A method for designing the limit value of the dynamic pressure angle of attack product of launch vehicles

Abstract

This invention discloses a design method for limiting the dynamic pressure angle of attack product of launch vehicles, comprising the following steps: First, based on flight parameters, obtain the loads used in each section of the launch vehicle, including the bending moment load of the rocket body structure section, the static bending moment load component, the axial compression load, and the pressurization gas pressure in the propellant tanks; second, based on the used loads, perform a strength review of the strength calculations for each section and obtain the structural residual coefficients for each section; then, obtain the load deviation caused by the thrust deviation and obtain the remaining load, including the equivalent load residual and the bending moment residual; third, determine whether the trajectory design adopts a traditional non-load reduction design or a passive load reduction design. If a traditional non-load reduction trajectory design is adopted, an iterative algorithm is used to calculate the critical value of qα; otherwise, a fast equivalent algorithm is used to calculate the critical value of qα; finally, based on the calculated critical value of qα, fully explore the structural bearing capacity under the premise of absolutely ensuring structural safety, and set the pre-launch qα limiting value considering uncertainties.

Description

Technical Field

[0001] This invention relates to a method for designing the limit value of the dynamic pressure angle of attack product of a launch vehicle. Background Technology

[0002] Before rocket launch, high-altitude winds are continuously measured, and the product of dynamic pressure and angle of attack (qα) is calculated at various flight times (or altitudes). Stronger horizontal winds increase the qα value, leading to increased dynamic pressure and angle of attack, and consequently, increased lateral static load. Rocket load design conditions primarily refer to conditions such as buffeting, maximum normal force, and maximum dynamic pressure during flight through windy areas. The rocket structure often has a certain strength surplus coefficient, allowing for a certain increment beyond the design qα value. The critical qα value, where the strength surplus coefficient decreases to 1.0 during high-wind flight, represents the limit the rocket structure can withstand. To ensure structural safety and consider unpredictable load influences, a qα limit is set as a condition for allowing launch. Summary of the Invention

[0003] The technical problem solved by this invention is as follows: In order to solve the above-mentioned technical problem, this invention proposes a design method for limiting the dynamic pressure angle of attack product of launch vehicles. Under the premise of absolutely ensuring structural safety, this method fully explores the structural bearing capacity, provides a pre-launch qα limiting value, and allows for comparison with the pre-launch qα value to determine whether the structural strength launch conditions are met.

[0004] The technical solution of this invention is: a method for designing the limit value of the dynamic pressure angle of attack product of a launch vehicle, comprising:

[0005] The payloads used in each section of the launch vehicle are obtained based on flight parameters;

[0006] Based on the load used, the strength calculation of each section is reviewed to obtain the structural residual coefficient η of each section of the launch vehicle.

[0007] Based on the structural residual coefficient η of each section of the launch vehicle, the load deviation ΔN caused by the thrust deviation is obtained, and the load residual is calculated.

[0008] Determine whether the ballistic design uses a traditional non-load-reducing trajectory or a passive load-reducing trajectory, and calculate the critical value qα. lj ;

[0009] Based on the calculation of the critical value qα lj Under the premise of absolutely ensuring structural safety, the structural load-bearing capacity should be fully explored, and a series of uncertainties, including system bias, should be considered to set the pre-launch limit value qα. max, li m.

[0010] The loads used in each section of the launch vehicle include: the bending moment load M0 of the flight section of the rocket body structure and the static bending moment load component M.0s The axial compressive load N0 on the cross section of the rocket body structure during flight and the pressurization gas pressure P in the storage tank.

[0011] The step of reviewing the strength calculations of each section based on the applied load to obtain the structural residual coefficient η of each section of the launch vehicle includes:

[0012]

[0013]

[0014] In the formula, Z lj The critical equivalent axial compression load for the instability of the compartment is given by denoted as D, where D is the diameter of the compartment and R is the radius of the compartment.

[0015] The remaining load includes the equivalent axial compression load remaining Z. sy Residual bending moment M sy .

[0016] The process of obtaining the load deviation ΔN caused by the thrust deviation and calculating the remaining load includes:

[0017] ΔN=N (1+ ) Px -N0

[0018]

[0019] Z sy =ηZ0-Z s

[0020]

[0021] In the formula, N (1+)Px The axial load Z is calculated to increase the thrust. s The initial state is equivalent to axial compression load.

[0022] The ballistic design used in the judgment process employs either a traditional non-load-reducing trajectory or a passive load-reducing trajectory, and the critical value qα is calculated. lj If a traditional non-reduced load trajectory is used, an iterative algorithm is employed; otherwise, a fast equivalent algorithm is used.

