Specific Impulse Converter
The Specific Impulse Converter converts between Isp (seconds), exhaust velocity (m/s), and thrust-specific fuel consumption. Includes a propellant comparison table for 12+ fuel/oxidizer pairs, an engine database with real performance data, and an SVG bar chart comparing propulsion types — free, no signup required.
Unit Converter
Propellant Comparison
| Propellant Pairs | Fuel | Oxidizer | Isp Range (s) | Engine Type |
|---|---|---|---|---|
| LOX/RP-1 | RP-1 (Kerosene) | Liquid Oxygen (LOX) | 270–311 | Liquid Bipropellant |
| LOX/LH2 | Liquid Hydrogen (LH2) | Liquid Oxygen (LOX) | 380–462 | Liquid Bipropellant |
| LOX/CH4 | Liquid Methane (CH4) | Liquid Oxygen (LOX) | 305–363 | Liquid Bipropellant |
| N2O4/UDMH | UDMH | Nitrogen Tetroxide (N2O4) | 285–320 | Liquid Bipropellant |
| LOX/Ethanol | Ethanol (75%) | Liquid Oxygen (LOX) | 250–285 | Liquid Bipropellant |
| Solid APCP | Aluminum / HTPB binder | Ammonium Perchlorate (AP) | 220–270 | Solid |
| Solid HTPB/NH4ClO4 | HTPB | Ammonium Perchlorate (NH4ClO4) | 240–260 | Solid |
| Hydrazine Monoprop | Hydrazine (N2H4) | Catalytic decomposition (none) | 200–235 | Liquid Monopropellant |
| Cold Gas N2 | Nitrogen (N2) | None (cold gas) | 60–80 | Liquid Monopropellant |
| Xenon Ion (Gridded) | Xenon (Xe) | None (electric) | 1500–5000 | Ion / Electric |
| Hall-effect Xe | Xenon (Xe) | None (electric) | 1200–3000 | Ion / Electric |
| Colloid / FEEP | Ionic liquid / Liquid metal | None (electric) | 2000–8000 | Ion / Electric |
| Nuclear Thermal H2 | Liquid Hydrogen (LH2) | None (nuclear heated) | 800–1000 | Nuclear Thermal |
Engine Database
| Engine | Isp (sea level) (s) | Isp (vacuum) (s) | Thrust (vac) (kN) | Propellant |
|---|---|---|---|---|
| Merlin 1D | 282 | 311 | 981.0 | LOX/RP-1 |
| Raptor V2 | 327 | 363 | 2550.0 | LOX/CH4 |
| RS-25 (SSME) | 366 | 452 | 2279.0 | LOX/LH2 |
| RD-180 | 311 | 338 | 4152.0 | LOX/RP-1 |
| RL-10B-2 | N/A | 462 | 110.0 | LOX/LH2 |
| Vulcain 2 | N/A | 431 | 1359.0 | LOX/LH2 |
| BE-4 | N/A | 340 | 2400.0 | LOX/CH4 |
| Rutherford (Vac) | 311 | 343 | 25.8 | LOX/RP-1 |
| NEXT-C | N/A | 4190 | 0.000236 | Xenon Ion (Gridded) |
| PPS-1350 (Safran) | N/A | 1660 | 0.000088 | Hall-effect Xe |
Isp Comparison Chart
Tem uma sugestão?
Solicite uma nova ferramenta ou sugira melhorias — junte-se à nossa comunidade no Slack!
What is Specific Impulse?
Specific impulse (Isp) is the key measure of rocket engine efficiency, defined as the thrust produced per unit weight of propellant consumed per second. Measured in seconds, it equals exhaust velocity divided by standard gravity: Isp = Ve / g₀. Higher Isp means more thrust per kilogram of propellant, directly translating to more delta-V for a given mass ratio. Chemical rockets achieve 200-460s, with LOX/LH2 being the highest-performing chemical propellant. Ion engines reach 1,000-10,000s but with much lower thrust, making them ideal for deep-space missions where time is less critical than fuel efficiency.
How to Use This Converter
- Enter a specific impulse value in seconds, or exhaust velocity in m/s
- Optionally enter thrust to calculate mass flow rate
- Click Convert to see all equivalent values
- Browse the propellant comparison table to compare fuel/oxidizer combinations
- Check the engine database for real-world performance data
Frequently Asked Questions
Why is Isp measured in seconds?
Specific impulse in seconds represents how long one kilogram of propellant can produce one kilogram-force (9.807 N) of thrust. An engine with Isp = 300s means 1 kg of propellant provides 9.807 N for 300 seconds (or 2943 N·s total impulse per kg). This unit is convenient because it's independent of the measurement system — 300s means the same whether you think in metric or imperial units.
Why do ion engines have much higher Isp than chemical rockets?
Ion engines accelerate propellant (usually xenon) using electric fields to velocities of 20-50 km/s, compared to 2-4.5 km/s for chemical exhaust. Since Isp = Ve/g₀, higher exhaust velocity means higher Isp. However, the mass flow rate is tiny (milligrams/second), so thrust is very low (millinewtons to newtons). This makes ion engines ideal for long-duration deep space missions but useless for launch.
How does Isp relate to delta-V?
The Tsiolkovsky rocket equation directly links them: ΔV = Isp × g₀ × ln(m₀/mf). Doubling Isp doubles your delta-V for the same mass ratio. This is why engine efficiency matters so much — RS-25 (Isp 452s) achieves 45% more ΔV per mass ratio than Merlin 1D (Isp 311s). For interplanetary missions requiring 10+ km/s of ΔV, high-Isp engines dramatically reduce propellant requirements.
Ferramentas Relacionadas
Calculadora de Código de Cores de Resistores
Decodifique as faixas de cores de resistores para encontrar valores de resistência
Experimente →Calculadora de Vida Útil de Bateria
Estime quanto tempo sua bateria vai durar com base na capacidade e consumo de corrente
Experimente →Calculadora de Resistor para LED
Calcule o resistor correto para qualquer circuito de LED
Experimente →