Specific impulse (abbr. isp) was the parameter for rating the performance of a rocket engine. This parameter gives information on the amount of pounds or kilograms of thrust are derived from the consumption of a pound or kilogram of propellant in one second.
The semi-solid propellant Moyerite (Synthetic) and the hypergolic propellant Gronerium compound 3983 had a low specific impulse of 450 isp. These propellants was used in ullage thruster devices and emergency jettison thrusters. (TNG: "Night Terrors")