Thermal performance analysis method for protective layer of lunar base and protective layer structure

Abstract

The invention discloses a thermal performance analysis method for a protective layer of a lunar base and a protective layer structure. The method comprises the following steps: establishing a thermal balance equation including solar radiation, lunar internal heat, non-blackbody radiation and lunar albedo radiation; performing thermal analysis based on a heat transfer theory basic theory equation and a heat balance equation to obtain a thermodynamic micro-equation of the lunar surface and the protective layer; solving the obtained thermodynamic micro-equation to obtain temperature field distribution; determining the relationship between the lunar soil protective layer thickness and temperature fluctuation based on finite element analysis; and determining the thickness of the lunar soil protective layer based on the relationship between the thickness of the lunar soil protective layer and temperature fluctuation, and constructing the protective layer based on the determined thickness of the lunar soil protective layer. By adopting the method and the protective layer, the protective capability of the protective layer structure is improved.

Description

Technical Field

[0001] This invention relates to the field of lunar base construction technology, and in particular to a method for analyzing the thermal performance of a protective layer for a lunar base and the structure of the protective layer. Background Technology

[0002] In today's rapidly developing society, the Earth's surface is no longer sufficient to meet human needs. Humanity has begun to explore the deep sea, deep earth, and even deep space, attempting to expand its living space. Deep space exploration appears particularly challenging, and the Moon has become the first step in this journey. A lunar base can support higher-level deep space exploration and rapidly advance deep space exploration and outer space exploration. This research covers various aspects, including lunar environment adaptability assessment and base structure design, aiming to lay a solid scientific and technological foundation for future lunar exploration and utilization. Therefore, the planning and key technology research of lunar research bases are receiving increasing attention.

[0003] Currently, existing lunar base protection technologies have the following shortcomings: inflatable structures have poor resistance to micrometeorite impacts (e.g., the critical load factor of the NASA TransHab prototype is <10); the construction cycle of 3D-printed lunar soil structures is long (single module molding >240 hours); the lunar soil protective layer mostly uses 100mm-200mm of lunar soil, with a day-night temperature difference >50K, and the design of the insulation layer thickness lacks quantitative basis. Summary of the Invention

[0004] The purpose of this invention is to provide a method for analyzing the thermal performance of the protective layer of a lunar base and the structure of the protective layer, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides a method for analyzing the thermal performance of the protective layer of a lunar base, comprising the following steps: S1. Establish a heat balance equation that includes solar radiation, lunar internal heat, non-blackbody radiation, and lunar albedo radiation. S2. Based on the fundamental theoretical equations of heat transfer and the thermal balance equations, thermal analysis is performed to obtain the thermodynamic micro-equations of the lunar surface and the protective layer. S3. Solve the obtained thermodynamic microequations to obtain the temperature field distribution; S4. Determine the relationship between the thickness of the lunar soil protective layer and temperature fluctuations based on finite element analysis; S5. Determine the thickness of the lunar soil protective layer based on the relationship between the thickness of the lunar soil protective layer and temperature fluctuations.

[0006] Preferably, in step S1, solar radiation, lunar internal heat, non-blackbody radiation, and lunar albedo radiation include: The formula for solar radiation is: ; ; In the formula, This represents the maximum solar radiation power. The time of one complete lunar phase cycle It is the length of a day in the lunar calendar. Solar radiation power, The surface area that receives radiation; Calculated solar radiation energy With surface absorption rate Multiplying them together gives the solar radiation on the lunar surface. ; The formula for the heat inside the moon is: ; In the formula, This refers to the internal heating power. Heat from the moon's interior With surface absorption rate Multiplying them together gives the amount of heat inside the moon relative to its surface. ; The formula for non-blackbody radiation is: ; In the formula, This is the Stefan-Boltzmann constant. The absolute temperature of the object's surface. For surface emissivity, This refers to non-blackbody radiation energy. The formula for lunar albedo radiation is: ; In the formula, Reflecting energy from the moon , representing the reflectivity of the lunar surface. This is the angle of incidence of the sun.

[0007] Preferably, in step S1, the established heat balance equation is the heat balance equation during the steady-state period of the lunar surface, where the size of the incident heat source is equal to the size of the outflowing heat source, and the formula is: ; In the formula, Solar radiation, Heat from the moon's interior It is non-blackbody radiation. The lunar albedo radiation consists of solar radiation and lunar internal heat as the incident heat source, and non-blackbody radiation and lunar albedo radiation as the outflow heat source.

