Method and device for capturing a tumbling space object

Abstract

According to one aspect of the invention, a method is provided that includes propelling a servicing spacecraft toward the object, deploying one or more counter masses away from the servicing spacecraft bus to offset the center of mass of the servicing spacecraft within the empty volume, approaching the object, positioning the center of mass of the servicing spacecraft at approximately the same location as the center of mass of the object, imparting angular momentum to the servicing spacecraft to match the tumble rate of the object, and contacting the object by one or more mechanical attachments to the servicing spacecraft.

Description

Technical Field

[0001]

[0001] Embodiments of the present invention relate to a method and device for capturing a tumbling space object.

Background Art

[0002]

[0002] Various techniques have been proposed to attenuate the angular velocity of an object in orbit using an external control torque. This is a process known as detumbling.

[0003]

[0003] For example, U.S. Patent No. 8,226,046B2 discloses a method for stabilizing unstable space debris. The method includes applying a force to the unstable space debris at a target point on the unstable space debris to generate stabilized space debris. This force is generated by an air collision of a gas plume provided by an adjacent satellite with the unstable space debris. This force is sufficient to generate a torque on the unstable space debris that reduces the rotational momentum about one or more of the axes of rotation of the unstable space debris.

[0004]

[0004] However, the prior art methods have significant limitations, including the inability to safely and economically attenuate the angular velocity of an object in orbit.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006]

[0007] In view of the above situation, aspects of the present invention provide a method and device for capturing a tumbling space object that can attenuate the angular velocity of an object in an orbit.

[0007]

[0008] According to one aspect of the present invention, there is provided a method including propelling a servicing spacecraft towards an object, deploying one or more countermasses away from the servicing spacecraft bus to offset the center of mass of the servicing spacecraft, approaching the servicing spacecraft to the object, positioning the center of mass of the servicing spacecraft at approximately the same position as the center of mass of the object, imparting angular momentum to the servicing spacecraft to match the tumble rate of the object, and contacting the object by one or more mechanical attachments to the servicing spacecraft.

[0008]

[0009] According to another aspect of the present invention, there is provided a spacecraft including a bus, one or more countermasses, and a truss connecting the bus and the one or more countermasses. The truss is configured to deploy one or more countermasses away from the bus to offset the center of mass of the spacecraft within an empty volume.

Brief Description of the Drawings

[0009]

Figure 1

[0010] Shows a countermass and a spacecraft bus in a storage configuration for launch.

Figure 2

[0010] Shows the deployment of an extensible and foldable truss structure connecting a countermass and a spacecraft bus.

Figure 3

[0010] Shows a spacecraft bus imparting angular momentum to a system of a spacecraft bus and a countermass connected by an extensible and foldable truss structure.

Figure 4

[0010] Shows two countermasses and a spacecraft bus in a storage configuration for launch.

Figure 5

[0010] Shown is the deployment of an extensible and foldable truss structure that connects two counter masses and a spacecraft bus.

Figure 6

[0010] Shown is a spacecraft bus that imparts angular momentum to a system of a spacecraft bus and two counter masses connected by an extensible and foldable truss structure.

Figure 7

[0010] Shown is a spacecraft approaching a client object that is tumbling arbitrarily about three axes.

Figure 8

[0010] Shown is a spacecraft that aligns its center of mass with a client object.

Figure 9

[0010] Shown is a spacecraft that uses angular momentum to match the tumble rate of a client object and make all relative motion zero.

Figure 10

[0010] Shown is a spacecraft that safely grasps a client object with zero relative velocity and rotation.

Figure 11

[0010] A flowchart showing the steps of a computer-implemented method for designing one or more counter masses.

Mode for Carrying Out the Invention

[0010]

[0011] Embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that in each figure, components denoted by the same reference numerals have the same or similar configurations.

[0011]

[0012] Space debris and derelict satellites are expected to be tumbling about any axis in space. To remove such objects, physical contact by a servicing spacecraft is required, first to perform detumbling and then to remove the object from orbit.

[0012]

[0013] If an object has a large relative velocity or relative rotation with respect to a service spacecraft, attempting physical contact will pose a risk of collision and impact to both objects, potentially causing damage or increasing space debris. Therefore, it is desirable to reduce the relative velocity and rotation by performing any of the following operations.

[0013]

[0014] Option 1: Reduce the absolute rotation rate of the object by non-contact means such as the use of ion beams, electromagnetic induction, or fluid forces.

[0014]

[0015] Option 2: Use propulsion to place the service spacecraft in a forced motion orbit around the object, aligning the tumbling rate to make the relative rotation zero.

