Abstract: An active nutation damping system for a spacecraft may comprise a nutation sensor controlling an actuator, a thruster say, via a control system so as to produce nutation opposing torques. Following the realization that performance limits on known systems may be due to a simplistic dynamic analysis which assumes the spacecraft to be a rigid body when it may in fact comprise one or more oscillatory elements, for example a fuel tank in which fuel is able to `slosh` about freely, the damping system herein is operable to identify two types of nutation component, for one of which appropriate opposing torque components are generated while, for the other type, torque components are generated that, at first sight, would appear to increase the nutation components but which, in fact, improve the overall nutation damping performance.

Abstract: New means are providedfor securing the free end of a roll of photographic film against unwinding. The means comprises a strip of flexible plastic which clings to the photographic film, at the free end of the roll and also on the body of the roll adjacent the free end.