Impact of premixing on the propulsion performance of N2O/hydrocarbon thrusters: a combined numerical and experimental study

Nitrous oxide (N ₂ O)-based bipropellant systems utilizing self-pressurizing hydrocarbon fuels offer a promising non-toxic alternative for space propulsion applications. However, a systematic comparison between non-premixed and premixed combustion modes under controlled operational conditions remains unreported. This study quantitatively evaluates the propulsion performance of a 10 N-class N ₂ O/C ₂ H ₆ thruster using a combined framework of three-dimensional numerical simulations and hot-fire experiments. A non-premixed unlike-impinging injector was compared against two premixed configurations under identical propellant mass flow rates, mixture ratios, and combustor geometries. Numerically, the premixed like-doublet impinging configuration showed a 16.4% increase in thrust over the non-premixed baseline, and these trends were successfully validated through hot-fire tests. While the single-hole configuration experienced flashback, the premixed like-doublet thruster sustained stable 5-s combustion, delivering a sea-level thrust of 5.34 N and a specific impulse ( Iₛₚ ) of 111 s. This represents an 11.1% increase in Iₛₚ over the non-premixed baseline, along with a characteristic velocity rise from 1336 to 1350 m/s. This improvement is attributed to enhanced propellant mixing and a more uniform axial flow field through the nozzle. This comprehensive numerical and experimental investigation demonstrates the definitive performance advantages of the premixed injection strategy, providing critical design benchmarks for next-generation high-performance propulsion systems.