[0015]

[0016] Option 1 has not yet been proven, there is a risk of additional damage to the tumbling object, and it usually requires the consumption of resources carried on the service spacecraft.

[0016]

[0017] Option 2 requires frequent and high thrust to achieve zero relative motion. Also, this requires a significant consumption of fuel resources carried on the service spacecraft.

[0017]

[0018] In both cases, resource consumption requires a large launch mass depending on the number of objects to be captured, which significantly increases costs.

[0018]

[0019] A method of making the relative rotation rate between an object and a service spacecraft zero without using consumable resources theoretically enables unlimited capture. The embodiments described herein propose a novel solution that uses mechanically generated angular momentum to achieve zero relative rotation with respect to an object. The mechanically generated momentum does not require the consumption of large amounts of resources.

[0019]

[0020] The present invention generally relates to methods and devices for capturing tumbling space debris, which methods and devices can attenuate the angular velocity of an object in orbit.

[0020]

[0021] Figure 1 shows the cosmic ray bus 1 and the countermass 3 in a storage configuration for launch.

[0021]

[0022] The structure and basic systems of a space vehicle are generally referred to as a cosmic ray bus. The bus is a general name that can be applied to the spacecraft infrastructure that supports the main subsystems of the spacecraft. All spacecraft launched to date have had a bus housing electronics and a computer. The cosmic ray bus 1 can be, for example, a Boeing DS&S 702, a Lockheed Martin Space Systems A2100 Alphabus, an INVAP ARSAT-3K, an Airbus D&S Eurostar, an ISRO I-1K, I-2K, I-3K, I-4K, I-6K, and an Indian Mini Satellite bus, a NASA Ames MCSB, an SSL 1300, an Orbital ATK GEOStar, and a Mitsubishi Electric DS2000. Embodiments of the present invention may utilize a custom bus assembled using various components supplied by various manufacturers. In some mission profiles, a very high-performance propulsion system may be required. In a standard spacecraft mission, it may not be necessary to specially configure the bus. A mission according to the present invention may have unique requirements that cannot be achieved with off-the-shelf buses. In such cases, for example, the computer, power system, and payload are custom designed and assembled.

[0022]

[0023] The countermass 3 can be spherical for high volume efficiency or cubic which may be easier to manufacture. The countermass 3 can be made of aluminum or other metals. Steel is not ideal to use in some cases because it has high mass efficiency but does not burn easily in the atmosphere. Also, it should be noted that the countermass does not need to be dumb or single-purpose. In other words, the countermass can house batteries, fuel, thrusters, sensors, reaction wheels, or other high-density equipment used by a servicer. In this way, the countermass can reduce the overall mass of the servicer and serve a dual purpose, eliminating the need to "double" the total mass.

[0023]

[0024] Figure 2 shows the deployment of the truss structure 5 connecting the countermass 3 and the cosmic ray bus 1.

[0024]

[0025] A truss is an assembly of beam members or other elements that creates a rigid structure. In some embodiments, the truss is a structure that benefits from the inherent stability and weight distribution of triangles. By connecting a network of triangles and evenly distributing stress throughout the structure, many practical advantages can be provided.

[0025]

[0026] The truss structure 5 can be made of aluminum or a composite material such as carbon fiber reinforced polymer (CFRP). The circular truss is thought to be similar to the circular ring truss structure commonly used to deploy extremely large antenna reflectors within geostationary orbits. In an expandable and contractible truss structure, one size is suitable for a range of target object sizes, but contraction is technically difficult, so it may be advantageous to have truss structures of different diameter classes, such as 1 - 5m and 10m. The length of the robotic arm of a spacecraft defines the maximum range between the object and the servicer. With a longer robotic arm, it is possible to use a larger truss structure to capture smaller objects.

[0026]

[0027] In the configuration of the collapsible truss structure 5, a cable and pulley system can be used, which is particularly suitable for a circular truss structure. In a linear arm truss structure, the arm can be bent using a joint motor. In a non-collapsible configuration, a spring or a carbon fiber tape spring can be used for deployment.

[0027]

[0028] Sufficient clearance to deploy the truss structure 5 depends on the size of the object to be captured. Sufficient clearance enables circumvention of the object by rotation and an empty volume with a diameter larger than the client object. A specific clearance is required for safety, but the clearance is limited by the length of the robotic arm. In one exemplary embodiment, a robotic arm of about 2 meters is used, but longer robotic arms are also possible. Thus, the truss structure may need to deploy within 2 meters of the client object.

