Acceleration measures how quickly velocity changes over time. In a rocket launch, engine thrust pushes upward while gravity pulls downward, so the rocket’s acceleration depends on the resulting net force and its current mass. section 8.5 section 8.8
A rocket simulation calculates acceleration incrementally:
- Subtract the rocket’s weight from engine thrust to obtain net force: F = thrust − mass × g. section 8.8
- Divide net force by current mass to obtain acceleration: a = F / m. section 8.8
- Update velocity with Δv = a × Δt, then update altitude with Δh = v × Δt. section 8.8
- Recalculate mass as propellant is consumed, because changing mass changes acceleration even when thrust stays constant. section 8.5
Simulating a launch
A Julia launch! function starts with zero velocity and altitude, then repeats small time steps. It computes net force, stops when fuel is exhausted or force is no longer positive, and accumulates altitude. With a Rutherford engine, a small tank, and a 300 kg payload, launch!(rocket, 0.5) returns 45.0 seconds and an altitude of 31117.8036364191. section 8.8
