Passive thermal control system for lunar beacon

Abstract

A passive thermal control system for lunar beacons belongs to the field of spacecraft thermal control technology. This invention addresses the problems of traditional mechanical temperature control switches, such as complex structures, insufficient contact reliability, and unsuitability for spacecraft use. It includes a temperature-controlled unit housed within the beacon body; a thermal control circuit comprising a passive thermal control switch, a heating element, and a thermal insulation circuit connected in series; the passive thermal control switch and the temperature-controlled unit are thermally coupled through thermal radiation from the lunar vacuum environment; when the temperature of the temperature-controlled unit reaches the set upper limit of its operating temperature, the passive thermal control switch automatically disconnects after receiving heat through thermal radiation, and the thermal insulation circuit stops supplying power to the heating element, thus cooling the temperature-controlled unit; when the temperature of the temperature-controlled unit reaches the set lower limit of its operating temperature, the passive thermal control switch automatically closes as the temperature decreases, and the thermal insulation circuit supplies power to the heating element, thus heating the temperature-controlled unit. This invention effectively improves temperature control accuracy and meets the requirements for spacecraft use.

Description

Technical Field

[0001] This invention relates to a passive thermal control system for lunar beacons, belonging to the field of spacecraft thermal control technology. Background Technology

[0002] Existing mechanical temperature control switches mainly include bimetallic strip temperature control switches, pressure temperature control switches, thermistor ferrite temperature control switches, and shape memory alloy temperature control switches.

[0003] Bimetallic strip temperature switches utilize the difference in thermal expansion coefficients between two different metals. By combining two different metals, the difference in thermal expansion coefficients causes the bimetallic strip to bend when the temperature changes, thus controlling the opening and closing of conductive contacts to achieve temperature control. Its structure is simple and it is widely used in household appliances such as rice cookers. However, because the thermal expansion coefficients of metals are generally very low, the degree of bending of the bimetallic strip is not sensitive to temperature changes, resulting in lower temperature control accuracy and a longer response time.

[0004] Pressure-type temperature switches utilize the principle of thermal expansion and contraction of a temperature-sensitive material within a capillary tube. When the temperature changes, the material expands and contracts due to heat, causing a change in pressure within the capillary. This pressure change is transmitted to the bellows and drives the mechanism to control the opening and closing of the contacts, thus achieving temperature control. However, due to the size limitations of the capillary tube and diaphragm, these temperature switches are generally large and have relatively low temperature control accuracy, and are mostly used in large household appliances such as refrigerators and air conditioners.

[0005] Thermistor-based temperature switches utilize the principle of drastic magnetic changes in thermistors near a specific temperature (Curie temperature). Thermistors are temperature-sensitive magnetic materials; when the temperature is below the Curie temperature, they become magnetic, attracting a permanent magnet to close the contacts and activate the switch. When the temperature is above the Curie temperature, the thermistor loses its magnetism, opening the contacts and disengaging the switch. While their temperature control accuracy can reach ±1℃, their abrupt magnetic changes can cause magnetic moment interference in spacecraft, potentially affecting attitude control and the detection missions of scientific payloads.

[0006] Shape memory alloy (GM) thermal switches utilize the phase transformation of GM alloys to control the switching on and off states. GM alloys possess two phases: martensite at low temperatures and austenite at high temperatures. As temperature changes, the GM alloy transforms between these two phases, causing the spring to lengthen / shorten, driving the contacts and thus controlling the switch's on / off state. GM alloy springs can be categorized into single-stroke and double-stroke types. Single-stroke GM alloy springs can perform a single action but require external force to reset; while double-stroke GM alloy springs can repeatedly cycle without external force. This design allows for precise control of the phase transformation temperature by adjusting the GM alloy spring composition, offering advantages such as high driving force and large deformation. However, current designs mostly employ a combination of single-stroke GM alloy springs and bias springs, resulting in a complex structure and often simple surface contact, leading to insufficient reliability.

[0007] In summary, existing mechanical temperature control switches have the following drawbacks: except for bimetallic strip temperature control switches, most designs require independent reset components, resulting in a large number of parts and complex structures; current designs mostly use surface contact or sliding contact, leading to low contact pressure; they have poor aerospace adaptability, pressure-type temperature control switches are too large, thermistor ferrite temperature control switches suffer from magnetic interference problems, and shape memory alloy thermal switches have complex structures and insufficient contact reliability, making it difficult to meet the requirements of spacecraft for portability, compactness, and high reliability. Summary of the Invention

[0008] To address the problems of traditional mechanical temperature control switches being complex in structure, having insufficient contact reliability, and being unsuitable for use on spacecraft, this invention provides a passive thermal control system for lunar beacons.

