Compared with other simulators

A yes links the page that shows it; a partly or a no links the page that shows what the tool does instead, and says it in words below the table. For HPR Sim, a yes links the page of this site that covers it, and a no links the roadmap entry that brings it.

A yes says nothing of accuracy, least of all past the speed of sound: HPR Sim’s own drag there is rough and can be off either way (Drag through the speed of sound), OpenRocket’s documentation aims only at low supersonic speeds, and no tool’s accuracy there has been set against a logged flight here. The rows also leave out much that a tool may have, such as plots, parts catalogs and recovery design: check a tool’s own pages before you switch.

What none of the others has. Of the capabilities above, as far as each tool’s documentation shows, HPR Sim alone flies a design file from a command line and names the known gaps in its models that bear on each flight, and which way each pushes the numbers where that is known: each of the others’ cells in those rows says no.

Where HPR Sim has less. Each row where another tool says yes and HPR Sim doesn’t, with the milestone that brings it:

• Draws and edits a design in a window: OpenRocket and RASAero II do; HPR Sim doesn’t yet (M9.1, Desktop app shell).
• Estimates the speed at which the fins flutter: RocketPy does; HPR Sim does in part (M6.6, Submission packs).
• Reads an altimeter’s flight log: RocketPy does; HPR Sim does in part (M7.1, Flight log importers).
• Flies airbrakes driven by a control law: RocketPy does; HPR Sim doesn’t yet (M6.4, Airbrakes).
• Flies a hybrid or liquid motor with its tanks: RocketPy does; HPR Sim doesn’t yet (M11.3, Certified hybrids).

Each cell’s note. Every partly and no says what the page its cell links to shows instead; a yes may carry a limit its documentation states.

• Opens an OpenRocket .ork design file. RocketPy (no): it has no .ork reader; a design is typed in as Python. RASAero II (no): it opens its own files and imports RockSim’s; its manual names no OpenRocket format.
• Writes a design to an .ork file. RocketPy (no): nothing in its guide or reference writes a design file for another program. RASAero II (no): it saves its own format only.
• Draws and edits a design in a window. HPR Sim (no): no window yet; it flies a design drawn in OpenRocket. RocketPy (no): it is a Python library, with no window.
• Flies in six degrees of freedom. RASAero II (no): it flies two degrees of freedom in calm air and three with weathercocking when a wind is entered.
• Flies a rocket of more than one stage. RocketPy (partly): it has no stage object or separation event; a flight can start where another ended, with a rocket of its own for each stage.
• Works out drag and stability past the speed of sound. OpenRocket (yes): its technical documentation aims at reasonable estimates at transonic and low supersonic speeds. RocketPy (partly): its drag comes from curves the user supplies, and its center of pressure varies with Mach, but its reference names no method past the speed of sound. RASAero II (yes): its manual gives drag, normal force and center of pressure from Mach 0.01 to Mach 25.
• Flies a design many times with its inputs scattered, for a landing spread. OpenRocket (no): its newest release’s notes add none, its features page lists it as planned, and the landing-spread page in its guide is on the development branch only. RASAero II (no): neither its contents nor its flight chapter has a spread or a Monte Carlo.
• Fetches a launch day’s forecast, reanalysis or balloon sounding into the flight. OpenRocket (partly): its newest release adds wind by height, typed in or read from a file, but fetches nothing. RASAero II (no): the launch site takes a temperature, a pressure and one wind speed, on the standard atmosphere.
• Flies a design file from a command line. OpenRocket (no): its command-line arguments set options for the window; none flies a design. RocketPy (no): it is a Python library; the terminal only installs it. RASAero II (no): it runs from its window; its manual describes no command.
• Flies a design from a Python script. OpenRocket (no): its documentation covers a Java interface only; the separate orhelper package isn’t in it. RASAero II (no): its manual describes no scripting.
• Estimates the speed at which the fins flutter. HPR Sim (partly): in the Rust library; the command line and Python don’t print it yet, which the submission packs bring. OpenRocket (no): its features page lists fin flutter as planned. RocketPy (yes): an estimate from the same NACA criterion HPR Sim uses, which its documentation calls only an estimate. RASAero II (no): its manual never mentions flutter.
• Reads an altimeter’s flight log. HPR Sim (partly): it reads PerfectFlite’s logs only, so far. OpenRocket (no): its features page lists importing altimeter data as planned. RocketPy (yes): its examples read a log saved as CSV and set it beside a flight. RASAero II (no): it suggests writing the altimeter’s readings into the design’s comments, to compare by hand.
• Flies airbrakes driven by a control law. HPR Sim (no): no airbrakes yet. OpenRocket (no): its example extensions control roll, not drag; airbrakes would need a Java extension of one’s own. RASAero II (no): its manual describes no airbrakes or control.
• Flies a hybrid or liquid motor with its tanks. HPR Sim (no): commercial solid motors only until its first full release. OpenRocket (no): a motor is a thrust-curve file; its features page lists hybrids as planned. RocketPy (yes): its tanks drain as the user prescribes; nothing predicts the flow. RASAero II (no): a motor is a thrust-curve file or one from its own list.
• Warns when a flight leaves its models’ assumptions. RocketPy (no): its flight warning says the rocket is unstable at motor ignition, which is about the rocket, not its models. RASAero II (no): its warnings, of a marginal and of an unstable rocket, are about the rocket, not its models.
• Names the known gaps in its models that bear on each flight, and which way each pushes the numbers where that is known. OpenRocket (no): its warnings, as its technical documentation and its newest release’s notes describe them, name a broken assumption and leave it to the user to judge whether the results still hold; none says which way they err. RocketPy (no): its warnings say nothing of its models’ errors. RASAero II (no): its tips give general settings for a conservative altitude, not a flight’s own gaps.

