ENH: Acceleration data to trigger parachutes

[giovaniceotto]

Is your feature request related to a problem? Please describe. Currently, custom functions used to trigger parachutes (events) only have access to Pressure and the State Vector (position, velocity, attitude, angular rates).

However, real-world flight computers (avionics) heavily rely on Accelerometers (IMU) to detect flight phases (e.g., Liftoff, Motor Burnout, Apogee).

• Example: A user wants to deploy a drogue parachute only if the rocket detects it is under free-fall (approx 0g total acceleration) or has detected a specific deceleration curve.

Because RocketPy does not expose acceleration to the trigger, users cannot simulate these realistic avionics algorithms.

Describe the solution you'd like I would like to update the Flight class event handling logic to pass acceleration data to the parachute trigger callbacks.

The trigger signature should ideally support:

def my_trigger(p, y, u_dot):
    # p = pressure
    # y = state vector [x, y, z, vx, vy, vz...]
    # u_dot = derivative [vx, vy, vz, ax, ay, az...]
    
    vertical_acceleration = u_dot[5] 
    return vertical_acceleration < -9.0 # Deploy if falling

Implementation Details

• Target File: rocketpy/flight/flight.py
• Mechanism: Inside the event wrapper methods (which interface with scipy.integrate), we need to explicitly call self.u_dot(t, y) to obtain the current derivatives.
• Performance Note: Calling u_dot inside the event checker effectively doubles the physics load for event detection. This is acceptable for the gained accuracy, but we should document it.
• Noise: Ideally, we should allow a way to inject "sensor noise" into this acceleration before passing it to the trigger, simulating a real MEMS accelerometer.

Acceptance Criteria

• [ ] Update Flight class to calculate u_dot inside the event checking loop.
• [ ] Pass the acceleration components (or the full u_dot) to the user-defined trigger function.
• [ ] Add a tutorial example showing how to trigger a parachute based on "Motor Burnout" (sudden drop in acceleration).

Additional Context

• Currently, the state vector y contains [x, y, z, vx, vy, vz, ...].
• The acceleration [ax, ay, az] is only available after computing the derivative u_dot.

[Gui-FernandesBR]

@FranzYuri can you please take a look at this since it's releated to parachute functions? I think you'll like it!!

Might not be too complicated, but let's use some minutes during the week to discuss if needed

[giovaniceotto]

@MateusStano, these may help you:

• https://github.com/scipy/scipy/commit/7e2ddf86c5f8df9642f330e4a1d09f838e953306
• https://computing.llnl.gov/sites/default/files/ODEPACK_pub2_u113855.pdf (page 93)