[0008] Preferably, the thermodynamic microequation in step S2 is: ; In the formula, For time; The depth of the weathering layer; For depth; For the quality of the weathered layer; For the specific heat of the weathered layer, To allow the heat source to flow out, It is the incident heat source.

[0009] Preferably, in step S3, the fourth-order Runge-Kutta method is used to solve the obtained thermodynamic microequations to obtain the temperature field distribution.

[0010] Preferably, the relationship between the thickness of the lunar soil protective layer and temperature fluctuation in step S4 includes: when the temperature of the lunar soil protective layer is set to 100K, 200K, 300K and 400K, and the thickness of the lunar soil protective layer is not less than 400mm, the steady-state temperature converges to 220±10K.

[0011] The present invention also provides a protective layer structure for a lunar base, comprising a rectangular steel frame, arched steel, a PVC membrane layer, and a protective layer. The protective layer includes a solidified lunar regolith layer and a lunar regolith protective layer, which are connected to the rectangular steel frame at equal intervals. The PVC membrane layer is disposed above multiple arched steel sections. The solidified lunar regolith layer consists of two layers, and the lunar regolith protective layer is disposed between the solidified lunar regolith layers. The thickness of the lunar regolith protective layer is determined based on a method for analyzing the thermal performance of a protective layer for a lunar base.

[0012] Preferably, the spacing between adjacent arched steel sections is 1.2m-1.8m, and they are fixedly connected to the rectangular steel frame by a locking buckle. The span of the arched steel section is 10m-15m, and the arch height is 5m-8m.

[0013] Preferably, the thickness of the lunar soil protective layer is not less than 400 mm and the thermal conductivity is not greater than 0.05 W / m·K.

[0014] Preferably, the solidified lunar soil layer includes an upper solidified lunar soil layer and a lower solidified lunar soil layer, wherein the lower solidified lunar soil layer abuts against the PVC film layer.

[0015] Therefore, the present invention employs the above-described method for analyzing the thermal performance of a protective layer for a lunar base and the structure of the protective layer, which has the following beneficial effects: (1) The protective layer structure adopts a composite structure of skeleton-PVC film-lunar soil protective layer, which has high stability and fast construction speed, and solves the problems of poor resistance to micro meteorite impact of inflatable structure and long construction cycle of 3D printed lunar soil structure. (2) By conducting thermal analysis on the lunar surface and the protective layer, the optimal thickness of the lunar soil protective layer was determined, which improved the protective capability of the protective layer structure.

[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0017] Figure 1 This is a flowchart of a method according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of an embodiment of the present invention; Figure 3 This is a schematic diagram of the lunar soil covering layer according to an embodiment of the present invention; Figure Labels 1. Rectangular steel frame; 2. Arched steel; 3. PVC film layer; 4. Protective layer; 41. Lower solidified lunar soil layer; 42. Loose lunar soil layer; 43. Upper solidified lunar soil layer. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. In the description of the present invention, it should be noted that the terms "upper," "lower," "inner," "outer," etc., indicating orientation or positional relationships are based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationships commonly used when the product of the invention is in use. They are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0019] Example Reference Figure 1 This invention provides a method for analyzing the thermal performance of a protective layer for a lunar base. The protective layer habitat is constructed at the lunar equator. The analysis method includes the following steps: S1. Establish a heat balance equation that includes solar radiation, lunar internal heat, non-blackbody radiation, and lunar albedo radiation. Among these, The formula for solar radiation is: ; ; In the formula, The maximum solar radiant power is 1450 kW. , The duration of a complete lunar cycle (approximately 29.53 days) It is the length of a day in the lunar calendar. Solar radiation power, The surface area that receives radiation; Calculated solar radiation energy With surface absorption rate Multiplying them together gives the solar radiation on the lunar surface. The absorption rate was 0.87.

[0020] The formula for the heat inside the moon is: ; In the formula, This is the internal heating power, approximately .

[0021] Heat from the moon's interior With surface absorption rate Multiplying them together gives the amount of heat inside the moon relative to its surface. The absorption rate was 0.87.

