Reaction wheel for a satellite

Abstract

An inertia disk for a reaction wheel assembly for a spacecraft is provided. The inertia disk includes a body that has an inner portion and a lip. The inner portion is proximate to a center of the body, and the inner portion spans from the center to the lip. The lip has a thickness that is greater than a thickness of the inner portion. The body of the inertia disk is at least partially made of aluminum.

Description

REACTION WHEEL FOR A SATELLITECROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 523,999, filed in the U.S. Patent and Trademark Office on June 29, 2023, which is incorporated herein by reference in its entirety for all purposes.FIELD

[0002] The present disclosure relates generally to a reaction wheel that can provide high momentum storage capability to a large satellite. In at least one example, reaction wheel can be used with a low earth orbit (LEO) satellite, a medium earth orbit (MEO) satellite, and / or a geostationary equatorial orbit (GEO) satellite.BACKGROUND

[0003] Conventional reaction wheels use mass optimized materials and, as a result, they are manufactured out of stainless steel, which increases material costs and reduces demisability of the reaction wheel. Additionally, conventional reaction wheels are designed to operate at relatively high operating speeds, which induces jitter on the spacecraft and reduces the service life of bearings.BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Implementations of the present technology will now be described, by way of example only, with reference to the attached figures, wherein:

[0005] FIG. 1 illustrates an environment for the reaction wheel assembly, according to the present disclosure;

[0006] FIG. 2A illustrates the reaction wheel assembly in a cross-sectional view;

[0007] FIG. 2B illustrates the reaction wheel assembly in a cross-sectional view;

[0008] FIG. 2C illustrates the reaction wheel assembly in a cross-sectional view;

[0009] FIG. 2D illustrates the reaction wheel assembly in a cross-sectional view without the top of the enclosure;

[0010] FIG. 2E illustrates the reaction wheel assembly in a perspective view without the top of the enclosure;

[0011] FIG. 3 is a schematic illustrating a configuration of a motor and controller for a reaction wheel assembly;

[0012] FIG. 4 illustrates a modal survey of the reaction wheel; and

[0013] FIG. 5 is a graph illustrating target combinations of ring height and ring diameter to achieve a target stiffness and moment of inertia.SUMMARY

[0014] Aspects of the present disclosure include an inertia disk for a reaction wheel assembly for a spacecraft. The inertia disk includes a body that has an inner portion and a lip. The inner portion is proximate a center of the body such that the inner portion spans from the center to the lip. The lip has a thickness that is greater than a thickness of the inner portion. The body is made of aluminum.

[0015] In various possible examples, the body is substantially cylindrical.

[0016] In various possible examples, the body is made of aluminum 7075-T7.

[0017] In various possible examples, the aluminum has a melting point of less than about1000 degrees Celsius. In some examples, the aluminum has a melting point of less than 700 degrees Celsius. In some examples, the aluminum has a melting point between about 477 degrees Celsius and about 635 degrees Celsius.

[0018] In various possible examples, the body can rotate about the center at a rotational speed to provide a predetermined momentum storage. In some examples, the rotational speed is less than or equal to about 4000 rotations per minute. In some examples, the rotational speed is less than or equal to about 3000 rotations per minute.

[0019] Aspects of the present disclosure include a reaction wheel assembly for a spacecraft.The reaction wheel assembly includes an inertia disk and an enclosure. The inertia disk includes a body that has an inner portion and a lip. The inner portion is proximate a center of the body such that the inner portion spans from the center to the lip. The lip has a thickness that is greater than a thickness of the inner portion. The body is made of aluminum. The enclosure can receive the inertia disk.

[0020] In various possible examples, the enclosure includes a vacuum chamber. In some examples, the enclosure includes a vacuum fitting that can be coupled with a vacuum pump. In some examples, the enclosure is integrated with the vacuum chamber.

[0021] In various possible examples, the enclosure is made of aluminum.

[0022] In various possible examples, the body is substantially cylindrical.

[0023] In various possible examples, the body is made of aluminum 7075-T7.

[0024] In various possible examples, the aluminum has a melting point of less than about1000 degrees Celsius. In some examples, the aluminum has a melting point of less than 700 degrees Celsius. In some examples, the aluminum has a melting point between about 477 degrees Celsius and about 635 degrees Celsius.

