The German OTRAG launch vehicle family is a planned launch vehicle family which was optimized for a low launch price, at the expense of complex technology or a low launch mass. It's history is closely linked to the engineer Lutz Kayser.
The creation of the OTRAG
Lutz Kayser worked as a teen already on rockets and later studied aerospace engineering as student of Eugen Saenger at the Stuttgart University. He is member of the German Association for space research (GfW) since 1954. He likely adopted the clustered rocket concept from O. Lutz, Dadieu and Wolfgang Pilz, who in turn learned the clustered rocket concept from the works of J. Winkler, published between 1928 and 1930. Winkler's concept described a cluster of multiple identical units of 10 tons thrust.
Lutz Kayser was a member of a student group of spaceflight-interested individuals, which was supported by Irene Saenger-Bredt, the wife of Eugen Sänger. Kayser developed rocket engines on the yard of his father's house, who was director of the Südzucker AG. He owned a 5m tall test stand there.
In the summer of 1971, the German government tasked four companies to find a cheaper alternative to the Europa IIIB rocket, which later developed into the Ariane 1 launch vehicle. The new rocket should have been cheaper than the Europe II rocket, and should not exceed the 2 billion DM R&D costs of the Europa III rocket. Among the established aerospace companies ERNO, Dornier and MAN, the forth research contract went to the start-up company Technologieforschung GmbH. This company was founded by Lutz Kayser in 1971. Each of the research contracts was worth 250,000 DM. The Dornier proposal, where Kayser's brother worked, was never released to the public.
The concepts of ERNO and MAN predicted R&D cost savings of 10-20% by reusing parts of the Europa rocket. The proposal of the Technologieforschung GmbH was on the other hand a radical new concept: The launch vehicle should consist of six modules in the first stage. Each module was having 36 rocket engines, using Kerosine and Nitric Acid as propellants. The second stage was a single module with 36 engines. Control in the yaw and pitch plane would happen by throttling the outside engines.