PROPULSION DESIGN TOOL · REV 07

Rocket Injector Calculator

01
DESIGN TARGET

Injector design mode

Calculate the required orifice diameter from the target mass flow.

02
OXIDIZER CIRCUIT

Oxidizer setup

GOxProperty preset · Example gas conditionCompressible gasReady
03
FUEL CIRCUIT

Fuel setup

EthanolProperty preset · Approx. 20 °CIncompressible liquidReady
Flow assumptionεε = 1 (not applied)Liquid density is treated as constant.
04
ELEMENT CONFIGURATION

Injector type

IMPINGING · UNLIKE DOUBLET

Jet angles

TMR DEFINITIONOxidizer momentum ÷ Fuel momentumTMRO/F = (ṁV)oxidizer / (ṁV)fuel

Angles are measured from the injector-face normal. The momentum balance predicts the resultant sheet direction, not the full spray-fan spread.

CALCULATION OUTPUT

Inputs are ready

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

05
CALCULATION MODEL

Mass flow equations

COMPRESSIBLE · GOx
qm = Cd / √(1 − β⁴) × ε × π/4 × d² × √(2ρ₁Δp)
INCOMPRESSIBLE · LIQUIDS
qm = Cd / √(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.

INJECTOR ANALYSIS · SIZING

Design results

GOx / Ethanol · Target O/F 1.000 · 0.10000 kg/s total

PROPELLANT SPLITGOx / Ethanol
GOx0.05000kg/s
+
Ethanol0.05000kg/s
Target total 0.10000 kg/sTarget O/F 1.000
OXIDIZERGOx
Required orifice diameter—mm / hole
Total open area
— mm²
Diameter ratio
—
Injection velocity
— m/s
FUELEthanol
Required orifice diameter—mm / hole
Total open area
— mm²
Diameter ratio
—
Injection velocity
— m/s
IMPINGING ELEMENT · UNLIKE DOUBLET

Momentum balance

NUMERATOROXIDIZER÷DENOMINATORFUEL
TMRO/F
—
(ṁV)oxidizer / (ṁV)fuel
Geometric included angle
—
αox + αfuel
Resultant sheet angle
—
—

Preliminary momentum-vector estimate. Atomization and actual spray-fan width require test data or a validated correlation for the selected element geometry.

OXFUELRESULTANTINJECTOR FACE NORMAL
OXIDIZERGOx
D = 20.00 mmd = — mmP₁P₂1 × orifice
FUELEthanol
D = 20.00 mmd = — mmP₁P₂1 × orifice

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