Team #5 RCS Payload
Team #5 RCS Data (10/25/2019)
Flight 0 (Two Month RCS)
Launch Date: October 25th, 2019
In October of 2019, the Two Month Reaction Control System (RCS) challenge teams launched the club's first cold-gas thruster balloon payloads. As part of the Two Month onboarding program, student's were tasked with designing and building payloads equipped with thrusters to stabilize payload rotation. This was a previously unexplored concept for payload stabilization that had not yet been tested by the Space Hardware Club.
These payloads utilized 18g CO2 cartridges as propellant controlled by fast-acting solenoid valves. This limited propellant size meant that these payloads could only attempt to stabilize for a short period of time before expelling all of their stored gas.
On the evening of October 25th, 2019, five RCS payloads were launched during the Two Month launch event. Of these teams, Team #5 demonstrated successful angular velocity stabilization within a desired +/- 70 degree/sec threshold at an altitude of 15 km.
Data from this flight showed that gas thrusters could affect the rotation of balloon payloads. After the conclusion of Two Month, members of Team #5 began designing a larger, more powerful gas thruster payload concept based on the lessons learned from the RCS challenge.
This led to the creation of the High Altitude Visual Orientation Control (HAVOC) project.
HAVOC team filling the first balloon
HAVOC Payload ascending above the UAH Campus
Launch Date: April 11th, 2021
After over a year of development, the first HAVOC Cyclone payload was flown on the morning of April 11th, 2021. The objective of this flight was to evaluate the performance of the brand new in a high altitude environment. Unlike the RCS challenge payloads which had a small CO2 propellant source, the Cyclone payload was equipped with a carbon fiber wrapped high pressure air (HPA) tank, containing 50 cubic inches of compressed air stored at 4,000 psi. This improved propellant source allowed the Cyclone payload to stabilize for much longer than the RCS challenge payload.
For this first mission, the Cyclone payload was programmed to activate stabilization at 15 km (the same altitude as the RCS payload flight) and to maintain angular velocity within a +/- 40 deg/sec threshold.
Shortly after launch, the payload camera system failed but internal data recording functioned throughout the entire flight. A secondary payload carrying a 360-degree camera mounted above the Cyclone payload was able to capture video of the payload attached to the line.
ASCENDING FLIGHT DESCENDING FLIGHT
Data from Flight #1 (April 11th, 2021)
Upon activation of the stabilization algorithm at 15km, the payload very quickly corrected its excess rotation, bringing its angular velocity within the +/- 40 degree/second threshold. The payload successfully maintained this threshold all the way up to balloon burst at approximately 25km. Upon successful deployment of the line parachute, the payload was able to maintain its velocity within the defined bounds during most of the descent period.
Period of stabilization: 1hr 9min 52sec
Total flight time: 1hr 49min 15sec
This successful demonstration of the long-duration stabilization capabilities of the Cylone design validated many of the design choices that the team had made in the previous year. The failure of the camera system led to the implementation of more reliable, GoPro style cameras for future flights.
Payload footage just after balloon burst
Launch Date: July 13th, 2021
On July 13th, 2021 the 2nd HAVOC flight was undertaken. To make up for the lack of video from the inaugural flight, a new camera was mounted onboard the payload. This mission was flown with the exact same goals as the first flight, to stabilize rate of rotation within a +/-40 deg/sec threshold starting at an altitude of 15km.
While the camera system did work throughout the entire flight, the payload's internal data recorder was not configured correctly and so did not collect data during the flight. However, from the recovered flight video we can see and hear the operation of the gas thrusters. With this footage we could visualize how the thrusters impact the rotation of the payload.
Payload footage from Flight #2 (July 13th, 2021)
Payload footage from Flight #3 (April 9th, 2022)
Upon landing the payload struck a pine tree, breaking both of its lever arms
Launch Date: April 9th, 2022
After two successful flights for stabilizing angular velocity, flight number 3 was the first to attempt to maintain a fixed payload azimuth. In preparation for future solar eclipse events over North America the HAVOC team began refining the payload control code to better maintain a targeted orientation, which would be needed to capture high-altitude video of a solar eclipse.
