Born: 1903-01-23. Died: 1974-11-16.
Riedel headed rocket engine development at Peenemuende after the death of Thiel in 1944 and was Director of the Development Facility at Karlshagen. By January 1947 he was working with von Braun's team at Fort Bliss, Texas, brought there under Project Paperclip. However Riedel did not get on with von Braun, and was leader of several rocket team members taken on by North American later that year. There he played the key role in the transfer of German rocket engine technology to the United States. In 1947-1951 the planned single-chamber version of the V-2 engine was developed and updated by the combined German-American team for the Navaho cruise missile. This engine was also applied to the Redstone ballistic missile, and its descendants powered the Thor, Jupiter, Atlas, and Saturn I rockets.
In late 1951 several scientists, aeronautical engineers and interested persons established a UFO study group in California. Edward J. Sullivan, a North American Aviation employee, was the spark plug of the organization. Riedel was another prominent member. A denunciation of Riedel as a Nazi by another North American employee, Victor Black, led to an interview by the CIA in February 1953. Riedel later returned to Germany and died at Hamburg.
The production series of V-2's are exploding in flight, and the engineers cannot determine the reason. Peenemuende engineers sought to recover 30% of the missiles for detailed examination. This showed that re-entry heating did not weaken the missile's structure. There was no scorching of the 0.6 mm thick paint applied to the interior of the missile. Only the outer paint showed signs of scorching. The missile still suffered in-flight explosions - attributed to the re-entry heating of 480 deg C and residual propellant vapours that still escaped despite the better sealing. Dornberger thought the liquid oxygen tank was the problem, while Von Braun suspected the alcohol tank. To try to determine the cause, five V-2's were shot with the engine running until all of the alcohol was depleted. These were followed by six shots with improved glass wool insulation of the liquid oxygen tank, over the objections of Riedel III, head of manufacturing at Peenemuende. Three of these shots were made in one morning, and all went off course. These were in turn followed by a series of highly instrumented launches from Peenemuende. The improvements developed as a result of these tests improved the missile reliability from 30% to 70% immediately, and then the reliability slowly increased to 80% as additional changes were made. Only in the last months of the war was it found that the forward part of the outer hull was failing in flight. Once this was strengthened with a belt of sheet metal, the V-2 achieved essentially 100% reliability.
This entire process was going on while production was ramping up at the underground facility at Mittelwerk. There was pressure from the highest quarters to get the missile fielded and attacks on England underway. Every change resulting from these tests and research meant that the production line at Mittelwerk had to be stopped, and retrofits made to undelivered missiles.