A little over a year ago (2019 into early 2020), we had the pleasure of being consultants to the Case Rocket Teams, one of the competitive student project teams at CWRU.
The rocket team sought to transmit video from their rocket during flight and receive it on the ground. They had purchased an initial set of equipment and performed a test run, but the initial results were not encouraging.
Video from the rocket could only be seen when it was on the ground, the signal was far too noisy to make out anything when the rocket was in flight. So the rocket team sought out us as consultants to see if we could improve the situation.
We met with them, and after learning about our client’s needs, came up with some ideas, including different antenna choices for transmitter and receiver. Together, we all decided that a ground-based test would be the best way to verify our choices.
We started by taking antennas out to the engineering quad, and testing them at short distances. We were able to observe some effect, and made some predictions about what would work best, before moving on to a full scale test that would match the distance the rocket would travel when in flight.
Rocket team members identified a stretch along the Lake Erie waterfront that was the same length as the rocket’s expected maximum altitude. We divided into groups, and send one group with the transmitter (which would be in the eventual rocket) to one end of the path, and the other group with the receiver to the other end. Both groups brought several antennas to test with.
The path along the Cleveland waterfront where we tested antenna combinations.
It was a beautiful day, and we had a clear view across the water to the other group’s site (they were just barely visible in our binoculars). We qualitatively identified how well the system was working by watching the video quality on a laptop at the receiving end.
We were able to identify the effects of signal polarization, antenna gain, and antenna patterns on the received signal. We identified what seemed to be the best combination of antennas and even managed to go to the farmers market afterwards!
The day was a lot of fun, and it was nice to see the concepts we knew play out as we held the antennas.
We also calculated a rough link budget that agreed with what we saw in our tests.
On the rocket team’s next practice launch, they were able to record video and demonstrate that our changes had in fact improved the quality of the video! Unlike before, they could now see almost all of the flight, with only a brief interruption as the rocket rotated at the peak of its travel.
Unfortunately, we weren’t able to see the improved solution fly in competition (if memory serves, this was because the competition was later in the year and was canceled due to COVID-19). However, we still achieved our technical goals, and made some friends in the process. We hope to see the live video system in flight in competition, but in the meantime, check out the Case Rocket Team website, they’re awesome!
—Aidan Montare, KB3UMD