A method for reducing jet tab exposure during thrust vector control.

Abstract

A method for thrust vector control of a vehicle utilizing jet tabs is presented. Jet tabs are used to create a lateral control moment on the vehicle by rotating the tabs into a rocket plume and varying the thrust vectoring angle. The method involves simultaneously rolling the vehicle during thrust vector control maneuvers to reduce the maximum exposure of the tabs to the rocket plume. The method allows for aggressive pitch-over maneuvers while reducing the risk of tab failure due to excessive exposure.

Description

[Technical Field]

[0001] The present disclosure relates generally to thrust vector control systems, and more particularly to methods of using a thrust vector control system with a jet tab assembly to control pitchover maneuvers. [Background technology]

[0002] Pitch-over maneuvers are used to orient a vertically launched missile in a desired direction immediately after launch or shortly thereafter. Pitch-over maneuvers constrain other missile performance metrics, such as minimum and maximum engagement range and the missile's overall kinematics, including speed and maneuverability. Because pitch-over maneuvers occur shortly after launch, the missile's speed is relatively low.

[0003] Air vehicle control actuation systems typically utilize aerodynamic fins to control the air vehicle's velocity vector during flight. However, due to the low initial velocity of the air vehicle immediately after launch, fin-based control is typically ineffective at generating a moment large enough to achieve large pitchover maneuvers. Therefore, thrust vector control is used to control the air vehicle after launch and achieve stability and maneuverability during periods of low dynamic pressure.

[0004] There are various methods for producing thrust vector control, including movable nozzles, thrust vanes, and jet tabs. For example, a jet tab assembly is attached to the exit end of a vehicle's rocket nozzle. It consists of multiple tabs that can be independently rotated into and out of the plume to change the thrust angle as needed. When a single jet tab of a jet tab assembly rotates into the plume, it produces a thrust vector angle in a single plane. Rotating different combinations of jet tabs into the plume produces different thrust vector angles in different planes. The deflected thrust angle of the vehicle generates a moment that can be used to control the vehicle laterally.

[0005] However, the risk of excessive exposure of one or more jet tabs in a jet tab assembly to the jet flames can lead to several problems related to the jet tab assembly and pitchover performance. Specifically, excessive exposure of one or more jet tabs in a jet tab assembly to the jet flames during a pitchover maneuver can cause tab ablation, resulting in reduced effectiveness in generating the desired thrust vector angle. Thermal damage to the jet tab assembly can also limit tab motion due to cracks in the jet tab, slugs between the jet tab and the scraper ring, or warpage of the scraper ring or shaft. Furthermore, there is a risk of thermal damage to the jet tab assembly's motor or electronics. Both of these effects of excessive jet tab exposure limit pitchover maneuvers and overall vehicle performance.

[0006] Traditional solutions to these problems include incorporating ablative or other exotic materials, such as tungsten and composites, to withstand exposure to the jet blast, but these materials can be expensive and impractical. Other solutions include limiting the jet tab exposure by simply limiting pitch-over performance. Summary of the Invention

[0007] Described herein is an improved method for thrust vector control using jet tabs after launch. To reduce the maximum jet tab exposure of the vehicle jet tab assembly to the vehicle plume after launch, the vehicle is controlled to roll simultaneously with the pitchover maneuver. As the vehicle rolls, the lateral control system must sequentially utilize various combinations of tabs to achieve the desired thrust angle vector. In this manner, the exposure of each jet tab to the vehicle plume during thrust vectoring is more evenly distributed, reducing the maximum exposure of each individual tab.

[0008] Thus, according to aspects of the present disclosure, a method for thrust vector control of a vehicle includes launching the vehicle so that a plume emerges from an exit end of a rocket nozzle of the vehicle, and varying the thrust vector angle of the plume to impart a lateral control moment to the vehicle. The method also includes rolling the vehicle while simultaneously varying the thrust vector angle of the plume.

[0009] According to an embodiment of any paragraph(s) of the present disclosure, varying the thrust vector angle of the plume includes controlling a jet tab assembly of the projectile.