[0022] Non-blackbody radiation: All objects in space constantly emit radiant energy, the amount of which depends on their temperature and the overall properties of their surface. By definition, a blackbody absorbs all incident radiation, therefore its surface absorptivity is... Because the Moon does not absorb all the radiant energy reaching its surface, it is called a non-blackbody surface. The formula for the total emitted power of non-blackbody radiation is: ; In the formula, This is the Stefan-Boltzmann constant. The absolute temperature of the object's surface. For surface emissivity, take 0.97. This refers to non-blackbody radiation energy.

[0023] Lunar albedo radiation: Of all the solar radiation affecting the lunar surface, a portion is reflected back into space; this radiation is called albedo radiation, and the formula for albedo radiation is: ; In the formula, Reflecting energy from the moon , where is the reflectivity of the lunar surface, taken as 0.13. This is the angle of incidence of the sun.

[0024] During steady state, the magnitude of the incident heat source must be equal to the magnitude of the outflow heat source. Assuming sufficient time to reach steady state, this will result in no net increase or loss of heat within the system. Therefore, the heat balance formula is: ; or .

[0025] The values ​​of lunar surface parameters are shown in Table 1. Based on the lunar surface parameters, the unknown variable T was solved, and the steady-state temperature of the lunar surface was found to be 387.1 K.

[0026] Table 1 Lunar surface parameters

[0027] S2. Based on the fundamental theoretical equations of heat transfer and the thermal balance equation, thermal analysis is performed to obtain the thermodynamic micro-equations of the lunar surface and the protective layer.

[0028] The fundamental theoretical equations of heat transfer are as follows: Considering the heat transfer between the lunar surface and the protective layer, as well as the heat transfer process within the protective layer, it follows Fourier's law and satisfies the following equation: ; In the formula, Heat flux density ; Thermal conductivity; This represents the temperature gradient along the direction.

[0029] Considering the convective heat transfer within the protective layer, the convective heat transfer follows Newton's law of cooling and satisfies the following equation; ; In the formula, Heat flux density ; The convective heat transfer coefficient; This represents the temperature difference between the solid surface and the fluid.

[0030] Considering the temperature field of the lunar base's protective layer and structure, a three-dimensional unsteady heat conduction equation is used to establish the governing equations, as shown below: ; In the formula, For temperature; For time; Thermal conductivity; Specific heat capacity; For density.

[0031] Solar radiation has a known heat flux density on the sun-facing side of the lunar base's protective layer structure. Therefore, the boundary conditions of the structure can be expressed by the following formula.

[0032] ; In the formula, The heat flux density at the boundary; Let be a known heat flux density function on the boundary.

[0033] Considering the internal convection environment, the expression for the boundary conditions of the internal structure of the lunar base's protective layer is as follows: ; In the formula, The heat transfer coefficient is... The ambient temperature.

[0034] The external structure of the lunar base's protective layer is in a complex thermal radiation environment, and the expression for its radiation boundary conditions is as follows.

[0035] ; In the formula, The direction of the outward normal to the surface; The ambient temperature.

[0036] In this embodiment, the initial condition is set at the beginning of lunar noon. At this time, the temperature values ​​at various points of the lunar base's protective layer are expressed as follows: ; In the formula, Given a temperature function.

[0037] To analytically determine the expected temperature variation period at and below the lunar surface, thermal analysis must be performed using the described incident and output heat sources. The lunar surface is defined as the outermost layer of the lunar regolith, which is considered to have a uniform depth of 2 cm across the entire lunar surface. Therefore, the thermal analysis is based solely on the lunar surface, excluding depth, resulting in the following thermodynamic microequation: ; In the formula, For time; The depth of the weathering layer; For depth; For the quality of the weathered layer; For the specific heat of the weathered layer, To allow the heat source to flow out, It is the incident heat source.

[0038] S3. Solve the obtained thermodynamic microequations using the fourth-order Runge-Kutta method to obtain the temperature field distribution. The process includes: First, the corresponding input-output expressions are directly substituted into the thermodynamic differential equation using the numerical integration approximation method, resulting in the following equation; .

[0039] Then, the fourth-order Runge-Kutta method is used to solve the problem, and the process is as follows: First, we define a theoretical ordinary differential equation model, with the following formula: ; ; ; In the formula, and These are the initial conditions for time and temperature, respectively.

[0040] Then, using the Euler method to approximate the existing ordinary differential equation, which is the basis of the Runge-Kutta method, we obtain: ; In the formula, , The index of the iteration step. The total number of iterations represents the total number of steps in the entire numerical solution process, which determines the scope and accuracy of the calculation (the more steps, the higher the accuracy in theory, but the greater the computational load).

