NASA ROCETS Liquid Propulsion Modeling (.roc, .deck)

The @modelscript/rocets package (languages/rocets) provides native compilation, simulation, and analysis for NASA ROCETS (Rocket Engine Transient Simulator) liquid propellant rocket engine decks and turbomachinery maps. It delivers multi-syntax parsing, embedded Fortran user routine bridge via @modelscript/fortran, pre-flight static propulsion diagnostics (M8001–M8014), direct continuous DAE arena lowering into @modelscript/runtime (IDaeBuilder), a coupled steady-state power and flow balance solver, dynamic start/shutdown transient integration, multi-domain projections to Modelica 3.x and FMI SSP, and interactive Piping & Instrumentation Diagram (P&ID) vector schematic generation.

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Supported File Specifications

Extension	Format	Key Structural Features
.roc / .deck	Engine Model Deck	Tagged DECK, COMPONENTS, PARAMS, S0, PORTS, CONNECTIONS, BALANCE blocks
.map / .dat	Turbomachinery Maps	Multidimensional speed-flow-head and efficiency performance tables for pumps and turbines
.f / .for	User Subroutines	Embedded or external Fortran routines for custom fluid properties and component characteristics

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Architecture & Compilation Pipeline

Rendering diagram...

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Propulsion Component Library

NASA ROCETS provides specialized thermodynamic and turbomachinery modules for rocket engine architectures:

Module	Category	Description	Primary Parameters & States
CHAMBER / TC	Combustion	Thrust chamber & convergent-divergent supersonic nozzle expansion	$P_c,A_t,\epsilon ,V_c,c^{\ast },O/F$
PUMP	Turbomachinery	Centrifugal / axial propellant pump	$\mathrm{\Delta }P,\eta ,\rho ,\dot{m},P_{\text{shaft}}$
TURBINE	Turbomachinery	Gas-driven drive turbine	$PR,\eta ,T_{\text{in}},c_p,P_{\text{shaft}}$
SHAFT	Mechanical	Turbopump rotating assembly	$J,\omega ,N_{\text{rpm}},{\tau }_{\text{turb}},{\tau }_{\text{pump}}$
COOLING_JACKET	Thermal	Regenerative nozzle cooling jacket	$T_{\text{wall}},Q_{\text{gas}},Q_{\text{cool}},h_g,\mathrm{\Delta }{P}_{\text{cool}}$
VALVE / ORIFICE	Fluid	Throttle, cavitating venturi, or shutoff valve	$C_v,\text{position},\mathrm{\Delta }P$
JUNCTION	Fluid	Propellant flow splitter or mixing manifold	$\sum \dot{m}=0,P_{\text{node}}$

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Propellants & Thermodynamics

The @modelscript/rocets thermo engine provides:

• Cryogenic & Hydrocarbon Propellants: Standard properties for Liquid Oxygen (LOX), Liquid Hydrogen (LH2), Liquid Methane (LCH4), and RP-1 kerosene.
• NASA CEA Combustion Curves: Chemical equilibrium calculations of characteristic velocity ($c^{\ast }$), adiabatic flame temperature ($T_c$), isentropic expansion exponent ($\gamma$), and molecular weight.
• Gas Dynamics: Isentropic supersonic nozzle expansion with Mach area relations, vacuum and sea level thrust, and vacuum/SL specific impulse ($I_{sp}$).
• Bartz Convective Heat Transfer: Gas-side throat heat transfer coefficient ($h_g$) for regenerative cooling circuit sizing.

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Pre-Flight Diagnostic Rules

14 rules9 error5 warning Run with msx lint

All severitieserrorwarning

Code	Rule	Severity	Message
M8001	unconnected-fluid-port	error	Fluid port '<comp>.<port>' is not connected in the propellant flow circuit.
M8002	fluid-type-mismatch	error	Incompatible fluid stream connection '<conn>': cannot mix '<fromFluid>' into '<toFluid>' without a combustion chamber.
M8003	shaft-power-imbalance	error	Turbopump shaft '<shaftId>' power imbalance: <reason>.
M8004	unbalanced-flow-split	error	Mass conservation failure at junction '<junct>': inlet and outlet flow mismatch exceeds tolerance (|\u0394m| = <value> kg/s).
M8005	pump-cavitation-risk	warning	Pump '<pumpId>' inlet suction pressure is below required NPSH margin (margin: <value> kPa). Cavitation risk.
M8006	negative-chamber-pressure	error	Non-physical pressure at '<comp>': computed pressure is <val> Pa (must be > 0).
M8007	combustion-temperature-limit	warning	Gas temperature at '<comp>' (<value> K) exceeds throat thermal structural limit (<limitK> K).
M8008	invalid-valve-schedule	error	Invalid valve actuation profile for '<valveId>': <reason>.
M8009	choked-flow-inconsistency	warning	Supersonic nozzle expansion at '<comp>' is not choked (pressure ratio Pc/Pa = <value> < 1.89).
M8010	user-fortran-routine-error	error	Fortran user routine in component '<comp>' has syntax or semantic error: <msg>.
M8011	extreme-mixture-ratio	warning	Engine mixture ratio (O/F = <value>) at '<comp>' is outside stable combustion limits.
M8012	missing-fluid-table	error	Propellant fluid table for '<fluid>' is not loaded in the session.
M8013	turbine-overspeed-hazard	warning	Turbopump shaft '<shaft>' speed (<value> RPM) exceeds maximum burst rating (<maxRpm> RPM).
M8014	closed-flow-circuit	error	Pump '<pumpId>' discharge is completely blocked with no open valve or recirculation path.

