Add a motor inside a body tube or motor mount. Its mass and CG become part of the rocket, and its thrust curve is used when you simulate the flight.
Add a motor#
Pick Motor from the Propulsion group in the parts toolbar. Motors mount inside a body tube or motor mount, and the placement proposal lands them there automatically. The parent tube matters: the picker uses its diameter and length to filter what fits.
Choose from the catalog#
The motor field in the details panel opens the selection dialog. The catalog is seeded from the ThrustCurve.org database — real thrust curves, dimensions, delays and masses across manufacturers — and the filter rail narrows it down:
- Manufacturer
Any single manufacturer, everything at once — or Mine, just your own motors.
- Diameter and length
Range sliders, each with a Limit to parent switch that caps the range at what the mount can physically take. The diameter limit is on by default.
- Impulse class
A class range — from the A-B-C of model rocketry up through high-power letters.
Results search and sort like a table. Once a motor is installed, the chart icon next to its name previews the thrust curve without leaving the panel.
Use your own motors#
Motors created in the motor builder appear in the same picker, marked Mine, and install like catalog motors. Run the motor simulation before selecting one for a rocket. If the motor uses static-fire data, the flight simulation uses the measured thrust curve instead of the simulated one (Static Fire Data).
Set the ejection delay#
The Ejection Charge section shows the delay options the installed motor supports — fixed drilled delays as a set of choices, an adjustable delay as a field with a slider, or nothing at all for a motor without a charge. A Disable Ejection switch plugs the motor entirely. The delay matters the moment a recovery device deploys on ejection or a stage separates on the charge — Recovery & Staging covers both, and Configuring a Motor covers defining the hardware side on a custom motor.
Cluster motors#
Flip the Cluster switch in the motor's Placement block and one motor becomes a radial pattern: set the count, the ring radius and a start angle. The default radius packs the motors tangent to each other around the centerline. A cluster stays a single tree entry — edit the motor once and every instance follows — but it renders and simulates as the full set of motors (Radial patterns explains the geometry).
Like any part, a motor's mass and CG can be overridden with measured values. Validation also checks the total first-stage thrust against liftoff weight before the simulation can run.