[0028]

[0029] FIG. 3 shows the spacecraft bus 1 that provides angular momentum to the system of the spacecraft bus 1 and the countermass 3 connected by the expandable and foldable truss structure 5.

[0029]

[0030] In prior art methods of capturing tumbling space debris, attempts have been made to match the motion of the service spacecraft to that of the client object. When the client object is rotating about a single axis, the service spacecraft can use thrusters to match the angular velocity so that there is no relative motion. When the client object has angular velocities in all three axis directions, the service spacecraft must utilize frequent and high thrusts to achieve zero relative motion, which requires significant consumption of the fuel resources carried on the service spacecraft.

[0030]

[0031] Embodiments of the present disclosure can match the motion of the service spacecraft to that of the client object 51 (Figs. 7 to 10). First, the center of mass 7 of the truss structure 5 connecting the countermass 3 and the spacecraft bus 1 is positioned at approximately the same position as the center of mass of the object 51. Then, the spacecraft bus 1 can achieve a tumbling state that matches the client object 51 using the angular momentum generated mechanically (or by other means).

[0031]

[0032] The angular momentum can be provided by the torque generated by a flywheel or a magnetorquer on the spacecraft bus 1. However, for a 15 m diameter structure moving at 3 degrees per second, there is no commercially available flywheel that can achieve such a large angular momentum. Control moment gyroscopes may be used, but in this situation, it may be more efficient to generate torque using chemical thrusters. Since the torque is equal to four times the distance from the axis of rotation to the point where the force is applied, the firing of thrusters mounted away from the center of gravity of the service mechanism provides a fuel-efficient means of generating torque. The thrusters mounted on the spacecraft bus 1 can generate torque along the appropriate axis to achieve the desired rotational state. Thrusters mounted along the truss structure or at other locations on the countermass 3 can improve the efficiency of providing torque along additional axes and can help to zero the linear momentum transfer. Thrusters at one end can provide torque and linear momentum changes. Thrusters at the opposite end can separate the angular momentum thrust. Thus, thrusters and flywheels perform the same function.

[0032]

[0033] Fig. 4 shows the countermasses 11 and 13 and the spacecraft bus 9 in the storage configuration for launch.

[0033]

[0034] Generally, a launch vehicle suitable for launching the spacecraft bus 1 and the countermass 3 is also suitable for launching the spacecraft bus 9 and the countermasses 11 and 13. Typically, embodiments with two or more countermasses are suitable for the same type of launch vehicle as embodiments with one countermass, but the mass of the embodiments can vary widely, and in some embodiments, a different launch vehicle may be required.

[0034]

[0035] Often, satellites in civilian, research, and government services are miniaturized into various forms for launch and transportation and then deployed into various shapes during service. The storage configuration can be folded in various ways depending on the spacecraft bus used. Embodiments of the present invention, unlike typical satellites, have one or more countermasses, and due to the shape, weight, and size of the countermasses, special attention to the configuration is required during launch.

[0035]

[0036] FIG. 5 shows the deployment of the truss structure 15 connecting the countermasses 11 and 13 to the spacecraft bus 9.

[0036]

[0037] In some embodiments, two or more countermasses are deployed. In a linear type truss structure, since the center of gravity and the safe volume must be separated, there must be two or more countermasses. Otherwise, a linear truss with a single countermass will pass directly through the center of gravity within the safe volume. Each linear deployment must deploy the countermass away from the center of gravity. This offsets the center of gravity in both the X and Y directions. The offset in the Y direction must be balanced by another countermass in the -Y direction. In the case of a circular or circular segment truss structure, this problem is solved by separating the center of gravity within the safe volume. Also, when the angular momentum of the service machine system is provided by thrusters, it is advantageous to position the thrusters at a distance away from the X-axis to increase the moment arm of the thrusters. With a single countermass on the same axis as the bus, it is difficult to efficiently impart this momentum (by the thrusters). From a functional perspective, having additional countermasses promotes providing redundancy and making the system even more robust.

[0037]

[0038] In various embodiments, the truss structure 5, the spacecraft bus 9, and the countermasses 11 and 13 can be arranged in many different ways. The countermasses 11 and 13 can be relatively close to or far from each other, and can also be near or far from the spacecraft bus. Different configurations provide different advantages in terms of service. In a circular structure, there is no limit to how close or far the countermasses are arranged, and in some embodiments, the countermasses can move along the circular truss structure.

[0038]

[0039] FIG. 6 shows a spacecraft bus 9 that imparts angular momentum to a system of a spacecraft bus 9 and countermasses 11 and 13 connected by an expandable and foldable truss structure 15.

