KR100381686B1 - System and method for increasing the durability of a sapphire window in high stress environments - Google Patents

Abstract

The dome assembly 50 is suitable for use in a missile 32 having a longitudinal axis 42 parallel to its thrust vector. The dome 50 of the present invention comprises a sapphire crystal 30 having a crystallographic structure comprising positive n-planes 12, positive r-planes 14 and c-plane 16. The surface around the missile sensor provides space for installing crystals 30 and 50 such that one of the positive r-planes faces the direction of travel relative to the airflow 36 impinging upon the missile 32 during missile flight. to provide. Projection of the positive r-plane normals onto the airflow vector 36 points to the tail. By designing nominal conditions, the r-plane 14 is roughly bisected by the plane formed by the normal of the c-plane 16 and the airflow vector 36. In the illustrated embodiment, the dome assembly 50 includes an x-ray device for placing r-planes within the sensor dome 50. The rotating plate (not shown) orients the sensor dome 50 such that the first r-plane 14 faces the direction in which the impingement airflow 36 flows. The r-plane normal 38 of the second r-plane forms an angle of about 60 with respect to the impingement air stream 36. The rotating plate includes a motor (not shown) for direct orienting the grating planes 12, 14, 16 of the dome 50 so as to maximize the strength of the dome 50 against the stress applied.

Description

SYSTEM AND METHOD FOR INCREASING THE DURABILITY OF A SAPPHIRE WINDOW IN HIGH STRESS ENVIRONMENTS}

Advanced missile systems are used in a variety of applications, from transporting explosives to launching satellites. Such applications typically require rigorous performance. Missile detection and tracking are important features that affect missile performance.

The missile may be equipped with a combination of infrared sensors, radar sensors and optical sensors for missile guidance, ie terminal homing. These sensors and the accompanying sensor housings are sometimes exposed to extreme thermal loads. As a result, sensor damage and signal interference occur. This is especially noticeable in infrared (IR) sensors. Typically, the IR sensor is wrapped in a sapphire housing called an IR dome. At the high speeds required by most missiles, the IR dome will produce a strong bow shock caused by the high rate of pressure change and the corresponding thermal load of temperature. This heat can cause cracks in the IR dome. Any cracks in the IR dome caused by local heat can degrade missile performance.

In order to reduce the extreme temperature loads on IR sensors and domes, systems using cooling gases have been developed. The system typically includes a pressurized-canister of argon stored within the missile body. As the heat load on the IR dome increases, cooling gas is released from the protection device through the nozzle towards the IR dome. Unfortunately, because the cooling argon gas has a different refractive index than the atmosphere, it bends the signals entering the IR dome, resulting in missile tracking errors. In addition, the protection device is bulky. The excess weight reduces the range of the missile, and the space constraints imposed by the protective devices increase the complexity or price of the missile system. In addition, timely gas discharge is difficult due to the thermal load of the IR dome.

Other methods of protecting the missile from extreme heat loads and damage from weather and particulates include reducing the missile speed and reducing the exposure time of the IR dome. Both methods degrade missile performance. In addition, there is a method to reduce the thermal load on the IR dome by installing a protrusion toward the IR dome. However, these methods add additional cost and weight to the missile.

Accordingly, there is a need for a technology that provides a cost- and space-efficient system and method for preventing or reducing the cracking of missile sensor housings and windows without degrading the performance of the missile.

<Summary of invention>

The need for the technology can be solved by the sensor dome assembly of the present invention. In the illustrated embodiment, the assembly of the present invention is suitable for using a missile having a longitudinal axis parallel to its thrust vector. The assembly includes a single crystal dome or window of crystallographic structure with a plurality of inclined faces. The surface around the missile sensor provides space to install the crystals so that they can be oriented in a clocked manner, thereby solving resolved shear stresses that act on the faces corresponding to the crystallographic r-plane. It can be minimized.

In a particular embodiment, if the dome or window is mounted on the missile side and the crystal is sapphire, it has a, c, r and n-planes. The positive direction of the c-plane normal vector is nearly perpendicular to the base of the infrared dome and passes out toward the center of the dome or window from the missile to the outside. In addition, the positive r-plane normal is defined as the component in which the r-plane normal is projected onto the c-plane normal vector is in the positive c-plane normal direction.

In this preferred orientation, the r-plane is roughly bisected by the plane formed by the airflow vector and the crystallographic c-axis. The positive normal to this r-plane has the component facing the aft.

