What is "syntin"

Syntin is a hydrocarbon with the molecular formula CH used as a rocket fuel. It is a mixture of cis and trans isomers. It has a density of 0.851 g/mL, and a boiling point of 158 °C. Due to the presence of three strained cyclopropane rings, the molecule has high positive enthalpy of formation: ΔH°(l)= 133 kJ/mol (980 kJ/kg, the average value for the isomeric mixture), bringing additional energy during the combustion process. Thus, it has advantages over the traditional hydrocarbon fuels, such as RP-1, due to higher density, lower viscosity and higher specific heat of oxidation.

Syntin was used in the Soviet Union and later Russia in 1980s-1990s as fuel for the Soyuz-U2 rocket. It was first synthesized in USSR in the 1960s and brought to mass production in the 1970s. It was prepared in a multi-step synthetic process from common hydrocarbon sources:

After dissolution of the USSR, the production of this fuel became too expensive and was halted.