[0009] The present invention discloses a passive thermal control system for a lunar beacon, wherein the lunar beacon is positioned in a high-vacuum environment on the lunar surface; the system includes a beacon body; and further includes:

[0010] The temperature-controlled unit is located inside the beacon body;

[0011] The thermal control circuit includes a passive thermal control switch, a heating element, and a heat preservation circuit connected in series.

[0012] The passive thermal control switch and the temperature-controlled unit are thermally coupled through thermal radiation from the lunar vacuum environment.

[0013] When the temperature of the temperature-controlled unit reaches the set upper limit of the working temperature, the passive thermal control switch automatically disconnects after receiving heat through thermal radiation, the heat preservation circuit stops supplying power to the heating element, the heating element stops working, and the temperature-controlled unit cools down.

[0014] When the temperature of the controlled unit reaches the lower limit of the set operating temperature, the passive thermal control switch automatically closes as the temperature decreases, the heat preservation circuit supplies power to the heating element, the heating element starts to work, and the controlled unit heats up.

[0015] According to the lunar beacon passive thermal control system of the present invention, the passive thermal control switch includes a base, an outer spring, a shape memory alloy spring, an insulating base, a conductive sheet, and a guide post.

[0016] The base has three concentric positioning bosses at its center. The inner ring groove formed by the three positioning bosses is used to fix one end of the memory alloy spring, and the outer ring groove is used to fix one end of the outer spring.

[0017] The insulating base includes an inner insulating base and an outer insulating base. The inner insulating base is formed by an inner insulating disk and an inner support column, creating a T-shaped structure. The outer insulating base is formed by an outer insulating disk and an outer support column, creating a T-shaped structure. Both the inner and outer insulating bases have a central through hole, with the central through hole of the outer insulating base being larger than that of the inner insulating base. The inner insulating base is positioned above the outer insulating base. The other end of the shape memory alloy spring passes through the outer insulating base and is connected and fixed to the inner support column. The other end of the outer spring is connected and fixed to the outer support column.

[0018] Conductive sheets are respectively installed on the opposing surfaces of the inner and outer insulating discs, and the two conductive sheets are respectively connected to the two connection terminals of the heat preservation circuit through wires;

[0019] The guide post is connected between the innermost ring positioning boss of the base and the central through hole of the inner ring insulating base;

[0020] When the ambient temperature on the lunar surface rises and the temperature of the controlled unit reaches the upper limit of the set operating temperature, the controlled unit transfers heat to the shape memory alloy spring through thermal radiation, causing the shape memory alloy spring to extend, driving the two conductive plates to separate, disconnecting the heat preservation circuit, and stopping the heating element from heating. When the ambient temperature on the lunar surface drops and the temperature of the controlled unit reaches the lower limit of the set operating temperature, the shape memory alloy spring contracts, driving the two conductive plates to contact, connecting the heat preservation circuit, and the heating element starts heating to keep the controlled unit warm.

[0021] According to the passive thermal control system for lunar beacons of the present invention, positioning bosses are provided on the lower surface of the inner insulating disk and the upper surface of the outer insulating disk to form positioning slots for fixing corresponding conductive sheets. Each positioning slot has a gap with the corresponding conductive sheet for installing and fixing the conductive sheet.

[0022] According to the passive thermal control system for lunar beacons of the present invention, the conductive sheet disposed on the inner insulating disk is used as the inner ring conductive sheet, and the conductive sheet disposed on the outer insulating disk is used as the outer ring conductive sheet. Three spherical protrusions are uniformly disposed on the upper surface of the outer ring conductive sheet along the circumference to form a point contact array.

[0023] According to the lunar beacon passive thermal control system of the present invention, notches are provided on both the inner and outer insulating disks to provide space for welding operations of the conductive sheet and the wire.

[0024] According to the lunar beacon passive thermal control system of the present invention, there are gaps between the shape memory alloy spring and the corresponding positions of the inner and outer insulating bases, and the lower edge outer surface of the inner support column and the upper edge surface of the inner wall of the outer insulating disk are both chamfered.