[0010] According to another embodiment of any paragraph(s) of the present disclosure, the jet tab assembly includes a plurality of jet tabs rotatably mounted to an exit end of the rocket nozzle of the projectile, and the step of controlling the jet tab assembly includes rotating one or more jet tabs of the plurality of jet tabs into the projectile plume exiting the exit end of the rocket nozzle of the projectile.

[0011] According to another embodiment of any paragraph(s) of the present disclosure, launching the projectiles includes launching the projectiles vertically.

[0012] According to another embodiment of any paragraph(s) of the present disclosure, the step of rolling the projectile begins before the step of varying the thrust vector angle of the plume.

[0013] According to another embodiment of any paragraph(s) of the present disclosure, the step of rolling the projectile begins after the step of varying the thrust vector angle of the plume.

[0014] According to another embodiment of any paragraph(s) of the present disclosure, the step of rolling the projectile begins simultaneously with the step of varying the thrust vector angle of the plume.

[0015] According to another embodiment of any paragraph(s) of the present disclosure, the step of rolling the projectile includes rolling the projectile at a roll angular velocity that reduces the maximum exposure of any one of the plurality of jet tabs.

[0016] According to another aspect of the present disclosure, a vehicle includes a thrust vector control device configured to vary a thrust vector angle of a plume exiting an exit end of a rocket nozzle of the vehicle after launch of the vehicle, and a roll control device configured to roll the vehicle simultaneously with the variation of the thrust vector angle of the plume by the thrust vector control device.

[0017] According to an embodiment of any paragraph or paragraphs of the present disclosure, the projectile further includes a jet tab assembly, and the thrust vector control device is configured to control the jet tab assembly to vary the thrust vector angle of the plume.

[0018] According to another embodiment of any paragraph(s) of the present disclosure, the jet tab assembly is attached to the exit end of a rocket nozzle of the vehicle.

[0019] According to another embodiment of any paragraph(s) of the present disclosure, the jet tab assembly includes a plurality of jet tabs rotatably mounted to an exit end of a rocket nozzle of the projectile, and the thrust vector control device is configured to rotate one or more jet tabs of the plurality of jet tabs into the plume of the projectile.

[0020] According to another embodiment of any paragraph(s) of the present disclosure, the roll control device is configured to begin rolling the projectile before the thrust vector control device is configured to begin changing the thrust vector angle of the plume.

[0021] According to another embodiment of any paragraph(s) of the present disclosure, the roll control device is configured to begin rolling the projectile after the thrust vector control device is configured to begin changing the thrust vector angle of the plume.

[0022] According to another embodiment of any paragraph(s) of the present disclosure, the roll control device is configured to begin rolling the projectile at the same time that the thrust vector control device is configured to begin changing the thrust vector angle of the plume.

[0023] The following description and the accompanying drawings set forth in detail certain exemplary embodiments described in this disclosure. However, these embodiments are indicative of but a few of the various ways in which the principles of the present disclosure may be employed. Other objects, advantages, and novel features will become apparent from the following detailed description when considered in conjunction with the drawings.

[0024] The accompanying drawings illustrate various aspects of the present disclosure. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a schematic diagram of a flying object. [Figure 2] FIG. 2 is an exploded schematic view of the jet tab assembly of the projectile of FIG. 1. [Figure 3] FIG. 3 is a perspective view of the jet tab assembly of FIG. 2. [Figure 4] 1 is a graph showing tab exposure over time for four jet tabs on a jet tab assembly during a prior art pitch-over maneuver. [Figure 5] 10 is a graph illustrating tab exposure over time for four jet tabs on a jet tab assembly during a pitch-over maneuver in accordance with the method of the present disclosure. [Figure 6] 1 is a flowchart of a method for controlling the thrust direction of a flying object. DETAILED DESCRIPTION OF THE INVENTION

