Michael Neufeld - The Rocket and the Reich

The failure of the A-3s thus confirmed and strengthened the trend that had begun in 1936. If breakthroughs in the key technologies were needed to build something as revolutionary as a ballistic missile, the rocket program would have to spend much more money and build much more in-house expertise. But the A-3s were the epitome of what von Braun later called “successful failures” in the rocket business. So much had been learned from this experience that, given the highly favorable political and budget climate of the late 1930s, the technical obstacles could almost certainly be overcome. In the years between 1936 and 1941 the Army Ordnance group would do precisely that.

Notwithstanding the important advances the Army group had made in the A-3 and rocket aircraft programs, the technological challenge of the A-4 remained gigantic. The engine would have to be seventeen times more powerful than the largest rocket motor so far constructed; the missile would have to fly at nearly five times the speed of sound when no Ordnance rocket had even approached the sound barrier; and the vehicle would have to be guided to targets nearly 300 kilometers away, when no liquid-fuel rocket built by the Germans had ever traveled more than a few thousand meters vertically. The A-3 failures only underlined how far away the engineers were from solving the guidance and control problem in particular. Yet by late 1941 Peenemünde had in its possession the technologies essential to the success of the A-4, and the first versions of that rocket were on the test stand.

The foundation for that remarkable technological achievement was Ordnance’s ability to mobilize money, manpower, and matériel for the ballistic missile project—something it was able to do because of the high priority placed on rocketry by the Army High Command. Access to resources alone, however, did not automatically lead to the dramatic breakthroughs necessary for the A-4. Under the leadership of Becker, Dornberger, and von Braun, the liquid-fuel program had to expand its engineering staff greatly, put innovative leaders at the head of critical projects, and gain control over additional research capability in universities and corporations. The research process itself had to be altered so that trial-and-error testing was replaced, where possible, with a more scientific and theoretical approach, although that became apparent only over time. The result, especially after the A-3 guidance failures, was to accelerate further the growth of the large government laboratory at the heart of Peenemünde-East. At the beginning of 1938 the facility had 411 employees. By September 1939 that number had tripled. 1Although no figures are available for late 1941, the number of people in development (as opposed to the new A-4 Production Plant) must have nearly tripled again to at least three thousand engineers, craftsmen, and office workers. With that vastly expanded staff came a corresponding increase in the facilities and materials available for research and testing.

While access to additional university and corporate laboratories was essential to the project, the massive buildup of in-house research and development capability was a critical factor in Peenemünde’s success. It was not enough to attract highly talented engineers who could produce fundamentally new ideas, nor did it suffice to have those individuals led by excellent managers like von Braun and Dornberger. Only the possession of a lavishly funded and staffed organization allowed the rocket group to create working technology in a very short time. Dornberger’s in-house or “everything-under-one-roof” philosophy made a further contribution by fostering internal communication and increasing efficiency. In combination, these assets and strengths gave Peenemünde mastery, in only five years, of the three technologies key to the A-4’s success: large liquid-fuel rocket engines, supersonic aerodynamics, and guidance and control.

Walter Thiel’s transfer to the rocket section toward the end of 1936 was a milestone on the road to the ballistic missile. Within months his analytical and scientific approach would result in a reconsideration of the entire direction in which engine design had been proceeding under Walter Riedel and Wernher von Braun. Their 1,500-kg-thrust motor, the one that powered the A-3 and the A-5, was a big step forward in size and efficiency, but it was taking the Ordnance group down a deadend road. Based on practical experience and the limited theoretical calculations in von Braun’s 1934 dissertation, Kummersdorf’s engines had become longer and longer. That had been done to give fuel and oxidizer droplets enough time to evaporate, mix, and burn properly. But the 25-ton engine threatened to become completely unwieldy, and the efficiency of combustion in the 1,500-kg motor still left something to be desired. It was significantly below the target performance—an exhaust velocity of about 2,000 m/sec—that would be needed to get the most out of the chosen combination of alcohol and liquid oxygen at a combustion chamber pressure of 10 atmospheres. 2

Thiel, a pale, dark-haired, intense individual in horn-rimmed glasses, fitted one of the stereotypes of the German scientist of the Nazi period. He was loyal to the regime but too focused on his work to be very political. As far as is known, he never joined the Party. In the style of the German university professor, he could be authoritarian and arrogant to his subordinates. He was also high-strung and subject to episodes of depression when under stress; Dornberger and von Braun had to smooth over many conflicts. But Thiel brought to the rocket group a doctorate in chemical engineering, keen theoretical insight, tremendous ambition, and an imaginative mind. As Wahmke’s replacement in the research section, he had been a consultant to Hellmuth Walter, had experimented with hydrogen peroxide engines in the laboratory himself, and had supervised a graduate student working on the fundamental processes of combustion in a Heylandt 20-kg-thrust motor. 3

Thiel’s initial program in early 1937 continued to focus on basic research into all areas of rocket propulsion, including exotic propellants like liquid hydrogen. He also outlined ambitious plans for cooperation with academic institutes in developing more heat-resistant metal alloys, a better theory of combustion, and more thorough temperature and composition measurements of burning exhaust jets. Thiel was forced, however, to depend on Ordnance’s own resources at Kummersdorf and Peenemünde. Although von Braun’s group had been working with two or three academic institutes in aerodynamics and measuring techniques since 1935–36, the Army’s obsession with security kept contacts with research institutions to a minimum before the outbreak of World War II. 4Ordnance’s goal was to develop and produce a ballistic missile in the deepest secrecy and then to use it without warning during a war. For any hint of the German rocket program to reach the outside world not only would ruin the effect of surprise but might also encourage other powers to pursue the technology more intensely. Virtually all proposals for contracting research outside Ordnance were therefore rejected to minimize the danger of security leaks.

Despite that handicap, in 1937–38 Thiel came quickly to four of the innovations that would make an efficient 25-ton-thrust motor possible. The first was an injection system that greatly improved the atomization and mixing of the two propellants. The 1,500-kg engine had used a modification of the old Heylandt system, with a mushroom-shaped injector extending down from the top of the motor, spraying watered alcohol upward toward the liquid-oxygen injectors. Dornberger claims the credit for having suggested small “centrifugal” nozzles that tended to atomize propellant droplets more completely, while spraying them outward in a rotational motion that produced better mixing. Thiel promptly began working with the Schlick firm, which produced the nozzles. By July 1937 he had demonstrated that fitting an injector with centrifugal nozzle holes to a 1,500-kg motor produced an immediate increase in exhaust velocity from 1,700 to 1,900 m/sec. A higher exhaust velocity meant a more efficient use of propellants and also improved the steering forces of the jet vanes by up to 20 percent. 5