Model Rocketry

I have a few questions about model rocketry and aerospace…trying to make a model rocket?

1) How is the thrust of a rocket engine is determined?
2) What is the thrust of an A8-3 rocket engine?
3) Why do satellites have different velocities depending on their altitude?

1. By firing on a test stand, which includes a measuring device such as a strain gauge. Estes sells engines rated by thrust (a B has twice the thrust of an A, and a C doubles again, and so on) and sub-rated by thrust profile and features such as ignition for a subsequent stage on a multi-stage rocket. Thrust is measured in newton-seconds; a newton is a unit of force equal to about 0.22 pounds. For a rocket to fly at all, its thrust must exceed its launch weight, measured in newtons.
2. See the package; it will say. Estes also publishes a flyer with engine specifications; get a copy at your dealer.
3. We are out of the realm of model rocketry here. In orbit, a satellite would go in a straight line except for the earth’s gravity, which bends the orbit into a circle or ellipse. At a higher altitude, not only is the earth’s gravity reduced (it diminishes as the square of the distance from the center of the earth), but the orbit is larger so the curvature is less. Thus, less speed is required to maintain orbit.

German V-2 Model Rocket with 8000-lbs of thrust