FIELD OF THE DISCLOSURE

The present disclosure relates to guided munitions and more particularly to a system and method for accurately determining range-to-go for command detonation of a projectile.

BACKGROUND OF THE DISCLOSURE

Precise command detonation maximizes the warhead effects against a target and is highly depended on the “range to go” or “time to go” prior to or after impact. Depending on the target and the warhead fragment pattern there is an optimum distance in front of the target for soft target (UAS, aircraft, combatants, etc.). For structures, a distance “after” the target, or a delayed detonation, may be useful when flight through a window is preferred, for example. In either case, knowing the time accurately has been difficult. Many simple rounds have used spin counters and by knowing the target range and the number of revolution/meter from the projectile rifling, one can program the round to detonate after a particular spin count. However, these and other conventional techniques rely on knowing the range to extreme accuracy prior to launch and are totally ineffective for moving targets. What is typically lacking is an architecture that measures the “time-to-go” to the actual target and thereby improves accuracy.

Wherefore it is an object of the present disclosure to overcome the above-mentioned shortcomings and drawbacks associated with conventional guided munitions.

SUMMARY OF THE DISCLOSURE

One aspect of the present disclosure is a system comprising of a radio frequency (RF) or laser short energy pulse (10 to 100 ns) that illuminates a projectile's rear sensor and one or more targets. The energy of the short energy pulse is reflected off the target and is received by a second sensor on the nose of the projectile. The first sensor detects the pulse energy as it passes by the projectile, generating a Tzero(i.e., the start of a range finding clock). The clock is stopped when the target's reflected energy is detected by the second sensor at Treflected. The time differential represents the round trip time between the projectile and the target which can be converted to a range.

In one embodiment of the system of the present disclosure, the system uses the measured RF or laser energy detection from sensor1and sensor2in a simple limit trip switch approach. When the time-to-go is time <0.0015 seconds, or the like, it will detonate. In certain embodiments, the time is dependent on the projectile speed, warhead ideal detonation distance, and other factors. The “time-to-go” could be a time variable programmed at launch and/or could be negative (e.g., when flying through a window).

Another embodiment of the present disclosure determines the lateral offset between the projectile's trajectory and the target's actual position (i.e., a lateral miss distance). In this embodiment, the projectile's rear sensor(s) can determine the projectile's velocity by measuring the time increase between each pulse interval. The time base of each illumination pulse or the pulse repetition interval (PRI) serves as means to measure the time expansion between pulse intervals. If the projectile was not moving, the PRI would match the expected PRI. For a 40 Hz system, the PRI is 25 milliseconds, a projectile at MACH 3 would travel 25 meters. The 25 meters→81 feet→81 nanosecond (speed of light) increases the PRI time base which can be measured and tracked. By convolving the velocity with the “time-to-go,” one can determine the lateral offset, thereby improving/optimizing the accuracy of the detonation.

Yet another aspect of the present disclosure is A guided projectile, comprising; a tail sensor located on a tail portion of the guided projectile for detecting a laser or radio frequency signal; a forward sensor located on a forward portion of the guided projectile and detecting a reflected laser or radio frequency signal from a target; a computer readable storage device having instructions, which when executed by a processor, cause the processor to execute: determining a first time at which the laser beam is detected via the tail detector; determining a second time at which the reflected signal is detected via the front detector; comparing the first time to the second time to determine a time delay; determining an azimuth and an elevation of the guided projectile based on the detected laser or radio frequency signal by the tail detector; and determining one or more of the following using the time delay between detection by the tail detector and detection by the front detector: a lateral offset between the projectile and the target; a time-to-go for the projectile to reach the target; and a range-to-go for the projectile to reach the target.

These aspects of the disclosure are not meant to be exclusive and other features, aspects, and advantages of the present disclosure will be readily apparent to those of ordinary skill in the art when read in conjunction with the following description, appended claims, and accompanying drawings.

