rocketpy-simulation

name	rocketpy-simulation
description	Understand how generated parameters.json maps onto the RocketPy API (Environment, SolidMotor/Motor, Rocket, Flight) and how nb_builder.py assembles a runnable RocketPy notebook. Use when editing nb_builder.py, changing what a component contributes to the notebook, debugging a generated simulation, or aligning output with a RocketPy version.

RocketPy simulation mapping

rocketserializer produces inputs for RocketPy (rocketpy>=1.1.0). The generated notebook (nb_builder.NotebookBuilder) reads parameters.json and constructs a standard RocketPy simulation. Keep the mapping below in mind when changing extraction or the builder.

The RocketPy objects the notebook builds

The build_* methods in NotebookBuilder map settings sections onto RocketPy classes:

• build_environment → Environment (latitude, longitude, elevation, date, atmospheric model). Fed by settings["environment"] + settings["flight"].
• build_motor → a motor object (e.g. SolidMotor) using settings["motors"], with thrust_source pointing at the generated thrust_source.csv.
• build_rocket → Rocket with mass/inertia/radius from settings["rocket"], the power_off/power_on drag from the generated drag_curve.csv, then aerodynamic surfaces added via add_nose, add_trapezoidal_fins / add_elliptical_fins, add_tail, and parachutes via add_parachute, plus rail buttons.
• build_flight → Flight (rocket + environment + rail length + inclination + heading).
• build_compare_results → compares RocketPy output against settings["stored_results"] (the values OpenRocket itself computed), which is how a user sanity-checks the conversion.

Practical guidance

• The builder is a codegen step: each method appends notebook cells (nbf.v4), so you are writing Python source strings that must run under the pinned rocketpy version. When you reference a RocketPy method/argument, verify it exists in that version's API rather than assuming.
• Coordinate systems and positions matter: RocketPy places surfaces relative to a reference (nose tip / center of dry mass). The positions come from open_rocket_wrangler — if a surface lands in the wrong place in the simulation, suspect the position map, not RocketPy.
• stored_results are the ground truth from OpenRocket (apogee, max velocity, etc.). Use them to validate: a good conversion makes the RocketPy Flight results land close to the stored ones.

When aligning with RocketPy

If a generated notebook fails to run, first reproduce with an example (ork2notebook --filepath "examples/NDRT--Rocket--2020/rocket.ork") and open the notebook. Fix the offending build_* method's emitted code, not the extraction, unless the underlying parameter is genuinely wrong in parameters.json.