|
N2O4/A50 IspVac = 316.237 sec MRcore = 1.96146 MRthruster = 1.66724 Rt = 5.97141 in At = 112.022 in**2 Pc = 100 psia Fvac = 20500 lbf |
 |
 |
 |
Apollo SPS | |
| RocketIsp version 0.1.12 | Sunday, Jul 19, 2026 at 09:17AM |
|
N2O4/A50 IspVac = 316.237 sec MRcore = 1.96146 MRthruster = 1.66724 Rt = 5.97141 in At = 112.022 in**2 Pc = 100 psia Fvac = 20500 lbf |
|
|
|
|
| Geometry |
|---|
| Input | |||
|---|---|---|---|
| Parameter = | Value | Alt Value | Description |
| cham_conv_deg = | 30.00 deg | half angle of conical convergent section | |
| CR = | 2.5 | chamber contraction ratio (Ainj / Athroat) | |
| eps = | 62.5 | nozzle area ratio (Aexit / Athroat) | |
| LchamberInp = | None in | user input value of chamber length (will override all other entries) | |
| LchmMin = | 2.000 in |
5.080 cm 0.167 ft |
minimum chamber length (will override LchmOvrDt) |
| LchmOvrDt = | 3.1 | ratio of chamber length to throat diameter (Lcham / Dthrt) | |
| LnozInp = | None in | user input nozzle length (will override pcentBell) | |
| pcentBell = | 72.3 | nozzle percent bell (Lnoz / L_15deg_cone) | |
| RchmConv = | 1 | radius of curvature at start of convergent section (Rconv / Rthrt) | |
| RdwnThroat = | 1 | radius of curvature just downstream of throat (Rdownstream / Rthrt) | |
| Rthrt = | 5.971 in |
15.167 cm 0.498 ft |
throat radius |
| RupThroat = | 1.5 | radius of curvature just upstream of throat (Rupstream / Rthrt) | |
| Output | |||
|---|---|---|---|
| Parameter = | Value | Alt Value | Description |
| Ainj = | 280.055 in**2 | 1806.804 cm**2 | area of injector |
| At = | 112.022 in**2 | 722.722 cm**2 | throat area |
| Dexit = | 94.416 in |
239.817 cm 7.868 ft |
nozzle exit diameter |
| Dinj = | 18.883 in |
47.963 cm 1.574 ft |
diameter of injector |
| Dthrt = | 11.943 in |
30.335 cm 0.995 ft |
throat diameter |
| entrance_angle = | 36.79 deg | nozzle initial expansion angle | |
| exit_angle = | 9.34 deg | nozzle exit angle | |
| Lcham_conv = | 10.011 in |
25.427 cm 0.834 ft |
length of convergent section of chamber |
| Lcham_cyl = | 27.012 in |
68.611 cm 2.251 ft |
length of cylindrical section of chamber |
| Lnoz = | 111.268 in |
282.621 cm 9.272 ft |
nozzle length |
| Ltotal = | 148.291 in |
376.658 cm 12.358 ft |
nozzle + chamber length |
| Rinj = | 9.442 in |
23.982 cm 0.787 ft |
radius of injector |
| Vcham = | 9464.2 in**3 | 155090.9 cm**3 | approximate chamber volume |
| N2O4/A50 Core Stream Tube |
|---|
| Input | |||
|---|---|---|---|
| Parameter = | Value | Alt Value | Description |
| adjCstarODE = | 1 | multiplier on NASA CEA code value of cstar ODE (default is 1.0) | |
| adjIspIdeal = | 1 | multiplier on NASA CEA code value of Isp ODE (default is 1.0) | |
| CdThroat = | 0.990299 |
Cd of throat (RocketThruster object may override) (MLP fit) |
|
| fuelName = | A50 | name of fuel (e.g. MMH, LH2) | |
| ignore_noz_sep = | 0 | flag to force nozzle flow separation to be ignored (USE WITH CAUTION) | |
| MRcore = | 1.96146 | mixture ratio of core flow (ox flow rate / fuel flow rate) | |
| oxName = | N2O4 | name of oxidizer (e.g. N2O4, LOX) | |
| Pamb = | 0.00 psia |
0.00 MPa 0.00 atm 0.00 bar |
ambient pressure (for example sea level is 14.7 psia) |
| Pc = | 100.0 psia |
0.69 MPa 6.80 atm 6.89 bar |
chamber pressure |
| Output | |||
|---|---|---|---|
| Parameter = | Value | Alt Value | Description |
| CfAmbDel = | 1.83 | delivered ambient thrust coefficient | |
| CfVacDel = | 1.83 | delivered vacuum thrust coefficient | |
| CfVacIdeal = | 1.97386 | ideal vacuum thrust coefficient | |
| cstarERE = | 5507.0 ft/s | 1678.5 m/s | delivered core cstar |
| cstarODE = | 5619.3 ft/s | 1712.8 m/s | core ideal cstar |
| FvacBarrier = | 5914.2 lbf | 26307.5 N | vacuum thrust due to barrier stream tube |
| FvacCore = | 14585.8 lbf | 64881.0 N | vacuum thrust due to core stream tube |
| FvacTotal = | 20500.0 lbf | 91188.5 N | total vacuum thrust |
| gammaChm = | 1.12968 | core gas ratio of specific heats (Cp/Cv) | |
| IspDel = | 316.24 sec |
3101.22 N-sec/kg 3.10 km/sec |
