Equations · equation
Specific Impulse
Rocketry · 1920
- Equation
- I_sp = v_e / g₀ = F / (ṁ·g₀)
- Field
- Rocketry
- Named After
- Robert Goddard · Hermann Oberth
- Symbols
- I_sp engine efficiency in seconds · v_e exhaust velocity · g₀ standard gravity (9.81 m/s²) · F thrust · ṁ propellant mass flow rate
- Year
- 1920
Significance
How many seconds one kilogram of propellant can produce one kilogram-force of thrust — the miles-per-gallon of rocket engines. Solid boosters ~250 s, kerosene ~300, hydrogen ~450, ion drives thousands (but a whisper of thrust). Every mission trade-off begins by reading this number off the engine's data sheet.
Referenced by
constant
element
equation
machine
Open on the Equations shelf — the interactive card, the filters, and everything alongside it.