Aeronautics and astronautics – Missile stabilization or trajectory control – Automatic guidance
Reexamination Certificate
2001-12-05
2004-09-14
Gregory, Bernarr E. (Department: 3662)
Aeronautics and astronautics
Missile stabilization or trajectory control
Automatic guidance
C244S003100, C244S003160, C244S003190, C342S062000
Reexamination Certificate
active
06789763
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to air-to-air missiles and, in particular, it concerns methods for operating such missiles for targets outside the field-of-view of a radar system, or independent of the presence of a radar system.
The extremely high speed of modern air-to-air combat stretches the capabilities of a human pilot to their limits. Faced with complex aircraft instrumentation and high-tech weapon systems, a pilot is required to achieve split-second reaction times as supersonic aircraft pass each other at relative speeds up to thousands of miles per hour. Various high performance target-seeking air-to-air missiles have been developed to operate under these conditions. However, many factors generally limit the usefulness of such missiles to greatly less than their theoretical performance capabilities.
Specifically, and with reference to
FIGS. 1 and 2
, it should be noted that operation of air-to-air missiles is generally integrated with a radar system of an aircraft. A typical sequence of operation is illustrated in the left portion of
FIG. 1
as follows. First, at step
10
, the radar detects (acquires) a target and, usually under the control of the pilot, directs the seeker of the missile to track the target (step
12
). Once both the radar and the missile seeker are locked-on to a target, the two tracking directions are typically displayed to the pilot superimposed on a display, thereby allowing the pilot to verify visually that the missile is successfully tracking the intended target (step
14
). Advantageously, information about the target, such as range-derived data from the radar measurements and tracking direction information, together with predefined information regarding the performance limitations of the missile and flight data from the aircraft systems are processed to determine whether a number of criteria indicative of the capability of the missile to reach the target are satisfied (step
16
). This information is typically represented graphically on a head-up-display (HUD) combined with data from the radar, allowing visual interpretation by the pilot of whether the target is within the maximum range and other performance limitations of the missile prior to firing.
Although the close integration of missile operation with the radar system provides very effective operation within the field-of-view of the radar, it also leads to severe limitations outside that range. Thus, as shown in the right portion of
FIG. 1
, target acquisition through the radar system is clearly not possible outside the field-of-view of the radar system (
10
′). In the event that a target is initially acquired by the radar system while within its field-of-view, the tracking of step
12
may continue outside the radar field-of-view (
12
′). However, the target verification is no longer available (
14
′) with the result that the pilot cannot be sure that the missile is in fact tracking the intended target. Similarly, the calculation of performance limitations criteria ceases (
16
′) as soon as the target leaves the radar field-of-view such that the pilot lacks all indications as to whether the missile is capable of reaching the intended target.
The significance of these limitation will be better appreciated with reference to FIG.
2
. As shown here, the field-of-view
18
of the radar system of a combat aircraft does not generally extend more than 60° above the boresight direction, and is frequently limited in practice to nearer 30°. In contrast, the field-of-view
20
of the seeker of a high performance air-to-air missile is generally much wider, in many cases lying in the 80°-90° range. As a result, in very many cases, a target may be inaccessible despite being visible to the pilot and within the capabilities of the missile to track and destroy.
One example in which the large blind region of the radar system presents a critical limitation to operation of air-to-air missiles relates to what is known as the “vertical mode”. A predominant course of action in air-to-air combat situations is for the pilot to pull the nose of the aircraft “up” (in the pilot's frame of reference) so as to draw the nose towards a target. In this case, the target is generally visible to the pilot at a high angle above his head and, by continuing to pull the nose up, the pilot attempts to reduce this angle to bring the target more in front of him. A “vertical mode” seeks to acquire a target located “upwards” in the pilot's frame of reference to allow the pilot to fire a missile at the earliest possible opportunity. However, a vertical mode based upon the radar system is once again limited to the low angle of inclination covered by the radar, thereby greatly delaying acquisition of the target.
One approach to facilitating target acquisition and verification outside the field-of-view of the radar system is by use of a helmet-mounted cueing system. This employs a magnetic or an optical system to monitor the position of a helmet provided with a helmet-mounted head-up display. In this case, in a cueing mode, the missile seeker is enslaved to follow an optical axis of the display which moves together with the helmet. Cueing is achieved by the pilot turning his head, and hence the helmet, to bring the optical axis into alignment with the target.
While providing a partial solution to the problem of target acquisition and verification, helmet-mounted displays and cueing systems suffer from a large number of disadvantages. Firstly, the components mounted in the helmet add greatly to the weight of the helmet This weight becomes multiplied numerous times under high-acceleration conditions, becoming a major source of fatigue and stress for the pilot. Secondly, these systems generally require alignment of the optical axis of the helmet with the target to be designated. Although this can be achieved over a range of angles beyond the radar field-of-view, operation of the system is still limited by the angular range of helmet motion which the pilot can achieve, which is typically smaller than the actual field of view both of the pilot and of the seeker. Furthermore, shifting of the entire head together with the heavy helmet to the required angle under high acceleration conditions may require great effort, and may cause significant delay in the cueing procedure. Thirdly, the helmet-mounted display typically requires very substantial connections between the helmet and other devices within the aircraft. These connections generally include a significant power supply and electrical and/or optical fibers for carrying projected information for the display. Such connections pose a significant safety hazard for the pilot, particularly with respect to emergency ejection where a special guillotine is required to sever the connections in case of emergency. The supply of a high voltage power line to within the helmet is also viewed as a particular safety hazard. Fourthly, the addition of helmet-mounted displays and cueing systems fails to provide any indication to the pilot regarding the capability of the missile to reach the target when the target lies outside the radar field-of-view. Finally, the integration of a head mounted display and cueing system into the aircraft systems is a highly expensive project, requiring adaptation of numerous subsystems, with all the complications of safety and reliability evaluation procedures and the like which this entails.
There is therefore a need for methods of operating an air-to-air missile which would allow effective operation of the missile with respect to targets lying outside the radar field-of-view, or altogether independent of a radar system, without requiring use of a helmet-mounted display. It would also be highly advantageous to provide a missile configured to provide effective modes of operation with respect to targets lying outside the radar field-of-view, or altogether independent of a radar system.
SUMMARY OF THE INVENTION
The present invention is a method for operating a short range, air-to-air missile, and a corres
Friedman Mark M.
Gregory Bernarr E.
Rafael-Armament Development Authority Ltd.
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