[0039]

[0040] The total momentum of the system of spacecraft bus 9, countermasses 11 and 13, and client object 51 is maintained approximately constant if external forces are negligible, as expected in some embodiments.

[0040]

[0041] In various embodiments, spacecraft bus 9 and countermasses 11 and 13 can match the velocity and rotation of client object 51, or spacecraft bus 9, countermasses 11 and 13, and client object 51 can match a third velocity and rotation that is initially not associated with any of the system.

[0041]

[0042] FIG. 7 shows a system including spacecraft bus 9, countermasses 11 and 13, and an extensible and foldable truss structure 15 approaching a client object 51 that is arbitrarily tumbling about three axes.

[0042]

[0043] The motion of a tumbling client object 51 in space is a combination of the translation of the center of mass of the client object 51 and the rotation about one or more axes passing through the center of mass of the client object 51.

[0043]

[0044] In an embodiment, three rotational axes of client object 51 can be identified. When client object 51 rotates about one of these axes at a specific angular velocity, the angular momentum of client object 51 is given by the product of the angular velocity corresponding to this rotational axis and the moment of inertia. These moments of inertia are called principal moments of inertia, and the rotational axes are called principal rotational axes.

[0044]

[0045] The client object 51 can have translational motion in the front / back, up / down, and left / right directions along three perpendicular axes, as well as rotation about the three perpendicular axes. These rotations are often referred to as yaw (vertical axis), pitch (left / right axis), and roll (front / back axis). In addition to rotation about the principal axis of the client object 51, rocking, swaying, or nodding motions can occur, which result in an axis change known as nutation. In some systems carrying large amounts of liquid, more chaotic characteristics can be added to the rotation by a sloshing mechanism, but this is expected to be minimal in most clients where the liquid is consumed, discharged, or frozen before capture.

[0045]

[0046] FIG. 8 shows a system including a spacecraft bus 9, countermasses 11 and 13, and an extensible and foldable truss structure 15, with the center of mass aligned with the client object 51.

[0046]

[0047] Embodiments can use different methods to calibrate the alignment with the center of mass of the client object 51. The spacecraft bus 9 can include 3D vision sensors such as stereo cameras or light detection and ranging (LiDAR) sensors to measure parameters (position, orientation, angular velocity, and acceleration, etc.) of the client object 51. The spacecraft bus 9 can also include devices for measuring parameters (position, orientation, angular velocity, and acceleration, etc.) of a system including the spacecraft bus 9, countermasses 11 and 13, and truss structure 15. The data is generally transmitted to the ground via an RF communication link. This is to further process the tumble rate and sensor data so that the ground system and ground engineers can better understand the dynamic characteristics of the client.

[0047]

[0048] Figure 9 shows a system including a spacecraft bus 9, counter masses 11 and 13, and an extensible and foldable truss structure 15 that uses angular momentum to match the tumble rate of a client object 51 and set all relative motion to zero.

[0048]

[0049] This can be done one axis at a time, but if chemical thrusters are used, combining axial momentum operations may provide a limited advantage from a fuel efficiency perspective. Depending on the client's tumbling rate and mode, it will take several minutes, but is expected to be less than an hour.

[0049]

[0050] Momentum can be generated by mechanical flywheels, also known as reaction wheels, also known as momentum wheels. Another hardware option used for extremely high torques is one or more control moment gyroscopes, which are more power efficient than reaction wheels but very expensive. Angular momentum is not transferred from the bus to the client object until a mechanical connection via a robotic arm or other device is made. At the time of mechanical connection, angular momentum is transferred to reduce the absolute rotation rate of the combined system. In some situations, using thrusters may be more time efficient.

[0050]

[0051] The service vehicle can accommodate multiple clients, including those rotating at low speeds and those rotating at high speeds. In some cases, the rotation speed is affected by how the object fails. Tumbling objects may slow down over time, but external forces may also accelerate the tumble rate. The tumble rate can be expressed in radians per second, but radians per second does not fully define the tumbling mode. The tumbling mode is typically assessed from the ground using a telescope or radar. However, a more accurate description can be made by a spacecraft very close to the object.

[0051]

[0052] Figure 10 shows that an appendage 53 from a system including a spacecraft bus 9, countermasses 11 and 13, and an extensible and foldable truss structure 15 safely holds a client object 51 with zero relative velocity and rotation.

