File specification

Specification of the OpenRocket design file format (.ork) and the component preset file format (.orc).

This page describes the two file formats used by OpenRocket:

• .ork — the rocket design file, which stores a complete rocket design and all its simulations.
• .orc — the component preset file, which defines a database of standard rocket parts.

.ork design file

OpenRocket design file (.ork)

The .ork file format stores a complete rocket design including all components, materials, motor configurations, simulation settings, and simulation results.

File architecture

A .ork file is a ZIP archive containing an XML file and any associated graphics (e.g. decal images). The main rocket design XML is stored inside the archive as rocket.ork.

To inspect the contents of a .ork file:

1. Rename the file

   Rename the file extension from .ork to .zip.

2. Extract the archive

   Open the resulting .zip file with any ZIP extraction tool.

3. Open the XML

   The main design is in the file named rocket.ork inside the archive. Open it in any text editor. As of format version 1.11, a preview.png thumbnail is also included.

OpenRocket also accepts the .ork.gz extension for backward compatibility, but the plain .ork extension is recommended for all new files.

Developer reference

The reading and writing code is located in the core module:

Reading (.ork → rocket model):

Class	Purpose
OpenRocketLoader.java	Main entry point for loading a .ork file
OpenRocketContentHandler.java	SAX content handler for the XML
ComponentHandler.java	Dispatches parsing to the correct component handler
ComponentParameterHandler.java	Reads common component parameters
Specialized handlers	SimulationConditionsHandler.java, WindHandler.java, MotorHandler.java, etc.

All reader classes are in core/src/main/java/info/openrocket/core/file/openrocket/importt/.

Writing (rocket model → .ork):

Class	Purpose
OpenRocketSaver.java	Main entry point for saving a .ork file
RocketComponentSaver.java	Base class with shared saving logic
NoseConeSaver.java, BodyTubeSaver.java, etc.	Component-specific savers

All writer classes are in core/src/main/java/info/openrocket/core/file/openrocket/savers/.

Version history

The format version is declared in the version attribute of the root <openrocket> element. The version number follows semantic versioning: major version increases indicate backward-incompatible changes; minor version increases are backward-compatible additions.

Version	OpenRocket release	Key changes
1.0	0.9.0	Initial public release
1.1	0.9.4	Fin tab support; tube coupler subcomponents
1.2	1.1.1	Motor digest tag for thrust curve identification
1.3	1.1.9	Launch longitude and geodetic method parameters
1.4	12.03	Launch rod and deployment velocity; stage separation events
1.5	12.09	Component presets; custom expressions; lower-stage separation event
1.6	13.04	Component appearances (decals and paint); configurable recovery/ignition/separation
1.7	15.03	Simulation extensions; tube fin support
1.8	22.02	Rail buttons, pod sets, parallel stages (boosters); PhotoStudio settings; override CD
1.9	23.09	Component IDs for flight event sources
1.10	24.12	Simulation warning priority; document preferences; multi-level wind model; warning flight events
1.11	25.xx	Simulation stepper method; table column preferences; preview image in ZIP; embedded thrust curve data

Root structure

Every .ork file begins with an XML declaration followed by an <openrocket> root element:

<?xml version='1.0' encoding='utf-8'?>
<openrocket version="1.12" creator="OpenRocket 25.xx">
  <rocket>
    <!-- Rocket definition -->
  </rocket>
  <simulations>
    <!-- Simulation data -->
  </simulations>
  <photostudio>
    <!-- PhotoStudio settings -->
  </photostudio>
  <docprefs>
    <!-- Document preferences -->
  </docprefs>
</openrocket>

Rocket element

The <rocket> element holds the rocket metadata and all component definitions:

<rocket>
  <name>My Rocket</name>
  <id>[UUID]</id>
  <designer>Jane Smith</designer>
  <designtype>sport</designtype>
  <revision>Rev A</revision>
  <motorconfiguration configid="[UUID]" default="true">
    <stage number="0" active="true"/>
  </motorconfiguration>
  <subcomponents>
    <!-- Nose cone, body tubes, fins, etc. -->
  </subcomponents>
</rocket>

Key attributes:

Element	Description
name	Rocket design name
id	UUID auto-generated by OpenRocket
designer	Designer’s name
designtype	One of: scratch, kit, makeitgo, educational, sport, competition
motorconfiguration	One entry per defined motor configuration
subcomponents	Container for all rocket components

Common component attributes

All rocket components share these common child elements:

Element	Description
id	UUID auto-generated by OpenRocket
name	Component name
finish	Surface finish type
material	Material with type (bulk/surface/line), density, and optional group
axialoffset	Position along the rocket axis
radialdirection	Angular direction for radially placed components

Component tags

Structural components

Nose cone (<nosecone>):

<nosecone>
  <name>Nose cone</name>
  <id>[UUID]</id>
  <material type="bulk" density="500.0">Basswood</material>
  <length>0.22</length>
  <thickness>0.002</thickness>
  <shape>power</shape>
  <shapeclipped>false</shapeclipped>
  <shapeparameter>0.4</shapeparameter>
  <aftradius>0.075</aftradius>
</nosecone>

Supported <shape> values: ogive, conical, ellipsoid, power, parabolic, haack.

