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Corporal Type 2

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US Army Fact Sheet

Type II Corporal

As the testing program had continued from 1951 through 1952, many shortcomings of the Type I CORPORAL system had become apparent. Deficiencies became particularly obvious as the participating agencies began planning for the Army's tactical utilization of the system. But solutions were made possible by the increased knowledge of the flight environment and the determination of the effects of vibration on components, achieved as the program progressed. The resulting redesign of components led to development of the Type II (XM2E-I) CORPORAL.

In January 1953, an Army Ordnance Corps contract, ORD-437, was awarded to Firestone for production of 465 of the new Type II missiles. At the time, the Type II components had not yet been fully defined. But by the end of the year 1953, JPL had given most of the information to the contractor.

A significant change from the Type I system was in the Doppler unit. The operating frequency was increased from the fixed-tuned DOVAP instrumentation frequency of 38 megacycles to the UHF region, using a tunable missile transponder with an input frequency range of 450 to 480 megacycles. Minor improvements were incorporated in the radar link to provide better tactical operation. The launcher, erector and servicing platform also were redesigned for the Type II system. Originally, the CORPORAL missile was intended as a general test vehicle for the study of guided missile problems. Its design was undertaken at a time when most phases of the science of missile aerodynamics were relatively unknown. The design progressed through a series of configurations, and with each new configuration the accuracy with which aerodynamic data could be predicted showed improvement. The CORPORAL missiles fired after Round 11, on 10 October 1951, all had essentially the same aerodynamic configuration. The two standard versions, Type I and Type II, differed principally in that Type I carried four DOVAP antenna spikes mounted on two fairings in the yaw plane of the missile. As part of the redesign for Round 11, the 96-inch long nose shape used in earlier CORPORAL rounds was abandoned, and a 68.5-inch nose shape was adopted. This change was effected in order to reduce overall missile length.

In the absence of adequate flight instrumentation directed specifically toward the measurement of aerodynamic characteristics of the CORPORAL missile, data obtained from individual rounds were of limited usefulness. However, data and experience gained from firing a large number of rounds were used to determine drag coefficients and atmospheric densities. Estimates were based on published meteorological data and pre shoot and post shoot data obtained at WSPG. DOVAP measurements gave information on position in space, velocity and acceleration. The basic specification for the CORPORAL propulsion unit required that the rocket motor be capable of delivering 20,000 pounds of thrust for approximately 60 seconds. A liquid cooled motor was selected for development. The Type II fuel-cooled motor developed 20,000 pounds of thrust for durations up to 64 seconds and utilized compressed air to pump a propellant combination of stabilized fuming nitric acid (SENA) as the oxidizer and aniline-furfuryl alcohol-hydrazine mixture as the fuel. Selection of this propellant system and development of the axially cooled rocket motor eventually proved to be one of the major achievements of the CORPORAL program. The motors used in all the Firestone rounds were static tested on facilities at WSPG before being flight tested with the other missile components.

Type II Firing Program

Concerning the first firings of the Type II CORPORAL rounds at White Sands Missile Range, the JPL report said:

"The first Type II prototype round was flown on 8 October 1953. This missile was a Type I with components modified by this Laboratory. This round impacted 234 meters short and 116 meters right, well within the tactical CPE."

The first ORD-437 missile manufactured by Firestone was flown on 28 October 1954, just one year after the first prototype operation. This round impacted 43 meters short and 169 meters right of the target. During the interval between the prototype and production Type II firings, most of the flights were Type I rounds containing nearly complete Type II modifications. These rounds used electronic components manufactured by Gilfillan, whereas, in Type I, Firestone had contracted directly with various electronic manufacturers for flight electronic equipment. In Type II production, all of the missile electronic units were procured through Gilfillan. On an ORD-468 contract, Gilfillan also undertook improvement of both the ground and flight electronic equipment. The Jet Propulsion Laboratory provided technical advice and consultation and performed evaluation testing in the field.

The Jet Propulsion Laboratory fired 57 Type II rounds between the first ORD-437 firing on 28 October 1954 and the end of the Calendar Year 1955. This contractor program was scheduled to continue in 1956. The Engineer-User team fired 21 Type II rounds between February and December 1955. This program also was incomplete as of the end of 1955 and was scheduled to continue during the following year. Meanwhile, both CORPORAL R&D rounds and CORPORAL Test Vehicle rounds were being fired by project personnel at White Sands Proving Ground. The Type II evaluation program was expected to be completed by mid 1957.

In the fall of 1954, the Engineer-User team and Jet Propulsion Laboratory worked together on four missile firings which comprised Operation Sandspit. This program was both an evaluation of Type II procedures testing and check out equipment, and a training exercise on the Type II missile. After a limited amount of training, the E-U team members in turn instructed other E-U personnel in Type II operational procedures. A complete Type II system arrived in February 1955 and the E-U team then proceeded with thorough proof tests of the Type II equipment. The team also undertook the check out of three Type II rounds which had been scheduled for climatic experimentation by the WSPG Electro-Mechanical Laboratories (EML). Although some formal classroom training was conducted, a new Engineer-User team learned mostly through actual work on the missiles.

The aggregate CPE for all of the production Type II rounds fired by Jet Propulsion Laboratory was 350 meters, as compared with the desired CPE of 300 meters. Other rounds were fired for special experiments, but no attempt was made to record those flights for accuracy because accuracy was only incidental to their operations. While aborted flights would be considered as penalties in tactical operations, one evaluation was made with "aborts" not counted and thus showed a much better accuracy record for the systems. In this evaluation, the aggregate CPE for all of the production Type II rounds fired by JPL was only 150 meters.

Future Projection

By the end of Fiscal Year 1955, the total dollar value of all CORPORAL contracts which had been executed was $199,423,694. This included $39,470,388 in the Research and Development program, $159,248,719 in the Industrial program, and $704,587 in the Field Service program. However, even though the contracts had been awarded by 30 June 1955, actual delivery of many items contracted for in the Industrial and Field Services programs was not scheduled until the Calendar Year 1956. Completion of some contracts awarded in the Research and Development program also was scheduled for 1956 or later.

As the Calendar Year 1955 ended, the Army was preparing to send several Type II CORPORAL battalions to Europe to replace the 259th Field Artillery Missile Battalion, which was still equipped with the Type I CORPORAL. Meanwhile, the Type II evaluation program was scheduled to continue at White Sands Proving Ground, with firings planned both by Jet Propulsion Laboratory and the Engineer-User team. Training firings by Army Field Forces units and by British troops also were scheduled at WSPG for 1956.

Plans for improving the Type II CORPORAL were being made. It had been decided to simplify equipment and operations wherever possible, to redesign the electronic components, and to replace the batteries and motor generator with an air turbines alternator. Studies also were being initiated to determine design improvements that would increase the system's reliability and reduce its vulnerability to electronic countermeasures.