[0023] If a traditional non-reduced load trajectory is used, an iterative algorithm is employed:

[0024]

[0025] Get the value of k at this point and substitute it into qα. lj =kqα0;

[0026] In the formula, k is the attack and swing angle amplification factor, α0 and δ0 are the initial state attack angle and swing angle, respectively, and α k δk For the current angle of attack and angle of rotation, Z k M k N k The equivalent axial compression, bending moment, and axial compression load for the current state;

[0027] Otherwise, use the fast equivalent algorithm:

[0028] qα lj =λqα0

[0029]

[0030] In the formula, λ is the residual coefficient of the lateral static load.

[0031] The pre-launch amplitude limit qα is set considering system deviation uncertainties. max, lim, including:

[0032]

[0033] qα max,lim =(1-θ)qα max,lj

[0034] In the formula, qa max,lj The critical state qα is the maximum value, qα max,0 Let qα be the maximum value of the initial state, θ be the uncertainty factor of the system deviation, and λ be the value of the initial state. min This represents the minimum residual coefficient for lateral static load.

[0035] The beneficial effects of this invention are as follows: The qα limit value design method for launch vehicles proposed in this invention can provide qα limit value conditions based on the load-bearing capacity of the rocket body structure and the flight load conditions. It can fully explore the load-bearing capacity of the structure, improve the launch probability, and provide a basis for judging whether the rocket structure meets the safe launch conditions before launch, for use in pre-launch decision-making at the launch site. Attached Figure Description

[0036] Figure 1 This is a flowchart of a method for designing the qα limit value of a launch vehicle according to the present invention.

[0037] Figure 2 These are the curves showing the changes in the critical value and the amplitude limit of qα as a function of flight altitude.

[0038] Figure 3 These are the curves showing the changes in the critical value of qα and the amplitude limit of qα over flight time. Detailed Implementation

[0039] like Figure 1 As shown in the figure, the specific implementation process of the design method for limiting the dynamic pressure angle of attack product of a launch vehicle according to an embodiment of the present invention is as follows:

[0040] S1, based on flight parameters such as equivalent diameter D, flight pressure q, flight aerodynamic angle of attack α0, and engine tilt angle δ0, can be pre-designed and provided by relevant professionals to obtain the loads used in each section of the launch vehicle, including the bending moment load M0 of the flight section's structural cross-section and the static bending moment load component M. 0s The axial compressive load N0 on the cross section of the rocket body structure during flight and the pressurized gas pressure P in the storage tank are provided in advance by the load specialist based on the flight parameters.

[0041] S2 performs a strength review on the strength calculations of each section based on the applied load, and obtains the structural residual coefficient η of each section of the launch vehicle:

[0042]

[0043]

[0044] In the formula, Z lj This is the critical load for the section to become unstable.

[0045] S3 obtains the load deviation ΔN caused by the thrust deviation and calculates the remaining load, including the equivalent remaining load Z. sy Residual bending moment M sy :

[0046] ΔN=N (1+ ) Px -N0

[0047]

[0048] Z sy =Z lj -Z s =ηZ0-Z s

[0049]

[0050] In the formula, N (1+)Px The axial load Z is calculated to increase the thrust. s The initial state is axial compressive load.

[0051] S4 determines whether the ballistic design uses a traditional non-load-reducing trajectory or a passive load-reducing trajectory, and calculates the critical value qα. lj :

[0052] If a traditional non-reduced load trajectory is used, an iterative algorithm is employed:

[0053]

[0054] qa lj =kqa0, until Z k =Z lj

[0055] In the formula, k is the attack and swing angle amplification factor, α0 and δ0 are the initial state attack angle and swing angle, respectively, and α k δ k For the current angle of attack and angle of rotation, Z k M k N k The equivalent axial compression, bending moment, and axial compression load for the current state are given. Otherwise, a fast equivalent algorithm is used:

[0056] Otherwise, use the fast equivalent algorithm:

[0057]

[0058] qα lj =λqα0

[0059] In the formula, λ is the residual coefficient of transverse static load, and M sy This represents the static bending moment load component.

[0060] In S5, the pre-launch qα limit value is set to consider system bias uncertainties. max,lim :

[0061]

[0062] qα max,lim =(1-θ)qα max,lj

[0063] In the formula, qa max,0 λ represents the maximum value of qα in the initial state. min θ represents the minimum residual coefficient of the transverse static load, and θ represents the uncertainty factor of the system deviation.

[0064] The application of the present invention will be described below with reference to specific embodiments.

