Michael Neufeld - The Rocket and the Reich

Although the creation of a truly cooperative and skilled workforce was impossible in the conditions of slavery, and many technical issues remained troublesome, by the end of the summer the production problems had largely been solved, and the missile was ready to be deployed. Six more months had been lost, however, including delays caused by the airbursts. In addition, the first half-year’s production had been used up in testing, and consistent monthly output totals could not be sustained. After delivering 253 missiles to the Army in April and 437 in May, Mittelwerk shipped only 132 in June and 86 in July. That uneven record reflected not only stoppages because of the airburst question but also political interference due to the failure of the A-4’s promoters to deliver on their promises. Kammler’s position in the Fighter Staff enabled him to secure the use of the first twenty cross tunnels of the Mittelwerk for the production of aircraft engines by the Junkers company. The Mittelwerk had to compress all its facilities into tunnels 21–46 starting in May or June, disrupting production. 71

A further problem was that Hitler became infatuated with the V-1, which, after months of delay, was first launched against London on June 13, a week after the Allies landed in Normandy. Although the “buzz-bomb” campaign got off to a weak start, the Luftwaffe soon began firing hundreds of cruise missiles a week across the Channel, with a significant short-term impact on the morale of a war-weary British population. Later that month the delighted Führer told Speer to cut back A-4 production to 150 a month in order to put more resources into V-1 manufacturing. By late August, however, it became clear that this weapon had failed to change the course of the war. The Führer put renewed emphasis and hope on the A-4 (V-2). Afterward, from September 1944 through February 1945, Mittelwerk hit its stride, assembling six hundred to seven hundred missiles a month, or more than twenty a day. In early September the first A-4s were fired in anger. The ballistic missile had finally become a weapon. 72

While Peenemünde struggled to make the A-4 work, the center also became increasingly preoccupied with the anti-aircraft missile program. In August 1944, 1,116 employees were working on Wasserfall, nearly a quarter of those in development. Moreover, that figure may not have counted the many top people, starting with Wernher von Braun, who had been giving a significant fraction of their time to the interservice project since early 1943. Although Wasserfall is often treated as a footnote to the A-4 story, it was the second principal task of the Army rocket center in the last two years of the war. It was also a project that showed, perhaps even more clearly than the A-4, how the growing desperation of the Third Reich’s leadership led to self-delusion and to the squandering of crucial resources on weapons that had no chance of altering the course of the war. 73

After Göring’s approval of anti-aircraft missile development in September 1942, Ordnance had begun to design a small solid-propellant rocket (the C-1) with a range and maximum altitude of 20 kilometers (65,000 feet), and a larger liquid-fueled one (the C-2) with the same ceiling but a 50-kilometer range. The C-1 was quickly dropped by the Luftwaffe, probably because it overlapped with the work of the Rheinmetall-Borsig firm on a two-stage, solid-propellant anti-aircraft missile called Rheintochter (Rhine Maiden). Peenemünde was left with the C-2, which received the name Wasserfall no later than March 1943. In order to save development time and wind tunnel testing, the Army had always specified an external shape based upon the A-4. In the spring and summer of 1943, the missile emerged from the drawing boards of Ludwig Roth’s Projects Office, which was now simply a Wasserfall design bureau. The missile would be 8.9 meters (28.5 feet) high, with a maximum diameter of just under a meter, and it would be powered by an engine of 8 metric tons thrust, about one-third that of the A-4. 74

There were only two obvious external differences between the Wasserfall and its precursor. First, in order to provide increased maneuverability—a quality unnecessary in a ballistic missile—the anti-aircraft missile received four wings in a cross-wing configuration. As originally laid out by Roth’s section, the wings were straight rather than swept back, but Hermann’s wind-tunnel group demonstrated by mid-1943 that this design was unsatisfactory: the aerodynamic center of pressure moved toward the tail at supersonic velocities, making the missile too stable and therefore too hard to maneuver. By a combination of perceptive guesswork and trial-and-error testing, the aerodynamicists were able to come up with an effective design before the evacuation of the wind tunnels began in October 1943. The new wings had a backward sweep along their leading edges and were set farther back on the body, with the impressive result that Wasserfall’s center of pressure did not wander much in relation to its center of gravity, even as velocity increased from zero to Mach 3. The second noticeable difference between the A-4 and Wasserfall was the much enlarged air vanes on the bottom of the tail fins. Although Wasserfall also had jet vanes in the rocket exhaust, the air vanes would play a much larger role, because the missile would continue maneuvering toward its target even after engine burnout. A ballistic missile, by contrast, coasts unguided after cutoff. 75

Internally, Wasserfall incorporated a number of lessons from the A-4 program. In order to simplify the missile, permit the long-term storage of propellants in the tanks, and eliminate the problems of manufacturing alcohol and handling liquid oxygen, the engine would use a combination of a nitric acid oxidizer and a hydrocarbon fuel called Visol (vinyl ethyl ether). With additives, the two propellants were hypergolic, that is, they ignited on contact, eliminating the need for a pyrotechnic igniter. Wasserfall’s engine also had a single injector plate instead of multiple “pots.” In addition, the missile’s tanks were integral to the main body, avoiding the A-4’s structural framework inside the skin. Peenemünde had chosen that design in 1939 out of engineering conservatism; not enough was known at the time about the forces that would be exerted on the ballistic missile’s structure. That margin for error proved useful, however, in making the A-4 a weapon that could survive rough handling in the field. 76

The stresses of military deployment were naturally a consideration for Wasserfall too, but its integral tank structure could more easily bear higher loads, because von Braun’s engineers had decided to return to pressure-fed engines. As in the A-5 and earlier rockets, compressed nitrogen would force the propellants into the combustion chamber, making the missile simpler and more capable of prolonged storage in the field; the complicated turbopump/steam-generator system could be eliminated. The number of valves would be reduced as well by employing special bursting membranes that would be blown open when a charge was fired to open the nitrogen tank. In principle, the triggering of the charge would result in the automatic opening of the pipelines to the engine, followed by ignition and liftoff.

The preliminary design phase, through the year 1943, thus went fairly well. Pursuant to it request by von Braun and his engineers, who had learned a lesson from the troubled history of the A-4 and the Peenemünde Production Plant, the missile was also made easier to manufacture by bringing the advice of an experienced firm into the project. At the May 1943 “comparison shoot,” Field Marshal Milch announced that Henschel, which had built rocket-assisted glide bombs and was designing its own anti-aircraft missile, the Schmetterling (Butterfly), would act as a consultant. By autumn Henschel designers were able to suggest useful modifications that would facilitate mass production. 77