[0025] In various possible examples, the body can rotate about the center at a rotational speed to provide a predetermined momentum storage. In some examples, the rotational speed is less than or equal to about 4000 rotations per minute. In some examples, the rotational speed is less than or equal to about 3000 rotations per minute.

[0026] In various possible examples, the reaction wheel assembly includes a motor driver coupled with the center of the inertia disk such that rotation of the inertia disk causes the motor driver to rotate. In some examples, the motor driver is coupled with a motor so that the motor driver can provide between 120 watts and about 300 watts. In some examples, the motor driver can provide between 200 watts and about 250 watts. In some examples, the motor driver can provide about 140 watts.

[0027] Aspects of the present disclosure include a spacecraft that includes a motor and a reaction wheel assembly. The reaction wheel assembly includes an inertia disk, an enclosure, and a motor driver. The inertia disk includes a body that has an inner portion and a lip. The inner portion is proximate a center of the body such that the inner portion spans from the center to the lip. The lip has a thickness that is greater than a thickness of the inner portion. The body is made of aluminum. The enclosure can receive the inertia disk. The motor driver is coupled with the center of the inertia disk such that rotation of the inertia disk causes the motor driver to rotate. In some examples, the motor driver is coupled with the motor so that the motor driver can provide between 120 watts and about 300 watts.

[0028] In various possible examples, the spacecraft includes a satellite.DETAILED DESCRIPTION

[0029] Various embodiments of the disclosure are discussed in detail below. While specific implementations are discussed, it should be understood that this is done for illustration purposes only. A person skilled in the relevant art will recognize that other components and configurations may be used without parting from the spirit and scope of the disclosure.

[0030] Additional features and advantages of the disclosure will be set forth in the description which follows, and in part will be obvious from the description, or can be learned by practice of the principles disclosed herein. The features and advantages of the disclosure can be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other features of the disclosure will become more fully apparent from the following description and appended claims, or can be learned by the practice of the principles set forth herein.

[0031] It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures, and components have not been described in detail so as not to obscure the related relevant feature being described. The drawings are not necessarily to scale and the proportions of certain parts may be exaggerated to better illustrate details and features. The description is not to be considered as limiting the scope of the embodiments described herein.

[0032] Provided herein is a space-rated aluminum reaction wheel that provides high momentum storage capability to a spacecraft, for example a large satellite. In some examples, the spacecraft can be a low earth orbit (LEO) satellite, medium earth orbit (MEO) satellite, or a geostationary equatorial orbit (GEO) satellite. The reaction wheel has a high momentum storage capacity, which, in some examples, is at least 100 Newton-Meter-Second (N-m-s) (i.e., 100 N-m- s and greater). The reaction wheel disclosed herein includes an aluminum inertia disk, an integrated vacuum compartment, and / or an aluminum enclosure, which may provide significant benefits over conventional systems. For example, the reaction wheel of the present disclosure may have areduced cost, improved demisability, and / or improved manufacturability over conventional reaction wheels.

[0033] The aluminum inertia disk of the reaction wheel disclosed herein trades volume and mass to enable lower material costs and increased demisability to aid in end-of-life disposal of the spacecraft. The geometry of the inertia disk provides high stiffness with a high moment of inertia to enable reduced operating speeds which in turn can reduce induced jitter and required power while increasing margin for bearing operating life. The design contains features to improve manufacturability through the use of a high mass vacuum compartment integrated into the reaction wheel chassis which enables flight-like (e.g., as in orbit, etc.) characterization and testing of the wheel without the need for a dedicated, high-cost vacuum chamber. The thick, heavy aluminum enclosure allows for the use of readily available electronics, which significantly reduces cost and increases performance without compromising radiation performance in a variety of orbits.

[0034] Conventional reaction wheel designs have been driven by mass and volume constraints, utilizing mass optimized materials and technology. Although the designs of these conventional systems may be mass optimal, the designs result in significant tradeoffs. For example, in conventional systems, the inertia disk is constructed of stainless steel to maximize packing density; however, this results in higher material costs and reduced demisability as a result of the relatively high melting point of the material. Additionally, conventional systems utilize higher operating speeds (in some cases 6000 revolutions per minute (RPM) or higher) to reduce the required disk moment of inertia to drive down mass, which results in reduced bearing life and higher vibrational noise induced on the spacecraft. This noise can often result in unacceptable spacecraft jitter, necessitating the need for complex isolation schemes which increase integrated system costs. Conventional systems require a higher test complexity. Either the reaction wheels are tested in ambient pressure conditions, which are not flight-like, or the reaction wheels require the use of a large thermal vacuum chamber to achieve flight-like conditions, which increases the test cost and complexity. Moreover, conventional systems incorporate radiation hardened electronics components, which require less shielding but have significantly higher cost and reduced performance compared to readily available components.