[0065] The application of this invention will be illustrated using a certain type of launch vehicle as an example. According to this invention, the S1 flight parameters are: equivalent diameter D = 3.35m, flight pressure q = 20209Pa, flight aerodynamic angle of attack α0 = 9.60°, and core stage engine tilt angle δ. 0,xj =0.99°, booster engine sway angle δ 0,zt =0.66°, obtain the loads used in each section of the launch vehicle. Taking the first-stage liquid oxygen tank section as an example, the bending moment load M0 of the rocket body structure section during flight is 2542 kN·m, and the static bending moment load component M 0s =1805kN·m, axial compressive load N0 of the cross section of the rocket body structure during flight =1172kN, and pressurized gas pressure P of the storage tank =271kPa are provided in advance by the load specialist based on the flight parameters.

[0066] According to S2 of the present invention, the structural residual coefficients of each section of the launch vehicle are calculated:

[0067] Z0 = 4207kN

[0068] η = 1.16

[0069] According to S3 of the present invention, the load deviation ΔN caused by the thrust deviation is obtained, and the remaining load is calculated, including the equivalent remaining load Z. sy Residual bending moment M sy :

[0070] ΔN = 35kN

[0071] Z s =4241kN

[0072] Z sy =637kN

[0073] M sy =534kN·m

[0074] According to S4 of the present invention, a fast equivalent algorithm is used to calculate the critical value qα. lj :

[0075] λ = 1.296

[0076] qα lj = 4387 Pa·rad

[0077] According to S5 of the present invention, the pre-launch amplitude limit qα is set considering the uncertainty of system deviation. max,lim :

[0078] qa max,lj = 4372 Pa·rad

[0079] qα max,lim =3935 Pa·rad

[0080] like Figure 2 As shown, the curves of the qα critical value and qα limit value as a function of flight altitude are presented. Figure 3 As shown, the curves of the qα critical value and qα limit value as a function of flight time are presented. The qα limit value can be set according to the flight time or flight altitude. It is approximately 3300 Pa·rad in the transonic flight segment, not less than 3600 Pa·rad in the high wind area, and not less than 3000 Pa·rad in other flight segments.

[0081] The qα amplitude limit design method for launch vehicles proposed in this invention can provide qα amplitude limit conditions based on the load-bearing capacity of the rocket body structure and the flight load conditions, providing a basis for pre-launch judgment on whether the rocket structure meets the safe launch conditions, and can be used for pre-launch decision-making at the launch site.

[0082] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments without departing from the spirit and principles of the present invention, based on the essence of the present invention, shall fall within the protection scope of the present invention.

Claims

1. A method for designing the limiting value of the dynamic pressure angle-of-attack product of a launch vehicle, characterized in that, include: The payloads used in each section of the launch vehicle are obtained based on flight parameters; The strength calculations for each section were reviewed based on the applied load, and the structural residual coefficients of each section of the launch vehicle were obtained. ; Based on the structural residual coefficients of each section of the launch vehicle Obtain the load deviation caused by the thrust deviation. Calculate the remaining load; Determine whether the ballistic design uses a traditional non-load-reducing trajectory or a passive load-reducing trajectory, and calculate... critical value ; According to calculations critical value Under the premise of absolutely ensuring structural safety, fully explore the structural load-bearing capacity, and consider the uncertainties of system deviations in the pre-launch settings. Limit value ; The loads used in each section of the launch vehicle include: bending moment load of the cross-section of the rocket body structure during flight. Static bending moment load components Axial compression load on the cross section of the rocket body structure during flight. , Storage tank pressurization gas pressure ; The strength calculations for each section are reviewed based on the applied load to obtain the structural residual coefficients for each section of the launch vehicle. ,include: In the formula, This is the critical equivalent axial compression load for the section's instability. For the diameter of the compartment, The radius of the compartment; The remaining load includes the remaining equivalent axial compression load. Residual bending moment ; The amount of load deviation caused by thrust deviation is obtained. Calculate the remaining load, including: In the formula, The axial load was calculated to increase the thrust. The initial state is equivalent to axial compression load; The trajectory design used in the judgment adopts either a traditional non-load-reducing trajectory or a passive load-reducing trajectory, and the calculation... critical value If a traditional non-reduced load trajectory is used, an iterative algorithm is employed; otherwise, a fast equivalent algorithm is used. If a traditional non-reduced load trajectory is used, an iterative algorithm is employed: In the formula, This is the amplification factor for the swing angle. , For the initial angle of attack and yaw angle, , For the current state of attack angle and angle of attack, , , The equivalent axial compression, bending moment, and axial compression load for the current state; Otherwise, use the fast equivalent algorithm: In the formula, This is the residual coefficient for lateral static load.

2. The method for designing the limiting value of the dynamic pressure angle-of-attack product of a launch vehicle according to claim 1, characterized in that, The pre-launch settings take into account system bias and uncertainty factors. Limit value ,include: In the formula, Critical state Maximum value Initial state Maximum value For systematic bias and uncertainty factors, This represents the minimum residual coefficient for lateral static load.

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