Target seeking head for a missile

A target seeking head mounted in the dome of a missile comprises a gyro rotor including a mid-portion forming a convex calotte-shaped peripheral surface. The convex calotte-shaped peripheral surface is surrounded substantially concentrically by a concave calotte-shaped bearing surface stationary with respect to the missile. A small gap is formed between the two surfaces and pressurized gas is introduced into the gap to form a gas bearing centering the gyro in the center of curvature of the convex calotte-shaped peripheral surface thereof. A target seeking scanning device comprises an annular parabolic mirror formed at the mid-portion of the gyro and a plane mirror imaging a field of view located in infinity in the plane of a detector mounted stationary with respect to the missile.

The invention relates to a target seeking head for a missile, comprising: 
a gyro rotor mounted for rotation about a spin axis, which rotor is mounted 
in the missile for angular movement of its spin axis with two degrees of 
freedom, and a target field scanning device with an optical system 
arranged on the gyro rotor, and a central, stationary detector. 
Such a target seeking head is for example known from the German Pat. No. 1 
406 578. 
In the prior art target seeking head the gyro rotor is universally 
angularly movable and mounted on a central supporting member for rotation 
about its spin axis. It is mounted, for example, by means of a gimbal 
arrangement with ball bearings. The gyro rotor carries a target field 
scanning device, which comprises an optical system in the form of a folded 
mirror optics with an annular concave mirror and a plane mirror. A field 
of view located in infinity is imaged by the concave mirror, over the 
plane mirror in an image plane. A modulation disc (reticle) rotating with 
the gyro rotor is located in the image plane. A detector responding to the 
radiation of a target to be followed is arranged on the central supporting 
member and is exposed to the radiation passing through the modulation 
disc. The gyro rotor with the target field scanning device is arranged at 
the tip of a missile, which tip is closed by a radiation transparent dome. 
In the prior art target seeking head the gyro rotor is radially magnetized 
and surrounded by an annular coil. The signals of the detector are 
amplified and applied to the annular coil and exert torques on the 
radially magnetized gyro rotor, by which torques the spin axis of the gyro 
rotor and therewith the optical axis of the target field scanning device 
are precessed to a target and caused to follow this target continuously. 
The signals applied to the annular coil are at the same time applied to 
the control system of the missile. 
By the gyro rotor interfering motions of the missile are neutralized at the 
target field scanning device. The target field scanning device operating 
with a rather narrow field of view is aligned to a target and continuously 
caused to follow the target. The signals applied to the annular coil and 
to the control system are proportional to the angular speed of the sight 
line in space, as it is required for proportional navigation. The gyro 
rotor is for example accelerated to its operational speed of rotation by 
blowing gas under pressure against it and then runs freely down during the 
flight of the missile. 
Target seeking heads of this type are transiently subjected to high 
accelerations and are then locked and supported, in order to dissipate the 
acceleration forces. The prior art constructions with Cardan joints and 
ball bearings require very expensive supporting and locking devices. The 
limit of the acceleration stability is achieved, where supporting of all 
structural elements and thus dissipation of the forces is no longer 
possible. With ball bearings the limit is there, where the balls are 
pressed into the bearing surface. 
A further disadvantage of the prior art target seeking head is that the 
gimbal arrangement requires comparatively much space. Thereby only little 
space is available for the detector. 
The gimbal bearings of the gimbal arrangement have a friction not to be 
neglected. In order to achieve sufficient stabilizing qualities of the 
gyro rotor in spite of this friction, a rather large moment of inertia and 
thus a rather large weight of the gyro rotor is required. This large 
weight of the gyro rotor complicates supporting against high 
accelerations. 
It is the object of the invention to design a target seeking head of the 
type defined in the beginning, such that supporting of the gyro rotor with 
high accelerations is facilitated, more space is available for the 
detector, and by reduction of the friction, good stabilizing qualities are 
achieved also with a gyro rotor having small weight. 
According to the invention this object is achieved in that 
(a) the gyro rotor has a convex calotte-shaped peripheral surface, 
(b) this surface is surrounded by a concave callote-shaped bearing surface 
substantially concentric thereto and stationary with respect to the 
missile, while forming a narrow air gap, and 
(c) pressurized gas conduits open into the bearing surface, through which 
conduits pressurized gas is permitted to be introduced into the air gap 
for centered air bearing of the gyro rotor, freely movable to all sides. 
In the arrangement according to the invention the central gimbal 
arrangement is omitted, whereby more space is available in the center for 
example for the detector. The rotor is mounted through a gas bearing, 
whereby the friction is reduced. Thus the required stabilizing qualities 
can be achieved throughout the whole flight phase also with use of a 
smaller and more lightweight gyro rotor. Because the ball radii of the 
peripheral and bearing surfaces differ only very slightly, the gyro rotor 
engages the bearing surface with its peripheral surface virtually areally, 
at high accelerations. Thereby the acceleration forces can be dissipated 
via a rather large engaging surface, without lasting deformations 
occuring. Supplementary supporting mechanisms are not required. 
It is known to design the gyro rotor of a free gyro as a ball, which is 
arranged in a hollow-spherical bearing surface while forming a narrow air 
gap, pressurized gas being permitted to be introduced via pressurized gas 
conduits into this air gap, which gas retains the ball centered to the 
bearing surface. The ball rotates about a spin axis. Furthermore it is 
mounted for free angular motion with its spin axis relative to the bearing 
surface (French Pat. No. 1 501 166). This prior art arrangement is not a 
target seeking head but a position gyro for navigation purposes, with 
which the position of the spin axis is picked off as reference direction. 
There the completely ball-shaped design of the gyro rotor is an essential 
characteristic. The gyro rotor is not allowed to be supported on the 
bearing surface with high accelerations. 
Further modifications of the invention are subject matter of the sub-claims 
.

