methods for manufacturing outlet nozzles for use in rocket motors are disclosed . the methods include providing an inner wall , positioning an outer wall around the inner wall , positioning spacers in the space between the inner and outer walls , and laser welding between the spacers and at least one of the inner and outer walls in order to form cooling ducts between the spacers and to provide t - shaped joints between the spacers and at least one of the inner and outer walls , the t - shaped joints including a rounded shape within the cooling ducts .