A method for extending the range of guided rockets using a single-chamber dual-thrust ratio design

Abstract

This invention discloses a method for extending the range of guided rockets using a single-chamber, dual-thrust design. By rationally designing the guided rocket's acceleration process after launch, this method effectively reduces energy loss during passage through dense atmosphere, improves the guided rocket's energy conversion efficiency, and ultimately, with a comparable charge, enables the guided rocket to achieve greater mechanical energy at the end of its active phase, thereby effectively increasing its range. A notable feature of this method is that the end of the guided rocket's active phase is located at a higher altitude, thereby achieving a better thermal environment in the active phase while simultaneously increasing its range.

Description

Technical Field

[0001] The invention belongs to the field of rocket technology, and particularly relates to a method for increasing the range of a guided rocket. Background Art

[0002] In recent years, with advancements in aerodynamic, structural, and propulsion design technologies, the range of guided rockets has gradually increased. However, with the ever-changing international landscape and future combat scenarios, most guided rockets still face significant demand for increased range. Due to constraints such as vehicle size and launch method, the size and scale of guided rockets are often strictly restricted. Improving aerodynamic performance has its design bottlenecks. Under the limited envelope and large loading requirements, it is difficult to come up with an aerodynamic shape scheme with a high lift-to-drag ratio that is conducive to range extension. Lightweighting of structural design is another effective way to achieve range extension of guided rockets. However, with the transition of guided rocket material selection from metal to composites, lightweight design is gradually approaching its limit, and it is difficult to achieve a significant range extension effect (and the cost of relying on composite materials to achieve lightweight range extension is high). The performance of solid rocket engines has improved significantly in recent years. Foreign reports have shown that the theoretical specific impulse of composite charge has reached about 280s. However, in actual engineering design, due to the requirements of loading process, mass production, and wide temperature operation, the maximum achievable specific impulse is often quite different from the theoretical level. When the loading ratio has gradually approached the limit, increasing the energy of solid rocket engines to improve range capability also has its technical bottlenecks. Whether it is aerodynamics, structure or power energy level, optimizing the design of the three can achieve an improvement in overall range performance. Commonly used range-extending methods generally include drag reduction design, lightweight design, and increasing or replacing high-energy charges. However, these three approaches all require a high level of breakthrough in the basic research of their respective disciplines, and it is difficult to produce a qualitative breakthrough in a short period of time.

[0003] Therefore, the range-extending challenge facing guided rockets is equivalent to how to achieve increased range through overall design optimization within the existing aerodynamic shape, structural mass, and power energy levels. One feasible approach is to study how to rationally utilize the limited energy of existing solid rocket motors. By adjusting the energy utilization during exterior ballistic flight through interior ballistic design, this approach improves the acceleration characteristics of guided rockets during exterior ballistic flight, reduces energy losses from traversing the dense atmosphere, enhances high-altitude acceleration capabilities, and ultimately achieves a longer range for guided rockets.

[0004] Compared to liquid rockets, solid rocket engines have a narrower range of adjustable internal ballistics. This range is determined by the charge type and burning rate, and the thrust and flow-per-second curves are subsequently determined accordingly. Single-chamber, multi-thrust solid rocket engines are an effective approach to achieving energy distribution in solid rocket engines. Unlike single-chamber, single-thrust solid rocket engines, which have a relatively constant thrust curve, single-chamber, multi-thrust solid rocket engines offer more flexible adjustment capabilities. Among these, single-chamber, dual-thrust solid rocket engines are a relatively simple and commonly used single-chamber, multi-thrust scheme. While many researchers have focused on the impact of this type of engine on its external ballistic acceleration characteristics, a systematic design method for utilizing this scheme to extend range has yet to be established. Using a single-chamber, dual-thrust solid rocket engine with a carefully proportioned design is an effective means of extending range within strict constraints on size, shape, and charge energy levels. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, the present invention provides a method for extending the range of guided rockets using a single-chamber, dual-thrust design. By rationally designing the guided rocket's acceleration process after launch, this method effectively reduces energy loss during passage through dense atmosphere, improves the guided rocket's energy conversion efficiency, and ultimately, with a comparable charge, enables the guided rocket to achieve greater mechanical energy at the end of its active phase, thereby effectively extending its range. A notable feature of the present method is that the guided rocket's active phase is located at a higher altitude, thereby achieving a better thermal environment in the active phase while simultaneously increasing its range.

