HPR Sim

A flight simulator for rockets on commercial solid motors. It reads an OpenRocket .ork design file as it is and flies it in six degrees of freedom, the rocket’s position along three axes and its rotation about three, while the motor burns and the mass and balance point move. It prints the apogee, the speeds, the stability margin, the events from liftoff to landing and the known gaps in its models that bear on that flight, each with the side it pushes the numbers to.

It comes three ways, all from one code base, and none needs a network to fly a rocket:

• The command line, hpr: fly a file, scatter its inputs to see the spread (Monte Carlo dispersion), look up and convert motors, read an altimeter’s log, and fetch a launch day’s weather (The command line).
• The Python package: the same flights from a script or a notebook (Python).
• The Rust library: the simulator inside a program of your own (Getting started).

Every model cites a published source, tests pin each one, and the results against RocketPy, OpenRocket and real flights are committed to the repository (Accuracy). It is early: the first release is out, and Start here lists what works today and what doesn’t yet.

• A flier with a design file who wants a second opinion on a flight before it flies, with the known gaps stated rather than hidden.
• A team that needs a flight’s spread, not one number: hpr mc flies the file many times with its inputs scattered.
• A developer who wants a simulator inside a program, a test or a notebook, offline, with the same numbers from the same inputs and seed on one machine.

It is not yet for a rocket on a hybrid, liquid or research motor, which it doesn’t fly, nor for drawing a design: it reads one made in OpenRocket. A design editor comes with the app.

• The command line: download the archive for your system from the releases page and put hpr on your path, or, with Rust installed, run cargo install fusionspace-hpr-cli --locked.
• The Python package: pip install fusionspace-hpr, then from fusionspace import hpr.
• The library: cargo add fusionspace-hpr in your own Rust project.

Install a release lists the systems each file serves, and what to do on macOS when it can’t check the program.

• A tour of HPR Sim: fly the guide rocket, read what it prints, scatter its inputs, fly it again from Python, and see how HPR Sim did on a public flight.
• Compared with other simulators: what HPR Sim, OpenRocket, RocketPy and RASAero II each do, what has been measured side by side, and where HPR Sim has less.
• The task pages: Fly your .ork, Pick a motor, Check stability for a certification flight, Monte Carlo dispersion and Reading a flight log.
• Before you rely on a number: Trusting a simulation.

Sources. The public flights are among those RocketPy’s documentation flies against their teams’ logs; the logged flights are published by university rocketry teams, rocketry courses and hobbyists. Both fly in ERA5 weather: generated using Copernicus Climate Change Service information 2026, and contains modified Copernicus Climate Change Service information 2026; neither the European Commission nor ECMWF is responsible for any use made of it. The logged flights’ report gives the full attribution and the ERA5 citations.