[0025] According to the passive thermal control system for lunar beacons of the present invention, the material of the shape memory alloy spring is NiTi-based two-way shape memory alloy; when the temperature control point of the controlled unit is -25°C, the low-temperature phase transition point of the shape memory alloy spring is selected as -20°C, and the low-temperature length is 20mm; the high-temperature phase transition point of the shape memory alloy spring is 0°C, and the high-temperature length is 30mm.

[0026] According to the lunar beacon passive thermal control system of the present invention, the outer spring is made of stainless steel; the conductive sheet is made of beryllium copper; and the surface of the conductive sheet has a gold-plated layer.

[0027] According to the lunar beacon passive thermal control system of the present invention, both the base and the insulating base are made of polyimide material.

[0028] According to the passive thermal control system for lunar beacons of the present invention, the guide post is made of polyimide material, and the bottom of the guide post is fixedly connected to the base by bolts; the guide post is polished and has a gap between it and the inner ring insulating base.

[0029] The beneficial effects of this invention: This invention addresses the thermal insulation requirements of equipment on the lunar surface. The lunar surface environment is harsh; during the lunar day, exposed to sunlight, the surface temperature can reach 120°C; however, due to the lack of an atmosphere for insulation, the temperature plummets to -180°C during the lunar night. To ensure the normal storage of each unit during the lunar night and the normal operation of the lunar surface equipment during the next lunar day, it is necessary to insulate key components of the temperature-controlled units, such as batteries. This invention designs a passive thermal control system with high temperature control accuracy, high reliability, and a lightweight and compact design. Compared with existing designs, this invention uses a two-way memory alloy spring to replace the original single-way memory alloy spring and return spring, resulting in a simpler structure. Simultaneously, the contact design of the conductive sheet improves contact reliability and temperature control sensitivity; the addition of an outer spring releases contact stress, reduces the stress of the memory alloy spring, and reduces contact wear, effectively improving the lifespan of the thermal control system and meeting the requirements of spacecraft use.

[0030] This invention has fewer parts and a simpler structure: it uses a two-way memory alloy spring as the driving mechanism, replacing the traditional single-way memory alloy spring and offset spring reset mechanism, which simplifies the overall structure and reduces the number of parts.

[0031] High reliability and long service life: An outer spring is added to release contact pressure, reducing stress on the shape memory alloy spring and alleviating contact wear, thus improving the service life of the shape memory alloy spring and contacts. Simultaneously, a three-point contact design is adopted at the contacts, providing structural redundancy and improving the reliability of temperature control.

[0032] High temperature control accuracy: It adopts a three-point spherical raised contact. Due to the small contact area, the contact pressure required under the same pressure is small, which makes the temperature control more sensitive to temperature changes and effectively improves the temperature control accuracy. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the passive thermal control switch in the lunar beacon passive thermal control system described in this invention;

[0034] Figure 2 This is the front view of the passive thermal control switch in the lunar beacon passive thermal control system;

[0035] Figure 3 yes Figure 2 Side view;

[0036] Figure 4 yes Figure 2 Top view;

[0037] Figure 5 This is a schematic diagram of the inner and outer insulating bases;

[0038] Figure 6 This is a schematic diagram of the inner and outer conductive sheets;

[0039] Figure 7 This is a structural diagram of the base. Detailed Implementation

[0040] 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, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Specific Implementation Method 1: Combination Figures 1 to 7 As shown, the present invention provides a passive thermal control system for a lunar beacon, wherein the lunar beacon is positioned in the high vacuum environment of the lunar surface; it includes a beacon body; and further includes:

[0042] The temperature-controlled unit is located inside the beacon body;

[0043] The thermal control circuit includes a passive thermal control switch, a heating element, and a heat preservation circuit connected in series.

[0044] The passive thermal control switch and the temperature-controlled unit are thermally coupled through thermal radiation from the lunar vacuum environment.

[0045] When the temperature of the temperature-controlled unit reaches the set upper limit of the working temperature, the passive thermal control switch automatically disconnects after receiving heat through thermal radiation, the heat preservation circuit stops supplying power to the heating element, the heating element stops working, and the temperature-controlled unit cools down.

[0046] When the temperature of the controlled unit reaches the lower limit of the set operating temperature, the passive thermal control switch automatically closes as the temperature decreases, the heat preservation circuit supplies power to the heating element, the heating element starts to work, and the controlled unit heats up.

