The invention relates in general to ballistic munitions and in particular to ballistic projectiles that measure conditions in the launching tube.
Military organizations have always needed a device to obtain information about the interior ballistic environment of cannon launching projectiles. Knowledge of launching conditions is used to design cannons and munitions to achieve optimum launching and accuracy. Only within the past 50 years have scientists started placing sensors into projectiles to record the interior ballistic event. Early electronic devices were pressure sensors that were hard-wired to a data acquisition system located near the cannon. When the projectile was launched, the data acquisition system would record several milliseconds of data before the wire was broken.
More recently, commercially available electronics have allowed the instrumentation of projectiles with small accelerometer sensors and pressure gages. These devices either recorded or telemetered data at a relatively low frequency rate, thus missing phenomena or smoothing out the data. Additionally, these older devices were one-time shot devices that were destroyed during the test.
It is an object of the invention to provide an instrumented ballistic test projectile that senses and transmits interior (inside of gun tube) ballistic information in realtime.
It is another object of the invention to provide an instrumented ballistic test projectile that is reusable, with little or no refurbishment.
It is a further object of the invention to provide an instrumented ballistic test projectile that measures base pressure and side wall pressure.
One aspect of the invention is a ballistic test projectile comprising a nose section including a windshield and aft of the windshield, an ogive; a body section aft of the nose section, the body section comprising a generally cylindrical body connected to the ogive; a base section aft of the body section, the base section comprising a base adapter connected to the body and a base bottom connected to the base adapter; a base pressure gage disposed in the base bottom; at least one side pressure gage disposed in the body; and an electronics cup disposed in the body, the electronics cup comprising a battery cup, a signal conditioning cup, a multiplexer cup, an accelerometer cup and a transmitter cup.
The invention will be better understood, and further objects, features, and advantages thereof will become more apparent from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings.
In the drawings, which are not necessarily to scale, like or corresponding parts are denoted by like or corresponding reference numerals.
The invention comprises a projectile that senses and transmits the interior ballistic event in realtime. The primary interest is in conditions inside the launch tube, however, the projectile may also be used to measure and transmit data once the projectile has exited the launch tube. The projectile may be launched from a cannon tube or mortar tube, for example. The instrumented ballistic test projectile is rugged enough so that most of its components are reusable, with limited refurbishment. The present invention withstands the high acceleration and spin rate of the cannon launching environment.
A combined telemetry and sensor system and hardened projectile body allow the capture of the pressurized environment on the base and side of the projectile as it is being launched. A tri-axial accelerometer module senses the acceleration forces in all three linear directions. The signals from the sensors are combined and transmitted at an extremely high rate so as not to degrade the signals. Receiving antennae located near the muzzle exit of the cannon receive the signals from the on-board transmitter. A ground station receives and records the data. The projectile can be recovered and, with minor refurbishment, reused. Reusing the projectile saves money.
The invention incorporates a modularized power supply, accelerometer module and signal conditioning and telemetry system with an integrated antenna. In one embodiment, the telemetry system is an analog system which multiplexes signals and then transmits them. In another embodiment, the telemetry system is a digital system. The modularized system easily plugs into the projectile body, which has integral pressure gages in the side wall and in the base. Several gages are located in the wall and generally one gage is located in the base. An ogive and windshield make up the forward section of the projectile, protecting the electronics from gun launch and ground impact. In the event that the ground impact damages the windshield or ogive, these parts are easily replaceable.
During launch, the slip band obturator is destroyed. The slip band obtrurator is a band on the base of the projectile that seals the expanding cannon gases from leaking past the projectile. The base easily comes off and can be replaced if damaged. When the base is removed, the obturator band is then replaced.
A base pressure gage 28 is disposed in the base bottom 26. The base pressure gage 28 measures pressure at the base of the projectile 10. At least one side pressure gage 30 is disposed in the body 22. Preferably, a plurality of side pressure gages 30 (for example, four) are disposed circumferentially around the body 22 equidistant from each other. Side pressure gages 30 measure pressure along the side wall of projectile 10. Passageways 34 in body 22 connect the side pressure gages 30 to the side wall pressure field. An electronics cup 32 is disposed in the body 22 and includes a battery cup 36, a signal conditioning cup 38, a multiplexer cup 40, an accelerometer cup 42 and a transmitter cup 44.
The base pressure gage 28 with shim 64 is disposed in a protective base gage holder 46. Shim 56, O-ring 58 and rear nut 60 fit on the aft end of the base gage holder 46. A base gage tube 48 threads into the forward end of the base gage holder 46. A base tube captive ring 52 attaches the base gage tube 48 to the rear nacelle 50. Coaxial plug 66 electrically connects the base pressure gage 28 to wiring (not shown) inside the rear nacelle 50.
An obturator 54 and obturator ring 62 (
The electronic “cups” plug into and are stacked on top of each other in the electronics cup 32. Because functionality is separated by “cup”, the overall function of the electronics cup 32 may be varied by substituting other component cups (not shown). The plug-in modularity of the electronics cup 32 makes the projectile 10 easily reconfigurable. Also, in case the electronic components are damaged, the cups are easily replaceable, so that the projectile 10 has a short down time.
Experience has shown that the projectile 10 may land on its nose or its base. The ogive 20 preferably comprises aluminum. If the ogive 20 and windshield 18 (
While the invention has been described with reference to certain preferred embodiments, numerous changes, alterations and modifications to the described embodiments are possible without departing from the spirit and scope of the invention as defined in the appended claims, and equivalents thereof.
The inventions described herein may be manufactured, used and licensed by or for the U.S. Government for U.S. Government purposes.
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