MOLE GUIDANCE SYSTEM

United States Patent im

Coyne

mi 3,712,391 [45] Jan. 23, 1973

[54] MOLE GUIDANCE SYSTEM

[75] Inventor: James Christopher Coyne, New Providence, N.J.

[73] Assignee: Bell Telephone Laboratories, Inc., Murray Hill, Berkeley Heights, N.J.

[22] Filed: June 28, 1971

[21] Appl. No.: 157,570

Related U.S. Application Data

[63] Continuation of Ser. No. 792,893, Dec. 27, 1968.

[52] U.S.C1 175/26, 175/45,175/61

[51 ] Int. CI E21b 47/022, E21b 47/024

[58] Field of Search 175/26, 45; 61/72.7; 340/32;

114/21 R, 21 W, 23

[56] References Cited

UNITED STATES PATENTS

3,461,979 8/1969 Newfarmer 175/56 X

3,525,405 8/1970 Coyne et al 175/45 X

3,529,682 9/1970 Coyne et al 340/32 X

3,544,957 12/1970 Smetanin et al 175/45 X

3,589,454 6/1971 Coyne 175/26

FOREIGN PATENTS OR APPLICATIONS 1,240,830 7/1971 Great Britain 175/45

Primary Examiner—Samuel Feinberg
Assistant Examiner—James M. Hanley
Attorney—R. J. Guenther et al.

[57] ABSTRACT

A subterranean missile is equipped with three mutually orthogonal coils in its body and a fourth suitably fixed in an articulatable steering member. The missile is guided along any desired underground trajectory defined with reference to a coordinate system including the plane of a dipole-quadrupole antenna system laid on the ground above. Voltages induced in the noncenterline body coils are used in a closed feedback loop to maintain the resultant magnetic field circularly polarized at the mole location. Heading errors are then revealed as a voltage phasor on the centerline coil. Rotation of the steering member sufficiently to bring the voltage induced in its coil into phase with the centerline coil voltage also aligns the steering member such that its articulation will reduce the heading error to zero. Any new trajectory may be defined as a suitable new voltage added to the centerline coil voltage.

1 Claim, 13 Drawing Figures