Advanced: Using DynamicObject Basilisk Modules

Basilisk modules such as spacecraft are members of the DynamicObject class. This means they still have the regular Basilisk reset() and updateState() methods, but they also have a state machine and integrator build in as these modules have to integrate internal ordinate differential equations (ODEs).

Basilisk modules such as spacecraft and spacecraftSystem inherit from the DynamicObject class. These modules include the standard reset() and updateState() methods, but also incorporate a built-in state machine and numerical integrator to solve internal ordinary differential equations (ODEs).

A key feature of DynamicObject is the ability to synchronize integration across multiple instances of these modules. This is particularly useful in scenarios where dynamics are coupled—such as two spacecraft interacting through force or torque-based effectors.

Suppose you have two spacecraft instances, scObject and scObject2, and you want their dynamic integration to be synchronized. This can be achieved from Python using the following command:

scObject.syncDynamicsIntegration(scObject2)

This call links the integration of scObject2 to that of scObject. Even if scObject is configured to run in a task executing at 10 Hz using an RK4 integrator, and scObject2 is in a separate task running at 1 Hz with an RK2 integrator, the integration setup of the primary object (scObject) overrides the configuration of the secondary synced object. As a result, both objects are integrated using the RK4 integrator at 10 Hz. However, the updateState() method of scObject2 is still called at its task’s update rate of 1 Hz.

Note

The syncDynamicsIntegration() method is not limited to linking two DynamicObject instances. The primary DynamicObject maintains a list of all synced objects. This allows you to synchronize the integration across any number of DynamicObject instances.

The integration algorithm is determined by the integrator assigned to the primary DynamicObject. By default, this is the Runge-Kutta 4 (RK4) method. Regardless of the integrator settings on secondary objects, the integration configuration of the primary object takes precedence.