It was more about making it than what it does. We were in a pandemic lockdown and I needed to make something. It's all machined and fabricated parts. I designed it and fabricated it over a period of a couple months. The design is tongue in cheek assault-ghostbuster style. It operates on compressed air. At around 150 psi, it would launch a sub size (1 7/8") tennis ball about 150 yards or a small potato about the same. It's a single shot on a charge. Lots of fun for a while, but like I said, I made it to do something. ... and get a good grade on it. It was a request from the neighbors down the street. Specifically, the wife asked if I could make something like this for her husband's gift from her. I showed her progress along the way as the design evolved on the fly. She had some ideas as well (she was a Hollywood movie studio costume designer on some major movies) which I purposely incorporated to make her part of the the gift to her husband.Did you make that? What's the propellant? Range with a tennis ball? How many launches per tank?