RP1LOX

RP-1 LOX refers to a rocket propellant pair consisting of RP-1, a refined kerosene, and liquid oxygen (LOX) as the oxidizer. RP-1 is a dense hydrocarbon fuel chosen for storage stability and cost, while LOX is cryogenic. In typical use, the propellants are combined at a mass ratio of roughly 2.3–2.6:1 (LOX:RP-1), though engines may vary to optimize performance and stability.

History and use: RP-1/LOX became a standard first-stage propellant in the mid-20th century and powered engines such as the F-1 on the Saturn V and many Atlas/Delta designs. In modern programs, SpaceX's Merlin engines rely on RP-1/LOX, and the RD-180 used on Atlas V also employs this combination. It remains common where cost, density, and multi-engine compatibility are priorities.

Performance and design: The combination yields high thrust with relatively simple hardware and moderate specific impulse, typically around 300 seconds in vacuum and lower at sea level. Its advantages include high propellant density, ease of handling, and lower cost compared with cryogenics like liquid hydrogen. Disadvantages include soot and coke formation, sensitivity to propellant cleanliness, and lower efficiency than liquid hydrogen.

Safety and environmental: LOX accelerates combustion of hydrocarbons, so leaks near fuel can cause rapid, intense fires; kerosene is flammable and releases soot. Handling requires rigorous safety protocols, compatible storage, and fire protection. Despite drawbacks, RP-1/LOX remains widely used for first-stage propulsion due to its performance-to-cost balance.