[0006] The technical solution adopted by the present invention to solve the technical problem includes the following steps:

[0007] Step 1: Analysis of acceleration characteristics requirements for the active phase of the guided rocket;

[0008] The guided rocket needs to overcome the air resistance to do work in the active phase of flight. The air resistance D is expressed as:

[0009]

[0010] Where: C d is the drag coefficient, S ref is the reference area, ρ is the atmospheric density, and V is the velocity;

[0011] Step 2: Guided rocket solid rocket range performance evaluation model;

[0012] First, establish the exterior ballistic range evaluation model:

[0013]

[0014]

[0015]

[0016]

[0017]

[0018] Where: r is the distance from the center of the earth; θ is the ballistic inclination; S is the range; P is the engine thrust; α is the angle of attack; X is the drag, Y is the lift; g is the acceleration due to gravity; m is the mass of the entire missile; mdot is the engine flow rate per second;

[0019] Let the total impulse ratio of the two stages of the single-chamber dual-thrust solid rocket engine be k1 and the two-stage working time ratio be k2. During the iteration process, the thrust of the two stages is obtained by the average thrust, that is:

[0020]

[0021] Where: T total is the total engine impulse, t f is the total working time of the engine, and t is the current working time of the engine;

[0022] With r, S, V, θ, m, α as state variables, the rate of change of angle of attack is the control variable, k1 and k2 are the parameters to be optimized, and the exterior trajectory establishes the relationship between the angle of attack and the rudder angle based on the instantaneous equilibrium assumption. The maximum range is used as the performance indicator, which is expressed as:

[0023] J=-S end (8)

[0024] Step 3: Calculate the parameters of the combined ratio of internal and external trajectories;

[0025] A numerical optimization method is used for iterative optimization. By optimizing the ratio parameters, the external ballistics obtains real-time thrust data, thereby driving the external ballistic range optimization. The results of the external ballistic range optimization are fed back to the internal ballistics iteration process to drive the update of the ratio parameters. After the algorithm convergence conditions are met, the external ballistics outputs the range result, and the internal ballistics outputs the ratio parameters k1 and k2.

[0026] Step 4: Improve the solid rocket engine scheme based on the ratio parameters and verify the range capability of the actual thrust curve of the rocket. If the index requirements are met, the range extension design is completed; if not, the iterative design continues.

[0027] Preferably, the numerical optimization method is one of an interior point method, a convex optimization method, and a Gaussian pseudospectral method.

[0028] Preferably, the numerical optimization method is a Gaussian pseudospectral method.

[0029] Preferably, the ratio parameters k1=1, k2=1 / 3, that is, the total impulse ratio is 1:1. This set of parameters is the ideal extended-range ratio design parameters.

[0030] The beneficial effects of the present invention are as follows:

[0031] 1. Compared to aerodynamic shape, structural design, and motor charge performance, improving exterior ballistic range capability by adjusting the interior ballistic characteristics of a solid rocket motor is a design approach that requires minimal modification to the base design and has minimal impact on aerodynamics and structure. Compared to existing range-extending methods, this invention can rapidly increase the range capability of a guided rocket without significantly increasing the size of the guided rocket. Because the overall projectile shape and key structural parameters remain unchanged, the impact on the design's reliability is minimal.

[0032] 2. This invention provides a set of optimal design parameters, validated by numerous projects, that can be used to extend the range of guided rockets, missiles, and other weaponry powered by solid rocket motors. This method is simple, reliable, and extensively validated, effectively enhancing the performance of medium- and long-range guided rockets and possesses considerable potential for widespread adoption. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is the curve of atmospheric density changing with altitude.

[0034] Figure 2 is the ideal thrust curve corresponding to the ratio parameters.

[0035] Figure 3 This is a trajectory comparison curve between single-chamber single-push and single-chamber double-push.

[0036] Figure 4 This is a comparison curve of speed and Mach number between single-chamber single-thrust and single-chamber dual-thrust. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to the accompanying drawings and examples.

[0038] The technical problem to be solved by the present invention is: how to adjust the energy distribution of the solid engine by adopting a single-chamber dual-thrust ratio design when the aerodynamic shape, structural parameters and engine energy level of the guided rocket are basically determined, thereby improving the external ballistic acceleration characteristics and increasing the range capability of the guided rocket.

[0039] To solve the above technical problems, the present invention provides a design method for improving the exterior ballistic range capability by adjusting the energy ratio of the two stages of the solid rocket engine using a single-chamber dual-thrust scheme under equivalent energy levels. At the same time, a set of widely verified and easy-to-implement ratio parameters are provided for reference design.

[0040] A method for extending the range of a guided rocket using a single-chamber dual-thrust ratio design is described, and the specific implementation method is as follows.

