I'm developing a mathematical model of model solid rocket engine

behavior. There's plenty of thrust/time curves available, but no

mass/time curves that I'm aware of for model engines.

Currently I'm assuming that propellent mass varies linearly over

the burn time of the engine. This strikes me as only being realistic

for a pure end-burner propellant grain, and I'm looking for a better

model of this behavior that applies to all grain configurations.

Would a better approximation be to make mass decrease proportionally

to the ratio of the integral of thrust/time over total impulse? This

would assume that basically more thrust -> more propellant burned. I

am unsure if this is the correct physics (for instance, pressure plays

a large role as well). I am trying to develop as accurate as possible

a model given the typical data available for model rocket engines.

This is what I'm thinking of trying:

cmass = casing mass

pmass = propellant mass

t = time

F(t) = force at time t

Integral from 0 to t F(t) dt

mass(t) = cmass + pmass - pmass * ----------------------------

total impulse

Is this what WRASP, etc. use? Any other suggestions?

----------------------------------------------------------------------

Reply via newsgroup please. Email address is invalid to eliminate

spam.