Advanced Flight Simulation

OpenRocket offers more advanced options for simulating flight. You can plot your rocket’s predicted acceleration, climb, eject and landing, make a prediction for how far downrange and in which direction your flight will land, and even experiment with different models of Earth’s geometry, as it affects your flight. Once you’re satisfied with a sim, you can export your data for analysis and charting in other packages.

Plotting your rocket’s flight

To begin learning about OpenRocket’s plotting features, first, click the Plot / Export button on the Flight simulations window.

The Plot / export Button.

On the Edit simulation panel, you’ll see tabs marked Plot data and Export data.

Plotting data

The Plot data tab opens first. Here you can define many parameters that will determine what values are plotted, and what events are marked on the plot.

The Plot / export window.

Here you’ll be able to quickly choose from a number of standard plots:

Standard plots

You’ll also be able to assign to the X and Y axes any one of over 50 parameters. If you click on the plot variable dropdown, you’ll see a search box and a list of variable categories. You can either scroll through the categories to find the parameter you want, or type in the search box to filter the list:

Select plot variable

Select a plot variable from the variable groups (left), or search for the desired variable (right).

The parameters are categorized in the following groups:

  • Time: Variables related to time

  • Position and Motion: Variables related to the position and motion of the rocket (e.g. altitude, position, velocity, acceleration)

  • Orientation: Variables related to the orientation of the rocket (e.g. pitch, yaw, roll)

  • Mass and Inertia: Variables related to the mass and inertia

  • Stability: Variables related to the stability of the rocket (e.g. CG, CP, stability margin)

  • Thrust and Drag: Variables related to the thrust and drag (e.g. thrust, TWR, drag)

  • Coefficients: Variables related to the calculation coefficients (e.g. normal force coefficient, roll moment coefficient)

  • Atmospheric Conditions: Variables related to the atmospheric conditions (e.g. air pressure, wind velocity)

  • Characteristic Numbers: Variables related to the characteristic numbers (e.g. Mach number, Reynolds number)

  • Reference Values: Variables related to the reference values (e.g. reference area, reference length)

  • Simulation Information: Variables related to the simulation information (e.g. simulation time step)

  • Custom: (User-defined parameters)

You can assign multiple parameters to the Y-axis, and choose whether their scales appear on the left, or the right side of the plot. You can add Y-axis parameters with the New Y-axis plot type button, or delete parameters from the plot with the X buttons. (The X-axis takes only a single plotted parameter, typically Time).

Additionally, you can choose from several flight events, any or all of which can be called out on your plot, in reference to the simulated time of occurrence.

Setting Y-axes and Events for plotting

Plotted results

Below you can see a plot of A simple model rocket, simulation number 4, flying on a C6-5. Note that the five events checked in the above screen have been marked on the plot (some very close to each other, or to the edge): Motor ignition, Motor burnout, Apogee, Recovery device deployment, and Ground hit.

You can also see that the three Y-axis parameters described above: Altitude, Vertical velocity, and Vertical acceleration appear as lines of three different colors.

A Plot of the simulation.

As your rockets get more complex, with features like dual-deploy, air-start and multiple stages, your plots can grow in complexity to simulate their expected behavior. Below is a plot (from the example rockets) of a “High Power Airstart” rocket, modeled after a Patriot missile. The central motor starts on the launch pad, while the surrounding motors start while the rocket is in the air (hence, an “airstart”). The plot records the separate motor start events, and the deployment of both a drogue, and a main parachute.

A Plot of Sim #5 of the "High Power Airstart" example rocket.

Notice what’s happening in the plot above: The rocket is losing velocity - the blue line - before the airstart occurs. This is probably not what we want.

However, simulation number 3 of the same rocket, below, has an earlier airstart, and looks like it should work as expected. Looking at the slight wiggle in the velocity curve, we could also try another simulation to provide a little bit more margin for error.

A Plot of Sim #3 of the "High Power Airstart" example rocket.

Launch Conditions and Simulation Options

From the Plot data window, you can click the << Edit:guilabel: button to configure Launch conditions, and Simulation options before you plot.

Launch conditions

OpenRocket can simulate conditions at the launch site, so you can estimate how winds will direct your flight, and how far downrange your rocket will drift.

In the screen shown below, you can set parameters (and units) for wind, and for your Launch site, you can set the Latitude, Longitude and Altitude, as well as Atmospheric conditions. Note that Atmospheric conditions affect your rocket’s ascent velocity, as well as the local Speed of Sound.

This is also the panel where you can set the length of your launch rod or rail. This length will affect whether your simulation passes or fails, when it’s evaluated for minimum speed off the rod.

The Edit simulation window: Launch conditions.

Simulation options

In the Simulation options tab, the Simulator options let you choose the shape of the simulated Earth in your calculations (doing so does not affect the Earth background in Photo Studio), and you can choose the time-resolution of the simulation. This is also the place where you add and set up Simulation extensions, which are beyond this guide’s purpose.

