The PB51 was designed by Tommy Borsboom. The design was meant as a third-year internship program. The name is in honour of his father, PB.
The PB features a propellant combination of potassium nitrate (KNO3) and sorbitol (C6H12O14). The grain configuration is in a bates variant. The motor case is a combination of aluminium and composites. The nozzle is made out of graphite part in a bell shape and an aluminium part in conical shape. The engine is fully seperable and thus easy for maintenance. One of the requirements set is that the engine must survive two launches. This true.
The engine produces a mighty 1008 Newtons of maximum thrust. It has a total impulse of 3350 Ns. This allows the team to shoot rockets up to 2.5 kilometres. The engine has a maximum acceleration of 12 g's. The maximum operating chamber pressure is 45.1 bar and the maximum chamber pressure is 110 bar.