Patent GB-867363-A (GB)
Title: Interception control computer
Inventor: PARKER ERIC
IPC: F41G9/00
Filed: 1957-03-04
Abstract: 867,363. Radar. DECCA RECORD CO. Ltd. Feb. 24, 1958 [March 4, 1957], No. 7181/57. Class 40(7) [Also in Group XX] A computer for the control of the interception of a target craft by an interceptor craft comprises a first input member, the angular position of which may be set in accordance with the track of the target, a second input member, the angular position of which may be set in accordance with the bearing of the interceptor craft from the target and mechanical computing means coupled to said input members and set in accordance with the relative speeds of the interceptor craft and target craft for combining the settings of the input members to provide an output indication representing the direction of the straight line track required for the interceptor craft to make an interception. The problem is illustrated in Fig. 1 showing a target T moving in a direction TA defined with reference to a datum direction TO (e.g. North) by an angle #. An interceptor craft is at F and its bearing from the target is α. It is required to find the course FI to be followed by the interceptor to make an interception at I so that TI and FI are in the ratio of the speeds of the target and interceptor crafts. The interceptor course is defined by the angle # relatively to the target course or (#+#) relatively to the datum direction. In the apparatus shown in Fig. 8 knobs 94, 95 control potentiometers 98, 99 which produce voltages to determine the directions of marker traces on a radar scan which are adjusted by rotation of the knobs into alignment with the target track and the bearing of the interceptor from the target. A potentiometer 127 controls the length of the latter trace to represent the distance from target to interceptor. The knobs 94, 95 are thus rotated to positions representative of the angles #, α respectively. The shaft 97 of the knob 95 rotates through gearing 113, 112 a disc 110 having a radial slot 109. The shaft 96 of the knob 94 rotates through gearing 100, 101 a disc 102 supported concentrically with the disc 110 on rollers 103. A member 105 is adjustable, by means of a screw 125, along a radial slot 104 in the disc 102 to a position representing the ratio of target and interceptor speeds. This member is the mounting for a crank 107 having its pin 108 engaged in the slot 109. The angular position of this crank represents the required interceptor track and is transmitted to a dial 115, viewed through a window 116, by a jointed drive 114. The angle may be transmitted by radio link to a guided missile. A potentiometer 124 may be rotated by the same drive to produce voltages to provide a marker trace representing the interceptor track on the radar scan. Differentials inserted respectively between the drive 114 and the shafts 96 and 97 may be provided to produce respectively the "attack angle" # and the "antenna train angle", i.e. angle TFI. The same result may be obtained by reading pointers on the shafts 96 and 97 against scales rotated by the drive 114. In another embodiment, a plate having a slot corresponding to the slot 104 remains stationary while the member 110 is rotated in terms of (#-α) produced by a differential. The rotation of the crank 107 then represents 0 and is added to α in a further differential to produce the interceptor track. A simplified embodiment, Fig. 2, is shown to produce an approximate result which is usually sufficiently accurate and comprises knobs 9, 14 on which the angles #, α are set, the differential 17 producing (#-α). A gear 19 multiplies this by a factor representing the ratio of target and interceptor speeds. The result, appearing on the shaft 20 and displayed by the pointer 28, is the angle # which is added to # in a differential 21 to produce interceptor track. The differential 21 may be dispensed with by driving a pointer directly from the shaft 20 and reading it against a dial driven from the knob 9. The accuracy of a computer as shown in Fig. 2 may be improved by making the ratio of the gear 19 a function of (#-α). Specifications 744,640, 837,201 and 867,301 are referred to.