[0047] Furthermore, in this embodiment, the passive thermal control switch is positioned close to the unit being controlled in temperature, combined with... Figure 1 As shown, it includes a base 1, an outer spring 2, a shape memory alloy spring 3, an insulating base 4, a conductive sheet 5, and a guide post 6.

[0048] like Figure 7 As shown, the base 1 has a concentric three-ring positioning boss at its center. The inner ring groove formed by the three-ring positioning boss is used to fix one end of the memory alloy spring 3, and the outer ring groove is used to fix one end of the outer ring spring 2.

[0049] The insulating base 4 includes an inner insulating base and an outer insulating base. The inner insulating base is formed by an inner insulating disk and an inner support column, creating a T-shaped structure. The outer insulating base is formed by an outer insulating disk and an outer support column, creating a T-shaped structure. Both the inner and outer insulating bases have a central through hole, with the central through hole of the outer insulating base being larger than that of the inner insulating base. The inner insulating base is positioned above the outer insulating base. The other end of the shape memory alloy spring 3 passes through the outer insulating base and is fixedly connected to the inner support column. The other end of the outer spring 2 is fixedly connected to the outer support column.

[0050] Conductive sheets 5 are respectively provided on the opposing surfaces of the inner and outer insulating discs, and the two conductive sheets 5 are respectively connected to the two connection terminals of the heat preservation circuit through wires;

[0051] The guide post 6 is connected through the innermost ring positioning boss of the base 1 and the central through hole of the inner ring insulating base;

[0052] The temperature-controlled unit transfers heat to the memory alloy spring 3 through thermal radiation, causing the length of the memory alloy spring 3 to change, driving the two conductive sheets 5 to contact or separate, thereby making the heat preservation circuit open or closed.

[0053] When the ambient temperature on the lunar surface rises and the temperature of the controlled unit reaches the upper limit of the set operating temperature, the controlled unit transfers heat to the shape memory alloy spring through thermal radiation, causing the shape memory alloy spring to extend, driving the two conductive plates to separate, disconnecting the heat preservation circuit, and stopping the heating element from heating. When the ambient temperature on the lunar surface drops and the temperature of the controlled unit reaches the lower limit of the set operating temperature, the shape memory alloy spring contracts, driving the two conductive plates to contact, connecting the heat preservation circuit, and the heating element starts heating to keep the controlled unit warm.

[0054] The passive thermal control switch in this embodiment can be set within a 5cm distance range of the temperature-controlled unit as needed.

[0055] like Figures 2 to 4 As shown, the passive thermal control switch described in this embodiment has external dimensions of φ40mm×36.5mm.

[0056] The shape memory alloy spring 3 serves as the primary temperature sensing element. The controlled temperature unit transfers heat to the shape memory alloy spring through thermal radiation, causing a change in the spring's length. This, in turn, drives the conductive sheet to contact / separate, controlling the on / off state of the insulation circuit. Considering the slow heat transfer rate due to thermal radiation in a vacuum environment, the temperature change of the shape memory alloy spring exhibits a certain lag compared to the controlled temperature unit. To prevent excessive contact stress when the switch is on, which could affect the lifespan of the shape memory alloy spring and contacts, an outer spring is added to release the contact stress. The insulating base prevents the shape memory alloy spring and the outer spring from being connected to the circuit, avoiding the creation of an additional circuit that could cause the spring itself to generate heat and incorrectly estimate the temperature of the controlled temperature unit.

[0057] Considering the uneven heating of the shape memory alloy spring and the potential bending and tilting during assembly, guide posts are added to guide the spring's extension and contraction, preventing excessive bending. The base provides mounting positioning for both the shape memory alloy spring and the outer coil spring, while also providing mounting holes for easy installation on lunar surface equipment.

[0058] Furthermore, combined with Figure 5 As shown, positioning bosses are provided on the lower surface of the inner insulating disk and the upper surface of the outer insulating disk to form positioning slots for fixing the corresponding conductive sheet 5. Each positioning slot has a gap with the corresponding conductive sheet 5 for installing and fixing the conductive sheet.

[0059] The conductive sheet 5 on the inner insulating disk is used as the inner ring conductive sheet, and the conductive sheet 5 on the outer insulating disk is used as the outer ring conductive sheet. Three spherical protrusions are evenly arranged circumferentially on the upper surface of the outer ring conductive sheet to form a point contact array. Figure 6 As shown. The surface of the spherical raised contact can be soldered with wires for connection to the insulation circuit.

