This part is from Real Scale Boosters
mass:
0.75
TechRequired:
heavyAerodynamics
engine_data:
standard
{"isp"=>{"vac"=>350.0, "atmo"=>300.0}, "propellant_ratios"=>{"SolidFuel"=>1.0}, "max_thrust"=>50.0}
resources:
SolidFuel
0.5