Rockets and their propellants, overview. Propellant is the chemical mixture burned to produce thrust in rockets and consists of a fuel and an oxidizer. A fuel is a substance that burns when combined with oxygen producing gas for propulsion. An oxidizer is an agent that releases oxygen for combination with a fuel. The ratio of oxidizer to fuel is called the mixture ratio. Propellants are classified according to their state – liquid, solid, or hybrid.
The gauge for rating the efficiency of rocket propellants is specific impulse, stated in seconds. Specific impulse indicates how many pounds (or kilograms) of thrust are obtained by the consumption of one pound (or kilogram) of propellant in one second. Specific impulse is characteristic of the type of propellant, however, its exact value will vary to some extent with the operating conditions and design of the rocket engine.
Specific impulse (ISP)
Specific impulse (usually abbreviated Isp) is a measure of how efficiently a reaction mass engine (a rocket using propellant or a jet engine using fuel) creates thrust. For engines whose reaction mass is only the fuel they carry, specific impulse is exactly proportional to the effective exhaust gas velocity.
Thus, the specific impulse can be defined as the proportion of the speed of expelling the propellant from the nozzle and measured in second. A higher specific impulse is the higher speed of ejection of the propellant. This speed is monitored to measure the quality of the engine, in other terms, how fast the engines burn fuel to lift off the Rocket.
Specific impulse (table)
| Rockets performance (specific impulse) | ||||
|---|---|---|---|---|
| Rocket | Stage | Engines | Propellant | ISP, Specific impulse (in seconds) (vacuum or sea level) |
| Atlas/Centaur (1962) | 1 2 3 | 2 x Rocketdyne YLR89-NA7 Rocketdyne YLR105-NA7 2 x P&W RL-10A-3-3 | RP-1 / LOX RP-1 / LOX LH2 / LOX | 292 vac 309 vac 444 vac |
| Titan II (1964) | 1 2 | 2 x Rocketdyne LR-87-AJ-5 Rocketdyne LR-91-AJ-5 | Aerozine 50 / NTO Aerozine 50 / NTO | 259 sl 312 vac |
| Saturn V (1967) | 1 2 3 | 5 x Rocketdyne F-1 5 x Rocketdyne J-2 Rocketdyne J-2 | RP-1 / LOX LH2 / LOX LH2 / LOX | 260 sl 424 vac 424 vac |
| Space Shuttle (1981) | 0 OMS | 2 x Thiokol SRB (Booster) 2 x Aerojet OMS | PBAN Solid MMH / LOX | 269 vac 455 vac 313 vac 260-280 vac |
| Delta II (1989) | 0 1 2 | 9 x Castor 4A (Booster) Rocketdyne RS-27 Rocketdyne AJ10-118K | HTPB Solid RP-1 / LOX Aerozine 50 / NTO | 266 vac 295 vac 321 vac |
| Ariane 5 (2023) | 0 1 | 2 x Booster, P241, EAP (Booster) Vulcain 2, EPC Aestus, EPS L-10 | HTPB Solid LH2 / LOX MMH / N2O4 | 275 sl 434 vac |
| Ariane 6 (2024) | 0 1 2 | 2 or 4 x Avio P120 (Ariane 62, 64) (Booster) Vulcain 2.1 Vinci | HTPB Solid LH2 / LOX LH2 / LOX | 278 vac – – |
| VEGA (2012) | 1 2 3 4 | Avio P80 Zefiro23 Zefiro9 AVUM ModuleRD-843 | HTPB Solid HTPB Solid HTBB Solid UDMH / N2O2 | 280 vac 288 vac 296 vac 315 vac |
| VEGA-C (2022) | 1 2 3 4 | 2 or 4 x Avio P120C Zefiro40 Zefiro9 AVUM+ | HTPB Solid HTPB Solid HTPB Solid UDMH / N2O2 | 278 vac 293 vac 294 vac 315 vac |
| Terran 1 (2023) | 1 2 | 9 x Aeon 1 Aeon 1 Vac | CH4 / LOX CH4 / LOX | 360 vac 360 vac |
| Starship (2023) | 1 2 | Raptor 2 (Raptor 3 = +18%) Raptor vac | CH4 / LOX CH4 / LOX | 350 vac 380 vac |
| SLS (5 block) (2022) | 0 1 2 | 2 x Orbital ATK 5 segment (Booster) 4 x Rocketdyne RS-25 (Core) 1 x ICPS RL10B (ICPS) | PBAN Solid LH2 / LOX LH2 / LOX | 269 vac 452,3 vac (4.436 km/s) 465 vac |
| New Glenn (2024) | 1 2 | 7 x BE-3U 2 x BE-3U | CH4 / LOX CH4 / LOX | ? ? |
| Falcon 9 FT (2018) | 1 2 | 9 x Merlin 1D+ 1 x Merlin ID Vac | RP-1 / LOX RP-1 / LOX | 311 vac 348 vac |
| Falcon 9 Heavy (2018) | 0 1 2 | 2 x Boosters (2 x 9 Merlin 1D per Booster) 9 x Merlin 1D 1 x Merlin 1D Vac | Chilled RP-1 / Subcooled LOX Chilled RP-1 / Subcooled LOX RP-1 / LOX | 311 vac 282 vac 348 vac |
| Vulcan Centaur (2024) | 0 1 2 | 0, 2, 4 or 6 GEM-63XL (Booster) 2 x BE-4 (Blue Origin) 2 x RL-10 | Graphite-Epoxy-Motor (GEM) CH4 / LOX LH2 / LOX | 280 vac ? 454 vac |
| Terran R (2026) | 1 2 | 13 x Aeon R 1 x Aeon Vac | LCH4 / LOX LCH4 / LOX | ? ? |
| Zhuque-2 (2023) | 1 2 | 4 x TQ-12 1 x TQ-12 + vernier engine | LCH4 / LOX – | ? |
| – | – – | – | – – | – |
Footnote
- Sources: Aerospace dashboard, Artemis I sequence of events, funkystuff.org, Spaceflight Now, Space.com, SpaceNews, Spaceflight.com, SciTechDaily, Launch pad
- Outgoing: NASA, SpaceX, ESA
- Keywords: Performance parameter