Abstract: Tracking means for establishing a line-of-sight between a control point to which the second craft is being guided and tracking the line-of-sight to follow the second craft and deriving a signal .sub.a representing the rate of rotation of the line-of-sight about the control point; monitoring means for deriving a signal representing the displacement e of the first craft from the line-of-sight, a signal representing the range R.sub.m between the first craft and the control point, and a signal representing the rate of change R.sub.m of the range R.sub.m, presetting means for providing a signal representing a positive quantity k; and a computer for deriving signals representing .sub.c, .sub.c, and k to satisfy the equation ##EQU1## and minimize the difference -.sub.a, k being initially set equal to k.sub.1 ; control means for deriving from the representations provided by the computer a signal representing f(e)+R.sub.m .sub.c +2R.sub.m .sub.

Abstract: Tracking means for establishing a line-of-sight between a control point towards which the second craft is being guided and tracking the line-of-sight to follow the second craft and deriving a signal .theta..sub.a representing the rate of rotation of the line-of-sight about the control point; monitoring means for deriving a signal e representing the displacement of the first craft from the line-of-sight, a signal representing the range R.sub.m from the control point to the first craft and a signal representing the rate of of change R.sub.m of the range R.sub.m ; ranging means for deriving a signal representing the range R.sub.t from the control point to the second craft and a signal representing the rate of change R.sub.t of the range R.sub.t ; a computer for deriving representations of .theta..sub.c, .theta..sub.c and .theta..sub.c which satisfy the equation.sub.c =-2.theta..sub.c.sup.3 -3.theta..sub.c (R.sub.t /R.sub.t)where the difference .theta..sub.c -.theta..sub.

Abstract: A container blank comprises a base panel; wall panels joined to the base panel; and a lid panel joined to one of the wall panels along an edge thereof remote from its junction with the base panel. The junctions between the panels are formed by hinges which are integral with the panels. Interengageable fingers and openings are provided for releasably securing the walls in their erected condition, the fingers being disposed on edge portions of at least some of the wall panels for passing through the openings and hooking over edge portions of the adjacent wall panels.