance to the Rascal named "Blue Steel", which was carried on Avro Vulcan bombers. Preliminary studies were initiated by the British Air Staff with Avro in 1954, leading to a development contract in 1956. After a somewhat protracted development, Blue Steel conditionally entered service with the RAF in 1962, with full operational capability in 1963.

Avro Blue Steel

Blue Steel was somewhat bigger than Rascal, with a pair of small delta canards in the nose, and delta wings in the rear. The wingtips were turned down at a slight angle. There was a relatively small tailfin on top of the fuselage above the wings, and a corresponding but somewhat larger dorsal fin below the fuselage that folded to allow the carrier bomber to take off and land. Blue Steel used liquid propulsion, with kerosene fuel and high test peroxide oxidizer. There were two rocket chambers, one for boost thrust and the other for sustain thrust. It was guided by an INS and fitted with a megatonne-range "Red Snow" warhead.

   AVRO BLUE STEEL:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                4 meters            13 feet
   length                  10.7 meters         35 feet
   total weight            7,710 kilograms     17,000 pounds
   speed                   Mach 2.3
   cruise altitude         21,500 meters       70,500 feet
   range                   320 kilometers      200 MI / 175 NMI
   _____________________   _________________   _______________________

The Blue Steel was a workable but not entirely satisfactory weapon. Fueling the missile took a half hour at least, and the ground crews had to wear protective clothing to handle the high test peroxide. The range was also not as long as the RAF wanted, and for this reason work was begun on an improved Blue Steel Mark 2 even before the Mark 1 reached operational status.

Blue Steel Mark 2 was canceled in 1960 in favor of the US Skybolt air-launched missile, of which more is said below. The subsequent US cancellation of Skybolt in 1962 threw RAF nuclear strategy in confusion, and so the Blue Steel Mark 1 remained in service until 1969, when the burden of British nuclear deterrence shifted to the Polaris submarine-launched ballistic missile. In the early 1960s, the RAF went to low-level bomber operations and the control system of the Blue Steel was modified accordingly, with the missile using both thrust chambers at launch to climb to altitude. It was a workable fix, but it cut the range in half.

* The Douglas "AGM-87A Skybolt" was one of the more impressive (at least in principle) air-launched weapons ever conceived, amounting to an air-launched ballistic missile with a range of 1,600 kilometers (1,000 miles) and a megatonne-class warhead. Investigation on such a weapon began in the last half of the 1950s, with approval for development in early 1960.

Douglas AGM-87A Skybolt

The USAF planned to buy 1,000 Skybolts, with four carried by a B-52, fitted two to each underwing pylon. The British became very interested in the Skybolt as well and ordered 144; they were to be carried in pairs on the Avro Vulcan B.2, one under each wing, with an improved Vulcan B.3 on the drawing board that could carry six.

Skybolt development proved troublesome, since the missile was very complicated. The first five flight tests all failed; a test flight late in 1962 finally proved successful, but a few days later President John F. Kennedy canceled the project. The technical problems were not regarded as insurmountable, but the US was fielding plenty of other effective nuclear delivery systems at the time -- such as the Polaris submarine-launched missile, the Minuteman intercontinental ballistic missile, and the Hound Dog -- and the conclusion was that further development wouldn't be cost-effective.

The Americans had kept in close touch with their British counterparts through the development of Skybolt, and were aware that the cancellation was a serious blow to British strategic nuclear plans. They even offered to allow the British to continue work on the project with matching American funds, but the British felt that an American offer of Polaris missiles was a better strategic investment. Skybolt died; although most Vulcan B.2s had provisions for a stores pylon under each wing for a Skybolt, they were never used to carry that weapon, and the Vulcan B.3 never flew.

Skybolts on B-52

* The US did go on to develop a less ambitious air-launched missile. In 1963, Boeing began a privately-funded program to consider a short-range nuclear strike missile that would extend the usefulness of their B-52 bomber. In 1965, the US Air Force released a formal requirement for the weapon, under the designation "Weapon System 140A", and Boeing was awarded a production contract in 1966 for the "AGM-69A Short Range Attack Missile (SRAM)".

First launch of a powered SRAM, from a B-52, took place in 1969. Other test launches from the B-52 and the FB-111 took place over the next two years, leading to a production contract in 1971. First production delivery was in 1972, and 1,500 SRAMs were delivered by the time production ended in 1975.

AGM-69A SRAM

The SRAM was a simple spike of a missile with three small tailfins, and its clean and simple lines resulted in a very small radar cross-section. It was powered by a dual-thrust (boost-sustain) solid-fuel rocket motor.

   BOEING AGM-69A SRAM:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   length                  4.27 meters         14 feet
   total weight            1,000 kilograms     2,200 pounds
   speed                   Mach 3
   range                   160 kilometers      100 MI / 85 NMI
   _____________________   _________________   _______________________

SRAM was guided by an INS, though a passive radar homing version was also considered but not implemented. The INS offered four different flight modes:

The weapon was armed with a W-80 nuclear warhead with a yield of about 200 kilotonnes, and was initially intended mostly to suppress enemy defenses ahead of a B-52. However, a bomb is a bomb, and of course the missile could be used for attacking primary targets as well.

