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

rocket. During launch, one of the four

Viking Vikings were seafaring people originally from Scandinavia (present-day Denmark, Norway, and Sweden), who from the late 8th to the late 11th centuries raided, pirated, traded, and settled throughout parts of Europe.Roesdahl, pp. 9� ...

engines on the first stage developed a combustion instability which led to an engine fire, subsequent explosion and destruction of the vehicle. Following this event and starting with

Ariane 2 Ariane 2 was a European expendable space launch vehicle, operated by the European Space Agency (ESA) between 1986 and 1989 as part of Ariane family of rockets. The principal manufacturer for the Ariane 2 was Aérospatiale, while the lead agen ...

, the fuel was changed from pure UDMH to the mixture UH 25. UH 25 was used in Ariane rocket versions 2 through 4, and in the Indian GSLV Mk III. UH 25 is a mixture of 75%

UDMH Unsymmetrical dimethylhydrazine (abbreviated as UDMH; also known as 1,1-dimethylhydrazine, heptyl or Geptil) is a chemical compound with the formula H2NN(CH3)2 that is primarily used as a rocket propellant. At room temperature, UDMH is a colorle ...

and 25%

hydrazine hydrate Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly hazardous unless handled in solution as, for example, hydraz ...

.Tim Furniss: ''Ingenieure bei der Arbeit, Raumschiffe und Raketen'', Tessloff Verlag, Nürnberg (1989), Seite: 31 (German) It is

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. The ...

with

dinitrogen tetroxide Dinitrogen tetroxide, commonly referred to as nitrogen tetroxide (NTO), and occasionally (usually among ex-USSR/Russian rocket engineers) as amyl, is the chemical compound N2O4. It is a useful reagent in chemical synthesis. It forms an equilibrium ...

as oxidizer, and both can be stored as liquids at room temperature.

Danger

Like its components, UH 25 is flammable, toxic (carcinogenic) and corrosive.

Safety labels

References

This Article has been based on a translation of the Article UH 25 from the German-speaking Wikipedia in the Version from February 9, 2006 13:01 CET. A List of the main Authors (History) in accordance with GNU FDL i
here

Danger

Safety labels

See also

References

Further reading