[0041] 1. Analysis of acceleration characteristics requirements for the active phase of guided rockets;

[0042] The range capability of a guided rocket depends on the total mechanical energy obtained at the end of its active phase, which is derived from the solid rocket motor. Given a fixed energy level for the solid rocket motor, increasing range requires reducing energy losses during the active phase. During the active phase, a guided rocket must overcome air resistance to generate work. Air resistance D can be expressed as:

[0043]

[0044] Where: C d is the drag coefficient, S ref The reference area is determined by the aerodynamic shape. The two items are determined accordingly. Therefore, the main factors affecting the drag are the atmospheric density ρ and the velocity V. The atmospheric density changes with altitude as shown in the following figure. Figure 1 As shown, it can be seen that the air density decays exponentially with altitude. Therefore, the acceleration characteristics of the active phase of the guided rocket determine whether it can quickly pass through the dense atmosphere and reduce the energy dissipated to overcome air resistance.

[0045] 2. Range performance evaluation model for guided rocket solid rocket;

[0046] Range is an important indicator of the external ballistics that reflects the energy level of solid rocket motors. To facilitate the design, an external ballistic range evaluation model is first established:

[0047]

[0048]

[0049]

[0050]

[0051]

[0052] Where: r is the distance from the Earth's center; V is the projectile velocity; θ is the ballistic inclination; S is the range; P is the engine thrust; α is the angle of attack; X is the drag, Y is the lift; g is the acceleration due to gravity; m is the total mass of the projectile; and mdot is the engine flow rate per second. Let the total impulse ratio of the two stages of a single-chamber, dual-thrust solid rocket engine be k1 and the two-stage working time ratio be k2. During the iteration process, the thrust of the two stages is obtained by averaging the thrust, that is:

[0053]

[0054] Where: T total is the total engine impulse, t f is the total working time of the engine, t is the current working time of the engine. With r, S, V, θ, m, α as state variables, the rate of change of angle of attack is the control quantity, k1 and k2 are the parameters to be optimized, and the interior ballistic curve used for the design of the ratio parameters can be taken as Figure 2 The external trajectory establishes the relationship between the angle of attack and the rudder angle based on the instantaneous equilibrium assumption. Taking the maximum range as the performance indicator, it can be expressed as:

[0055] J=-S end (8)

[0056] 3. Calculation of internal and external ballistic joint ratio parameters;

[0057] After completing the solid rocket engine ratio parameter modeling, a numerical optimization method is used to iteratively optimize the above problem. A variety of numerical optimization methods can be used, such as interior point methods, convex optimization methods, and pseudospectral methods. The present invention uses the Gaussian pseudospectral method to solve the above optimal control problem. By optimizing the ratio parameters, the exterior ballistics obtains real-time thrust data, thereby driving the exterior ballistic range optimization. The results of the exterior ballistic range optimization are fed back to the interior ballistics iterative process to drive the update of the ratio parameters. After the algorithm convergence conditions are met, the exterior ballistics outputs the range result, and the interior ballistics outputs the ratio parameters k1 and k2.

[0058] Through extensive engineering practice, a well-verified set of ideal range-extending design parameters has emerged: k1 = 1, k2 = 1 / 3, resulting in a total impulse ratio of 1:1 and a time ratio of 1:3. Under these parameters, the solid rocket engine exhibits a short period of high thrust followed by a long period of low thrust, meeting the acceleration requirements of rapid initial passage through the dense atmosphere, followed by a long period of low thrust endurance. This helps minimize energy losses during passage through the dense atmosphere, while also effectively increasing the final trajectory height and mechanical energy accumulation at the end of the active phase through the long-term cumulative effect of the dual thrust.

[0059] 4. Improve the solid rocket engine according to the ratio parameters;

[0060] After obtaining the engine's ratio parameters, the overall team will submit the desired ratio parameters and the ideal internal ballistic thrust curve to the engine project team. The engine project team will then refine the solid rocket engine design based on the energy ratio requirements. After the engine project team completes the design based on the ideal thrust curve, it will provide feedback to the overall department for range capability verification based on the actual thrust curve. If the requirements are met, the range extension design is completed; if not, the design iteration will continue.