[0035] The presently disclosed reaction wheel addresses the shortcomings of conventional designs. In some examples of the reaction wheel disclosed herein, one or more reaction wheel components are manufactured out of aluminum (e.g., Aluminum 7075-T7), which has a lowmelting point, low cost, and high machinability. Additionally, in some examples, the wheel moment of inertia is sized assuming a lower maximum operating speed of 3000 RPM, which can result in significantly reduced vibration. In some examples of the reaction wheel disclosed herein, the wheel enclosure is configured to provide a vacuum pressure chamber with ports that enable the connection of a vacuum pump for testing. This enables the inertia disk compartment to be exposed to vacuum during ground testing while the assembly is tested in an ambient pressure environment, significantly increasing the flight-like testing capability with a simpler test setup and equipment. Additionally, readily available electronics are utilized throughout the motor driver design while retaining the capability to operate in LEO, MEO, and GEO radiation environments through the use of heavy shielding and anti-latchup mitigation features in the circuit design. This significantly reduces cost and enables the use of more readily available electronic components with higher performance capabilities.

[0036] FIG. 1 illustrates the reaction wheel assembly 100 in a space environment. The reaction wheel assembly 100 can be employed within (and / or coupled to) a spacecraft such as, for example a satellite 10. In some examples, the satellite 10 can include a low earth orbit (LEO) satellite, a medium earth orbit (MEO) satellite, or a geostationary equatorial orbit (GEO) satellite. When coupled to the satellite 10, the reaction wheel assembly 100 can provide high momentum storage capability (e.g., 100 N-m-s and higher) to the satellite 10. Although this disclosure refers to a reaction wheel assembly 100 configured for use in a satellite 10, the reaction wheel assembly 100 can be configured for use in other types of spacecraft.

[0037] FIGS. 2A-2E illustrate a reaction wheel assembly 100. The reaction wheel assembly 100 is illustrated in cross-sectional, perspective views in FIGS. 2A-2C. The reaction wheel assembly 100 is illustrated in a cross-sectional, perspective view with the top plate 220 omitted in FIG. 2D. The reaction wheel assembly 100 is illustrated in a perspective view with the top plate 220 removed in FIG. 2E. The reaction wheel assembly 100 can be employed in a spacecraft operable to fly and operate in outer space, such as satellite 10 (for example as illustrated in FIG. 1). In some examples, the reaction wheel assembly 100 can be coupled or otherwise mounted to the spacecraft. One or more components of the reaction wheel assembly 100 (e.g., inertia disk 200, enclosure 214) can be at least partially constructed of aluminum (e.g., aluminum alloy). In some examples, one or more components of the reaction wheel assembly 100 can be entirely constructedof aluminum. For example, one or more components of the reaction wheel assembly 100 can be constructed of aluminum 7075-T7.

[0038] The reaction wheel assembly 100 includes an inertia disk 200 (also referred to as a reaction wheel) that has a body 202. In some examples, the body 202 is at least partially constructed of aluminum. In some examples, the body 202 is at least 50% constructed of aluminum. In some examples, the body 202 is at least 75% constructed of aluminum. In some examples, the body 202 is entirely constructed of aluminum. For example, the body 202 can be constructed of aluminum 7075-T7. In at least one example, the aluminum has a melting point that is less than approximately 1,000 degrees Celsius. In some examples, the aluminum has a melting point that is less than approximately 700 degrees Celsius. In some examples, the aluminum has a melting point that is between approximately 477 degrees Celsius and approximately 635 degrees Celsius. When the body 202 of the inertia disk 200 is constructed of aluminum, the melting point of the body 202 corresponds to the melting point of the aluminum. Moreover, a high percentage of the body 202 being made of aluminum can be less expensive to manufacture and provide for better demisability over conventional systems constructed of stainless steel.

[0039] The body 202 defines a longitudinal axis LA and can have a center 204, an inner portion 206 proximate to and / or extending from the center 204, and a lip 208 (also referred to as an outer portion) that is opposite the center 204 in relation to the inner portion 206. The body 202 is operable to rotate about the center 204. In some examples, the longitudinal axis LA that extends through the center 204 of the body 202 defines an axis of rotation and the body 202 is operable to rotate about the axis of rotation (the longitudinal axis LA). The body 202 (e.g., center 204) can be coupled to a shaft 232, which can be coupled to a motor as discussed below.