Body tube (<bodytube>):

<bodytube>
  <name>Body tube</name>
  <id>[UUID]</id>
  <material type="bulk" density="680.0">Cardboard</material>
  <length>0.3</length>
  <thickness>0.002</thickness>
  <radius>auto</radius>
</bodytube>

Transition (<transition>): Connects two tubes of different diameters. Supports the same shapes as nose cones.

Fin sets

Trapezoidal fin set (<trapezoidfinset>):

<trapezoidfinset>
  <fincount>3</fincount>
  <thickness>0.003</thickness>
  <crosssection>square</crosssection>
  <rootchord>0.05</rootchord>
  <tipchord>0.05</tipchord>
  <sweeplength>0.025</sweeplength>
  <height>0.03</height>
</trapezoidfinset>

Elliptical fin set (<ellipticalfinset>): Requires <rootchord> and <height>.

Freeform fin set (<freeformfinset>): Uses <finpoints> with individual <point x="..." y="..."/> elements for arbitrary fin shapes.

Tube fin set (<tubefinset>): Cylindrical fins. Requires <radius>, <length>, and <thickness>.

Inner components

Inner tube (<innertube>): Motor mount tube inside a body tube. Supports cluster configurations.

Tube coupler (<tubecoupler>): Coupler tube connecting two body tube sections.

Centering ring (<centeringring>): Ring that centers an inner tube within a body tube.

Bulkhead (<bulkhead>): Solid disk that closes the end of a tube.

Engine block (<engineblock>): Ring that retains a motor inside an inner tube.

Launch guides

Launch lug (<launchlug>): Tube-style launch lug. Attributes include <radius>, <length>, <thickness>, and <instancecount>.

Rail button (<railbutton>): Rail launch guide. Attributes include <outerdiameter>, <innerdiameter>, <height>, <baseheight>, and <flangeheight>.

Recovery and mass components

Parachute (<parachute>): Attributes include <diameter>, <cd>, <linecount>, <linelength>, <deployevent>, <deployaltitude>, and <deploydelay>.

Streamer (<streamer>): Attributes include <striplength>, <stripwidth>, <deployevent>, <deployaltitude>, and <deploydelay>.

Shock cord (<shockcord>): Attributes include <cordlength> and <material>.

Mass component (<masscomponent>): Generic non-structural mass. Use <masscomponenttype> to differentiate between nose weight, recovery wadding, altimeter, etc.

Assemblies

Stage (<stage>): A stackable rocket stage. Attributes include <separationevent>, <separationaltitude>, and <separationdelay>.

Pod set (<podset>): A set of identical pods radially positioned around the rocket. Added in format version 1.8.

Parallel stage / booster (<parallelstage>): Side-mounted booster that separates during flight. Added in format version 1.8.

Motor mount

Any body tube or inner tube can be used as a motor mount. When it is, a <motormount> child element is present:

<bodytube>
  <!-- ...other tube attributes... -->
  <motormount>
    <ignitionevent>automatic</ignitionevent>
    <ignitiondelay>0.0</ignitiondelay>
    <overhang>0.003</overhang>
    <motor configid="[UUID]">
      <manufacturer>Estes</manufacturer>
      <designation>A8</designation>
      <diameter>0.018</diameter>
      <length>0.07</length>
      <delay>3.0</delay>
      <!-- Embedded thrust curve (added in version 1.11) -->
      <standarddelays>0,3,5,none</standarddelays>
      <thrustcurvepoint>0,0,0.035,0.0164</thrustcurvepoint>
      <thrustcurvepoint>1,9,0.035,0.0145</thrustcurvepoint>
    </motor>
  </motormount>
</bodytube>

As of format version 1.11, the full thrust curve is embedded directly in the <motor> element. When <thrustcurvepoint> elements are present, OpenRocket reconstructs the motor from the embedded data instead of looking it up in the motor database. This makes designs self-contained when sharing custom motors.

