The Viking rocket engines were members of a series of

bipropellant The highest specific impulse chemical rockets use liquid propellants (liquid-propellant rockets). They can consist of a single chemical (a monopropellant) or a mix of two chemicals, called bipropellants. Bipropellants can further be divided into ...

engines for the first and second stages of the Ariane 1 through Ariane 4 commercial launch vehicles, using storable,

hypergolic A hypergolic propellant is a rocket propellant combination used in a rocket engine, whose components spontaneously ignite when they come into contact with each other. The two propellant components usually consist of a fuel and an oxidizer. T ...

propellants: dinitrogen tetroxide and

UH 25 UH 25 is a fuel mixture for rockets. It was developed for the European Ariane 2–4 launch vehicles. UH 25 was developed after a disaster during flight 2 of the Ariane 1 rocket. During launch, one of the four Viking engines on the first stage deve ...

, a mixture of 75%

UDMH Unsymmetrical dimethylhydrazine (UDMH; 1,1-dimethylhydrazine, НДМГ or codenamed Geptil) is a chemical compound with the formula H2NN(CH3)2 that is used as a rocket propellant. It is a colorless liquid, with a sharp, fishy, ammonia-like smell ...

and 25% hydrazine (originally

). The earliest versions, developed in 1965, had a sea-level thrust of about 190 kN. By 1971, the thrust had improved to 540 kN, with resulting engine named Viking 1 and adopted for the Ariane program. The engine first flown on the

Ariane 1 Ariane 1 was the first rocket in the Ariane family of expendable launch systems. It was developed and operated by the European Space Agency (ESA), which had been formed in 1973, the same year that development of the launcher had commenced. A ...

rocket in 1979 was Viking 2, with thrust further improved to 611 kN. The version used on the

Ariane 4 The Ariane 4 was a European expendable space launch system, developed by the '' Centre national d'études spatiales'' (CNES), the French space agency, for the European Space Agency (ESA). It was manufactured by ArianeGroup and marketed by Ari ...

first stage, which used a cluster of four, had 667 kN thrust each. The second stage of Ariane used a single Viking. Over 1000 were built, and achieved a high level of reliability from early in the programme. The 144 Ariane 1 to 4 launchers used a total of 958 Viking engines. Only two engines led to a failure. The first failure (on second Ariane 1 flight 23 May 1980) was due to a chamber combustion instability. The vehicle had lost an attitude control and broke up. Several injector changes were implemented in the aftermath of the failure, and the fuel was changed from

. The second failure was of human origin: a rag had been left in a water coolant pipe during installation, resulting in a loss of thrust and vehicle breakup due to off-centre thrust during launch on 22 February 1990. Initially, all the engines were tested before being integrated on a launcher. Beginning in 1998, engineers, confident of the reliability of the engine, authorized the use of untested engines on launchers. One engine per year was tested, randomly taken from the assembly workshops. This confidence is very rare in the world of space engines. An unusual feature of the Viking engines is their water tank and water pump, used to cool the exhaust gasses of the gas generator. The hot exhaust of the gas generator is cooled by water injection to 620°C before being used to drive the three coaxial pumps (for water, fuel and oxidizer) and to pressurize the fuel tanks. The water was also used as a hydraulic fluid to actuate the valves.George Paul Sutton, "History of Liquid Propellant Rocket Engines", p. 799

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References

External links

Vernon, French manufacturer's history site. {{DEFAULTSORT:Viking (Rocket Engine) Rocket engines using hypergolic propellant Rocket engines using the gas-generator cycle

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External links