maximum speed/velocity? =advanced=

[shockwaveriderz]

at what point during the time the engine is thrusting is the maximum speed or velocity attained? Right at burnout?

my questions realtes to Estes Bp motors A-C typically.

 

[BobCox]

Not necessarily. If the thrust were constant during the length of the burn and then abruptly shut off, that would be true. In real life the thrust tapers off toward the end of the burn. Once the thrust becomes less than the drag force (plus the rocket's weight) , the rocket will start to slow.

 

[bobkrech]

As Bob Cox wrote, you've maxed velocity when thrust = drag + weight. (All forces in either pounds or newtons.)

The simpliest way to show this is to sim your bird in wRASP. It will give the time when the max velocity is reached.

Bob

 

[BobCox]

Shockie revised his original post to refer to Estes BP motors.
Their thrust is flat during most of the burn, then tails off pretty quickly at the end. The maximum velocity will occur a small fraction of a second before burnout.

According to RockSim, an Estes C6-3 drops from 4.44N to zero in about 30 ms. The maximum velocity happened about 15 ms before it dropped to zero.

For most practical purposes, you can say that burnout and max velocity happen at the same time.