[0040] The body 202 can rotate about the center 204 (e.g., longitudinal axis LA) at a rotational speed. In some examples, the rotational speed is less than or equal to approximately 4,000 rotations per minute (RPM), much less than conventional systems having rotational speeds of at least 6,000 RPM. In some examples, the rotational speed is less than or equal to approximately 3,000 RPM. When the body 202 rotates about the center 204 at a rotational speed, the body 202 provides momentum storage (e.g., predetermined momentum storage).

[0041] The body 202 of the inertia disk 200 provides momentum storage for the spacecraft (e.g., satellite 10 as illustrated for example in FIG. 1) by increasing or decreasing the rotational speed of the body 202. In some examples, the body 202 of the inertia disk 200 can rotate at a loweroperating speed than conventional systems, which reduces the vibration imparted on the spacecraft (e.g., satellite 10 as illustrated for example in FIG. 1).

[0042] Continuing with FIGS. 2A-2E, the body 202 extends radially outward from the center 204 (e.g., radially outward from the longitudinal axis LA). The inner portion 206 adjoins (or is proximate to) the center 204 of the body 202 such that the inner portion 206 extends radially outward from the center 204. The lip 208 adjoins and / or is coupled with the inner portion 206 such that the lip 208 extends radially outward from the inner portion 206. In this manner, the inner portion 206 spans from the center 204 to the lip 208. The body 202 can be generally cylindrical in shape. In some examples, the lip 208 defines a curvate surface along the perimeter of the lip 208.

[0043] The body 202 (e.g., center 204, inner portion 206, lip 208) of the inertia disk 200 can define one or more thickness in the axial direction (e.g., parallel to the longitudinal axis LA of the body 202). For example, the thickness TC of the center 204, the thickness TIP of the inner portion 206, and the thickness TL of the lip 208 each define a thickness in the axial direction of the body 202. In at least one example, the thickness TL of the lip 208 is greater than the thickness TIP of the inner portion 206. Accordingly, the thickness TIP of the inner portion 206 is less than the thickness TL of the lip 208. With the increased thickness TL of the lip 208, the weight of the lip 208 is greater than the weight of the inner portion 206. Accordingly, the rotational inertia extends outwards towards the lip 208 when the inertia disk 200 rotates. In some examples, the body 202 can be configured such that a greater amount of the weight of the body 202 is positioned towards the radial edge (e.g., the lip 208). For example, the inner body 206 may include holes or any other suitable mechanism or material to have lesser weight than the radial edge. Accordingly, the rotational inertia extends radially outwards towards the lip 208 when the inertia disk 200 rotates. However, the weight must be evenly balanced and / or distributed across the body 202 so that when the body 202 rotates, the balanced weight provides stabilization to the spacecraft.

[0044] In at least one example, the thickness TC of the center 204 is greater than the thickness TIP of the inner portion 206. Said another way, the thickness TIP of the inner portion 206 is less than the thickness TC of the center 204. In some examples, the thickness TC of the center 204 is approximately equal to the thickness TL of the lip 208.

[0045] The body 202 (e.g., center 204, inner portion 206, lip 208) of the inertia disk 200 can define one or more widths in the radial direction (e.g., perpendicular to the longitudinal axis LA of the body 202). For example, the width WC of the center 204, the width WIP of the inner portion206, and the width WL of the lip 208 each define a width in the radial direction of the body 202. Together, the width WC of the center 204, the width WIP of the inner portion 206, and the width WL of the lip 208 can define a radius of the body 202 of the inertia disk 200. In at least one example, the width WL of the lip 208 is less than the width WIP of the inner portion 206. Accordingly, the width WIP of the inner portion 206 is greater than the width WL of the lip 208. In at least one example, the width WC of the center 204 is less than the width WIP of the inner portion 206. Accordingly, the width WIP of the inner portion 206 is greater than the width WC of the center 204. In some examples, the width WC of the center 204 is less than the width WL of the lip 208. Accordingly, the width WL of the lip 208 is greater than the width WC of the center 204.

