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Peter Pak edited this page Apr 15, 2026 · 4 revisions

OpenRocket

The OpenRocket module bridges the Java-based OpenRocket simulator with the RocketSmith pipeline. It provides MCP tools for rocket design, simulation, motor database queries, and component tree generation.

MCP Tools

Tool Description
openrocket_new Create a new .ork design file with a named rocket
openrocket_component CRUD operations on rocket components; supports override_mass_kg for post-print calibration
openrocket_component (action="read") Generate a hierarchical component tree from an .ork file with mm-scaled dimensions, static stability, agent annotations, and ASCII side profile; writes gui/component_tree.json to the project directory. Optional out_path overrides the output location.
openrocket_flight Assign a motor and create a simulation configuration; writes flight JSON files to <project_dir>/flights/. Optional out_dir overrides the output directory.
openrocket_database Query the motor and component preset databases with filters

Component Tree Generation

openrocket_component (action="read") is the primary handoff between the OpenRocket agent and downstream agents (manufacturing, cadsmith). It:

  1. Opens the .ork file via orhelper and the OpenRocket JAR.
  2. Walks the component hierarchy, converting all dimensions from metres to millimetres.
  3. Parses each component's comment field for == agents == annotations (see below).
  4. Computes static stability via the Barrowman method.
  5. Renders an ASCII side profile of the rocket.
  6. Writes gui/component_tree.json to the project directory (or out_path if provided).

The output ComponentTree contains:

ComponentTree
  schema_version: int
  source_ork: str
  project_root: str
  generated_at: str (ISO 8601)
  rocket_name: str
  stages: list[Stage]
    name: str
    components: list[Component]
    cg, cp: QuantityField (mm)
    stability_cal: float
    max_diameter: QuantityField (mm)

Each Component carries typed dimensions, mass, material, human_notes, an optional agent annotation, and recursive children.

Stability Calculations

Static stability is computed in stability.py using the Barrowman method:

  • CG -- walks all components, accumulating mass * absolute_position to find the centre of gravity.
  • CP -- invokes OpenRocket's BarrowmanCalculator via JPype to compute the centre of pressure.
  • Stability margin -- (CP - CG) / max_diameter, reported in calibers. A value of 1.0--1.5 is nominal.

The StabilityResult dataclass holds cg_m, cp_m, max_diameter_m, and stability_cal.

Dimension Models

All dimension models use pintdantic (QuantityModel / QuantityField) so values carry physical units (default: mm). A discriminated union Dimensions selects the correct model via the kind field.

Model kind Key Fields
NoseConeDimensions nose_cone shape, length, base_od, wall
TubeDimensions tube length, od, id, motor_mount
TransitionDimensions transition shape, length, fore_od, aft_od, wall
FinSetDimensions fin_set fin_type, count, root_chord, tip_chord, span, sweep, thickness
RingDimensions ring od, id, thickness
RecoveryDimensions recovery diameter, length, packed_length, packed_diameter
GenericDimensions generic length, width, height, mass

The mapping from OpenRocket type names (e.g. TrapezoidFinSet) to dimension kind is handled by dimension_kind() using the _TYPE_TO_DIMENSION_KIND lookup table.

Agent Annotations

Component comments in the .ork file can contain structured agent data below an == agents == delimiter. The format is:

Human-readable notes go here.

== agents ==
fate: print
reason: Body tube is always a standalone printed part for AM
updated_by: manufacturing
updated_at: 2026-04-10T12:00:00+00:00
dfam_shoulder_length_mm: 30.0

Two functions in manufacturing.models handle this:

  • parse_comment(comment) -- splits a comment string into (human_notes, AgentAnnotation). Returns (None, None) for empty comments.
  • serialize_comment(human_notes, annotation) -- rebuilds the comment string from parts.

This format ensures agent annotations survive .ork regeneration -- human notes above the delimiter are preserved, and the agent section is re-parsed on each openrocket_component (action="read") call.

ASCII Art Rendering

openrocket_component (action="read") includes an ASCII side profile in its output. The rocket's external profile (nose cone, body tubes, fins, transitions) is rendered as a text-art diagram, giving a quick visual sanity check without needing a GUI.

The ASCII renderer lives in openrocket/ascii/ and produces a proportional side view based on the component dimensions extracted from the .ork file.

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