COMPACT RELEASE MECHANISM FOR NANOSATELITE

Abstract

The present invention relates to a compact nanosatellite release mechanism designed to hold a spherical test mass within a chamber where an experiment is conducted. In addition to holding the mass, the mechanism protects it from any physical phenomena that may occur during the nanosatellite launch, including the forces it is subjected to, the effects of the vacuum in space, and temperature changes. The test mass is held by two movable walls, one on the upper surface and the other on the lower surface of the chamber. These walls move simultaneously in opposite directions to support and position the sphere in the center of the chamber at all times. The mechanism consists of two lead screws that rotate in opposite directions, driven by a DC motor and a gear system.These lead screws are screwed into the upper and lower walls of the chamber, so their rotation results in the simultaneous translational displacement of the walls in opposite directions to compress and release the sphere.

Description

COMPACT NANOSATELLITE DELIVERY MECHANISM TECHNICAL FIELD OF THE INVENTION Within the aerospace field, there is the area of ​​nanosatellites, which have a mass between 1 and 10 kg. A special type of nanosatellite follows the CubeSat standard and is composed of one or more cubes with 10 cm sides. Due to its characteristics, this field requires a high degree of miniaturization in its development. The present invention comprises a compact and lightweight release mechanism for a 3-unit CubeSat nanosatellite containing a test mass. BACKGROUND OF THE INVENTION The compact release mechanism used in a nanosatellite is being developed to conduct the "free-floating test mass" experiment. This experiment involves keeping a test mass (in this case, a 20 mm diameter sphere) floating freely in the center of a hollow cubic chamber, isolating it from any external disturbance other than gravity, while the satellite is in orbit around the Earth. Currently, there are space missions that aim to perform this experiment and are required to create a release mechanism to hold the compressed test mass during launch and release it once the nanosatellite is in orbit. One such mission was Stanford University's "Drag-Free CubeSat" space mission, which planned to use a three-unit CubeSat nanosatellite and included such a release mechanism.The problem with this type of mechanism is that its operation, volume, and mass require further miniaturization to be functional and usable in conjunction with electric propulsion. This is primarily because the mechanism is not symmetrical, which complicates orientation control once in orbit; it is very heavy (1,025 kg); and it occupies half the total space of the nanosatellite, that is, 1.5 units out of a total of 3 available. These characteristics make it impossible to use electric propulsion to counteract the atmospheric drag experienced by the satellite in conjunction with this release mechanism.This is why, through multiple iterations and design revisions, we were able to create, from scratch, a new invention for the release mechanism. This mechanism proposes a new way of compressing the sphere during the launch of the rocket carrying the satellite, as well as releasing it once in orbit. This design reduces the mass and volume properties to achieve a better distribution of all the nanosatellite's components and allows the use of electric propulsion by freeing up the necessary space and weight within the satellite. The main characteristics of the proposed design are: • Symmetrical configuration. • Compact design. • Manufactured from lightweight and resistant materials. • Immobilization of the test mass during launch that resists the vibration generated by the rocket. • Release of the test mass exactly at the geometric center of the mechanism. • Centering of the test mass during orbit. • Two worm screws, with reversed threads between them, which ensure that the two caps of the test mass move slowly, simultaneously, at the same speed and in opposite directions. • Possibility of closing the experiment and recentering the test mass if it is necessary to save energy or turn off the experiment. This allows us to achieve a reduction of approximately 33% in volume and 26% in mass compared to the Stanford University design. This reduction is essential due to the very limited volume and weight of a nanosatellite and allows for the inclusion of other elements, such as electric propulsion, for the optimal development of the experiment. DESCRIPTION OF THE INVENTION BRIEF DESCRIPTION OF THE FIGURES Figure 1 illustrates a side perspective view of the nanosatellite release mechanism of the present invention. Figure Ib illustrates a schematic side view of the nanosatellite release mechanism of the present invention. Figure 2 illustrates a perspective view of the open release mechanism. Figure 3 illustrates a perspective view of the closed release mechanism. Figure 4 illustrates the position of the release mechanism within a nanosatellite. DETAILED DESCRIPTION OF THE INVENTION The mechanism of the present invention, in operation, compresses and releases a spherical test mass (20) by means of two movable walls that move linearly in opposite directions. Each of the two movable walls is screwed at both ends onto two ACME lead screws, one end of which has a right-hand thread and the other a left-hand thread. This configuration allows the movable walls to move in opposite directions simultaneously. Furthermore, the faces of the movable walls that hold the sphere have a concave surface that guides the sphere toward the center of the chamber when the mechanism is being compressed. The operation of the compact release mechanism of the present invention... COCCI η / 1 7(\7IGIY\tA allows for the development of an almost entirely symmetrical design, which substantially facilitates the distribution of the other components of the nanosatellite and allows the scientific objectives of the mission to be carried out correctly. Due to volume and mass constraints in the nanosatellite design, it is necessary to compact and optimize these two properties. The approximate volume of our invention is 1 unit, which represents only one-third of the total nanosatellite volume. This is a significant difference compared to other proposals, which exceed 1.5 volume units, occupying more than half of the total nanosatellite volume. Similarly, the mass of our invention is 759 grams, which is also less than other proposals that exceed 1000 grams. Optimizing mass and volume offers a substantial advantage, as it reduces the overall margin of error and allows for the use of more components within the nanosatellite, thus improving the precision of the scientific experiment. The materials of the release mechanism are a fundamental part of the mass reduction, so they are mainly limited to anodized 6061 aerospace grade aluminum, which is a lightweight metal that has the mechanical and thermal properties to withstand the environmental conditions of space. The nanosatellite release mechanism (MC) consists of two movable walls (9) that confine the spherical test mass (20) during launch and release it once the satellite is in orbit. The movable walls (9) have an internal concave surface that encloses the test mass (20) and also guides it toward the center should the mechanism close. As shown in Figure 1 of the preferred embodiment of the invention, the release mechanism (MC) is 97.88 mm long, 93.77 mm wide, and [cocc in / 1 znz / B / YiAi] 106 mm high. In turn, it has a total mass of 759 g, including all its components; preferred dimensions and weights, however, may vary below these specifications. In Figure 2, we can observe the release mechanism (RM) when it is open. The test mass (20) is floating inside the cube, and the concave surfaces of the movable walls enclosing the sphere are also visible. Similarly, in Figure 3, the release mechanism is shown when it is closed. The sphere remains completely static because the two movable walls compress it in the center of the cube. During the launch of the nanosatellite (NS), as illustrated in Figure 4, the release mechanism (RM) must be closed to ensure that the test mass (20) does not collide with other objects due to the vibrations and accelerations generated during rocket liftoff. The release mechanism is driven by a DC motor (6), which is coupled to a gear system that transmits rotational motion between the gears. The gears are mounted on the upper base (12), and two of them are coupled to two ACME lead screws (1), which in turn are screwed into the movable walls (9) that enclose or release the test mass (20) as needed. The purpose of the ACME lead screws (1) is to rotate in opposite directions and convert the rotational motion provided by the gears into translational motion in the opposite direction to the movable walls (9). To achieve this, each lead screw (1) has two threads in opposite directions. cocc in / 17Π7 / β / υιλι The two gears in the middle (E3 and 34) are each mounted on a shaft (7) where a ball bearing (2) is added between the shaft (7) and the gear bore to reduce friction between them. A drive gear (El) is coupled to the DC motor (6). The five gears and the lower end of the two ACME lead screws are secured to the upper (12) and lower (8) bases by retaining rings (10). The upper and lower bases (8, 12) have the function of containing the camera (3) in the center of the nanosatellite (NS), and the side walls (14a, 14b) comprise a plurality of holes (15) to be coupled by screws to the internal walls of the structure of the nanosatellite (NS). The chamber (3) has top and bottom covers (5) and blocks (4) to completely enclose the sphere housing, i.e., to close the empty spaces of the chamber and to ensure that it is completely isolated from any external disturbance, which also serves as the mount for the measuring sensors. More specifically, the present invention relates to a compact nanosatellite release mechanism comprising a structure formed by side walls (14a, 14b) joined together by means of an upper base (12) and a lower base (8), said side walls (14a, 14b), the upper base (12) and the lower base (8) have a configuration with cuts and holes such that it allows reducing the weight of the structure. Furthermore, the compact nanosatellite release mechanism comprises a gear system arranged in the upper base (12) that transmits motion to a first transmission gear (E2) by means of the drive gear (El) and to a second transmission gear (E5) by means of a first central gear (E3) and a second central gear (E4); lead screws (1) that receive motion respectively from each of said first transmission gear (E2) and the second transmission gear (E5) and are arranged perpendicularly with respect to the base COCCI Π / 1 7(\7IGIY\tA Ί superior (12), where the function of said lead screws (1) is to convert rotational motion to translational motion. To hold the test mass (20), the mechanism comprises an upper movable wall (9a) movably coupled to said first transmission gear (E2) and the second transmission gear (E5); a lower movable wall (9b) movably coupled to said first transmission gear (E2) and the second transmission gear (E5); and a chamber (3) housing a test mass (20) inside, which is held in a first position when the movable walls (9a, 9b) are in a closed position when the gear system is actuated in a first direction of motion transmission, and in an open position when the gear system is actuated in a second direction of motion transmission. The combination of all the elements that comprise the invention, and the relationship between each of these elements, results in a mechanism that can be used in conjunction with electric propulsion. This mechanism achieves balance and symmetry, facilitating orientation control once in orbit. This configuration allows the sphere to be repositioned in the center of the chamber when necessary, optimizing the sphere's calibration process. Furthermore, the symmetrical nature of the mechanism allows it to be placed precisely in the center of the nanosatellite, providing a better distribution of components. It also ensures that no contamination enters the chamber and that the sphere remains centered at all times during launch. The present invention also provides a method of operating the compact mechanism for COCCI η / 1 7(\7IGIY\tA nanosatellite described above, comprising the following stages: a) DC motor drive (6) coupled to the driving gear (El). b) Transmission of rotational motion between the driving gear (El) and all gears. c) Transmission of rotational motion from gears E2 and E5 to the feed screws (1) in opposite directions. d) Conversion of rotational motion of the lead screws (1) to linear motion in opposite directions on the moving walls (9) through the ACME threads. e) Linear displacement of the movable walls (9) until the test mass (20) is completely enclosed in the closing stage of the mechanism, or until it touches the internal walls of the chamber (3) in the opening stage. To demonstrate the functionality of the mechanism of the present invention, 3D-printed prototypes were created to identify design details not readily visible to the naked eye. Similarly, a metal prototype was fabricated to fully validate the mechanism's functionality and subject it to more rigorous testing to validate the finite element simulation results. The finite element simulation results, along with experimental results on the metal prototype, are designed to verify that the mechanism can withstand the vibration and forces associated with rocket liftoff during launch. The metal prototype is made of anodized 6061 aluminum and 316L stainless steel. However, it's important to note that the steel will not be used for the mechanism within the final nanosatellite design; it will only be used for the prototype because it is more readily available and its properties are similar to the material used in the final design (6A1 4V titanium). Stationary parts subjected to lower stress will be manufactured from aluminum, while moving parts (subjected to higher stress) will be manufactured from titanium.