At its top, the missile 10 has a dome 12 transmitting the used radiation, 
for example infrared radiation, behind which dome a target seeking head 14 
is arranged. The target seeking head 14 comprises a gyro rotor 18 mounted 
for rotation about a spin axis 16, which rotor is mounted in the missile 
10 for angular movement of its spin axis 16 with two degrees of freedom. 
In the illustration of the FIGURE, the spin axis 16 coincides with the 
missile longitudinal axis 20. Furthermore the target seeking head 14 
comprises a target field scanning device with an optical system 22 
arranged on the gyro rotor 18 and a central detector 24, which is arranged 
stationary on the supporting member 26. The gyro rotor 18 has a convex 
calotte-shaped peripheral surface 28. This surface 28 is surrounded by a 
concave calotte-shaped bearing surface 30 substantially concentric thereto 
and stationary with respect to the missile, while forming a narrow air gap 
32. Pressurized gas conduits 34, 36 open into the bearing surface 30, 
through which conduits pressurized gas is permitted to be introduced into 
the air gap for centered air bearing of the gyro rotor, freely movable to 
all sides. The gyro rotor 18 is annular and the detector 24 is arranged 
inside the central aperture 38 of the gyro rotor 18, stationary in the 
center of curvature of the bearing surface 30. 
The target seeking scanning device comprises the optical system 22 in form 
of a folded mirror optics with an annular parabolic mirror 40 and a plane 
mirror 42, a field of view located in infinity being imaged by the 
parabolic mirror 40 via the plane mirror 42 in the plane of the detector 
24 or on a modulation disc arranged in front of the detector. The 
parabolic mirror 40 is formed by the target side of the end face of the 
solid gyro rotor 18. 
The gyro rotor 18 has a mid-portion 44 of substantially annular disc-shape 
provided with a central aperture 38 and forming the parabolic mirror 40 
and an outer portion 46 of substantially sleeve-like shape, forming the 
convex calotte-shaped peripheral surface 28 and extending on both sides 
axially beyond the mid-portion 44 and pressurized gas conduits open into 
the bearing surface 30 in two circular arrays 34, 36 which are arranged 
substantially symmetric to the radial midplane 47 of the bearing surface 
30. On one side the mid-portion 44 forms the parabolic mirror 40, to which 
a cylindrical inner face 48 of the outer portion 46 is connected. On the 
other side the mid-portion 44 forms, adjacent the aperture 38, a truncated 
cone-shaped surface 50, to which a cylindrical inner surface 52 of the 
outer portion 46 is connected. The dimension is selected such that the 
mass central point of the gyro rotor 18 including the plane mirror 42 is 
located in the center of curvature of the convex calotte-shaped peripheral 
surface 28. 
The mass of the gyro rotor 18 is displaced outwards by the sleeve-like 
outer portion, such that with predetermined total mass the moment of 
inertia is increased. Also a rather large peripheral surface 28 results, 
through which the gyro rotor 18 is supported. The diameter of the inner 
surface 52 is a little smaller than the diameter of the inner surface 48, 
and the surface 50 extends axially a bit further than the parabolic mirror 
40, such that the larger mass of the gyro rotor 18 compensates the mass of 
the plane mirror 42 arranged on the target side and the mounting on the 
backward side, and the mass center of gravity of the gyro rotor 18 with 
the plane mirror 42 is located in the center of curvature of the 
peripheral surface 28. 
The bearing surface 30 is provided in a partition 54 extending 
perpendicular to the missile longitudinal axis 20. The partition 54 
contains a pair of annular conduits 56, 58 substantially symmetrical to 
the radial mid-plane 47 around the longitudinal axis 20, which conduits 
communicate with a pressurized gas supply conduit 60. The pressurized gas 
conduits 34 and 36 are formed by radial bores, which extend from the 
bearing surface 30 to the annular conduits 56, 58. The missile 10 has a 
radiation transmitting dome 12 on the target side of the partition 54, 
which dome forms the top of the missile 10. This dome together with the 
partition 54 defines a chamber 64. At least one longitudinal conduit 66 
for venting the pressured gas is provided in the partition 54, which gas 
flows out of the pressurized gas conduits 34 through the air gap 32 
between peripheral surface 28 of the gyro rotor 18 and bearing surface 30 
into the chamber 64, as indicated by the arrows 68. The housing of the 
missile 10 has lateral outlet openings 70 for the pressurized gas rearward 
of the partition 54, which gas flows through the longitudinal conduit 66 
or, as indicated by the arrows 72, from the pressurized gas conduits 36 
through the air gap 32 to the rearward side of the partition 54. 
In the target seeking head described the gyro rotor 18 is mounted through 
an air bearing by means of a bearing surface 30. This air bearing permits 
low-friction rotation of the gyro rotor 18 about its spin axis 16 as well 
as the universally angular alignment of the spin axis 16 with the target 
relatively to the missile 10. The bearing surface 30 serves, at the same 
time, for supporting the gyro rotor 18 with high accelerations, when the 
air bearing is not effective, the gyro rotor 18 engaging the bearing 
surface 30 substantially aerally, such that high accelerations can be 
taken up without lasting deformation of the portions. 
The target seeking head 14 can be aligned to the target in known manner, 
for example as set forth in the German Pat. No. 14 06 578.