• <standarddelays> — comma-separated list of standard delays in seconds; use none for plugged/no ejection charge.
• <thrustcurvepoint> — time,thrust,cg_x,mass in seconds, Newtons, meters, kilograms.

Simulation data

The <simulations> section contains one <simulation> element per simulation:

<simulations>
  <simulation status="loaded">
    <name>Simulation 1</name>
    <simulator>RK4Simulator</simulator>
    <calculator>BarrowmanCalculator</calculator>
    <conditions>
      <configid>[UUID]</configid>
      <launchrodlength>1.0</launchrodlength>
      <launchrodangle>0.0</launchrodangle>
      <launchaltitude>0.0</launchaltitude>
      <launchlatitude>45.0</launchlatitude>
      <atmosphere model="isa"/>
      <timestep>0.05</timestep>
      <wind model="average">
        <speed>2.0</speed>
        <direction>1.5707963267948966</direction>
        <standarddeviation>0.2</standarddeviation>
      </wind>
    </conditions>
    <flightdata maxaltitude="50.605" maxvelocity="29.249" timetoapogee="3.443"
                flighttime="15.89" groundhitvelocity="4.583"/>
  </simulation>
</simulations>

Wind models: OpenRocket supports two models:

<!-- Average wind model -->
<wind model="average">
  <speed>2.0</speed>
  <direction>1.5707963267948966</direction>
  <standarddeviation>0.2</standarddeviation>
</wind>

<!-- Multi-level wind model (added in version 1.10) -->
<wind model="multilevel" altituderef="agl">
  <windlevel altitude="0.0" speed="2.0" direction="1.57" standarddeviation="0.2"/>
  <windlevel altitude="100.0" speed="3.0" direction="1.57" standarddeviation="0.3"/>
  <windlevel altitude="500.0" speed="5.0" direction="1.60" standarddeviation="0.4"/>
</wind>

The altituderef attribute is either agl (above ground level) or msl (mean sea level).

Document preferences

The <docprefs> section stores document-wide settings including custom material definitions:

<docprefs>
  <docmaterials>
    <material>BULK|My Custom Material|680.0|1.2E9|Custom</material>
  </docmaterials>
</docprefs>

Material string format: {type}|{name}|{density}|{inPlaneShearModulus}|{group}. Older files may omit inPlaneShearModulus.

.orc component file

OpenRocket component file (.orc)

The .orc file format defines a database of standard rocket parts (component presets). Users can select presets from this database instead of entering all dimensions manually.

File architecture

A .orc file is a plain XML file. During the build process, all .orc files are serialized into a single binary file (system.ser) that is bundled inside the OpenRocket JAR. The component database is a Git submodule at core/resources-src/datafiles/openrocket-database.

The .orc format uses JAXB (Jakarta XML Binding) annotations for serialization and deserialization. This is different from the .ork format, which uses SAX parsing for reading and direct XML writing for saving.

Developer reference

Reading (.orc → ComponentPreset objects):

Class	Purpose
OpenRocketComponentLoader.java	Main loader
OpenRocketComponentDTO.java	Root XML data transfer object
BodyTubeDTO.java, NoseConeDTO.java, etc.	Component-specific DTOs
MaterialDTO.java	Material DTO
BaseComponentDTO.java	Shared base DTO

Writing (ComponentPreset objects → .orc):

The OpenRocketComponentSaver.java class uses JAXB marshalling from the same DTO classes.

All classes are in core/src/main/java/info/openrocket/core/preset/xml/.

Root structure

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<OpenRocketComponent>
  <Version>0.1</Version>
  <Materials>
    <!-- Material definitions -->
  </Materials>
  <Components>
    <!-- Component definitions -->
  </Components>
</OpenRocketComponent>

Materials

Material definitions have scope only within their .orc file. When a component from a preset is added to a .ork design, the material definition is copied into the design at that point. Later changes to the .orc file do not automatically update existing designs.

<Materials>
  <Material UnitsOfMeasure="g/cm3">
    <Name>Cardboard</Name>
    <Density>680.0</Density>
    <ShearModulus>1.2E9</ShearModulus>
    <Type>BULK</Type>
    <Group>PaperProducts</Group>
  </Material>
</Materials>

Supported UnitsOfMeasure values:

Category	Values
Bulk density	g/cm3, kg/m3, lb/ft3
Areal density	g/cm2, oz/in2
Line density	g/cm, oz/in

Material Type must be one of BULK, SURFACE, or LINE.

