We took our light and skinny (54mm minimum-diameter) rocket supersonic at the BALLS launch event over the weekend — it just rips into to the clouds, pulling 67g's going 0 to Mach 1.8 in 1.8 seconds. Cesaroni K940 White Thunder propellant. The rocket name (with Planet logo) is an homage to the Planet Labs team, who I first met at this launch location when they were testing the Phonesat payload idea as a NASA/Google project: https://flic.kr/p/8mUWbM We did a custom build using a very lightweight but strong tube (originally used in mortar casings) of a minimum-diameter airframe. So the rocket body is also the solid-rocket motor casing, and an aluminum rear retention ring secures it in place. The nosecone is also lightweight, and I know that it will collapse when going supersonic, so I tried an experiment using a series of duct-tape strips to help it hold together. Altogether, the rocket’s dry weight was just 1.7 lbs.