M-1378 Loki Red with extra long tracking smoke is the largest 54mm reload certified for hobby use, ever.
In a properly designed minimum diameter rocket, it is capable of breaking mach 3 and 34,000 feet. It features four hand cut grains which are tailor machined specifically for use in a motor with such a high length to diameter ratio. The grains and liner are pre-loaded before packaging to ensure proper fit and maximum propellant loading. A new single use nozzle was designed and developed specifically for use with the 54/4000 hardware. The highly efficient design of this nozzle is key in helping the reload produce 5,361Ns in a 54mm motor casing.
A heavily cropped photo of the University of Minnesota flying a minimum diameter rocket at Spaceport America on the M-1378. Photo by Harry Spears.