[0041] To improve the accuracy of the Euler method, the value must be reduced. The magnitude of the slope effectively allows the numerical solution to be evaluated more frequently, thus reducing errors in the solution. The fourth-order Runge-Kutta method uses a weighted average of four slope values ​​to approximate the next point on the solution curve. The general formula for calculating from multiple slope estimates is as follows.

[0042] ; in, is the weighting coefficient, and is the slope of each point in the interval.

[0043] As described above, the fourth-order Runge-Kutta method provides four slope estimates calculated at each step of the integration; these estimates are denoted as... , , , The calculation is as follows; ; ; ; ; Calculate the weighted average from it to determine The next value is given by the formula: .

[0044] S4. The relationship between the thickness of the lunar regolith protective layer and temperature fluctuations was determined based on finite element analysis. Specifically, the initial temperatures of the lunar regolith protective layer were set to 100K, 200K, 300K, and 400K, respectively. The thickness of the lunar regolith protective layer ranged from 0mm to 600mm, with a monitoring point set every 100mm. A simulation experiment covering 40 lunar days was conducted. When the lunar regolith thickness was not less than 400mm, the steady-state temperature converged to 220±10K. When the thickness was less than 400mm, convergence was not observed, and the temperature variation range was large, with fluctuations reaching as high as 54K at 100mm. When the thickness was 400mm and above, the steady-state temperature converged to 220K, with very small fluctuations.

[0045] S5. Determine the thickness of the lunar soil protective layer based on the relationship between the thickness of the lunar soil protective layer and temperature fluctuations.

[0046] Reference Figure 2-3 This invention also provides a protective layer structure for a lunar base, comprising a rectangular steel frame 1, Q235 arched steel 2 (elastic modulus ≥ 200 GPa), a PVC membrane layer 3, and a protective layer 4. The protective layer includes a solidified lunar regolith layer and a lunar regolith protective layer 42. Multiple arched steel 2 sections are provided and connected to the rectangular steel frame 1 at equal intervals. The PVC membrane layer 3 is positioned above the multiple arched steel 2 sections. The solidified lunar regolith layer consists of two layers, with the lunar regolith protective layer 42 positioned between the solidified lunar regolith layers. The lunar regolith protective layer 42 is a loose lunar regolith layer. The PVC membrane exhibits orthotropic characteristics, with an x / y elastic modulus of 1.35 / 1.15 GPa. The PVC membrane layer is supported by the steel frame, generating a certain amount of prestress during shaping. The membrane material has a light unit mass, and the membrane structure adapts to externally applied loads through changes in its shape. During this process, the radius of curvature of the membrane surface in the load direction gradually decreases, thereby improving the load resistance efficiency.

[0047] In this embodiment, the spacing between adjacent arched steel 2 ranges from 1.2m to 1.8m, and they are fixedly connected to the rectangular steel frame 1 by a locking buckle. The span of the arched steel 2 ranges from 10m to 15m, and the arch height ranges from 5m to 8m.

[0048] In this embodiment, the lunar soil protective layer 42 has a thickness of not less than 400 mm, a thermal conductivity of not more than 0.05 W / m·K, and a density of 1600-2000 kg / m³. 3 .

[0049] In this embodiment, the solidified lunar soil layer includes an upper solidified lunar soil layer 41 and a lower solidified lunar soil layer 43, with the lower solidified lunar soil layer 43 abutting against the PVC film layer 3. The upper solidified lunar soil layer 41 and the lower solidified lunar soil layer 43 are both 30 mm thick.

[0050] The in-situ construction process of the protective layer structure is as follows: Phase 1: The robot excavates the foundation (depth ≥ 1m) and fixes the steel frame that is fixedly connected to the rectangular steel frame 1 and the arched steel frame 2; Phase 2: Automatically unfold the PVC membrane and apply prestress (≥5MPa); Phase 3: Lunar soil coverage.

[0051] Through in-situ construction, the utilization rate of lunar soil is greater than 90%, and the amount of Earth-Moon material transportation is reduced by 60%.

