Abstract: A pyrotechnically driven device for restricting the area of the nozzle throat in a solid propellant rocket motor is disclosed. In one embodiment, the device includes a piston support mounted to the rocket motor in the exit cone. A restrictor is attached to a piston which is supported by the piston support. The restrictor is movable from a retracted position outside the nozzle throat to a restricting position within the throat upon actuation of the device. The piston and attached restrictor are driven by a pyrotechnic driving means that is actuatable separately from the solid propellant of the rocket motor. A locking means locks the restrictor in its restricting position.

Abstract: Various configurations of cylindrically shaped transducers are used as borehole seismic wave sources. The basic class of transducers of this invention has an outer shell that is generally cylindrical, and may be comprised of cylindrical sections. The shell or the sections may be pre-stressed or preformed to encourage certain bending motions. Depending on the configuration of the transducer, it approximates a monopole, dipole, or quadrupole radiator. Various actuating means, including magnetostrictive forces and piezoelectric forces, are used to drive the motions of the transducer. These transducers are especially useful for generating compressional, shear, or other elastic waves in solids. For example, in geophysical applications, the transducers are placed in boreholes for either hole-to-hole or single hole measurements.