The present disclosure relates to Hall-effect thrusters (HETs) for on-orbit spacecraft propulsion, and more particularly to a net magnetic dipole moment generated by the HET.
The disclosure provides a Hall-effect thruster assembly including a plurality of magnetic sources for creating a magnetic circuit. The plurality of magnetic sources are positioned between a first end and a second, opposite end of the Hall-effect thruster. The plurality of magnetic sources define a longitudinal axis extending through the first end and the second end. The first end is configured as a discharge end. A mount assembly is coupled to the second end. The mount assembly includes a body extending between a first side and a second side. The first side is coupled to the second end of the Hall-effect thruster. The body defines a cavity. The mount assembly further includes a receptacle positioned within the cavity. The mount assembly is further configured to secure the plurality of magnetic sources to a spacecraft. A plurality of discrete magnets are retained at least partially within the receptacle. The plurality of discrete magnets are positioned closer to the second side than the first side of the body. The plurality of discrete magnets are positioned relative to the plurality of magnetic sources by the mount assembly.
The disclosure provides, in another configuration, a Hall-effect thruster assembly including a plurality of magnetic sources for creating a magnetic circuit. The plurality of magnetic sources are positioned between a first end and a second, opposite end of the Hall-effect thruster. The plurality of magnetic sources define a longitudinal axis extending through the first end and the second end. The first end is configured as a discharge end. A mount assembly is coupled to the second end. The mount assembly is configured to secure the plurality of magnetic sources to a spacecraft. A magnetic element is supported by the mount assembly. The magnetic element is positioned relative to the plurality of magnetic sources by the mount assembly.
The disclosure provides, in yet another configuration, a mount assembly for a Hall-effect thruster. The Hall-effect thruster is operable to produce a thrust for spacecraft propulsion. The mount assembly includes a body configured to secure the Hall-effect thruster thereto. The body extends along a longitudinal axis between a first side and a second side. A magnetic element is supported by the body. The mount assembly is couplable to the Hall-effect thruster to position the magnetic element relative to a magnetic field generator for producing the thrust of the Hall-effect thruster.
The disclosure provides, in yet still another configuration, a mount assembly for a Hall-effect thruster. The mount assembly includes a body configured to secure the Hall-effect thruster thereto. The body extends along a longitudinal axis. At least one of a compensating magnetic element or a shield assembly is coupled to the body. The mount assembly is couplable to the Hall-effect thruster to position the at least one of the compensating magnetic element or the shield assembly relative to a plurality of magnetic sources within the Hall-effect thruster. During operation of the Hall-effect thruster, the plurality of magnetic sources create a first magnetic circuit having a magnetic dipole moment. During operation of the Hall-effect thruster, the at least one of the compensating magnetic element or the shield assembly is positioned to reduce an absolute value of the magnetic dipole moment of the Hall-effect thruster by a predetermined percentage in a direction along the longitudinal axis.
The disclosure provides, in another configuration, a Hall-effect thruster assembly including a plurality of magnetic sources for creating a magnetic circuit. The plurality of magnetic sources are positioned between a first end and a second, opposite end of the Hall-effect thruster. The first end is configured as a discharge end. A mount assembly is coupled to the second end. The mount assembly is configured to secure the Hall-effect thruster to a spacecraft. The Hall-effect thruster further includes a structure having a material selected from the group comprising of iron, ferrite, Mu-metal, Hyperco®, or other magnetic material having high permeability. The structure is supported by the mount assembly. The structure is positioned relative to the plurality of magnetic sources by the mount assembly.
The disclosure provides, in yet another configuration, a Hall-effect thruster assembly including a plurality of magnetic sources for creating a magnetic circuit. The plurality of magnetic sources is positioned between a first end and a second, opposite end of the Hall-effect thruster. The plurality of magnetic sources defines a longitudinal axis extending through the first end and the second end. The first end is configured as a discharge end. The magnetic circuit has a non-zero magnetic dipole moment. A mount assembly is coupled to the second end. The mount assembly is configured to secure the Hall-effect thruster to a spacecraft. The mount assembly includes a body having a cavity. A compensating magnetic element is received within the cavity. The compensating magnetic element is selectively positioned relative to the longitudinal axis and configured to reduce an absolute value of the non-zero magnetic dipole moment of the Hall-effect thruster by a predetermined percentage in a direction along the longitudinal axis.