[0060] Combination Figure 5As shown, notches are provided on both the inner and outer insulating disks to provide space for welding the conductive sheet 5 to the wire.

[0061] Assembly Relationship: The base serves as the supporting structure for the entire passive thermal control switch. Its surface is designed with spring positioning bosses, and the shape memory alloy spring and outer coil spring are glued to the base via these bosses. One end of each spring is fixedly connected to the base, while the other end is connected to the inner / outer coil insulating base, respectively. The inner / outer coil conductive plates are fixed to their respective insulating bases, with a contact structure on the side of the outer coil conductive plate facing the inner coil conductive plate. A gap exists between the inner and outer coil conductive plates, allowing the inner coil conductive plate to move axially under the drive of the shape memory alloy spring, achieving contact and separation. A guide post, connected to the base by screws, extends through the entire interior of the shape memory alloy spring.

[0062] Working process and principle: Initially, there is a gap between the inner and outer conductive plates. When the ambient temperature decreases, the shape memory alloy spring 3 contracts, driving the inner and outer conductive plates to contact each other, thus activating the insulation circuit. The heating element connected to the insulation circuit then begins to work, maintaining the temperature of the controlled unit. When the ambient temperature rises, the shape memory alloy spring 3 extends, driving the inner and outer conductive plates to separate, thus disconnecting the insulation circuit and stopping the heating element connected to the insulation circuit. This cycle repeats continuously, achieving the temperature control function of the controlled unit.

[0063] This implementation uses a two-way memory alloy spring as the temperature control drive, adds an outer spring to release contact stress, and employs a three-point spherical protrusion as a point contact array to meet the extreme environmental temperature control requirements of lunar beacons. It features a simple structure, high reliability, and high temperature control accuracy.

[0064] Combination Figure 5 As shown, there are gaps between the shape memory alloy spring 3 and the corresponding positions of the inner and outer insulating bases, and the lower edge of the inner support column and the upper edge of the inner wall of the outer insulating disk are both chamfered.

[0065] Structural design and parameter selection:

[0066] As an example, the material of the shape memory alloy spring 3 is a NiTi-based two-way shape memory alloy. When the temperature control point of the controlled unit is -25℃, due to the hysteresis of the shape memory alloy spring's temperature change, the low-temperature phase transition point of the shape memory alloy spring 3 is selected as -20℃, and the length in the low-temperature state is 20mm; the high-temperature phase transition point of the shape memory alloy spring 3 is 0℃, and the length in the high-temperature state is 30mm. Therefore, the maximum stroke of the shape memory alloy spring is... .

[0067] NiTi-based two-way shape memory alloys exhibit a reversible two-way shape memory effect, capable of cyclically elongating and contracting without the need for external force to reset. Their shear modulus... It increases as the temperature decreases.

[0068] Design the mean diameter of a shape memory alloy spring. wire diameter Valid number of laps Then the spring constant of the shape memory alloy spring can be calculated. :

[0069] .

[0070] As an example, the outer spring 2 is made of stainless steel;

[0071] Considering the material's low-temperature resistance, the outer spring is made of stainless steel, which can operate normally at temperatures above -60℃. Its shear modulus... Assume the contact pressure of the inner / outer conductive plates required for the passive thermal control switch to turn on. To relieve contact stress, the stiffness coefficient of the outer spring should be less than that of the shape memory alloy spring. The stiffness coefficient of the outer spring is designed based on experience. When the contact pressure reaches 0.5N, the compression of the shape memory alloy spring is... The compression of the outer spring Considering a 1mm compression allowance, the initial spacing between the two conductive sheets is 4mm. To prevent jamming, a certain gap is left between the shape memory alloy spring and the inner / outer insulating base. The outer spring's median diameter is designed... wire diameter Spring length 24mm, effective number of coils Then the spring constant of the outer spring can be calculated. :

[0072] ,

[0073] At this point, when the contact pressure reaches 0.5N, the compression of the shape memory alloy spring... Compression of a regular spring Compression margin It can meet the design requirements.

[0074] The conductive sheet 5 is made of beryllium copper; the surface of the conductive sheet 5 has a gold plating layer. Considering conductivity, oxidation resistance, and adaptability to vacuum environments, the surface of the conductive sheet is gold-plated.

[0075] Inner conductive sheet and outer conductive sheet, such as Figure 6As shown, the inner / outer ring conductive sheets are fixedly connected to the inner / outer ring insulating bases respectively, and the wires welded to their upper / lower surfaces are connected to the insulation circuit.

