OTRAG

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OTRAG
OTRAG CRPU

The OTRAG ( O rbital T ransport- and R aketen A ktien g ompany) was a German company that in the late 1970s and early 1980s to an alternative propulsion system for rockets worked. The company and its OTRAG rocket thus belong to the origins of non-state space travel .

development

The OTRAG rocket was supposed to represent an inexpensive alternative to the systems of the "Europe rocket" Ariane and the US space shuttle , which were still in the planning and development stage at the time . The rocket was developed by a private operator consortium (Orbital Transport und Raketen AG, Silent Society ). OTRAG was financed by numerous silent partners (1150 in 1978) to become a public limited company.

The project was headed by Lutz Kayser, a South German aerospace engineer . Kayser (1939–2017) was already engaged in rockets as a teenager, had studied aerospace engineering under Eugen Sänger at the Stuttgart University and had been a member of the Society for Space Research since 1954 . The board member was Kurt Debus , who was previously director of the Kennedy Space Center .

In 1971, Kayser founded Technologieforschung GmbH , which, along with ERNO, Dornier and MAN, was the fourth company to receive an order from the Federal Ministry of Research to develop an inexpensive alternative to the Europa III B rocket, which would later become the Ariane. The operation should be cheaper than the Europa II, while undercutting the development costs for the Europa III of DM 2 billion  . The company received a total of DM 4 million until 1974. After that, the ministry's attention turned to the Europa rocket.

concept

OTRAG relied on the concept of the bundle missile , which had already been proposed in the 1930s and also discussed in the Peenemünde Army Research Center . A missile should be built that should achieve the highest possible thrust with the simplest possible means . Technical parts of the concept, for example the radial injection method for rocket combustion chambers, were later brought to France by Wolfgang Pilz , where they were further developed in the Véronique and Ariane rockets .

In contrast to the launcher rockets that were widely used at the time and today, the rocket consisted of modular, nested propulsion tubes. At its tip, a carrier capsule of up to two - later planned: ten - tons, the weight of a common communications satellite at the time , could have been transported into a geostationary orbit .

This Common Rocket Propulsion Unit (CRPU) - in German "Uniform Rocket Engine Module" - was to be the basis for inexpensive medium and heavy launch vehicles for commercial and scientific payloads.

technology

The modules each represented individual liquid rockets and consisted of tubes that were three meters long and 27 centimeters in diameter. Eight of these pipes would be mounted on top of each other, held together by bayonet locks so that the launch vehicle would have used 24 m long tanks. The experimental rockets, on the other hand, only consisted of two and four tanks six and twelve meters in length, respectively. A separate engine was mounted under each tank, with a diameter of 27 cm and a length of one meter.

Kerosene and nitric acid in a volume ratio of 1: 3 were used as fuels ; one tank pipe was 66% filled with kerosene and the three above it with nitric acid. The ignition was carried out by a chemical initiator ( furfuryl alcohol ). The fuel was not delivered by pumps , as is usual with larger liquid rockets, but by electronically controlled ball valves , which could open and close the fuel tanks , which were under excess pressure . The overpressure in the tanks decreased from 40 bar at ignition to 15 bar at the end of combustion ( adiabatic pressure delivery ).

The engine consisted of a simple cylindrical combustion chamber with radial fuel injection . A graphite ring served as the nozzle neck, the initial opening width of which, to be selected in advance, regulated the starting thrust in a range from 5 to 50 kN. A coating made of phenolic resin and carbon fibers inside the rocket combustion chambers served as heat protection , which was aimed at burning during the burning time of 130 seconds ( ablative heat shield ).

Due to the relatively low-energy fuel combination, the relatively wide nozzle throat and the short nozzle, the specific impulse achieved was comparatively low. The information provided by OTRAG employees differ between 1,800 and 2,648 Ns / kg at 1 bar external pressure.

A 24 m long module with a one meter long engine weighed 1,508 kg, 1,130 kg of which was accounted for by the oxidizer nitric acid and 220 kg for the fuel kerosene. The curb weight was 153 kg, 65 kg of which was attributable to the engine and 88 kg to the tanks.

criticism

There was criticism of the concept as early as the 1980s. A study commissioned by the DFVLR (then the German Aerospace Agency) came to the conclusion in 1975 that the concept was not economical. Using the OTRAG information on the modules, Harry Ruppe calculated a significantly lower payload than stated by this, namely 3.6 instead of 10 tons. Lutz Kayser, on the other hand, assumed a significant increase in performance through a nozzle effect with many modules, without which the specific impulse and thus the payload was significantly lower. However, this effect was rejected as speculative by experts.

