upper ends of the motors to steady the same in the embodiment of fig1 and 2 the rack 4 contains twelve openings for supporting twelve rocket motors with six openings being equally spaced about concentric circles in the rack as shown in fig2 corresponding slots or openings are provided in the upper plate 12 any number of openings can be provided in the rack and plate for supporting a like number of motors in accordance with the dimensions of the plate and the diameters of the motors an indexing mechanism 16 is connected between the frame 2 and the rack 4 for incrementally rotating the rack the indexing mechanism preferably comprises an indexing motor 18 whose operation is controlled by a control device 20 in a conventional manner as will be set forth in greater detail below arranged beneath the rack 4 and connected with the frame 2 is the propellant filling assembly 22 although only one filling assembly is illustrated and described the apparatus preferably has a pair of filling assemblies whereby two motors can be filled simultaneously the propellant filling assembly 22 is mounted on a support carriage 24 as shown more particularly in fig3 and 4 the support carriage 24 includes vertical sleeves 26 which extend downwardly therefrom about fixed shafts 28 connected with the.