From Weapons Research to Weapons Development
Corporal’s acceleration shifted JPL’s emphasis from engineering research to large-scale development. Fundamental research continued, but at only a fraction of JPL’s budget, as engineering and production budgets for the Corporal project climbed dramatically.
Dunn and Pickering led the Corporal project. Dunn came to Pasadena in 1926 from South Africa to study aeronautical engineering under von Kar – man, completing his doctorate in six years. Associates characterized him as a decisive, orderly executive who organized JPL on a project-oriented model. Pickering came to Caltech from New Zealand, taking a Ph. D. in physics in 1936, then joining the electrical engineering faculty. He worked on electronics for cosmic ray studies and expanded into telemetry and guidance design in 1944 at JPL. In 1950, Pickering was head of JPL’s Electronics Department, along with being the Corporal project’s director. Pickering preferred an academic orientation, emphasizing technical excellence organized through working groups.13
In October 1951, JPL froze Corporal’s aerodynamic configuration, and Army Ordnance committed Corporal to limited production, selecting Firestone Tire and Rubber Company to manufacture the missile. JPL expanded its staff and used the production missiles for test firings.14 Test firings were disappointing, as electronic components frequently failed. Although JPL engineers realized that rocket engine vibrations were a factor, they had seriously underestimated the magnitude of the problem. As failures mounted, they began recording failure statistics. By summer 1953, with more than forty firings completed, JPL calculated missile reliability at only 48%, even with the electronics wired into two strings of components such that if a failure occurred in one set, the other would continue to operate.15 Reliability problems threatened to
undermine the project and with it the credibility of Army Ordnance officers and JPL engineers.
The majority of early Corporal failures were in electrical systems such as power, guidance, radar, and telemetry. According to JPL engineers, ‘‘Neither the reason for the failure nor the specific part failing is known in most instances; failures are commonly attributed to vibration.’’ Consequently, they tested components with a sine-wave vibration generator and at high and low temperatures. They found that some components had resonant frequencies that could lead to physical breakage. Engineers developed a program to test all electronic parts and changed both vendors and parts. They developed a rule of thumb to repair failures on the spot but redesign a component if it failed three times.16
Whereas aircraft structural vibrations typically occurred at predictable frequencies matching the rotation rate of propellers or jet engine rotors, rocket engines produced vibrations at near-random frequencies. In addition, high speeds and changing altitudes placed strong, highly variable aerodynamic forces and vibrations on the missile’s structure. These shook loose or severed wires, connectors, and soldered components, causing electrical short circuits and intermittent connections. The failures raised havoc with the electrical systems such as radio guidance, attitude control, and telemetry subsystems.17
One response was to acquire better flight data. Engineers placed accelerometers and strain gauges on the missile, and they sent the data through the radio system to be recorded on the ground. Because the speed of data collection and radio transmission was too slow to capture the full profile of high – frequency vibrations, engineers constructed algorithms to calculate vibration frequencies and amplitudes from the infrequent data samples. These algorithms were sufficiently complex and data-intensive to require the use of an IBM programmable computer. After much work on these data transmission, storage, and processing problems, engineers found vibrations to be highly unpredictable.18
Because of the expense and inconclusive flight test results, engineers constructed a vibration simulator to test individual components and component packages. They expanded component and package testing, and they formulated guidelines and standards.19 Vibration testing henceforth became a standard element of component qualification and missile development.
JPL engineers also theoretically analyzed missile reliability. Assuming that each component had a measurable failure rate, engineers estimated missile reliability simply by multiplying component reliability estimates. For example, for a missile with only two electronic components, where these components both had to operate and each had a 90% probability for successful operation, multiplying their reliability estimates together gave a combined reliability estimate of 0.9 X 0.9 = .81, or 81%. In this way, engineers estimated the decrease in reliability as they added electrical components. With calculations such as these, engineers determined that adding a second parallel “string” of components significantly improved missile reliability.20
In light of the Korean War and the tense situation in Europe, the army decided to deploy Corporal despite its severe reliability problems. Both JPL and the army soon realized that Corporal was not designed for operations. JPL engineers had initially designed Corporal purely as a research vehicle using World War II vintage hardware, much of it out of production. When failures occurred, researchers investigated and fixed them on the spot. The army sent military crews to White Sands to learn how to prepare and fire the missiles, but they did not have the expertise of professional engineers. JPL’s lack of operations experience showed in its poor documentation and frequent design changes. Poor training led to more failures and lower reliability, because operational reliability depended upon enlisted personnel to maintain and fire the missile.
Pushing Corporal into crash production aggravated the situation because the army had to use JPL’s sensitive laboratory equipment in the field. Many missiles failed tests because ground equipment had shifted out of tolerance. Even after relaxing tolerances, experience showed that on average, in the four hours necessary to prepare and fire a missile, one electronic component failed. The awkward, bulky equipment was extremely cumbersome. When a Corporal battalion moved, its convoy stretched sixteen miles!21
Flight instrumentation was another major problem. JPL engineers initially believed they needed little instrumentation for the tactical missile. This was a mistake. Jack James, an engineer assigned to this problem, reported that throughout a program of 111 development firings and 150 training rounds through June 1957, engineers and technicians modified every missile to install instrumentation. With thirty tactical ground systems capable of firing
Corporal but only eleven telemetering stations and two telemetry processing facilities (one at JPL and one at White Sands), telemetering stations had to be shipped to the firing site and all data sent to JPL or White Sands for analysis. Because JPL had few personnel trained to analyze test data, substantial delays ensued. These experiences taught James that good vehicle design required up-front consideration of testing and operational factors, with a design that incorporated sufficient instrumentation.22
As problems mounted, in November 1953 the army proposed to assign a commanding officer to JPL, a significant step toward turning it into a government arsenal. If the army wanted to control JPL, the trial balloon was ill-timed because it had little choice but to rely upon JPL to rapidly deploy Corporal. Although technical problems reduced JPL’s credibility, the urgency of speedy deployment weakened the army’s position even more. Army Ordnance backtracked and in 1954 gave JPL even more responsibility for Corporal. Because JPL was the only organization capable of making the missile work, army officers had little choice.23
The best efforts of JPL and the army improved Corporal’s reliability to an estimated 60%, the best achievable with its inherent design deficiencies. This left serious doubts as to its utility.24 Corporal’s real value was that it trained the army and JPL how to, and more importantly, how not to develop a missile. From this experience, JPL’s leaders recognized that academic, ad hoc design methods and loose organization were not sufficient to create an operational weapon. They vowed that on the next project, they would not repeat these mistakes.