Rocket Injector Calculator

DESIGN TARGET

Injector design mode

Calculate the required orifice diameter from the target mass flow.

Target O/F ratio Target total mass flow

OXIDIZER CIRCUIT

Oxidizer setup

GOxProperty preset · Example gas conditionCompressible gasReady

Discharge coefficientCd— Upstream passage diameterD Expansibility factorε— Upstream densityρ₁kg/m³ Pressure dropΔp Orifice countnpcs

FUEL CIRCUIT

Fuel setup

EthanolProperty preset · Approx. 20 °CIncompressible liquidReady

Discharge coefficientCd— Upstream passage diameterD

Flow assumptionεε = 1 (not applied)Liquid density is treated as constant.

Upstream densityρ₁kg/m³ Pressure dropΔp Orifice countnpcs

⚠ GOx is not an oxidizer permitted for use in Race2Space.

CALCULATION OUTPUT

Inputs are ready

Results remain separate from the input workspace and open in a focused report window.

CALCULATION MODEL

Mass flow equations

COMPRESSIBLE · GOx

q_m = C_d / √(1 − β⁴) × ε × π/4 × d² × √(2ρ₁Δp)

INCOMPRESSIBLE · LIQUIDS

q_m = C_d / √(1 − β⁴) × π/4 × d² × √(2ρΔp)

β is calculated as d/D. Sizing mode solves for d; Verification mode predicts flow from a manufactured d. The GOx equation does not independently detect choked flow.

Engineering note: The N2O calculation assumes single-phase liquid. Flashing or two-phase N2O requires an appropriate two-phase flow model.