Key Concepts: Rocket Propulsion

How Rockets Work

• Rockets propel themselves by expelling mass (exhaust gases) at high velocity — conservation of momentum in action.
• No external medium is needed — rockets work in the vacuum of space.

The Rocket Equation (Tsiolkovsky)

• Δv = v_e · ln(m₀/m_f), where v_e is exhaust velocity, m₀ is initial mass, and m_f is final mass.
• Higher exhaust velocity and larger mass ratio → greater speed change.

Thrust

• Thrust = v_e · (dm/dt) — the exhaust velocity times the rate of mass ejection.
• To lift off, thrust must exceed the rocket's weight (mg).

Staging

• Multi-stage rockets discard empty fuel tanks to reduce mass, dramatically improving efficiency and achievable Δv.