[0026] Referring initially to FIG. 1 , a vehicle 10 is depicted. The vehicle 10 includes a vehicle body 12 and a rocket nozzle 14 at an aft end 13 of the vehicle body 12. The vehicle 10 may further include a jet tub assembly 16 attached to an exit end 15 of the rocket nozzle 14, from which a plume 22 exits to propel the vehicle during launch and flight. The vehicle 10 includes a thrust vector control device 18 configured to vary the thrust vector angle of the plume 22 exiting the exit end 15 of the rocket nozzle 14 to impart a lateral control moment to the vehicle and change the velocity vector of the vehicle 10 after launch, as described in more detail below. The vehicle 10 also includes a roll control device 20 configured to roll the vehicle 10 in response to changes in the thrust vector angle of the plume 22 by the thrust vector control device 18, as described in more detail below. It will be understood that the air vehicle 10 is not limited to the features described and illustrated generally above, but may further include other features conventionally included in air vehicle 10.

[0027] As used herein, the term "controller" (e.g., "thrust vector controller 18" and "roll controller 20") should be interpreted broadly to include a system with a processor capable of executing instructions. Such instructions may be embodied in software and / or hardware, and / or any of various computer-readable media, memory, ROM, RAM, etc. Software includes, but is not limited to, one or more computer or processor instructions that can be interpreted, compiled, and / or executed to cause a computer, processor, or other electronic device to perform a function, action, or behavior in a desired manner. Instructions may be embodied in various forms, such as a routine, algorithm, module, method, thread, or program, e.g., code from a separate application or a dynamically or statically linked library. Software may also be implemented in various executable or loadable forms, including, but not limited to, a standalone program, a function call (local or remote), a servlet, an applet, instructions stored in memory, part of an operating system, or other types of executable instructions. Those skilled in the art will appreciate that the form of software may be dictated, for example, by the requirements of a desired application, the environment in which it will be run, or the desires of a designer / programmer, etc. It will also be appreciated that computer-readable or computer-executable instructions may be located within one logic or distributed among two or more communicating, cooperating, or parallel processing logics, and thus may be loaded or executed in serial, parallel, massively parallel, and / or other manners.

[0028] The thrust vector control device 18 may be configured to vary the thrust vector angle of the plume 22, for example, using a jet tab assembly 16. With reference to Figures 2 and 3, the jet tab assembly 16 may include multiple jet tabs 24. For example, as shown, the jet tab assembly 16 may include four jet tabs 24. However, it will be understood that a four-jet tab 24 configuration of the multiple jet tabs 24 is provided as a non-limiting example, and that the jet tab assembly 16 may have more than four jet tabs 24 or fewer than four jet tabs 24. Each jet tab 24 of the multiple jet tabs 24 is rotatably mounted to the exit end 15 of the rocket nozzle 14 of the vehicle.

[0029] In either embodiment, the thrust vector control device 18 is configured to independently control each jet tab 24 into and out of the plume 22 to variably control the thrust vectoring angle of the plume 22 and thereby impart a lateral control moment to the vehicle 10. For example, as described above with reference to jet tab assemblies used in the prior art, a single jet tab 24 may be rotated into the plume 22 exiting the exit end 15 of the rocket nozzle 14 to impart a thrust vectoring angle in a single plane. Various combinations of more than one jet tab 24 may be rotated into the plume 22 to impart various respective thrust vectoring angles in various respective planes, as desired to control the desired thrust vectoring angle of the plume 22.

[0030] The roll controller 20 is configured to roll the air vehicle 10 simultaneously with the change in thrust vector angle of the plume 22 by the thrust vector control device 18. For example, after launch of the air vehicle 10, the roll controller 20 is configured to begin rolling the air vehicle 10 as soon as the thrust vector control device 18 begins changing the thrust vector angle of the plume 22. In another embodiment, the roll controller 20 is configured to begin rolling the air vehicle 10 after the thrust vector control device 18 begins changing the thrust vector angle. Alternatively, the roll controller 20 is configured to begin rolling the air vehicle 10 before the thrust vector control device 18 begins changing the thrust vector angle. Various roll schedules can provide different levels of benefit. For example, the roll controller 20 can command a roll angular velocity that results in the air vehicle rolling direction making one full rotation during a pitchover maneuver. Alternatively, the roll controller 20 can command a roll angular velocity that results in the air vehicle rolling direction making one-half of a full rotation. It is understood that the maximum benefit of reducing tab maximum exposure achieved will depend on the application and will need to be optimized for the particular vehicle and desired pitch over performance.

