Specific impulse
Specific impulse (abbr. isp) was a measurement for rating the performance of a rocket engine. This measurement gives information on the number of pounds or kilograms of thrust that are derived from the consumption of a pound or kilogram of propellant in one second. 

The semi-solid propellant  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. ()

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Measurements