In the illustrated embodiment, the system of the present invention is implemented using an infrared missile sensor dome and includes an x-ray device to place an r-plane within the sensor dome. The rotating plate orients the sensor dome in the preferred orientation in which the first r-plane normal is rotated in the leeward direction of the wind. The projection of the second r-plane onto the c-plane of the r-plane normal is at an angle of about 60 degrees to the impingement airflow when projected onto the same plane. The rotating plate includes a motor for strategically oriented the lattice plane of the dome to maximize the strength of the dome against the applied stress.

<Brief Description of Drawings>

1A is an isometric view of a sapphire crystal showing the relative orientation of the lattice plane.

1B is a top view of the sapphire crystal of FIG. 1A.

2 illustrates the orientation of the lattice plane of sapphire crystals with respect to the missile direction and the airflow of the sapphire dome, in accordance with the teachings of the present invention.

3 is a top view of an IR dome mechanically processed and oriented such that the orientation of the lattice plane corresponds to the lattice plane orientation of the sapphire crystal of FIG.

This application claims priority from preliminary application No. 60 / 030,520, Dock No. PD-960429, filed November 12, 1996 in the United States. The present invention relates to a missile system. In particular, the present invention relates to a method for preventing cracks in the sapphire sensor housing and windows during missile flight.

Although the invention has been described with reference to exemplary embodiments for a particular application, it is obvious that the invention is not so limited. Those skilled in the art and the art provided herein will appreciate that further modifications, applications, and embodiments are possible within the technical scope and additional technical field in which the present invention may be fully utilized. will be.

1A is an isometric view of a typical sapphire crystal 10 showing the relative orientation of n-plane 12, r-plane 14, c-plane 16 and a-plane 18. As shown in FIG. When manufacturing a sensor window such as an IR dome, crystals 10 are grown and mechanically processed into a predetermined shape.

Typically, crystals 10 are cut out from large cylindrical boules using certain machinery. The resulting near net shape dome (not shown) is then ground and polished to its final size. The finished dome (shown in FIG. 3) is smooth but still has the same crystallographic structure as exhibited by crystal 10. 1A, 1B and 2 show only the orientation and orientation of the crystallographic plane in the final sapphire product. Specific c-planes, r-planes, a-planes and n-planes corresponding to c-plane 16, r-plane 14, a-plane 18 and n-plane 12, respectively, There are almost infinite overlaps throughout the final dome. Planes (not shown) parallel to planes 14, 16, and 18 are defined as being the same as planes 14, 16, and 18, respectively. For example, there are three a-planes 18, three r-planes 14, one c-plane 16 and six n-planes 12.

The primary type of failure and failure of the dome at high temperatures experienced during missile flight is along one or more crystallographic r-planes 14 throughout the machined dome or window (not shown). This is due to the decomposition shear stresses that appear.

The r-plane 14, n-plane 12 and c-plane 16 of the crystal 10 are r-plane normal 20, n-plane normal 22 and c-plane normal 24, respectively. It has a normal vector called. The c-plane normal 24 forms an angle of approximately 57.6 degrees with respect to the r-plane normal 20 and an angle of approximately 61 degrees with respect to the n-plane normal 22. The r-plane normal 20 forms an angle of approximately 32.4 degrees with respect to the m-axis (indicated by m) represented by the vector 26. m-axis 26 is perpendicular to c-plane normal 24. This c-plane normal 24 corresponds to the c-axis 24 as the normal to the c-plane 16.

To aid in a complete and accurate understanding of the invention described herein, the following are the basic rules defined.

1. The positive direction of the c-plane normal 24 is defined by a dome (shown in FIG. 3) from an infrared sensor (not shown) perpendicular to the c-plane 16 inside the missile (shown in FIG. 3). It is defined as the direction going through the center of the window to the external environment.

2. Positive r-plane normal 20 is defined as the projective component of the r-plane normal onto c-plane normal vector 24 in the direction of positive c-plane normal 24.

FIG. 1B is a top view of the sapphire crystal 10 of FIG. 1A. 1B shows the crystal structure of a typical IR dome (not shown). This figure looks at the negative c-axis direction from the positive c-axis (shown at 24 in FIG. 1A). Typically, this infrared (IR) dome is machined and placed on the missile regardless of the structural orientation of the crystal 10 except for the c-axis orientation. That is, the orientations of the n-plane 12, r-plane 14, and a-plane 18 are random.

