The OTRAG rocket was a West German modular satellite-delivery rocket developed by the OTRAG company (German: Orbital Transport- und Raketen-Aktiengesellschaft, or Orbital Transport and Rockets, Inc.) in the 1970s and 80s. The OTRAG rocket was to become a rocket built up from several mass-produced units, intended to carry satellites with a weight of 1-10 tons or more into orbit. Mass production meant that the vehicle was projected to have been 10x cheaper than conventional vehicles of similar capability. OTRAG was based in Stuttgart, and in the late 1970s and early 1980s planned to develop an alternative propulsion system for rockets. OTRAG was the first commercial developer and producer of space launch vehicles. The rocket was claimed to be an inexpensive alternative to existing launch systems through mass-production of Common Rocket Propulsion Units (CRPU).
Rocket design
OTRAG was a design quite different from conventional multistage rockets. The OTRAG design used parallel stages assembled from parallel tank tubes with flat bulkheads. The rockets were designed to carry loads up to two tons, the then usual weight of a communications satellite, into a geostationary orbit. It was planned to later increase the capacity to ten tons or more using multiple identical modules. The rocket was to consist of individual pipes, each 27 cm in diameter and six meters long. Four of these pipes would be installed one above the other resulting in a 24 meter long fuel and oxidizer tank with a rocket engine at the lower end making up a CRPU. The fuel was intended to be kerosene with a 50/50 mixture of nitric acid and dinitrogen tetroxide as an oxidiser. Ignition was provided by a small quantity of furfuryl alcohol injected before the fuel, which ignites hypergolically (immediately and energetically) upon contact with the nitric acid. To simplify the design, pumps were not used to move the fuel to the engines, instead the fuel tanks were only 66% filled, with compressed air in the remaining space to press propellants into the ablatively cooled combustion chamber. Thrust control is by partially closing the electromechanical propellant valves. Pitch and yaw control can thus be achieved by differential throttling. In principle this is extremely reliable and cheap in mass production. The modular design was intended to result in a large cost reduction due to economies of scale. The CRPU-based satellite launching rocket was estimated to cost approximately one tenth of conventional designs. Automated production processes for all components would reduce labor cost from 80% to 20% and remove the justification for reusability of spent stages. One large 4 stage configuration OTRAG 10K was supposed to launch a payload of 10,000 kg to a 185 km Orbit. The planned liftoff thrust was around 26 MN with a total mass of 2,300 tonnes:
stage 1 : 456 CRPU stage 2 : 114 CRPU stage 3 : 48 CRPU stage 4 : 7 CRPU
Flight history The engines were tested extensively on ground rigs, on both German and African test sites. Experiments were run with varying fuel and oxidiser formulations, as the general design was quite robust. Small, 4-unit vehicles were built and tested several sites: Shaba North in modern Democratic Republic of the Congo and Seba Oasis, Libya. The rockets used were 6 and 12 meters long, and obtained heights of 20 to 50 kilometres. The basic CRPU concept was shown to be workable, though some rockets experienced guidance or component failures. The last launch of an OTRAG rocket took place on September 19, 1983, at Esrange. Following this launch, the OTRAG rocket was to be used in high altitude research. Political pressure then shut down the project, as discussed in the OTRAG article. After the company had left Libya in 1987, some remaining equipment was confiscated by the government. However, enough parts and knowledge were missing to prevent Libya from continuing the project.
Corporate history
OTRAG was founded on October 17, 1974 by German aerospace engineer Lutz Kayser. OTRAG's goal was to develop, produce, and operate a low-cost satellite launch vehicle. It was the first private company to attempt to launch a private spacecraft. The OTRAG rocket was intended to be an inexpensive alternative to the European rocket Ariane and the NASA Space Shuttle. Kayser and a private consortium of six hundred European investors financed the development and production of the OTRAG satellite launch vehicle. Dr. Kurt H. Debus served as Chairman of the Board of OTRAG (1974–1980) after his retirement as director of NASA's Kennedy Space Center, and Dr. Wernher von Braun served as scientific adviser to Kayser. In the face of doubts by Debus and von Braun, Kayser chose in 1975 to set up testing and launch facilities in Shaba, Zaire (now Katanga Province, Democratic Republic of the Congo). Debus and von Braun were concerned about the possibility of Zairian acquisition of missile technology from the facilities. Kayser decided to proceed despite their opposition. Otrag's first test was on May 17, 1977, with the second successful launch on May 20, 1978. The third test, 16 days later, failed on June 5, 1978, with Zairian President Mobutu Sese Seko watching the launch. Political pressure to halt the company's operations mounted quickly. France and the Soviet Union were historically opposed to German long-distance rocket development and pressured the Zairian government into closing down the development facility in 1979. Immediately afterwards, Presidents Giscard d'Estaing of France and Leonid Brezhnev of the Soviet Union convinced the West German government to cancel the OTRAG project and close down its German operations. In 1980, OTRAG moved its production and testing facilities to a desert site in Libya. A series of successful tests was conducted at this site beginning in 1981. OTRAG shut down in 1987. As the company left Libya, Muammar Gaddafi confiscated all equipment and installations, hoping to later use the technology, and German investors lost their money.
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