How would you go about instrumenting and measuring the impulse provided by a rocket engine?

Question

Sigiloso · Accepted Answer

Measuring the exit velocity is not needed. Measure the thrust profile i.e. use a load cell to determine the engine's thrust as a function of time. Numerically integrate that to get total impulse.  To obtain specific impulse, divide the total impulse by the weight of the propellant (propellant mass times g).

Sigiloso · Answer

Fthrust = Isp*mass_flow_rate*g0

mass_flow_rate = density*area*velocity

Solve for Isp with unknowns collected from the test.

Set rocket engine up in a static test stand, and measure thrust. Also need to measure velocity at exit, all other variables should be known from fuel type and engine nozzle dimensions.

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