The Edit simulation window: Simulation options.

The Simulation options in the simulation configuration window

Aerodynamic lookup tables

OpenRocket normally uses the Extended Barrowman method to calculate aerodynamic forces (drag and stability) based on your rocket’s geometry. However, you can override these calculations by providing custom aerodynamic data from wind tunnel tests, CFD simulations, or other sources using CSV lookup tables.

To configure lookup tables, edit a simulation and navigate to the Simulation options. Then, under the Aerodynamic data section, click the Configure….

Drag lookup tables

Drag lookup tables allow you to specify custom drag coefficients (Cd) as a function of Mach number and optionally angle of attack (AoA). The CSV file must include:

  • A Mach column (required) - Mach number values

  • An AoA column (optional) - Angle of attack in degrees

  • A Cd column (required) - Drag coefficient values

Example drag lookup table:

Mach,AoA,Cd
0.0,0,0.25
0.0,5,0.30
0.0,10,0.35
0.5,0,0.30
0.5,5,0.36
0.5,10,0.42
1.0,0,0.35
1.0,5,0.40
1.0,10,0.45

If you don’t include an AoA column, the table will only interpolate based on Mach number:

Mach,Cd
0.0,0.25
0.5,0.30
1.0,0.35

Stability lookup tables

Stability lookup tables allow you to specify custom stability coefficients as a function of Mach number and optionally angle of attack. The CSV file must include:

  • A Mach column (required) - Mach number values

  • An AoA column (optional) - Angle of attack in degrees

  • A Cn column (required) - Normal force coefficient

  • A Cm column (required) - Pitching moment coefficient

  • A Cp column (required) - Center of pressure position (in meters from the nose)

Example stability lookup table:

Mach,AoA,Cn,Cm,Cp
0.0,0,0.10,0.01,0.50
0.0,5,0.15,0.02,0.52
0.0,10,0.20,0.03,0.55
0.5,0,0.12,0.015,0.51
0.5,5,0.18,0.025,0.53
0.5,10,0.25,0.035,0.56
1.0,0,0.15,0.02,0.52
1.0,5,0.22,0.03,0.54
1.0,10,0.30,0.04,0.58

CSV file format

  • Header row: The first non-empty, non-comment line must contain column names

  • Column names: Case-insensitive, spaces and underscores are ignored. “Angle of Attack” or “AoA” both work

  • Comments: Lines starting with # are preserved in the file but ignored during parsing

  • Blank lines: Empty lines are preserved in the file but ignored during parsing

  • Separator: Comma (,) is the default separator, but you can configure semicolon, tab, or space separators

  • Interpolation: Values are linearly interpolated between table points in both Mach and AoA dimensions

  • Clamping: Values outside the table range are clamped to the nearest edge value

Editing lookup table data

Once you’ve loaded a CSV file, you can edit the data directly in the configuration dialog. The text area shows the loaded data, which you can modify as needed. Your edits are automatically saved to the .ork file when you click OK.

Important features:

  • Data embedding: The CSV data is embedded directly in the .ork file, so your rocket design is self-contained and portable

  • Edit preservation: Any edits you make are preserved when you close and reopen the dialog or simulation window

  • Comment preservation: Comment lines (starting with #) are preserved in your edits

  • Refresh button: Use the refresh button (↻) next to Load from file… to reload the original CSV file if it still exists on disk

  • Field separator: You can change the CSV field separator (comma, semicolon, tab, or space) - the example format updates automatically

When lookup tables are used:

  • Individual component forces are set to zero (only total forces are calculated from the table)

  • The axial drag conversion uses the same polynomial as the Barrowman method

  • Stall margin is calculated from the maximum AoA in the stability table (if AoA data is present)

  • Damping moments are set to zero

When to use lookup tables

Lookup tables are useful when:

  • You have wind tunnel test data for your specific rocket design

  • You have CFD simulation results that you want to use in OpenRocket

  • You want to validate OpenRocket’s Barrowman calculations against experimental data

  • Your rocket has complex aerodynamic behavior not well-captured by the Barrowman method

  • You need angle-of-attack dependent coefficients beyond what Barrowman provides

Note that when lookup tables are configured, they completely replace the Barrowman calculations for drag and/or stability. You cannot mix lookup table data with Barrowman calculations.

Exporting Data

Located on the Plot / export panel, the Export Data tab (shown below) helps you set up a Comma-Separated Value (.csv) formatted file to export data from your simulations. You can export any or all of over 50 values (generally speaking, the list of parameters above, plus Coriolis acceleration). Optional Comments sections list any flight events (Apogee, for example) you selected for your simulation, as well as description and field descriptions.

You can choose separators other than comma, if you prefer semicolon, space, or TAB-delimited data. Once you have your data choices set up, clicking the Export button brings up a file dialog to choose a filename and location for your exported data.

The Export data window.

The Export data window.