Given the size of that thing I expect he's using something like this: https://estesrockets.com/collections/engines https://estesrockets.com/collections/engines

Given the size of that thing I expect he's using something like this: https://estesrockets.com/collections/engines https://estesrockets.com/collections/engines I believe there are now other players in this market. Looking at his website I see the gimbal being described as supporting up to 24mm engines. That corresponds to a standard D size engine and by my long-ago memory that burn looked reasonable for a D motor except the rocket was way too heavy for a safe launch (normal rockets rely on fins, they must get going fast enough while still riding the launch rail that they'll stay straight)--I'm sure he was staying well back! The landing burn seemed weaker--I wouldn't be surprised if that was a C, or perhaps even a high thrust B.