[0076] The inner conductive plate can move axially under the drive of the shape memory alloy spring, and its side facing the outer conductive plate is a flat annular contact surface. Considering the uneven heating of the spring itself, the unavoidable tilting and bending of the spring during product processing heat treatment and assembly, it is difficult to make the inner and outer conductive plates perfectly parallel. Their contact will degenerate from ideal surface contact to line contact or even point contact. Moreover, this passive thermal control switch is used in low-current scenarios, and reliable point contact is sufficient. Therefore, in order to improve contact sensitivity and achieve reliable point contact, the outer conductive plate facing the inner conductive plate is provided with three evenly distributed spherical protrusions.

[0077] As an example, both base 1 and insulating base 4 are made of polyimide material.

[0078] The insulating base material is polyimide, which features low-temperature resistance, good insulation performance, and high mechanical strength. The insulating base consists of an inner ring insulating base and an outer ring insulating base, such as... Figure 5 As shown, the inner and outer insulating bases are fixedly connected to the shape memory alloy spring and outer spring, respectively. Both the inner and outer rings are designed with conductive plate positioning bosses, with a 0.2mm gap on one side for mounting and fixing the conductive plates. To facilitate wire welding and prevent the wires from affecting the contact points, notches are provided in the inner and outer insulating bases to facilitate welding wires to the upper side of the inner conductive plate and the lower side of the outer conductive plate. The inner insulating base has an inner diameter of 3.9mm, an outer diameter of 12.1mm, and an overall height of 11mm. Its corresponding edges are chamfered to prevent hooking and jamming during the expansion and contraction of the shape memory alloy spring. The inner insulating base has an inner diameter of 6.6mm, an outer diameter of 12.1mm, and an overall height of 9mm, and is also chamfered.

[0079] Base such as Figure 7 As shown. The base surface is designed with positioning bosses to facilitate the installation and fixing of the shape memory alloy spring and the outer coil spring, and mounting holes are provided for the installation of guide columns and installation on spacecraft.

[0080] As an example, the guide post 6 is made of polyimide material, and the bottom of the guide post 6 is fixedly connected to the base 1 by bolts; the guide post 6 is polished and has a gap between it and the inner ring insulating base.

[0081] The guide post has a threaded hole at the bottom for fixing to the base with an M2.5 screw. The guide post has a diameter of 3.4mm and a length of 33mm. To prevent excessive friction between the guide post and the inner insulating base due to bending of the shape memory alloy spring, which would hinder the normal extension and contraction of the shape memory alloy spring, the surface of the guide post is polished, and a 0.5mm gap is left between it and the inner insulating base.

[0082] In summary, this invention uses a memory alloy spring as the driving structure for a passive thermal control switch design: by using a double-stroke memory alloy spring as the driving mechanism, the on / off state of the switch can be driven entirely by the bidirectional deformation of the double-stroke memory alloy spring, without the need for offset springs, levers, or other reset components, resulting in a simple structure and high reliability.

[0083] Key contact design: The outer conductive sheet adopts a three-point spherical raised contact. The contact is made of copper and gold-plated, which can convert the small spring pressure into a large contact pressure at the contact point, forming a reliable three-point contact. This improves reliability, contact sensitivity and temperature control accuracy, and can meet the needs of low current application scenarios.

[0084] Stress relief mechanism design: An outer spring is added as a stress relief mechanism. Due to the slow heat exchange rate from thermal radiation in a vacuum, passive thermal control switches exhibit a certain degree of hysteresis. The shape memory alloy spring may over-contract, leading to increased internal stress and affecting its service life. Therefore, the stiffness coefficient of the outer spring must be much smaller than that of the shape memory alloy spring. The deformation of the outer spring reduces contact stress and contact wear to some extent, effectively improving the service life of the passive thermal control switch.

[0085] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A passive thermal control system for a lunar beacon, wherein the lunar beacon is positioned in a high-vacuum environment on the lunar surface; characterized in that, Includes the beacon ontology; also includes: The temperature-controlled unit is located inside the beacon body; The thermal control circuit includes a passive thermal control switch, a heating element, and a heat preservation circuit connected in series. The passive thermal control switch and the temperature-controlled unit are thermally coupled through thermal radiation from the lunar vacuum environment. When the temperature of the temperature-controlled unit reaches the set upper limit of the working temperature, the passive thermal control switch automatically disconnects after receiving heat through thermal radiation, the heat preservation circuit stops supplying power to the heating element, the heating element stops working, and the temperature-controlled unit cools down. When the temperature of the controlled unit reaches the lower limit of the set operating temperature, the passive thermal control switch automatically closes as the temperature decreases, the heat preservation circuit supplies power to the heating element, the heating element starts to work, and the controlled unit heats up.

