A tailcone assembly for a submarine countermeasure includes a generally hemispherically shaped shell having a planar aft end and an annular open forward end. Fins are fixed to the shell equidistantly around the shell externally thereof, each of the fins having a planar outboard surface extending aft and inboard of the shell. Connector structure is on the forward end of the shell for connecting to an aft end of the countermeasure. A first aperture is disposed in a side of the shell and a cable extends from inside the shell therethrough. A second aperture extends through one of the fins and the cable extends therethrough. An opening is disposed centrally of the shell aft end, extends therethrough, and is adapted to retain a shaft assembly therein.