[0031] The thrust vector control device 18 and the roll control device 20 work together to maintain the thrust vector angle of the plume 22 during a pitchover maneuver. That is, as the air vehicle 10 rolls, the thrust vector control device 18 controls the multiple jet tabs 24 so that their exposure to the plume 22 is distributed among the multiple jet tabs 24, rather than just a single jet tab 24. For example, when the roll control device 20 rolls the air vehicle 10 into a first roll position, the thrust vector control device 18 rotates a first jet tab 24 of the multiple jet tabs 24 into the plume 22 to change the thrust vector angle of the plume 22. As the roll control device 20 rolls the vehicle 10 from the first roll position to the second roll position, the thrust vector control device 18 is configured to rotate the first jet tab 24 out of the flame 22 and rotate the second jet tab 24 adjacent to the first jet tab 24 into the flame 22, thereby maintaining the thrust vector angle of the flame 22 and the thrust direction of the vehicle 10 as the roll control device 20 rolls the vehicle. In this manner, the thrust vector control device 18 is configured to vary and maintain the thrust vector angle of the flame, and the roll control device 20 is configured to roll the vehicle 10 such that the maximum exposure of any given jet tab 24 of the multiple jet tabs 24 is reduced and distributed among the multiple jet tabs 24 while under control of the thrust vector control device 18.

[0032] FIG. 4 illustrates a graph showing tab exposure (y-axis) for each of four jet tabs in a jet tab assembly of a prior art air vehicle during a pitchover maneuver. As shown, over time (x-axis), one of the jet tabs receives significantly more exposure to the flame than the other jet tabs. This can lead to problems associated with jet tab overexposure, as discussed above. In contrast, FIG. 5 illustrates a graph showing tab exposure (y-axis) for each of four jet tabs in a jet tab assembly, such as the jet tab assembly 16 of the air vehicle 10, during a pitchover maneuver using the thrust vector control device 18 and roll control device 20 described herein. As shown, over time (x-axis) during the pitchover maneuver, the jet tabs' exposure to the flame 22 becomes more evenly distributed across each of the four jet tabs. For example, in the graph shown, a 34% reduction in maximum tab exposure is achieved at 60 degrees of roll during the pitchover maneuver. This reduction may keep maximum exposure below specified limits, allowing for desired pitch-over performance without risk of jet tab assembly failure.

[0033] 6 illustrates a flowchart of a method 100 for thrust vector control of a vehicle, such as the vehicle 10 described above. The method 100 includes launching the vehicle 102 so that a plume emerges from the exit end of the vehicle's rocket nozzle. Launching the vehicle 102 may include, for example, launching the vehicle vertically, which may require thrust vector control to change the vehicle's velocity vector.

[0034] Method 100 then includes step 104 of varying the thrust vectoring angle of the plume, thereby creating a lateral control moment that changes the velocity vector of the projectile. Varying the thrust vectoring angle of the plume may include controlling a jet tab assembly of the projectile, such as jet tab assembly 16 described above. The jet tab assembly may include multiple jet tabs rotatably mounted to the exit end of the projectile's rocket nozzle. Thus, controlling the jet tab assembly may include rotating one or more jet tabs of the multiple jet tabs into the projectile's plume exiting the exit end of the projectile's rocket nozzle.