[0052]

[0053] In an embodiment, the appendage 53 can be, among many alternatives, a robotic clamp or gripper, a robotic arm, or a robotic tentacle. After attachment, non-rigid coupling is not ideal here because angular momentum must be transferred to the client for de-tumbling. A tether connection (or net) is not reliable for momentum transfer.

[0053]

[0054] After rigidly coupling with a tumbling object, the service spacecraft reduces the absolute tumbling rate of the coupling system and de-tumbles the coupling system by applying torque through the rigid coupling with a flywheel, magnetic torquer, or thruster. Once the coupling system stops tumbling, other activities such as servicing, refueling, or relocation can be performed. If there are specific grasping points on the client object 51, the appendage 53 can be deployed to capture the client object 51 by these points. Or, if there are no such specific grasping points, the appendage 53 can grip the client object 51 at various points.

[0054]

[0055] Once holding of the client object 51 is achieved, the appendage 53 from a system including the spacecraft bus 9, countermasses 11 and 13, and an extensible and foldable truss structure 15 can adjust the grasping configuration in various ways to secure it for service or transportation. For example, robotic fingers can be used for stable transition when changing the grasping position, or a robotic latch mechanism can be used.

[0055]

[0056] FIG. 11 is a flowchart showing steps of a computer-implemented method for designing one or more counter masses, which is the subject of one embodiment. In the embodiment, many variations of this method are possible, and in fact, the order of steps may be changed for each embodiment.

[0056]

[0057] One embodiment is a computer-implemented method for calculating parameters of a spacecraft. The method includes inputting attributes of one or more target clients via one or more devices (101), inputting attributes of a spacecraft bus and a truss structure via one or more devices (103), and calculating, by one or more processors, desired properties of one or more counter masses according to a previously defined ranking (105). The devices can be various computer hardwares such as a mouse, a keyboard, or various memory types.

[0057]

[0058] The desired properties can be various design and aerospace parameters related to the predicted performance of one or more counter masses. Therefore, the output of the desired properties can provide useful information regarding the manufacturing process of one or more counter masses, including the materials used, the sizes of components and assemblies, and the shapes of components and assemblies.

[0058]

[0059] The desired properties can be output in various data formats, including various spreadsheet and word processing programs, and various file formats usable in computer-aided design.

[0059]

[0060] The previously defined ranking can add different amounts of weight according to the mission objectives related to that client to different design and aerospace parameters according to the received data related to the client. The previously defined ranking can be input via an I / O device such as a keyboard, a mouse, or a memory.

[0060]

[0061] Other embodiments may include calculating a target mass of fuel for a spacecraft bus (107). Other embodiments may include calculating one or more target times for launch, rendezvous, and disposal of a client object (109).

[0061]

[0062] The above-described embodiments are provided for the purpose of facilitating understanding of the present invention and are not intended to limit the interpretation of the present invention. Each element of the embodiments and their arrangements, materials, conditions, shapes, sizes, etc. are not limited to the examples described and may be changed as appropriate. Furthermore, the components described in the embodiments can be partially replaced or combined.

Claims

1. propelling a service spacecraft towards an object; deploying one or more countermasses away from the service spacecraft bus to offset the center of mass of the service spacecraft within an empty volume; bringing the service spacecraft closer to the object; positioning the center of mass of the service spacecraft at approximately the same position as the center of mass of the object; imparting angular momentum to the service spacecraft to match the tumble rate of the object; contacting the object by one or more mechanical attachments to the service spacecraft; A method comprising the above.

2. The method according to claim 1, further comprising applying torque to the object using one or more of ion beam, electromagnetic induction, magnetic torque, and fluid force.

3. A spacecraft comprising a bus, one or more countermasses, and a truss connecting the bus and the one or more countermasses, wherein the truss is configured to deploy the one or more countermasses away from the bus to offset the center of mass of the spacecraft within an empty volume, wherein the empty volume has a diameter larger than the diameter of the volume occupied by the space object about an axis passing through the center of mass of the space object to be captured.

4. The spacecraft according to claim 3, wherein the number of countermasses is in the range of 2 to 3.

5. The spacecraft according to claim 3 or 4, further comprising one or more mechanical attachments for gripping the object.

6. The spacecraft according to any one of claims 3 to 5, further comprising equipment for generating one or more of ion beam, electromagnetic induction, and fluid force.

7. The spacecraft according to any one of claims 3 to 6, wherein the structure of the truss is expandable.

8. The spacecraft according to any one of claims 3 to 7, wherein the structure of the truss is foldable.

9. The spacecraft according to any one of claims 3 to 8, wherein the structure of the truss is configured to deploy with sufficient clearance.

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