RPL Engine Workbench logo RPL Engine Workbenchby Rocket Propulsion Lab

Tutorial 02

Set propellants and chamber targets.

Define the thermochemical and operating basis before using injector, nozzle, Flowfield Studio, or export workflows.

What you will learn

How to select propellants, set O/F and inlet temperatures, choose a sizing basis, enter chamber and ambient conditions, set display units, and select thermochemistry assumptions.

Prerequisites

Create or load a project. For custom propellants, add them first in the Library tab. Use Tools > Engineering Settings... to switch between US Customary and SI engineering units.

Steps

  1. Open Define and select Propellants in the Sections list.
  2. Use Search oxidizer deck and Search fuel deck, then click or press Enter on the desired entries. The Mixture ratio and propellant conditions card updates the reference note for the selected pair.
  3. Enter Mixture ratio (O/F), Oxidizer inlet temp, and Fuel inlet temp. Use Find optimal O/F only when an embedded table is available and you want a preliminary peak-vacuum-Isp mixture-ratio estimate.
  4. Select Engine in the Define sections list. In Solve method, choose First-pass sizing for a single-pass design point or Coupled steady-state to iterate injector flow, feed pressure, O/F, mass flow, nozzle flow, and chamber pressure to consistency.
  5. In Sizing basis, choose one of Target vacuum thrust, Total mass flow, Injector geometry, Throat diameter, or Feed pressure. Enter the active known input in Known inputs.
  6. In Operating conditions, enter Chamber pressure, Ambient pressure, and Expansion ratio. In coupled mode, chamber pressure is the initial guess; the solved chamber pressure may differ.
  7. In Thermodynamics and nozzle model, choose Thermochemistry source: Auto, Tabulated CEA, Screening Correlation, or RocketCEA. Then choose Nozzle flow mode: Frozen or Equilibrium Estimate.
  8. Click Solve. Review Review > Solve summary and Review > Thermochemistry for the requested source, actual source, fallback reason when applicable, nozzle flow mode, and warnings before exporting.
Define Engine and Propellants sections after propellant and target entry
Propellant selection, sizing basis, operating conditions, and thermochemistry source.

Expected result

The Review tab shows a solved performance summary, thermochemistry source, nozzle flow mode, chamber state, station values, and any warnings. The status bar reports the solve outcome.

Common notes

  • Auto records the requested source and the actual source used. RocketCEA is optional and external; embedded tables and screening correlation are visibly labeled when used.
  • Screening Correlation is preliminary and should not be treated as CEA, validation data, or final design evidence.
  • If a numeric field is blank or invalid, the app blocks the solve and highlights the input instead of silently keeping an old value.