Generated from languages/rocets/src/lints/index.ts. All languages →

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Example ROCETS Engine Deck

DECK: GasGeneratorCycleEngine
TITLE: "Gas Generator Cycle Cryogenic Engine"

COMPONENTS:
  OPUMP TYPE=PUMP TITLE="LOX Turbopump" X=100 Y=150
    PARAMS: DELTA_P=14.0E6, ETA=0.78, RHO=1140.0
    PORTS: IN_P=0.3E6 FLUID=LOX DIR=in, OUT_P=14.3E6 FLUID=LOX DIR=out

  FPUMP TYPE=PUMP TITLE="LH2 Turbopump" X=100 Y=320
    PARAMS: DELTA_P=18.0E6, ETA=0.74, RHO=71.0
    PORTS: IN_P=0.2E6 FLUID=LH2 DIR=in, OUT_P=18.2E6 FLUID=LH2 DIR=out

  TURB01 TYPE=TURBINE TITLE="Drive Gas Turbine" X=320 Y=240
    PARAMS: PR=1.65, ETA=0.74, T_IN=950.0
    PORTS: IN_P=15.0E6, OUT_P=9.1E6

  SHAFT01 TYPE=SHAFT TITLE="Main Turbopump Shaft" X=210 Y=240
    PARAMS: INERTIA=0.1, SPEED_RPM=32000.0, MAX_RPM=40000.0
    S0: SPEED_RPM=32000.0

  CHAMBER TYPE=CHAMBER TITLE="Main Thrust Chamber" X=550 Y=240
    PARAMS: PC=10.0E6, MR=6.0, AT=0.035, EPS=50.0, VC=0.02
    S0: PC=10.0E6

  MAIN_OX_VALVE TYPE=VALVE TITLE="Main Oxidizer Valve" X=350 Y=150
    PARAMS: CV=0.005, POSITION=1.0

CONNECTIONS:
  OPUMP.OUT_P -> MAIN_OX_VALVE.IN_P
  MAIN_OX_VALVE.OUT_P -> CHAMBER.IN_OX
  FPUMP.OUT_P -> CHAMBER.IN_FUEL
  TURB01.OUT_P -> CHAMBER.IN_GAS
  SHAFT01.TORQUE_TURB -> TURB01.TORQUE
  SHAFT01.TORQUE_PUMP -> FPUMP.TORQUE

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Command Line Interface (msx rocets)

ModelScript provides full headless CLI tooling for NASA ROCETS models:

# Pre-flight linting of an engine deck
msx rocets lint engine.roc

# Print engine architecture summary and flow connections
msx rocets summary engine.roc

# Solve steady-state power and flow balance
msx rocets balance engine.roc --target-pc=12E6 --mr=6.0

# Simulate dynamic ignition and ramp transient
msx rocets simulate engine.roc --t-end=2.0

# Project to executable Modelica 3.x
msx rocets to-modelica engine.roc --out=Engine.mo

# Export to FMI 2.0/3.0 System Structure Description (SSP)
msx rocets to-ssp engine.roc --out=SystemStructure.ssd

# Render vector P&ID flow diagram
msx rocets diagram engine.roc --out=pid.svg

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VS Code & Web IDE Custom Editor

The @modelscript/ide-client package provides a dedicated dual-mode custom editor (modelscript.rocetsEditor):

• P&ID Vector Schematic: Interactive diagram with propellant stream color coding, zoom/pan navigation, and SVG export.
• Engine Balance Panel: Shaft power metrics, chamber stagnation conditions, sea level / vacuum thrust, and $I_{sp}$.
• Start Transient Viewer: Ignition ODE trajectory table and graphs ($P_c(t)$, $\text{RPM}(t)$, $F(t)$, $T_w(t)$).
• Module Netlist: Filterable tabular listing of modules, parameters, and ports.
• Pre-Flight Diagnostics: Live diagnostic warnings and error badges with click-to-line navigation.
• Projections: Side-by-side Modelica and FMI SSP code viewers with one-click export.