THRUST VECTOR CONTROL
BPS.SPACE SIGNAL R2
JUL. '19 - PRESENT
In June of 2019 I decided to form a thrust vector control project team under the University of Minnesota rocket team. Our goal is to design, build, and ultimately launch a high-power TVC rocket as a demonstration at the 2021 Spaceport America Cup. In order to get started, we invested in the Signal kit from BPS.space. Beginning with a kit allowed us to learn the basics of both the mechanical and software sides of thrust vector control. After mastering the kit, we will be able to move on to creating our own algorithms to run on a student-made flight computer that will control our own custom motor vectoring system. This system will then be scaled up to a full-scale high-power rocket.
The Signal flight computer runs a high speed control loop, prioritizing separate functions depending on the progress of the flight. Once burnout is detected, Signal centers and locks the vectoring mount. Focus is then set on detecting apogee and triggering pyro events.
The flight software programmed into Signal tracks vehicle flight dynamics while the rocket is powered on. Signal looks for cues to shift system states at liftoff, burnout, apogee, and landing. Especially regarding liftoff, this makes Signal's operation simple. Once the settings file is configured for flight, all that is required of the user is turning on the flight computer; Signal automatically enters the pad-idle mode. In pad-idle mode, Signal can detect launch in under 10ms. Once detected, thrust vectoring is activated, in-flight abort is armed, and high-frequency data logging begins
The thrust vector control motor mount is made from 3D printed PLA material. The mount uses two 9g servos, geared down for higher accuracy. The assembly can gimbal a motor ±5 degrees on each axis, X and Y. Though up to 40N of force will work with the mount, it works best with lower impulse motors, especially those with long burn times.
The basic design of our rocket that houses the Signal R2 kit is not too different from a standard amateur rocket of this size, except for the lack of fins. This rocket can fly on any 29mm motor, but we primarily choose low-impulse, long-burn motors. This gives us a slow, yet long, flight that allows us to clearly see the actual thrust vectoring occur. We constructed the rocket primarily out of cardboard since it saves weight and does not need to be overly strong, as the forces we are dealing with on this type of motor are very low. The rocket is configured for single parachute deployment at apogee, which varies from 100 to 1,000+ feet, depending on the motor.
This is a gif from the recording of our first successful thrust vector controlled flight. If you watch closely, you can see the rocket makes several adjustments throughout its flight to remain upright and stable. Additionally, at the end of the gif you can see our parachute deploy -- although our rocket did not get to a high enough altitude to allow sufficient time for full parachute deployment.
This was a huge success and step forward in the progression of working towards a full-scale high power thrust vector controlled rocket. Our next step is to develop our own TVC gimbal that works with the Signal flight computer, and then ultimately replace the flight computer as well with our own student researched and designed counterpart.