Flight number 3 was undertaken on April 9th, 2023, almost one year from the date of the first HAVOC Cyclone flight. For this mission the payload was instructed to maintain a fixed azimuth within a +/-15 degree dead-band. The payload would also perform a translation maneuver every 5 minutes, adjusting the azimuth setpoint in a step response. This was done to evaluate the effectiveness of the control code and the payloads response/settling time.
Also unlike previous flights, the Cyclone payload was now programmed to activate at a much lower altitude (200 meters) to see the difference in thruster performance due to difference in atmospheric pressure from low to high altitudes.
Upon activation at 0.2km, the payload thrusters lacked proper control authority and could not properly maintain payload heading. As the payload ascended to higher altitudes the thruster became more effective and more closely maintained heading to the desired setpoint and margin. However, even at these higher altitude the payload tended to overshot and oscillate, typical of an underdamped system response. Due to the ineffectiveness of thrusters at lower altitudes and constant overshooting the payload propellant supply was exhausted after 35 minutes of flight.
Based on the data from this flight, future missions were planned to activate stabilization at altitudes above 10km and control code was better tuned to avoid excessive oscillations.
Data from Flight #3 (April 9th, 2022)
Payload footage from Flight #3 (April 9th, 2022)
HAVOC team posing with payload prior to launch
Launch Date: June 11th, 2022
On June 11th, 2022 the 4th HAVOC flight was undertaken. This mission's goal was to test the Cyclone payload's ability to maintain a fixed azimuth, similar to flight number #3. Since the payload's gas supply was depleted at an altitude of 10km on the previous flight, the code for flight #4 was programmed to activate stabilization at 10km to further evaluate the effects of altitude on thruster performance and to help tune control algorithms for high-altitude flights.
Unfortunately, due to improper installation of the compressed air supply, the thrusters were not supplied with air during the flight. Because of this, no stabilization occurred during this flight. Despite this setback, the team used this flight to help improve launch procedures and avoid future issues with the payload's pneumatics system.
Flights #5 & #6
Launch Date: July 23rd, 2022
Due to the issues experienced on flight #4 the next flights were flown to repeat the same mission, maintaining a stable azimuth at altitudes above 10km. Further ground-testing since flight #4 improved the system's ability to correct rotation without excessive oscillations.
On July 23rd, 2022 a group of international STEM students visited the University of Alabama Huntsville as part of the PERSIST program. Members of the Space Hardware Club gave a presentation to these students, teaching them about the different projects the club works on. To finish out this session students were able to spectate the 5th HAVOC launch, which was launched from the UAH Greenway. This was also covered by local news outlets.
Due to an error in the flight software, the payload did not activate its control code at 10km as intended. This meant the payload performed no corrections during this flight and rotated freely. Upon recovery of the payload, assessment of the data and payload structure, the software error was fixed and the payload was immediately relaunched on flight #6
(TOP): Flight #5 data with no active stabilization, (BOTTOM): Flight #6 data with stabilization activated at 10km
Fortunately, the 6th flight successfully activated stabilization at 10km. We see from the data that the payload initially failed to maintain azimuth until reaching approximately 13km. Analysis of wind data from that day showed a fast moving jet was present at those altitudes, which might have overpowered the payload. After exiting the jet, the payload was able to maintain steady azimuth within a +/- 30 degree margin all the way to an altitude of ~22.5km. Here, the payload propellant supply was depleted and the payload rotated freely. This totalled 1 hour of stabilized flight.
The lack on stabilization on flight #5 allowed us to compare un-stabilized and stabilized rotation of the payload from flights on the same day, which demonstrated the effectiveness of the active thruster stabilization on correcting excess rotation.
Payload footage from Flight #6 (July 23rd, 2022)