Oberth already suggested using liquid fuels for rock­ets in the 1920s in order to achieve a higher dis­charge speed than with solids. In 1931 Paul Hey­landt devel­oped a 20 kg thrust engine for the HWA under Karl E. Becker, which was powered by liquid oxygen (LOX) and alcohol. In 1932 Nebel, Riedel and von Braun were also working with liquid oxygen on the rocket airport in Berlin-Tegel, and combined it with gasoline.

Apart from to the combination of LOX and etha­nol and/or gasoline, Wahmke was alternatively test­ing hydrogen peroxide as an oxidizer at Schumann’s institute. In cooperation with the institute, Hellmuth Walter (Walter Werke, Kiel) was also doing research with a hydrogen-peroxide-alcohol engine.

Thiel was a chemist, and he was hired by Schu­mann’s institute to do research on fuels. He accompa­nied the doctoral candidate Seifert, who was working on the process of combustion of the 20-kg engine built by Heylandt: “Bericht über Unter­su­chungen über die Eignung verschiede­ner Kraft­stoffe als Brennstoff für das Rauchspurge­rät II”. Here, the LOX/fuel, LOX/butane, LOX/benzene and LOX/varol combina­tions were analyzed. Thiel uti­lized the results of these tests later after he joined Dornberger in Kummersdorf West.

Thiel realized very early that the fuel used in Kum­mersdorf West, a mixture of LOX and alcohol, was not ideal. The boiling point of oxygen is -183°C. It was difficult to keep this low temperature, the oxi­dizer evaporated easily and the tanks had to be well insulated. Another disadvantage was the icing of rocket components that came into contact with the liquid oxygen. Furthermore, the non-hypergolic fuel needed some kind of ignition. This, for example, came as a glow igniter with a platinum-iridium alloy in 1938. Later, rubidium was used.

A report from 1938 shows that next to the known fuel components, research was also done on an Aurol oven. Aurol was a cover-up name for T-material (T-Stoff), also called H2O2 (see table).

The exploration of new fuels experienced a real boost by the employment of many new scientists in 1940, among them the chemist Gerhard Heller. Both Heller and Thiel wrote many reports on the enhanced com­bination of fuels respective patents.

For example, in 1941 they formulated the follow­ing: “a) Contrary to common belief, liquid oxygen is not the most effective, instead it is tetra-nitro-me­thane, nitric acids and nitrogen tetroxide. The impact of its higher density is that great, that its lower out­flow speed… is more than compensated. … d) Among the listed fuel combinations are the combina­tions tetra-nitro-methane-hydrocarbon (diesel, gaso­line, ben­zine) and nitric acid-hydrocarbon.

Next to the A4 engine, Thiel and his crew were working on other projects: A8, A9 (A4b or glider), A10 and on the anti-aircraft missile “Wasserfall” (Waterfall) C2.

As early as 1941, Thiel had made suggestions for a 180-t engine for the A10. He considered the fuel components liquid oxygen and ethanol to be already outdated. The basis was a mixture of “Salbei” (sage) and gasoil (see table).

The C2 was supposed to have hypergolic (self-ig­nit­ing) fuels. Thiel and Heller marked SV-material and visol (a combination of vinyl ether and aniline with a solvent iron compound) as fuels. The re­search team on the “Wasserfall” rocket included a namesake of Thiel: it was Adolf Thiel, a later member of the pa­perclip team. They were not related. Adolf Thiel worked at the Technical University Darmstadt with Prof. Walther on the “Wasserfall” rocket.

For security reasons, the fuel components were given code names. The following list shows the used ex­pressions and a selection of components:


Thiel’s professor in inorganic chemistry at the Tech­nical University of Breslau, Prof. Ruff, discov­ered monochloramine fluoride (CIF) in 1929 and synthe­sized additional and previously unknown fluo­rides, e.g. C3, chlorine trifluoride (CIF3), which was also called N-material (N-Stoff). C3 is a very strong oxidizer. In the early days there were considerations if it could be an addition for rocket fuels. Ruff had good con­tacts to Schumann and he was willing to collaborate with the institute in Berlin. A special production site for N-materials was set up in the for­ests around Falkenha­gen.

In 1942 Thiel received a phone call from Schu­mann, who asked him to test N-materials in rocket fuels. Thiel ordered the Technical University Darm­stadt to test the N-materials for the use with gasoil and nitric acid. The results showed that the outflow speed in­creased by only 2%, which meant they did not have an advantage to the two-component sys­tem.There­fore, the N-materials were not considered by Peene­münde, in addition CIF3 was highly danger­ous, diffi­cult to handle, and it posed a health risk to the work­ers.

Next to the selection of fuels and oxidizing agents, their mixture ratio “m” was also an important re­search feature. Dipl. Ing. Dollkopf (Technical Uni­versity Stuttgart) researched performance improve­ments of the A4 by applying different fuel mixture ratios. He discovered that there were no improve­ments between m = 0.8 and m = 1.So Thiel fixed the mixture ratio at m = 0.8 on February 2, 1943.

Nuclear propulsion seemed to become another inter­esting form of rocket propulsion. In August 1941 Thiel and von Braun requested an appointment with Schumann in order to receive monthly updates on the research development in this area. One of Schu­mann’s numerous positions included the presidency of the Uranverein (uranium club). However, the uranium program could not guarantee short-term success due to dwindling resources, and so this pro­gram remained a project for the future. 

In March 1943, Thiel wrote to von Braun from the office in Friedrichshafen/Bodensee, and he once again explained the problems of the current liquid oxygen/alcohol fuels: “…but I would never start again with liquid oxygen, if we had a new device today. The experience we are gaining now with sage and self-igniting materials with C2 are excellent.” During his absence (Thiel took a cure vacation) Hel­ler had to research on the possibility of a hypergolic oxygen-spirit mixture, Püllenberg had to work on a catalytic destroyer.

At the end of the day Thiel had no other choice than succumb to the targets of the Wehrmacht and the demands of war. The A4 went into production with liquid oxygen and ethanol technology. All other fuels would not have been available in sufficient quantities during wartime, and they would have made altera­tions on the engine necessary.

Years later the research of Thiel and his team were continued in the U.S. and the Soviet Union, e.g. the Jupiter rocket used a high-molecular fuel – kero­sene. The Saturn V – the rocket to the moon – was powered by hydrogen and oxygen.