Claims

1. A compact release mechanism (CM) for a nanosatellite (NS) comprising: A structure formed by side walls (14a, 14b) joined together by means of an upper base (12) and a lower base (8); A gear system arranged in the upper base (12) that transmits motion to a first transmission gear (E2) and a second transmission gear (E5); Lead screws (1) that receive motion respectively from each of said first transmission gear (E2) and the second transmission gear (E5) and are arranged perpendicularly with respect to the upper base (12); A movable upper wall (9a) movably coupled to said first transmission gear (E2) and the second transmission gear (E5); A movable lower wall (9b) movably coupled to said first transmission gear (E2) and the second transmission gear (E5);A chamber (3) that houses a test mass (20), which is held in a first position when the movable walls (9a, 9b) are in a closed position when the gear system is actuated in a first direction of motion transmission, and in an open position when the gear system is actuated in a second direction of motion transmission.; 2. The compact nanosatellite release mechanism according to claim 1, characterized in that the side walls (14a, 14b), the upper base (12) and the lower base (8) have a configuration with cuts and holes such that it allows reducing the weight of the structure.

3. The compact nanosatellite release mechanism according to claim 1, characterized in that the side walls (14a, 14b) comprise a plurality of holes (15) for coupling to the interior of the structure of a nanosatellite (NS).

4. The compact nanosatellite release mechanism according to claim 1, characterized in that it has a length of 97.88 mm, a width of 93.77 mm, and a height of 106 mm. Furthermore, it has a total mass of 759 g, including all its components.

5. The compact nanosatellite release mechanism according to claim 1, characterized in that it is made of 6061 aerospace grade aluminum.

6. The compact nanosatellite release mechanism according to claim 1, characterized in that the gear system transmits motion to a first transmission gear (E2) by means of the driving gear (El) and to a second transmission gear (E5) by means of a first central gear (E3) and a second central gear (E4); 7. A nanosatellite (NS) comprising a compact release mechanism (MC) as claimed in claim 1.

8. A method of operating the compact release mechanism (CM) as claimed in claim 1, comprising the following steps: a) Driving the DC motor (6) coupled to the drive gear (El). b) Transmitting rotational motion between the drive gear (El) and all the gears. c) Transmitting rotational motion from gears (E2) and (E5) to the lead screws (1) in opposite directions. d) Converting the rotational motion of the lead screws (1) to linear motion in opposite directions in the movable walls (9) via the ACME threads. e) Linear displacement of the movable walls (9) until they completely enclose the test mass (20) in the closing stage of the mechanism, or until they abut the inner walls of the chamber (3) in the opening stage.

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