BRAT
BRAT
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BRAT is a 3-inch sub-scale flight vehicle designed to test BRAT, a controlled airbrake system. On February 8th, BRAT was successfully launched on an Aerotech K1103X at Tripoli Association in Wisconsin (TAW), reaching 6,000ft. The data confirmed that airbrake system deployed all drag flaps as intended.
The airbrake system provides active trajectory control during ascent by deploying drag flaps after motor burnout to regulate deceleration and achieve a targeted apogee. The system consists of three subsystems: an Attitude Heading Reference System (AHRS), a course correction controller, and a mechanical execution system. The AHRS collects real-time flight data, including altitude, velocity, acceleration, temperature, and orientation, which is logged for post-flight analysis and passed to the controller. The course correction system compares measured flight data to the desired apogee and computes the required flap deployment. These commands drive a stepper motor that actuates the drag flaps through a compact mechanical assembly located aft of the rocket’s center of gravity, enabling precise extension and retraction while maintaining vehicle stability.
Airbrake
Airbrake
The Attitude Heading Reference System (AHRS) uses various accelerometer, gyroscope, and barometer readings to determine the rocket’s location and attitude during flight. The AHRS acts as the Navigation portion of the system. The System Controller reads the flight data from the AHRS and calculates the corrective actions needed to achieve the targeted apogee. This functions as the Guidance portion of the system. Lastly, using the corrective actions calculated by the System Controller, the Drag Flap System extends or retracts the Drag Flaps to alter the magnitude of the drag force. This is the Control portion of the system.
CFD Software was used to determine the influence drag flap extension angle and velocity have on the rocket’s drag coefficient. These curves will be used in the Correction Calculation Algorithm.
System Architecture
System Architecture
To accomplish active control, our air brake system needs to implement a feedback control loop. This can be broken down into 3 major steps: Sensor Data Acquisition/Processing, Correction Calculations, and Correction Execution.
February Test launch in Wisconsin
February Test launch in Wisconsin
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