[0061] 5. Design verification of a basic missile;

[0062] Taking a certain project as an example, under the condition that the missile body structure quality, aerodynamic shape and charge amount are unchanged, the single-chamber single-thrust scheme corresponds to a comprehensive specific impulse of 251s at sea level, and the single-chamber dual-thrust scheme corresponds to a comprehensive specific impulse of 240s at sea level. The single-chamber dual-thrust scheme is designed with the optimal ratio parameters of k1=1 and k2=1 / 3 for the single-chamber dual-thrust internal ballistics. The single-chamber single-thrust scheme corresponds to a maximum range capability of 508km, and the single-chamber dual-thrust scheme corresponds to a maximum range capability of 570km. The ballistic curve is shown in Figure 3 、 Figure 4 As can be seen, through the design of the internal ballistic ratio of the engine alone, the range can be increased by 62km without changing the overall parameters such as the length, weight, and shape of the missile, which is a significant range-extending effect. Under the condition that the overall shape and weight of the missile are basically determined, this scheme requires minimal changes to the entire missile, making it particularly suitable for improving the range of existing ammunition and can also be used for scheme optimization in the overall design stage. The proposed ratio parameters have been verified by a large number of projects and have a certain degree of universality, and can serve as a reference for solid rocket engine designers.

[0063] The outstanding advantage of the present invention is that, under the premise of keeping the existing projectile configuration unchanged, the interior ballistics of the solid rocket engine is reasonably designed, thereby achieving a significant increase in the range of the guided rocket under the premise of keeping the charge unchanged.

[0064] This method can be used not only for the overall design of newly developed missions but also for the range-extending improvements of existing guided rockets. It is an overall design approach that does not affect the guided rocket's aerodynamic shape, does not require an increase in engine charge, and has minimal demand for higher-specific-impulse charges. It can provide guided rockets with significant "extra" range capability, helping to better utilize the guided rocket's range capability within the existing solid rocket motor composite charge energy level, thereby improving the overall performance of the ammunition.

[0065] This method can effectively improve the optimality of the overall guided rocket design, reduce the difficulty of achieving range extension, and improve the overall cost-effectiveness of ammunition. The method is simple and reliable, and the design results have been extensively verified, showing great potential for widespread application.

Claims

1. A method for extending the range of a guided rocket using a single-chamber dual-thrust ratio design, characterized in that: The steps include: Step 1: Analysis of acceleration characteristics requirements for the active phase of the guided rocket; The guided rocket needs to overcome the air resistance to do work in the active phase of flight. The air resistance D is expressed as: Where: C d is the drag coefficient, S ref is the reference area, ρ is the atmospheric density, and V is the velocity; Step 2: Guided rocket solid rocket range performance evaluation model; First, establish the exterior ballistic range evaluation model: Where: r is the distance from the center of the earth; θ is the ballistic inclination; S is the range; P is the engine thrust; α is the angle of attack; X is the drag, Y is the lift; g is the acceleration due to gravity; m is the mass of the entire missile; mdot is the engine flow rate per second; Let the total impulse ratio of the two stages of the single-chamber dual-thrust solid rocket engine be k1 and the two-stage working time ratio be k2. During the iteration process, the thrust of the two stages is obtained by the average thrust, that is: Where: T total is the total engine impulse, t f is the total working time of the engine, and t is the current working time of the engine; With r, S, V, θ, m, α as state variables, the rate of change of angle of attack is the control variable, k1 and k2 are the parameters to be optimized, and the exterior trajectory establishes the relationship between the angle of attack and the rudder angle based on the instantaneous equilibrium assumption. The maximum range is used as the performance indicator, which is expressed as: J=-S end (8) Step 3: Calculate the parameters of the combined ratio of internal and external trajectories; A numerical optimization method is used for iterative optimization. By optimizing the ratio parameters, the external ballistics obtains real-time thrust data, thereby driving the external ballistic range optimization. The results of the external ballistic range optimization are fed back to the internal ballistics iteration process to drive the update of the ratio parameters. After the algorithm convergence conditions are met, the external ballistics outputs the range result, and the internal ballistics outputs the ratio parameters k1 and k2. Step 4: Improve the solid rocket engine scheme based on the ratio parameters and verify the range capability of the actual thrust curve of the rocket. If the index requirements are met, the range extension design is completed; if not, the iterative design continues.

2. A method for extending the range of a guided rocket using a single-chamber dual-thrust ratio design according to claim 1, characterized in that: The numerical optimization method is one of an interior point method, a convex optimization method, and a Gaussian pseudospectral method.

3. The method for extending the range of a guided rocket using a single-chamber dual-thrust ratio design according to claim 1, characterized in that: The numerical optimization method is Gaussian pseudospectral method.

4. The method for extending the range of a guided rocket using a single-chamber dual-thrust ratio design according to claim 1, characterized in that: The ratio parameters k1=1, k2=1 / 3, that is, the total impulse ratio is 1:

1. This group of parameters is the ideal range-extending ratio design parameters.

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