<=== thruster delivered vacuum Isp ===> |
| IspDel_core = | 320.29 sec |
3141.02 N-sec/kg 3.14 km/sec |
delivered Isp of core stream tube |
| IspODE = | 344.74 sec |
3380.78 N-sec/kg 3.38 km/sec |
core one dimensional equilibrium Isp |
| IspODF = | 315.37 sec |
3092.74 N-sec/kg 3.09 km/sec |
core frozen Isp |
| IspODK = | 332.97 sec |
3265.33 N-sec/kg 3.27 km/sec |
core one dimensional kinetic Isp |
| MRthruster = | 1.66724 | total thruster mixture ratio') | |
| MWchm = | 21.981 g/gmole | core gas molecular weight | |
| Pexit = | 0.1228 psia |
0.00 MPa 0.01 atm 0.01 bar |
nozzle exit pressure |
| TcODE = | 5616.7 degR |
3120.4 degK 2847.2 degC 5157.0 degF |
ideal core gas temperature |
| wdotFl = | 24.304 lbm/s | 11.024 kg/s | total fuel flow rate |
| wdotOx = | 40.521 lbm/s | 18.380 kg/s | total oxidizer flow rate |
| wdotTot = | 64.825 lbm/s | 29.404 kg/s | total propellant flow rate (ox+fuel) |
| At Injector Face | |||
| Parameter = | Value | Alt Value | Description |
| wdotFl_cInit = | 20.658 lbm/s | 9.371 kg/s | initial core fuel flow rate (before any entrainment) |
| wdotFlFFC = | 3.646 lbm/s | 1.654 kg/s | fuel film coolant flow rate injected at perimeter |
| wdotTot_cInit = | 61.179 lbm/s | 27.750 kg/s | initial core total flow rate (before any entrainment) |
| After Entrainment | |||
| Parameter = | Value | Alt Value | Description |
| wdotFl_b = | 8.927 lbm/s | 4.049 kg/s | barrier fuel flow rate (FFC + entrained) |
| wdotFl_c = | 15.377 lbm/s | 6.975 kg/s | final core fuel flow rate (injected - entrained) |
| wdotOx_b = | 10.359 lbm/s | 4.699 kg/s | barrier oxidizer flow rate (all entrained) |
| wdotOx_c = | 30.162 lbm/s | 13.681 kg/s | final core oxidizer flow rate (injected - entrained) |
| wdotTot_b = | 19.286 lbm/s | 8.748 kg/s | total barrier propellant flow rate (includes entrained) |
| wdotTot_c = | 45.539 lbm/s | 20.656 kg/s | total final core propellant flow rate (injected - entrained) |
| Efficiencies |
|---|
| Output | ||
|---|---|---|
| Parameter = | Value | Description |
| Isp = | 0.91731 | Overall Isp Efficiency |
| Noz = | 0.94804 | Nozzle Efficiency |
| ERE = | 0.98000 | (constant) Energy Release Efficiency of Chamber |
| FFC = | 0.98733 | (barrier calc) Fuel Film Cooling Efficiency of Chamber |
| Nozzle | ||
| Parameter = | Value | Description |
| Div = | 0.98851 | (simple fit eps=62.5, %bell=72.3) Divergence Efficiency of Nozzle |
| Kin = | 0.96585 | (MLP fit) Kinetic Efficiency of Nozzle |
| BL = | 0.99297 | (MLP fit) Boundary Layer Efficiency of Nozzle |
| Ignored Efficiencies |
|---|
| TP: Two Phase Efficiency of Nozzle |
| Barrier Stream Tube |
|---|
| Input | ||
|---|---|---|
| Parameter = | Value | Description |
| ko = | 0.035 | entrainment constant (typical value is 0.035, range from 0.03 to 0.06) |
| pcentFFC = | 15 | percent fuel film cooling ( FFC flowrate / total fuel flowrate) |
| Output | |||
|---|---|---|---|
| Parameter = | Value | Alt Value | Description |
| cstarERE_b = | 5503.6 ft/s | 1677.5 m/s | delivered cstar |
| cstarODE_b = | 5616.0 ft/s | 1711.7 m/s | ideal equilibrium cstar |
| fracEntr = | 0.25565 | fraction of core flow entrained into barrier | |
| fracKin_b = | 0.430115 | fraction of kinetic completion in barrier | |
| IspDel_b = | 306.65 sec |
3007.26 N-sec/kg 3.01 km/sec |
delivered vacuum barrier Isp |
| IspODE_b = | 323.253 | sec. ideal equilibrium barrier Isp | |
| IspODF_b = | 315.42 sec |
3093.25 N-sec/kg 3.09 km/sec |
ideal frozen barrier Isp |
| IspODK_b = | 318.79 sec |
3126.27 N-sec/kg 3.13 km/sec |
vacuum kinetic Isp of barrier |
| MRbarrier = | 1.16043 | barrier mixture ratio at throat | |
| MRwall = | 0.67534 | mixture ratio at throat wall | |
| TcODE_b = | 4887.1 degR |
2715.0 degK 2441.9 degC 4427.4 degF |
average ideal ODE temperature of barrier gas |
| Twallgas = | 3433.5 degR |
1907.5 degK 1634.3 degC 2973.8 degF |
temperature of gas at throat wall (cooler upstream) |
| WentrOvWcool = | 4.29021 | ratio of entrained flow rate to FFC flow rate | |