Understanding Rocket Equations

How do we arrive at the equations describing the relation between mass flow and thrust?

We are going to look at how we can explain we arrive at the equation that says that mass flow dm/dt is defined as:

dm/dt = F/(Isp * g₀)
dm/dt = F/vₑ
F = am
p = mv
F =  Δp/ Δt
  1. What the velocity v was when the snowball exited your hand.
  2. Weigh the snowball before it is thrown, to determine its mass m
F =  Δp/ Δt = m Δv / Δt = m(Δv / Δt) = ma
F =  Δp/ Δt = Δm v / Δt = v(Δm / Δt)
Δm / Δt = F/v
dm/dt = F/vₑ

How is Mass Flow Useful to Know?

If like me you are writing a simulation of a rocket launch, you want to know at every time step you simulate how much mass the rocket has. That will be influenced by how much fuel has been consumed. To determine the amount of fuel consumed in a time step of length Δt, you need to know the mass flow.

Geek dad, living in Oslo, Norway with passion for UX, Julia programming, science, teaching, reading and writing.

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