[0046] The geometry of the body 202 of the inertia disk 200 can provide both high stiffness and a high moment of inertia. In this manner, the inertia disk 200 can be operated at reduced speeds, which reduces jitter and power requirements while increasing the service life of the one or more bearings 212 (discussed below), compared to conventional systems. For example, FIG. 5 is a graph 500 illustrating ring height and diameter dimensions for the inertia disk (such as inertia disk 200 illustrated in FIG. 2) to achieve target stiffness and moment of inertia. The geometry of the body 202 of the inertia disk 200 can be scalable to achieve a target moment of inertia, which can be balanced against changes to the stiffness of the body 202. Scalable geometry includes the diameter of the body 202, thickness (e.g., height) of the lip 208, and overall mass distribution throughout the body 202.

[0047] Referring to FIGS. 2A-2D, the reaction wheel assembly 100 can include one or more bearing blocks 210 (e.g., bearing block 210a, 210b). Each bearing block 210 can include a bearing 212 (e.g., bearing 212a, 212b) therein. Each bearing 212 can be configured to rotate and to receive the center 204 of the body 202 of the inertia disk 200. In some examples, the reaction wheel assembly 100 includes an upper bearing block 210a that has an upper bearing 212a to receive the center 204. Additionally or separately, the reaction wheel assembly 100 includes a lower bearing block 210b that has a lower bearing 212b to receive the center 204. When each bearing 212 receives the center 204 of the body 202 of the inertia disk 200, a longitudinal axis of the bearing 212 can be parallel (or coincident) with the longitudinal axis LA of the body 202. Each bearing 212 is rotatable such that the body 202 can rotate about the center 204.

[0048] In some examples, the bearing blocks 210 (e.g., bearing block 210a, 210b) are generally cylindrical in shape and define a generally cylindrical opening to receive the bearing 212(e.g., bearing 212a, 212b) therein. In some examples, the bearing blocks 210 include one or more through-holes configured to receive a fastener (e.g., screw, bolt) therethrough to couple the bearing block 210 to the enclosure 214. In some examples, the bearing blocks 210 can be substantially spherical.

[0049] Continuing with FIGS. 2A-2E, the reaction wheel assembly 100 can include an enclosure 214 that is operable to receive the inertia disk 200 therein. The enclosure 214 can enclose the inertia disk 200 and internal components (e.g., electrical components) of the reaction wheel assembly 100. The enclosure 214 can be constructed of the same or similar materials as the body 202 of the inertia disk 200, as previously discussed. For example, in some examples, the enclosure 214 is at least partially constructed of aluminum (e.g., aluminum 7075-T7). In some examples, the enclosure 214 can be greater than 50% constructed of aluminum. In some examples, the enclosure 214 can be greater than 75% constructed of aluminum. In some examples, the enclosure 214 can be entirely constructed of aluminum. For example, the enclosure 214 can be constructed of thick, aluminum such that the mass of the aluminum provides enhanced shielding to the internal components. The enhanced shielding can allow for readily available electronic components to be used within the reaction wheel assembly 100 (e.g., enclosure 214). The ability to use readily available components within the reaction wheel assembly 100 can significantly reduce cost and increase performance over conventional systems, which use radiation hardened electronic components.

[0050] In some examples, the enclosure 214 includes a base plate 216, an enclosure housing 218, and / or a top plate 220. In some examples, a cross-section of the enclosure housing 218 (also referred to as a sidewall) is a generally rectangular (e.g., square) shape. In other examples, a crosssection of the enclosure housing 218 is a generally circular shape. In some examples, a handle 222 (as illustrated for example in FIGS. 2A-2C) extends outward from the enclosure 214 (e.g., top plate 220) such that the handle 222 can be grabbed. For example, the top plate 220 can be removably coupled (e.g., bolted, screwed, nailed, etc.) to the enclosure housing 218. The top bearing block 210a can be coupled to the top plate 220 of the enclosure 214 such that the top plate 220 supports the top bearing block 210a. The bottom bearing block 210b can be coupled to the base plate 216 of the enclosure 214 such that the base plate 216 supports the bottom bearing block 210b.