FIG. 2 is a diagram showing the direction of the lattice plane of the sapphire crystal piece 30 with respect to the direction of the missile 32 (not shown) and the direction to the sapphire dome and airflow according to the teachings of the present invention. The vector 34 pointing in the direction opposite to the direction of the airflow 36 is parallel to the c-plane 16. Vector 34 forms an angle of about 60 degrees with the projection of positive r-plane normal 38 onto c-plane 16. Degradation shear stress (not shown) along the r-plane is reduced.

The positive normal to the r-plane 14 faces the tail. The negative r-plane normal intersects the nominal airflow vector 36. The airflow vector 36 is aligned with the longitudinal axis 42 of the missile for no-pitch flight with nominal yaw. This longitudinal axis 42 is parallel to the thrust vector 40.

3 is a diagram of an infrared (IR) dome 50 mechanically processed and oriented such that the lattice plane orientation of the infrared (IR) dome corresponds to the lattice plane orientation of the sapphire crystal of FIG. 2. The dome 50 is cut from one large sapphire crystal and mechanically processed. The dome 50 has the same structural orientation for the crystal 30 schematically shown in FIG. 2 with respect to the crystal lattice plane, i.e., a-plane, r-plane, n-plane and c-plane. For example, the projection of the r-plane normal 38 into the c-plane (shown at 16 in FIG. 2) forms an angle of about 60 with respect to the impingement airflow vector (shown at 36 in FIG. 2).

The IR dome 50 is mounted on a rotating plate (not shown). This turntable includes a motor (not shown) for orienting the grating plane of the IR dome to maximize the strength of the IR dome against the stress applied.

The method according to the teachings of the present invention includes the following steps.

1. Obtaining sapphire crystals of sufficient size to apply to a particular IR dome or window,

2. mechanically processing the crystals to a size suitable for a particular application;

3. irradiating the crystals with x-rays to determine the orientation of the r-plane in the crystals, and

4. orienting the r-plane so that it is exposed to the minimum amount of shear stress as possible when exposed to the operating environment

Another method according to the teachings of the present invention includes the following steps.

1. Obtaining a prefabricated sapphire crystal IR dome or window,

2. irradiating the IR dome or window with x-rays to determine the location of the r-plane within the IR dome or window, and

3. Orienting the r-plane to expose as little shear stress as possible in a particular operating environment

A second alternative method in accordance with the teachings of the present invention includes the following steps.

1. obtaining a prefabricated single crystal sapphire IR dome,

2. irradiating the dome or window with x-rays to determine the orientation of the r-plane in the dome or window, and

3. Attaching the dome to the missile such that one of the positive r-plane normals proceeds in its direction of collision airflow and correspondingly induced stress during missile flight.

Thus, the present invention has been described only with respect to specific embodiments for specific applications. It is apparent that those of ordinary skill in the art and the present invention taught throughout this specification may further modify the applied technology and embodiments within the technical scope.

Accordingly, the appended claims are intended to cover all such applications, modifications, and embodiments within the scope of the invention.

Claims (10)

In the dome assembly 50 of the missile 32, the missile has a longitudinal axis 42 parallel to its thrust vector. The dome assembly 50, Sapphire crystals 30 having a crystallographic structure comprising predetermined positive r-planes 14, positive n-planes 12, and c-plane 16; And Mechanism 32 for installing the crystal 30 so that one of the positive r-planes 14 faces its airward against the airflow impacted by the missile 32 during missile flight. Dome assembly comprising a. The dome assembly of claim 1, wherein the projection onto the airflow vector (36) of the positive normal of one of the positive r-planes (14) during the missile flight indicates an aft. 2. The dome assembly of claim 1, wherein the projection of one of the positive r-plane (14) normals to the missile axis (42) points in the direction of the thrust vector (40). The projection of the positive normal of one of the positive r-planes (14) onto the c-plane (16) is opposite to the direction of airflow (36) impinging the missile (32). Dome assembly oriented 60 degrees relative to the oriented vector (38). The dome assembly of claim 1, wherein one r-plane (14) is bisected by a plane formed by the airflow vector (36) and the axis (24) of the c-plane (16). The dome assembly of claim 1, wherein the projection of the positive normal of the r-plane (14) onto the c-plane (16) is parallel to the thrust vector (40) of the missile (32) and points to the tail. 2. The dome assembly of claim 1, wherein one of the r-planes (14) intersects the longitudinal axis (42) of the missile (32) and faces the tail. The dome assembly of claim 1, wherein the dome assembly (50) is a sapphire window. The dome assembly of claim 1, wherein the dome assembly is an IR dome. The dome assembly of claim 1, further comprising an x-ray device for positioning and determining the relative orientation of the c-plane 16, r-planes 14 and n-planes 12 of the sapphire. .