Test flights

A launchable orbital payload carrier consisting of up to 1024 propellant tube modules was never made. A total of 18 documented test starts with individual drive elements took place from Shaba North ( Zaire ), Camp Tawiwa ( Libya ) and Esrange ( Sweden ) (Zaire: 3; Libya: 14; Sweden: 1). OTRAG and Kayser announced conflicting data on the flights.

In 1976 OTRAG leased the 100,000 km² site in Zaire. OTRAG set up a launch site ( Shaba North ) on a steeply sloping cliff at a height of 1,300 m above sea level to test the commercial rocket OTRAG. A total of three test starts took place here:

  • The first launch took place on May 17, 1977 and was used to test the drive units. The six-meter-long rocket rose to a height of 12 km (above sea level) after the scheduled burn time of approx. 10.5 s.
  • The second launch took place on the night of May 20, 1978. This time, the rocket, which was extended to 12 m, reached a height of 9 km (above sea level). The premature burnout occurred s (planned 24 s) by damage to the just after 20 ablative protected combustion chambers.
  • A third start on June 5, 1978 in the presence of the head of state Mobutu Sese Seko turned out to be a serious failure. The 12-meter long rocket came off course when it left the launch frame and crashed into a nearby valley after a few seconds. Nevertheless, even decades later, Kayser described this attempt as a 50% success.

Due to political pressure from France, the USA, Germany and the Soviet Union , the lease was terminated in April 1979 and OTRAG had to leave Zaire.

On March 1, 1981, the German OTRAG Orbital Transport und Raketen AG started another missile test on the Camp Tawiwa test site in the sparsely populated Sahara near the Seba oasis in Libya . The missile failed about 22 seconds after takeoff. After that there were no more public reports from OTRAG about launches. Some of the staff was employed by the Libyan military to develop missiles for Libya until 1987. According to his own statements, Lutz Kayser refused to work with the military and had to leave OTRAG.

His successor Frank Wukasch tried to improve the tense relationship with the German government by launching sounding rockets. On September 19, 1983, the DLR took off from the Esrange launch site in Sweden, but the rocket was destroyed by a payload after about two thirds of the planned drive time. After that the funds were used up and the company was liquidated by the shareholders in 1986. After the “expropriation”, Lutz Kayser worked on solar thermal power plants in Libya for over ten years .

Political references

According to press reports from the early 1980s, the project contradicted US and European plans for an orbital transport system based on multi-stage missiles. Other reports again suspected an international distrust of a possible nuclear rearmament in the Federal Republic of Germany and that the neighboring states of Libya objected for this reason. The then Foreign Minister Hans-Dietrich Genscher is said to have finally stopped the project under pressure from France in order not to compete with the “Europe rocket” Ariane , which was co-financed by Germany , and to avoid political entanglements.

The Federal Fiscal Court finally denied OTRAG's intention to make a profit, and the company had to be wound up after the funds had been used up. According to his statements, constructions and documents for the development of Lutz Kayser were returned to him in accordance with the contract, while according to statements by his vice-president Frank Wukasch they were still the property of the shareholders of OTRAG.

Legal proceedings

After years of investigations, the Munich I public prosecutor's office charged businessman Walter Z. in December 2001 with delivering parts for rockets to Libya from 1991 to 1996, contrary to the UN trade embargo that has been in force since 1992, and violating the Foreign Trade Act (AWG). Two other people were also charged. Z. belonged to the group around Lutz Kayser and OTRAG in the 1970s. He was arrested in 1998 and later released on bail.

21st century

The private US aerospace company Armadillo Aerospace , which was founded in 2000 and which also took part in the Ansari X-Prize , took up the concept of modular cluster engines in collaboration with Kayser. In 2006 the company announced the further development of this technology into a suborbital missile.

literature

documentary

Web links

Commons : OTRAG  - collection of images, videos and audio files

Individual evidence

  1. ^ Sven Grahn: The last OTRAG rocket - launched from Esrange. Retrieved February 5, 2012 .
  2. ↑ June 2006 Armadillo Aerospace Update. ( Memento from March 3, 2016 in the Internet Archive )
  3. ↑ Fly, Rocket, Fly! at filmportal.de ; otrag.com , website for the film; official trailer , YouTube; accessed August 2, 2020.