[0051] In some examples, the enclosure 214 includes a vacuum chamber 224, as illustrated for example in FIGS. 2A-2C. The vacuum chamber 224 can enable flight-like characterization and testing of the reaction wheel assembly 100 (e.g., inertia disk 200) without requiring the dedicated, high-cost vacuum chamber associated with conventional systems. In some examples, the vacuum chamber 224 can be defined within the enclosure 214. In some examples, the vacuum chamber 224 can be integrated with the enclosure 214. A vacuum fitting 226 can be fluidly coupled to the vacuum chamber 224 via an aperture extending through the enclosure 214 (e.g., top plate 220). In some examples, the vacuum fitting 226 includes a pressure gauge. In some examples, the vacuum fitting 226 is operable to be fluidly coupled to a vacuum pump, and the vacuum pump is operable to generate a vacuum within the vacuum chamber 224.

[0052] In some examples, the enclosure 214 (e.g., enclosure housing 218) can include one or more pass-throughs 228 (also referred to as electrical pass-throughs). Each pass-through 228 can be used to pass electrical wiring 230 through the enclosure 214. The electrical wiring 230 can be used to supply electrical power to internal components of the reaction wheel assembly 100. For example, when the motor is inside the enclosure 214 (as discussed below), the electrical wiring 230 can supply power to the motor.

[0053] In at least one example, the body 202 (e.g., center 204) of the inertia disk 200 can be coupled to a shaft 232 (also referred to as the motor shaft) such that rotating the shaft 232 correspondingly causes the body 202 to rotate about the center 204. The shaft 232 can also be coupled to a motor (also referred to as a motor driver), such that the motor is coupled (via shaft 232) to the body 202 (e.g., center 204) of the inertia disk 200. Operating the motor can cause the shaft 232 to rotate, which correspondingly causes the body 202 of the inertia disk 200 to rotate. The longitudinal axis of the shaft 232 can be coincident with the longitudinal axis LA of the body 202. In some examples, the motor can be positioned outside of (or external to) the enclosure 214. For example, the shaft 232 can extend through an opening in the enclosure 214. In other examples, the motor can be positioned within (or internal to) the enclosure 214.

[0054] Turning to FIG. 3, a schematic illustrates a configuration of a motor 300 and controller 302 for a reaction wheel assembly 100. The motor 300 is illustrated within the enclosure 214. The controller 302 (also referred to as the motor controller) can be in communication (e.g., via electrical wiring 230) to the motor 300, such that the controller 302 can be used to control the motor 300. In other words, the controller 302 can cause the motor 300 to cause the shaft 232 torotate, thereby causing the body 202 of the inertia disk 200 to rotate. For example, the controller 302 can determine that the spacecraft needs stabilization, and causes the motor 300 to start so that the body 202 of the inertia disk 200 rotates. The controller 302 can also determine the speed and / or length of time that the inertia disk 200 rotates based on feedback from the spacecraft.

[0055] In some examples, the controller 302 includes a printed circuit board assembly (PCBA). In some examples, the controller 302 can be positioned outside of (or external to) the enclosure 214. In some examples, the controller 302 can be positioned within (or internal to) the enclosure 214. In some examples, the enclosure 214 can include define sub- compartments 304 (e.g., sub-compartments 304a, 304b). In some examples, the controller 302 can be disposed within a second sub-compartment 304b that is separate from a first sub- compartment 304a that houses the inertia disk 200.

[0056] The power of the inertia disk 200 (e.g., body 202) is a function of the speed and torque command. In at least one example, at a maximum speed of approximately 3,000 RPM and a maximum torque of approximately 0.4 Newton-meters (Nm), the power of the shaft 232 is approximately 140 Watts (W). Thus, in some examples, the motor 300 is operable to provide approximately 140 W. In some examples, the maximum input power to the inertia disk 200 is between approximately 200 W and 250 W due to efficiency losses. Thus, in some examples, the motor 300 is operable to provide between approximately 200 W and approximately 250 W.

[0057] FIG. 4 illustrates a modal survey of the inertia disk 200 (also referred to as a reaction wheel). A modal survey is a Finite Element Analysis (FEA) that identifies the different bending modes of a structure as a function of natural frequencies. The modal survey illustrated in FIG. 4 was performed on a model of a reaction wheel (such as inertia disk 200 as illustrated for example in FIGS. 2A-2E). The modal structure, as illustrated in FIG. 4, exaggerates the identified bending modes to illustrate what these bending modes look like. For example, the angle is simply illustrating a bending mode that the reaction wheel may exhibit when subject to a specific frequency or disturbance of force.

