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Tetrahydromethylcyclopentadiene dimer.png
IUPAC name
Other names
Tetrahydromethylcyclopentadiene dimer; Tetrahydrodimethyldicyclopentadiene; THDMDCP; RJ-4; RJ4
ECHA InfoCard 100.045.638
Molar mass 164.29 g·mol−1
Density 0.915 g/cm3
Flash point 60 °C (140 °F; 333 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

TH-dimer, also called tetrahydromethylcyclopentadiene dimer[1] or RJ-4, is a liquid rocket propellant used in missiles and jet engines. For example, TH-dimer is used in the turbofan engine of the Tomahawk (missile) cruise missile. It is also a component of the jet fuel JP-9.

The fuel is non-volatile so it is safe to use on ships or submarines. It has a high flash point minimum of 60 °C.[2]

Chemically, TH-dimer is a mixture of isomeric saturated hydrocarbons derived from hydrogenation of the dimer of methylcyclopentadiene.[3]


  1. ^ Naval Submarine Base New London
  2. ^ Modern US Military Turbine Missile Fuel Specifications
  3. ^ US 4177217, Janoski, Edward J.; Mitchell, Richard E.; Schneider, Abraham, "Continuous conversion of dimethyldicyclopentadiene to endo-dimethyldicyclopentadiene, a missile fuel", issued 1979