Common component attributes

All component types share these child elements:

<Manufacturer>Estes</Manufacturer>
<PartNumber>BT-60</PartNumber>
<Description>Estes BT-60 body tube, 12 inches</Description>
<Material Type="BULK" Group="PaperProducts">Cardboard</Material>
<Mass Unit="kg">0.035892</Mass>
<Filled>true</Filled>
<Thumbnail>base64EncodedImageData</Thumbnail>

Thumbnail is an optional Base64-encoded PNG image for the component browser.

Component types

Body tube

<BodyTube>
  <InsideDiameter Unit="m">0.0657352</InsideDiameter>
  <OutsideDiameter Unit="m">0.06604</OutsideDiameter>
  <Length Unit="m">0.36195</Length>
</BodyTube>

Nose cone

<NoseCone>
  <Shape>ELLIPSOID</Shape>
  <ShapeParameter>1.0</ShapeParameter>
  <Filled>true</Filled>
  <OutsideDiameter Unit="m">0.06604</OutsideDiameter>
  <BaseDiameter Unit="m">0.06604</BaseDiameter>
  <ShoulderDiameter Unit="m">0.064922</ShoulderDiameter>
  <ShoulderLength Unit="m">0.0381</ShoulderLength>
  <Length Unit="m">0.1016</Length>
  <Thickness Unit="m">0.003175</Thickness>
</NoseCone>

Supported <Shape> values: CONICAL, ELLIPSOID, HAACK, OGIVE, PARABOLIC, POWER.

HAACK, OGIVE, PARABOLIC, and POWER support a shape parameter in the UI, but it cannot be specified in the .orc file.

Transition

<Transition>
  <Shape>OGIVE</Shape>
  <ForeOutsideDiameter Unit="m">0.067056</ForeOutsideDiameter>
  <ForeShoulderDiameter Unit="m">0.064973</ForeShoulderDiameter>
  <ForeShoulderLength Unit="m">0.0254</ForeShoulderLength>
  <AftOutsideDiameter Unit="m">0.03175</AftOutsideDiameter>
  <Length Unit="m">0.1524</Length>
  <Thickness Unit="m">0.003175</Thickness>
</Transition>

Centering ring, bulkhead, engine block

Centering ring:

<CenteringRing>
  <InsideDiameter Unit="m">0.0187452</InsideDiameter>
  <OutsideDiameter Unit="m">0.0240792</OutsideDiameter>
  <Thickness Unit="m">0.003175</Thickness>
  <Length Unit="m">0.00635</Length>
</CenteringRing>

Bulkhead:

<BulkHead>
  <Filled>true</Filled>
  <OutsideDiameter Unit="m">0.028702</OutsideDiameter>
  <Length Unit="m">0.0381</Length>
</BulkHead>

Engine block:

<EngineBlock>
  <InsideDiameter Unit="m">0.0131318</InsideDiameter>
  <OutsideDiameter Unit="m">0.0179832</OutsideDiameter>
  <Thickness Unit="m">0.003175</Thickness>
  <Length Unit="m">0.003175</Length>
</EngineBlock>

Launch guides

Launch lug:

<LaunchLug>
  <InsideDiameter Unit="m">0.0055626</InsideDiameter>
  <OutsideDiameter Unit="m">0.006096</OutsideDiameter>
  <Length Unit="m">0.0508</Length>
</LaunchLug>

Rail button:

<RailButton>
  <InnerDiameter Unit="m">0.008</InnerDiameter>
  <OuterDiameter Unit="m">0.0097</OuterDiameter>
  <Height Unit="m">0.0097</Height>
  <BaseHeight Unit="m">0.002</BaseHeight>
  <FlangeHeight Unit="m">0.002</FlangeHeight>
</RailButton>

Recovery components

Parachute:

<Parachute>
  <Diameter Unit="m">0.6096</Diameter>
  <DragCoefficient>0.80</DragCoefficient>
  <Sides>8</Sides>
  <LineCount>8</LineCount>
  <LineLength Unit="m">0.7493</LineLength>
</Parachute>

Streamer:

<Streamer>
  <Length Unit="m">0.5</Length>
  <Width Unit="m">0.05</Width>
  <Thickness Unit="m">0.00005</Thickness>
</Streamer>

Tube coupler:

<TubeCoupler>
  <InsideDiameter Unit="m">0.0</InsideDiameter>
  <OutsideDiameter Unit="m">0.017907</OutsideDiameter>
  <Length Unit="m">0.019050</Length>
</TubeCoupler>

Units of measure

All dimension attributes in .orc files use a Unit attribute:

Quantity	Supported units
Length	mm, cm, m, in, in/64, ft
Mass	g, kg, oz, lb
Density (bulk)	g/cm3, kg/m3, lb/ft3
Density (areal)	g/cm2, oz/in2
Density (line)	g/cm, oz/in