Among the numerous collegiate rocketry teams across the world, few have been able to electronically control a liquid rocket engine. The E-Reg team (short for electronic regulator) aims to place SEB among this selective group. Since our start in Fall 2021, we have developed software to process data from multiple sensors, as well as designed custom hardware to actuate ball valves, allowing us to control critical engine pressures in a feedback loop. Using 4 of these valves, our Quad E-Reg architecture not only enables unprecedented control over our propellant tank pressures, but also unlocks new, exciting capabilities – including throttling our engine at will. In 2022, we have worked tirelessly, developing, testing, and iterating on our system, culminating in a successful static fire in November, where we demonstrated E-Reg’s ability to precisely throttle the engine. While we have come a long way, many challenges remain ahead as we strive towards our ultimate goal: to enable SEB to soar past the Karman line and into space.
E-Reg was originally created with the aim of replacing the dome-loaded pressure regulators used on Eureka-1. Due to the mechanical design of these regulators, the maximum attainable pressure in our propellant tanks is severely limited and inconsistent. E-Reg is a complete game-changer, eliminating this pressure “cap” by using a closed-loop control system. A motor is connected to a ball valve, and by measuring tank pressures, the motor can open or close the ball valve slightly to keep the downstream pressure constant. With this setup and a PID control loop, we have complete control over our tank pressures.
More technical details, performance information, and details on our testing campaign can be found in Low-cost, Lightweight Electronic Flow Regulators for Throttling Liquid Rocket Engines by Vint Lee and Sohom Roy.
Our E-Reg firmware is all public on GitHub - including our regulation control loop and what we used for throttling.
Static fires!
With our EREG system aboard our old cart test stand, we were able to successfully hotfire for 5 seconds in October 2022. This burn beat the thrust record we had set with Lightbulb, clocking in at 3.0kN! In November 2022, the E-Reg team returned to the Mojave Desert for two additional hotfires! The first burn demonstrated our new ability to throttle with a 14 second long burn, throttling from 60% to 100%, both up and down, an accomplishment very few other teams can claim. For our second burn, we attempted a full duration static injector pressure burn, though running out of pressurant mid burn led to non optimal results.
EREG successfully flew on Eureka-2 in 2024! Thanks to our EREG system, we were able to sustain a nominal, 14-second burn which propelled Eureka-2 to SEB’s highest altitude yet.