[0058] FIG. 5 is a graph 500 illustrating ring height and diameter dimensions for an inertia disk (also referred to as a reaction wheel) to achieve target stiffness and moment of inertia, according to at least one example disclosed herein. Modeling was conducted to identify optimal design parameters needed to achieve target stiffness and moment of inertia. FIG. 5 illustrates ring height versus ring diameter for an aluminum reaction wheel. In the center of the graph 504, a targetarea 502 indicates various combinations of ring height and ring diameter for the reaction wheel to achieve the target stiffness and moment of inertia. The area 504 to the left of the target area 502 indicates combination of ring height and ring diameter that cannot produce the required moment of inertia. The area 506 to the right of the target area 502 indicates combinations of ring height and ring diameter that either cannot meet both the stiffness and moment of inertia requirements or that the geometry exceeds the minimum wall thickness of 3 millimeters (mm).

[0059] The embodiments shown and described above are only examples. Even though numerous characteristics and advantages of the present technology have been set forth in the foregoing description, together with details of the structure and function of the present disclosure, the disclosure is illustrative only, and changes may be made in the detail, especially in matters of shape, size and arrangement of the parts within the principles of the present disclosure to the full extent indicated by the broad general meaning of the terms used in the attached claims. It will therefore be appreciated that the embodiments described above may be modified within the scope of the appended claims.

Claims

CLAIMSWhat is claimed is:

1. An inertia disk for a spacecraft, the inertia disk comprising: a body including an inner portion and a lip, the inner portion being proximate a center of the body such that the inner portion spans from the center to the lip, the lip having a thickness greater than a thickness of the inner portion, wherein the body is at least partially made of aluminum.

2. The inertia disk of claim 1, wherein the aluminum is aluminum 7075-T7.

3. The inertia disk of claim 1, wherein the aluminum has a melting point of less than about 1000 degrees Celsius.

4. The inertia disk of claim 1, wherein the aluminum has a melting point between about 477 degrees Celsius and about 635 degrees Celsius.

5. The inertia disk of claim 1, wherein the body is operable to rotate about the center at a rotational speed to provide a predetermined momentum storage.

6. The inertia disk of claim 5, wherein the rotational speed is less than or equal to about 4000 rotations per minute.

7. A reaction wheel assembly for a spacecraft, the reaction wheel assembly comprising: an inertia disk including: a body including an inner portion and a lip, the inner portion being proximate a center of the body such that the inner portion spans from the center to the lip, the lip having a thickness greater than a thickness of the inner portion, wherein the body is at least partially made of aluminum; an enclosure operable to receive the inertia disk.

8. The reaction wheel assembly of claim 7, wherein the enclosure includes a vacuum chamber.

9. The reaction wheel assembly of claim 8, wherein the enclosure includes a vacuum fitting operable to be coupled with a vacuum pump.

10. The reaction wheel assembly of claim 8, wherein the enclosure is integrated with the vacuum chamber.

11. The reaction wheel assembly of claim 7, wherein the enclosure is at least partially made of aluminum.

12. The reaction wheel assembly of claim 7, wherein the aluminum is aluminum 7075-T7.

13. The reaction wheel assembly of claim 7, wherein the aluminum has a melting point of less than about 1000 degrees Celsius.

14. The reaction wheel assembly of claim 7, wherein the aluminum has a melting point between about 477 degrees Celsius and about 635 degrees Celsius.

15. The reaction wheel assembly of claim 7, wherein the body is operable to rotate about the center at a rotational speed to provide a predetermined momentum storage.

16. The reaction wheel assembly of claim 15, wherein the rotational speed is less than or equal to about 4000 rotations per minute.

17. The reaction wheel assembly of claim 7, further including a motor driver coupled with the center of the inertia disk such that rotation of the inertia disk causes the motor driver to rotate, wherein the motor driver is coupled with a motor so that the motor driver is operable to provide between 120 watts and about 300 watts.

18. The reaction wheel assembly of claim 17, wherein the motor driver is operable to provide between about 120 watts and about 300 watts.

19. A spacecraft comprising: a motor; a reaction wheel assembly including: an inertia disk including: a body including an inner portion and a lip, the inner portion being proximate a center of the body such that the inner portion spans from the center to the lip, the lip having a thickness greater than a thickness of the inner portion, wherein the body is at least partially made of aluminum; an enclosure operable to receive the inertia disk; and a motor driver coupled with the center of the inertia disk such that rotation of the inertia disk causes the motor driver to rotate, wherein the motor driver is coupled with the motor.

20. The spacecraft of claim 19, wherein the spacecraft includes a satellite.

Images