A B-52G could carry twelve SRAMs on its external pylons, with six on each pylon in double clusters of three, as well as eight on a rotary launcher in the bomb-bay that left room for free-fall weapons. An FB-111 could carry four SRAMs on its external pylons and two in its weapons bay, though in practice only four were carried, with two on the inner pylons and two in the weapons bay. The SRAM was carried on the FB-111A but not the FB-111C, which was assigned to the tactical instead of the strategic strike mission.

Development was begun of an enhanced "AGM-69B" for the B-1 bomber but was canceled when the B-1 program was terminated by the Carter Administration in 1977. The cancellation of the B-1 proved temporary, but the cancellation of the AGM-69B was not. When the B-1 was resurrected in the Reagan Administration, it was capable of carrying in each of its three bombbays a rotary eight round launcher for the AGM-69A, much like that of the B-52, for a maximum of 24 SRAMs. Existing AGM-69As were reconditioned with new solid-fuel motors and other changes to keep them operational, but the SRAM was finally taken out of service in 1990 due to warhead safety concerns.

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[3.8] FOOTNOTE: PROJECT PLUTO

* One of the more bizarre pieces of the story of US cruise missiles of the 1950s and early 1960s was a scheme to build a cruise missile with a nuclear-powered ramjet engine.

The nuclear ramjet effort, "Project Pluto", was initiated at the US Lawrence Livermore National Laboratory at the beginning of 1957. The idea was conceptually simple: instead of burning fuel as in a conventional ramjet, the air passing through the Pluto ramjet would flow through an atomic reactor core, expanding as it was heated and providing 156 kN (15,875 kgp / 35,000 lbf) thrust. Range would be effectively unlimited. Of course, building the reactor for such an engine was very difficult. "Tory", as the reactor was named, had to be powerful but compact and lightweight. It was to operate at 1,370 degrees Celsius (2,500 degrees Fahrenheit), a temperature level that challenged the materials technology of the time.

The cruise missile that would use the Pluto ramjet was designated the "Supersonic Low Altitude Missile (SLAM)". SLAM was to be launched with three solid-rocket boosters, and would cruise at Mach 3 low to the ground, finding targets using a terrain-matching system like that of the Matador.

SLAM would carry a number of fusion bombs and attack multiple targets. The development team also believed the Mach 3 shockwave would do considerable damage along its low-altitude flight path, and the Pluto ramjet's exhaust would scatter fallout behind it. In fact, once the missile had expended its load of bombs, it could simply fly around an enemy country, leaving a trail of radioactive fallout, until it was shot down or crashed.

The Pluto reactor effort involved the construction of an elaborate static test site at Jackass Flats in Nevada. An unmanned rail system was built to shuttle the reactor between the test range and the disassembly facility, where it would be taken apart by remote control for examination. The initial test of a prototype Tory reactor was conducted on 14 May 1961, with the system running for a few seconds at a fraction of full power. That was a proof-of-concept test, and it paved the way for a much improved Tory prototype, which was test-run several times in May 1964 at operational power. The exhaust proved less radioactive than expected.

However, by this time the military was unsurprisingly having second thoughts about the idea. It was simply too "dirty" and expensive, and the US was already fielding a ballistic missile force that could devastate any potential adversary, able to reach targets much faster than even the Mach-3 SLAM. Critics began to snipe that "SLAM" actually meant "Slow Low And Messy", and it became increasingly difficult to understand what the point of it was. Buying more ballistic missiles seemed far cheaper and more effective, and they were available, while SLAM wasn't even close to flying.

In fact, SLAM posed some hideous technical problems that had been swept under the rug at the outset. Test flights were going to be dirty if all went perfectly well, and if things could be assumed to go perfectly well, there would be no need for tests. The idea was to fly a prototype in circles over the Pacific Ocean and then crash it into the sea over a deep-ocean trench. If it decided the slip the leash, as Snarks had done many times, there was the frightening prospect that it might cruise over or be shot down into a populated area. Engineers have a saying: "If it hasn't been tested, it doesn't work." The corollary is that if it can't be tested, there's no way to ever be sure that it works.

Supersonic Low-Altitude Missile (SLAM)

Project Pluto was canceled by the Air Force and the US Atomic Energy Commission on 1 July 1964. Project cost to that time was $260 million USD in contemporary dollars, with a peak headcount of 450 people. The project did result in some advances in materials science, but fortunately it did not result in a production machine -- America did not need a weapon that was expensive, comparatively ineffective, untestable, and an environmental nightmare. Project Pluto remains something of a monument to the "atom crazy" mentality of the US at the time, as well as to Lawrence Livermore's occasional tendency to go off the deep end.

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