2. The lunar beacon passive thermal control system according to claim 1, characterized in that, The passive thermal control switch includes a base, an outer spring, a shape memory alloy spring, an insulating base, a conductive sheet, and a guide post. The base has three concentric positioning bosses at its center. The inner ring groove formed by the three positioning bosses is used to fix one end of the memory alloy spring, and the outer ring groove is used to fix one end of the outer spring. The insulating base includes an inner insulating base and an outer insulating base. The inner insulating base is formed by an inner insulating disk and an inner support column, creating a T-shaped structure. The outer insulating base is formed by an outer insulating disk and an outer support column, creating a T-shaped structure. Both the inner and outer insulating bases have a central through hole, with the central through hole of the outer insulating base being larger than that of the inner insulating base. The inner insulating base is positioned above the outer insulating base. The other end of the shape memory alloy spring passes through the outer insulating base and is connected and fixed to the inner support column. The other end of the outer spring is connected and fixed to the outer support column. Conductive sheets are respectively installed on the opposing surfaces of the inner and outer insulating discs, and the two conductive sheets are respectively connected to the two connection terminals of the heat preservation circuit through wires; The guide post is connected between the innermost ring positioning boss of the base and the central through hole of the inner ring insulating base; When the ambient temperature on the lunar surface rises and the temperature of the controlled unit reaches the upper limit of the set operating temperature, the controlled unit transfers heat to the shape memory alloy spring through thermal radiation, causing the shape memory alloy spring to extend, driving the two conductive plates to separate, disconnecting the heat preservation circuit, and stopping the heating element from heating. When the ambient temperature on the lunar surface drops and the temperature of the controlled unit reaches the lower limit of the set operating temperature, the shape memory alloy spring contracts, driving the two conductive plates to contact, connecting the heat preservation circuit, and the heating element starts heating to keep the controlled unit warm.

3. The lunar beacon passive thermal control system according to claim 2, characterized in that, Positioning bosses are provided on the lower surface of the inner insulating disk and the upper surface of the outer insulating disk to form positioning slots for fixing the corresponding conductive sheets. Each positioning slot has a gap with the corresponding conductive sheet for installing and fixing the conductive sheet.

4. The lunar beacon passive thermal control system according to claim 3, characterized in that, The conductive sheet on the inner insulating disk is used as the inner ring conductive sheet, and the conductive sheet on the outer insulating disk is used as the outer ring conductive sheet. Three spherical protrusions are evenly arranged on the upper surface of the outer ring conductive sheet to form a point contact array.

5. The lunar beacon passive thermal control system according to claim 3, characterized in that, Both the inner and outer insulating discs have notches to provide space for welding the conductive sheet and the wire.

6. The lunar beacon passive thermal control system according to claim 2, characterized in that, There are gaps between the shape memory alloy spring and the corresponding positions of the inner and outer insulating bases, and the lower edge of the inner support column and the upper edge of the inner wall of the outer insulating disk are both chamfered.

7. The lunar beacon passive thermal control system according to claim 2, characterized in that, The material of the shape memory alloy spring is NiTi-based two-way shape memory alloy; when the temperature control point of the temperature-controlled unit is -25℃, the low-temperature phase transition point of the shape memory alloy spring is selected as -20℃, and the length in the low-temperature state is 20mm; the high-temperature phase transition point of the shape memory alloy spring is 0℃, and the length in the high-temperature state is 30mm.

8. The lunar beacon passive thermal control system according to claim 2, characterized in that, The outer spring is made of stainless steel; the conductive sheet is made of beryllium copper; and the surface of the conductive sheet is plated with gold.

9. The lunar beacon passive thermal control system according to claim 2, characterized in that, Both the base and the insulating base are made of polyimide material.

10. The lunar beacon passive thermal control system according to claim 2, characterized in that, The guide post is made of polyimide material, and the bottom of the guide post is fixedly connected to the base by bolts; the guide post is polished and has a gap between it and the inner ring insulating base.

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