Set feed and boundary assumptions.

Steps

1. Open Define > Engine. For a closure calculation, select Coupled steady-state under Solve method.
2. In Feed boundary condition (coupled solve), choose the boundary that matches the information you actually have: Fixed injector ΔP/Pc, Fixed injector inlet pressure, or Fixed supply + est. losses.
3. Enter the active boundary fields. Use separate oxidizer and fuel values where shown; mismatched stream pressure drops can move the solved O/F.
4. Open Define > Hardware > Feed and enter line and valve assumptions. Treat these as preliminary pressure-budget inputs, not a detailed feed-network solve.
5. Open Systems > Pressurization. Select Blowdown, Regulated, or Pump-Fed, then enter the visible inputs for the selected architecture.
6. Open Systems > Mass Budget. Select tank material and geometry assumptions, then review wet mass, dry mass with margin, propellant mass, pressurant mass, and the mass breakdown table.
7. Run Solve again after changing feed, pressurization, injector, or nozzle inputs. Then use Review > Solve summary, Review > Injector, and Review > Exports for the auditable result.

Expected result

The coupled solve reports whether injector flow, chamber pressure, O/F, mass flow, and nozzle demand reached a consistent operating point. Systems outputs update from the solved performance and remain preliminary sizing estimates.

Common notes

• Fixed supply + est. losses is a labeled screening boundary condition. It should not be presented as a resolved feed-line model.
• If inlet pressure is below chamber pressure, injector flow is invalid and the app blocks or warns rather than hiding the condition.
• Pressurization and mass-budget results depend on burn duration, tank assumptions, propellant properties, and solved mass flow. Keep those assumptions with exported reports.