The Rocket Equation

The tyranny of the logarithm

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Rocket equation: $\Delta v = v_e \ln(m_0/m_f)$.
• Orbit needs about 9.4 km/s, so rockets are mostly propellant.
• Lower exhaust speed means an exponentially larger mass ratio.

Steps

1. Tsiolkovsky’s equation
2. Reaching orbit
3. Kerosene
4. Methane engines
5. Hydrogen fuel
6. What’s left for cargo?