[0035] Next, method 100 includes changing the thrust vectoring angle of the plume in step 104 while simultaneously rolling the projectile in step 106. By simultaneously changing the thrust vectoring angle of the plume using the jet tab assembly and rolling the projectile, the exposure of any one of the multiple jet tabs can be distributed among all of the multiple jet tabs, so that none of the multiple jet tabs reaches its maximum exposure limit and does not cause the related problems described above. Thus, the maximum exposure of any one of the one or more jet tabs to the plume can be reduced.

[0036] While the foregoing disclosure has been shown and described with respect to one or more specific preferred embodiments, it will be apparent that equivalent alterations and modifications will occur to those skilled in the art upon reading and understanding this specification and the accompanying drawings. In particular, with respect to the various functions performed by the aforementioned elements (components, assemblies, devices, compositions, etc.), the terms used to describe such elements (including references to "means") are intended, unless otherwise specified, to correspond to any element that performs the specified function of the described element (i.e., is functionally equivalent), even if it is not structurally equivalent to the disclosed structure that performs that function in the exemplary embodiment or embodiments illustrated herein. In addition, while a particular feature may be described above with respect to only one or more of some illustrated embodiments, such feature may be combined with one or more other features of other embodiments, as may be desirable or advantageous for any given or particular application.

Claims

1. A method for controlling the thrust direction of a flying object, comprising: launching the projectile so that a plume emerges from an exit end of a rocket nozzle of the projectile; generating a lateral control moment on the projectile by varying the thrust vector angle of the flame; changing the thrust deflection angle of the flame and simultaneously rolling the flying object; A method comprising the steps of:

2. The method of claim 1 , wherein varying the thrust vector angle of the plume comprises controlling a jet tab assembly of the projectile.

3. 3. The method of claim 2, wherein the jet tab assembly includes a plurality of jet tabs rotatably mounted to the exit end of the rocket nozzle of the projectile, and wherein the step of controlling the jet tab assembly includes rotating one or more jet tabs of the plurality of jet tabs into the plume of the projectile exiting the exit end of the rocket nozzle of the projectile.

4. The method of claim 1 , wherein launching the projectiles includes launching the projectiles vertically.

5. 4. The method of claim 1, wherein the step of rolling the projectile begins before the step of varying the thrust vector angle of the plume.

6. 4. The method of claim 1, wherein the step of rolling the projectile begins after the step of varying the thrust vector angle of the plume.

7. 4. The method of claim 1, wherein the step of rolling the projectile begins simultaneously with the step of varying the thrust vector angle of the plume.

8. 4. The method of claim 3, wherein the step of rolling the projectile includes rolling the projectile at a roll angular velocity that reduces a maximum exposure of any one of the plurality of jet tabs.

9. A flying object, a thrust vector control device configured to change a thrust vector angle of a flame exiting an exit end of a rocket nozzle of the projectile after launch of the projectile; a roll control device configured to roll the flying object simultaneously with the change in the thrust deflection angle of the flame by the thrust direction control device; The flying object comprising:

10. further comprising a jet tub assembly; 10. The air vehicle of claim 9, wherein the thrust vector control device is configured to control the jet tab assembly to vary the thrust vector angle of the plume.

11. The vehicle of claim 10 , wherein the jet tab assembly is attached to the outlet end of the rocket nozzle of the vehicle.

12. 11. The air vehicle of claim 10, wherein the jet tab assembly includes a plurality of jet tabs rotatably mounted to the exit end of the rocket nozzle of the air vehicle, and the thrust vector control device is configured to rotate one or more jet tabs of the plurality of jet tabs into the plume of the air vehicle.

13. 13. The flying vehicle of claim 9, wherein the roll control device is configured to begin rolling the flying vehicle before the thrust vector control device is configured to begin changing the thrust vector angle of the plume.

14. 13. The flying vehicle of claim 9, wherein the roll control device is configured to begin rolling the flying vehicle after the thrust vector control device is configured to begin changing the thrust vector angle of the plume.

15. 13. The flying vehicle of claim 9, wherein the roll control device is configured to begin rolling the flying vehicle at the same time that the thrust vector control device is configured to begin changing the thrust vector angle of the plume.

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