Engines Compared

Exhaust speed is everything

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

• Specific impulse $I_{sp} = v_e/g_0$: chemical about 300–450 s, ion engines thousands.
• Faster exhaust shrinks the mass ratio dramatically.
• Ion engines trade thrust for efficiency: tiny pushes for months.

Steps

1. Specific impulse
2. Hydrogen’s rating
3. Halve the fuel
4. Why not ion engines everywhere?
5. Patience pays
6. Hot and light