What are the common liquid rocket propellant combinations and their characteristics?

Common propellant combinations: LOX/LH2 (highest Isp ~450s, cryogenic, used in Space Shuttle main engine, RS-25), LOX/RP-1 (kerosene, Isp ~350s, higher density, Falcon 9, Saturn V first stage), LOX/Methane (Isp ~360s, easier handling than LH2, Raptor, BE-4), N2O4/UDMH (hypergolic, storable, Isp ~320s, used in spacecraft maneuvering), and Peroxide combinations (non-toxic, moderate Isp). Selection factors include: Isp, density (affects tank size), storability, toxicity, cost, ignition characteristics, and mission requirements. Cryogenic propellants offer best performance but require insulation and boil-off management; hypergolics enable simple, reliable ignition.