The pages read.

• HPR Sim: each cell links the page of this site that shows it, or the milestone that brings it.
• OpenRocket 24.12, released July 27, 2025, read on October 12, 2026. Its online guide is built from its development branch and describes features no release has yet, so what the release holds was read from its release notes. Its technical documentation is the edition its site still links; the page numbers in the titles are the printed ones, and the links open the file at them.
  • OpenRocket 24.12’s release notes
  • OpenRocket’s guide: Features
  • OpenRocket’s guide: Features, planned future features
  • OpenRocket’s guide: Getting Started
  • OpenRocket’s guide: Getting Started, the user interface
  • OpenRocket’s guide: Advanced Rocket Design, staging
  • OpenRocket’s guide: Command Line Arguments
  • OpenRocket’s guide: Using OpenRocket Core in External Applications
  • OpenRocket’s guide: Simulation Extensions
  • OpenRocket’s guide: Thrust Curves
  • OpenRocket’s technical documentation, supersonic drag (page 48)
  • OpenRocket’s technical documentation, warnings (page 78)
• RocketPy 1.13.0, released July 22, 2026, read on October 12, 2026.
  • RocketPy’s documentation: home
  • RocketPy’s guide: Flight Class Usage, initial conditions
  • RocketPy’s reference: the Rocket class
  • RocketPy’s guide: Monte Carlo class usage
  • RocketPy’s guide: Forecasts
  • RocketPy’s guide: Installation
  • RocketPy’s guide: First Simulation
  • RocketPy’s reference: fin flutter analysis
  • RocketPy’s guide: Flight Comparator
  • RocketPy’s guide: Air Brakes
  • RocketPy’s guide: Tanks Usage
  • RocketPy’s reference: Exceptions and Warnings
• RASAero II 1.0.2.0, released May 22, 2019, read on October 12, 2026. Its manual is for the same release; the page numbers below are the manual’s.
  • RASAero II’s download page
  • RASAero II’s manual, introduction (page 4)
  • RASAero II’s manual, contents (page 2)
  • RASAero II’s manual, files (page 8)
  • RASAero II’s manual, stages (page 49)
  • RASAero II’s manual, launch site (page 78)
  • RASAero II’s manual, altimeter data (page 82)
  • RASAero II’s manual, motors (page 93)
  • RASAero II’s manual, warnings and tips (page 114)

The scoreboard holds every comparison the project has measured, axis by axis, and a check that keeps HPR Sim’s numbers from getting worse. Of the table’s 16 capabilities, HPR Sim has 11 in full, OpenRocket 7 and RocketPy 8. The rows are the project’s choice, so the count leans toward what HPR Sim was built to do: read the rows, not the count.

• Apogee against logged flights. On 53 logged flights of fliers’ own designs, flown from the same files, HPR Sim’s apogee missed by 12.95% on average without signs and OpenRocket’s by 12.02%; with their signs, HPR Sim’s averaged +8.73% above the logged apogees and OpenRocket’s +7.79% above. OpenRocket is ahead on both: this is HPR Sim’s largest measured gap (report). The flights are a private collection whose license allows only aggregates, so they can’t be rerun from this repository. HPR Sim flew 61 of its 83 flights whose design is an OpenRocket file; the comparison holds the flights both tools flew, less those the report leaves out with its reasons, so a design HPR Sim can’t fly yet is in neither number. RocketPy hasn’t flown them, since it can’t open their .ork files.
• Apogee against public flights. On the 7 public flights HPR Sim missed by 6.04% on average without signs, outside the project’s own 5% target (report); they are among the university rockets RocketPy’s documentation flies against their teams’ logs. OpenRocket and RocketPy haven’t flown them here yet (M2.6, an open benchmark, and M2.9, the other tools’ cells).
• Steps to a first answer. From a design’s .ork file to its apogee and its landing spread, HPR Sim takes 2 commands at a command line, or 10 lines of Python. OpenRocket flies it in 7 clicks in its window, but its newest release has no Monte Carlo for the spread, and RocketPy’s Python can’t open the file. Each step is listed on the scoreboard.
• Round trips through OpenRocket’s file. HPR Sim reads an .ork file and writes it back, and OpenRocket flies the original and the copy. Of 151 configurations, 0 moved by more than 0.5%, and the largest change was 0.000191%; 2 of 75 designs didn’t make the trip (report).

• If you design in OpenRocket, keep designing there: HPR Sim flies the same file as it is, and sets beside OpenRocket’s numbers a second flight, its spread from the command line or Python, and the known gaps that bear on that flight, with the side each pushes where that is known.
• If you fly past the speed of sound, treat every tool’s apogee there as rough: HPR Sim’s supersonic drag is known to be off, either way, and neither its accuracy nor OpenRocket’s has been measured against a logged flight there yet (M2.3c7, faster than sound: published flights).
• If you need airbrakes, a hybrid or liquid motor, or a window to draw in, HPR Sim doesn’t have them yet; the list above names the tools that do and the milestone that brings each.

• See it work: A tour of HPR Sim.
• How close it has come to real flights: Accuracy and Trusting a simulation.
• What comes next and when: Decisions and roadmap.

Sources. The logged flights are a private collection of designs and their logs, from university rocketry teams, rocketry courses and hobbyists, shared as aggregates only; the public flights are among those RocketPy’s documentation flies against their teams’ logs. 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.