Road trip! On February 18, members of the Far Horizons team went on a field trip to the University of Michigan in Ann Arbor, to visit with leaders of the school’s enormously successful CubeSat and HAB teams.
Aerospace Engineering professor James Forbes described his work in attitude determination and control for a small balloon-borne observation platform. One of the key issues when using reaction wheels for attitude control is that of saturation: you can only spin a reaction wheel so fast. “Resetting” a reaction wheel involves dumping angular momentum into something else. On satellites, where there isn’t anything to push against, thrusters are used to counter the rotation caused by slowing down a reaction wheel. On balloon platforms, a good sink for angular momentum proves to be the balloon itself! This is the method employed by NASA’s large high altitude balloon platforms. According to Forbes, on those platforms, the reaction wheel used to mitigate payload spinning saturates in only a few seconds, so angular momentum is almost continually being dumped into the balloon by driving a motorized connection between the balloon and payload.
In addition to being our main point of contact for our visit, Atmospheric Sciences professor Aaron Ridley discussed several CubeSat projects he is working on, as well as the student-led Michigan Balloon Recovery & Satellite Testbed (MBuRST) HAB team. Engineering graduate student Nathan Hamet showed us the MBuRST lab and described the program. Students develop payload elements as part of their classwork, culminating in a number of balloon launches to field test their systems.
We had a full afternoon of fun engineering discussions with the good folks at U Mich. Just seeing their labs was incredibly instructive for us. They’ve built and operated some really capable CubeSats in spaces that might be a little bigger than our lab, but aren’t all that more sophisticated. That’s very reassuring! They’ve also offered to serve as external reviewers for our CubeSat science mission and engineering plans for the ELaNa proposal, and are happy to have us make use of their facilities for testing. They’ve been through the ELaNa process themselves, successfully, multiple times, so their direct experience will be an invaluable boost for our project.