[0052] Therefore, the present invention adopts the above-mentioned method for analyzing the thermal performance of the protective layer of a lunar base and the protective layer structure. By using a composite structure of skeleton-PVC film-lunar soil protective layer, the structure has high stability and fast construction speed. Furthermore, by conducting thermal analysis on the lunar surface and the protective layer, the optimal thickness of the lunar soil protective layer is determined, thereby improving the protective capability of the protective layer structure.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for analyzing the thermal performance of a shield of a lunar base, characterized in that, The method comprises the steps of: S1, establishing a heat balance equation including solar radiation, lunar internal heat, non-blackbody radiation and lunar albedo radiation; S2, performing thermal analysis based on a basic equation of heat transfer and the heat balance equation to obtain a thermodynamic micro-equation of the lunar surface and the protective layer; S3, solving the obtained thermodynamic micro-equation to obtain a temperature field distribution; S4, determining a relationship between the thickness of the lunar soil protective layer and temperature fluctuation based on finite element analysis; S5, determining the thickness of the lunar soil protective layer based on the relationship between the thickness of the lunar soil protective layer and temperature fluctuation.

2. The method of claim 1, wherein: In step S1, the solar radiation, lunar internal heat, non-blackbody radiation and lunar albedo radiation include: The formula of the solar radiation is: ； ； wherein is the maximum solar radiation power, is the time of a complete lunar phase, is the time of a solar day, is the solar radiation power, is the surface area receiving the radiation; The calculated solar radiant energy is multiplied by the surface absorptivity to obtain the solar radiation at the lunar surface; The formula of the lunar internal heat is: ； In the formula, Pint is the internal heating power; Heat from the moon's interior With surface absorption rate Multiplying them together gives the amount of heat inside the moon relative to its surface. ; The formula of the non-blackbody radiation is: ； wherein is the Stefan-Boltzmann constant, is the absolute temperature of the surface of the object, is the emissivity of the surface, is the non-blackbody radiated energy; The formula of the lunar albedo radiation is: ； wherein is the lunar reflected energy, is the lunar surface reflectivity, is the solar incidence angle.

3. The method of claim 2, wherein: In step S1, the established heat balance equation is a heat balance equation during the steady state of the lunar surface, the size of the incident heat source is equal to the size of the outflow heat source, and the formula is: ； In the formula, is the solar radiation, is the internal heat of the moon, is the non-blackbody radiation, is the lunar albedo radiation, wherein the solar radiation and the internal heat of the moon constitute the incident heat source, and the non-blackbody radiation and the lunar albedo radiation constitute the outflow heat source.

4. The method of claim 1, wherein, In step S2, the thermodynamic micro-equation is: ； wherein is time; is weathering layer depth; is depth; is weathering layer mass; is weathering layer specific heat, is outflow heat source, is incident heat source.

5. The method of claim 1, wherein: In step S3, the fourth-order Runge-Kutta method is used to solve the obtained thermodynamic micro-equation to obtain the temperature field distribution.

6. The method of claim 1, wherein: In step S4, the relationship between the thickness of the lunar soil protective layer and temperature fluctuation includes: the temperature of the lunar soil protective layer is set to 100K, 200K, 300K and 400K, and when the thickness of the lunar soil protective layer is not less than 400mm, the steady-state temperature converges to 220±10K.

7. A shield structure for a lunar base, characterized by: The protective layer comprises a rectangular steel frame, an arch-shaped steel, a PVC film layer and a protective layer, the protective layer comprises a solidified lunar soil layer and a lunar soil protective layer, the arch-shaped steel is provided with a plurality of arch-shaped steels which are connected to the rectangular steel frame at equal distances, the PVC film layer is arranged above the plurality of arch-shaped steels, the solidified lunar soil layer is provided with two layers, and the lunar soil protective layer is arranged between the two layers of the solidified lunar soil layer, and the thickness of the lunar soil protective layer is determined based on the protective layer thermal performance analysis method of the lunar base according to any one of claims 1-6.

8. A shield structure for a lunar base according to claim 7, wherein: The distance between adjacent arch-shaped steels ranges from 1.2m to 1.8m, and the arch-shaped steels are fixedly connected to the rectangular steel frame through a lock buckle, the span of the arch-shaped steel ranges from 10m to 15m, and the arch height ranges from 5m to 8m.

9. The shield structure of a lunar base according to claim 7, characterized in that: The thickness of the lunar soil protective layer is not less than 400mm, and the thermal conductivity coefficient is not greater than 0.05W / m·K.

10. The shield structure of a lunar base according to claim 7, wherein: The solidified lunar soil layer comprises an upper solidified lunar soil layer and a lower solidified lunar soil layer, and the lower solidified lunar soil layer abuts against the PVC film layer.

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