Patent Publication Number: US-7721648-B1

Title: External telemetry method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This is a divisional of prior application Ser. No. 10/988,106, filed Nov. 15, 2004 now U.S. Pat. No. 7,296,520. 

   BACKGROUND OF THE INVENTION 
   This invention relates in general to ammunition and explosives, and more particularly, to explosive-containing projectiles. 
   U.S. Pat. No. 6,349,652, issued to Hepner et al., describes an aeroballistic diagnostic system for obtaining information relative to the flight of a projectile launched from the bore of a gun. The projectile&#39;s functioning fuze mechanism is replaced with a fuze-shaped body containing a telemetry unit. The problem with using this diagnostic system is that it renders the projectile inoperable as originally designed. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of this invention to provide diagnostic measurements of in-flight characteristics of a projectile, while still allowing the projectile to function as originally designed. 
   This and other objects of the invention are achieved in one aspect by a method of assembling an external telemetry unit for a projectile comprising the steps of providing a shell whose inside is formed to match the contour of the projectile body, encircling the front of the shell with a flexible battery and flexible electronic circuitry, and covering the flexible battery and flexible electronic circuitry with a plurality of contoured antennas. 
   Another aspect of the invention involves a method of using an external telemetry unit comprising the steps of removing the fuze from a projectile having a projectile body and a fuze, sliding the unit over the front of the projectile body; reinstalling the fuze, firing the projectile, and observing the projectile data transmitted by the unit. 
   The invention has the advantage that in-flight diagnostic measurements relative to a projectile can be made with it without rendering the projectile inoperative. Furthermore, since the components of the invention are wrapped around the curved shape of the projectile in a flexible housing, this is done without changing the projectile&#39;s aerodynamic profile. 
   Additional advantages and features will become apparent as the subject invention becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein: 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic illustration of a projectile embodying the invention. 
       FIG. 2  is a partially exploded view of the external telemetry unit disconnected from the rest of the projectile of  FIG. 1  showing the unit disassembled with the antennas removed. 
       FIG. 3  is a full exploded view of the external telemetry unit disconnected from the rest of the projectile of  FIG. 1  showing the unit disassembled to its major components. 
   

   DETAILED DESCRIPTION 
   The invention as embodied in a typical projectile is illustrated in  FIG. 1 . The projectile includes a projectile body  11 , filled with an explosive bursting charge, and a fuze  13 , threaded onto the front end of the body by means of an adaptor  15 , for causing detonation of the charge as a result of impact with, or proximity to, a target. The projectile is itself known in the art and its detailed operation is well understood in the art. Such a projectile is shown for example in U.S. Pat. No. 6,349,652, whose disclosure is hereby incorporated by reference. In that patent, the functioning fuse is removed and replaced by an inert fuse body containing an internal telemetry unit. According to the present invention, the functioning fuse is not removed, and an external telemetry unit  17  is added to the projectile. 
   Referring to  FIGS. 2-3 , wherein like reference numerals designate like or corresponding parts, the external telemetry unit  17  is shown disconnected from the rest of the projectile shown in  FIG. 1 . The external telemetry unit  17  includes a shell  19  adapted to be inserted between the front of the projectile body  11  and the fuze  13 , and means on the front of the shell for obtaining projectile data while the projectile is in flight and transmitting the data to a ground station for analysis. The inside of the shell  19  is formed to match the contour of the projectile body  11  to be instrumented. While the data obtaining and transmitting means may take a variety of forms, conveniently it may take the form shown of a flexible battery  21 , flexible electronic circuitry  23  composed of components such as described in the afore-mentioned U.S. Pat. No. 6,349,652, and a pair of antennas  25  and  27 . The flexible battery  21  and flexible electronic circuitry  23  encircle the front of the shell  19 . Suitable flexible batteries may be purchased from Volta Flex, Menlo Park, Calif., for example. The flexible electronic circuitry may be manufactured using well-known printed circuit techniques. The antennas  25  and  27 , which may be L-band and S-band antennas, are wrapped around the flexible battery  21  and flexible electronic circuitry  23  and completely enclose them to protect them from the environment. The manufacture of the antennas  25  and  27  is within the capabilities of one skilled in the art. The antennas  25  and  27  are contoured like the projectile body  11  to keep the aerodynamic signature of the instrumented projectile body  11  as close as possible to the original. 
   In operation, the external telemetry unit  17  is powered up. Then, the fuze  13  of the projectile whose diagnostic measurements are to be provided is removed, and the user slides the external telemetry unit  17  over the front of the projectile body  11 . Next, the fuze  13  is reinstalled, holding the external telemetry unit  17  in place. Finally, the projectile is fired. While the projectile is in flight, the external telemetry unit  17  transmits projectile data to a ground station for analysis. When the projectile reaches its target, it detonates, as it was originally designed to do. 
   It is obvious that many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as described.