Project Information
- Category: Hardware
- Client: UMN Rocket Team
- Project date: Sep 2022 - Jun 2023
Project Objective
The avionics team must select suitable pressure sensors and design a PCB with the ability to collect and store pressure data through the flight of the rocket, with the goal of being able to measure airspeed.
Overview
For the 2023 Spaceport America Cup, the "Special Projects" sub-team's project was to build a pitot tube that could be placed within the nose of our rocket. Special Projects handled the structure, but was required to work with the avionics sub-team to construct a PCB for data collection. This PCB must be able to fit into the nosecone and have connections to the pitot tube through piping. It must have 6 different sensors, all of which output their data in analog. Therefore, an analog to digital converter was also needed. The data coming from this board was to be sent to a storage location away from the pitot tube itself. Initially this was supposed to be to the Universal Flight Computer that was already in the rocket, however it was later decided due to time constaints to install a Teensy microcontroller instead.
Final Product
The final design was a circular PCB that would fit the shape of the nosecone, with 4 large holes to accommodate the supports for the pitot tube itselt. Four more smaller holes provide mounting holes for the PCB itself. The pressure sensor chosen is the BPS130-HA100P-1SG. Six of these sensors were arranged in a pattern agreed upon by avionics and the special projects sub-teams to work best with the piping required for the pitot tube. All of these sensors went to one ADS8344E analog to digital converter (ADC). The ADC then sends it output to an offboard connector that eventually makes it's way to a Teensy microcontroller.
Conclusion
Shown below is the annotated plots of the pitot tubes performance in actual flight. The static pressure (top plot) measures atmospheric pressure around the rocket. It very clearly shows each stage of flight. From it sitting on the pad, launch, which is indicated by the beginning of decreasing pressure, and apogee, which is the point at which the rocket hits zero upward velocity and starts falling. Finally, each parachute stage is visable by the rate of change in altitude after apogee. Ground impact is the very last spike in pressure. The pitot pressure measures the static air pressure plus ram air pressure caused by the velocity of the rocket through the air. The same stages of flight are visable in this plot as well, but an additional point, motor burnout, is indicated by the sudden decrease in ram air pressure, as the rocket is no longer being accelerated by the motor, and instead being slowed by air resistance. These plots are exactly what we would expect to see on a nominal launch. In fact, it was the launch that won us the 2023 competition (by points)! This project was therefore a success.
