Off-Limit Testing of the Model R-4D 110 LBF (490 N) Bipropellant Rocket Engine

An off-limit hot fire test program was accomplished using the Aerojet production model R–4D 110 lbf (490 N) bipropellant rocket engine operating with MON-3 oxidizer and monomethylhydrazine (MMH) fuel. The purpose of the test program was to characterize the engines operational characteristics over a range of pulse mode duty cycles up to thermal equilibrium. These tests, over a wide range of pulse mode duty cycles, demonstrated the engines ability to safely operate at high heat load pulse mode duty cycles in the range of 590% and at thrust levels up to 125 lbf (556 N) which is significantly above the design level of 110 lbf (490 N.