Other aspects of the disclosure will become apparent by consideration of the detailed description and accompanying drawings.
Before any embodiments of the disclosure are explained in detail, it is to be understood that the disclosure is not limited in its application to the details of the formation and arrangement of components set forth in the following description or illustrated in the accompanying drawings. The disclosure is capable of supporting other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.
Referring to
As shown in
Because of the use of the magnetic field sources 40A-40C (e.g., electromagnetic coils or permanent magnets) and magnetic field flux guide material 30, the HET 10 produces a predetermined magnetic dipole moment (e.g., measured in Ampere square meter (A-m2)), which may now be referred to herein as the HET magnetic dipole moment. For example, the HET magnetic dipole moment may be between 2.5 A-m2 and 4.5 A-m2 (plus or minus (±)) in the direction of the longitudinal axis A. In some embodiments, the HET magnetic dipole moment is about 3.5 A-m2 (±). This moment may interact with other magnetic fields generated from other sources to produce a torque on the HET, and ultimately on a spacecraft on which the HET 10 is mounted. Other magnetic fields may include, for example, Earth's magnetic field, magnetic fields produced by other components on the spacecraft, etc. For example, when the spacecraft is flying in low Earth orbit, Earth's magnetic field may interact strongly with the magnetic field of the HET 10, thereby applying a significant torque to the spacecraft.
In addition, the magnetic field (magnetic dipole moment) of the HET 10 may be represented by a plurality of flux lines extending relative to the longitudinal axis A through the first and second ends 28, 24, respectively, of the HET 10. The flux lines (not shown) define an overall shape of the HET magnetic field. The flux lines can be affected by other magnetic fields generated from external magnetic sources proximate the HET 10.
The use of nulling magnets, shielding, or a combination of both in the HET 10 may reduce or achieve a near-zero net magnetic dipole moment of the HET 10 itself (e.g., ±0.5 A-m2) without affecting the actual magnetic circuit 56 of the magnetic field sources 40A, 40B and magnetic field flux guide material 30, thereby reducing the torque applied to the spacecraft by the other magnetic fields. For example, in some embodiments, the nulling magnets produce a compensating magnetic dipole moment, and a combination of the HET magnetic dipole moment and the compensating magnetic dipole moment results in a net magnetic dipole moment of the entire system of the HET 10. In other embodiments, the shielding or a combination of the nulling magnets and shielding inhibit or prevent the HET magnetic dipole moment from interacting with other magnetic dipole moments outside of the HET 10. Accordingly, the nulling magnets, shielding, or a combination of both in the HET 10 reduce an absolute value of the HET magnetic dipole moment in a direction along the longitudinal axis A. Furthermore, the nulling magnets, shielding, or a combination of both, may be positioned relative to the HET 10 to minimize or reduce the effect of the magnetic fields generated from the other sources on the overall shape of the magnetic field of the HET 10 proximate the first end 28 of the HET 10.
The mount assembly 160 includes a body 164 couplable to the HET 110. More specifically, the body 164 includes a first side 168 and a second side 170 spaced from the first side 168. A second end 124 of the HET 110 opposite the first end 128 is coupled to the first side 168 of the body 164. The mount assembly 160 is formed of non-magnetic material (e.g., aluminum). The mount assembly 160 is configured to support the HET 110 and is configured to securably retain the HET 110 to the spacecraft.
The mount assembly 160 includes a plurality of magnetic elements 172 (e.g., electromagnetic coils or permanent magnets) and a structure 174 configured to receive or contain the magnetic elements 172. In the illustrated embodiment, the plurality of magnetic elements 172 includes one element 172 positioned on the second side 170 of the body 164. The illustrated element 172 in one embodiment is a single, toroidal magnet radially spaced from the longitudinal axis 100A. In other embodiments, the plurality of magnetic elements 172 may be one or more discrete magnets positioned relative to the longitudinal axis 100A. These discrete magnetic elements may each be formed by an arc-shaped segment, rod-like shaped segment, box-like shaped segment, etc. Still further, the magnetic elements 172 may be positioned at select radial positions relative to the longitudinal axis 100A.
In the illustrated embodiment, the structure 174 has a shape matching with or complementary of the magnetic element 172. In particular, the illustrated structure 174 has a cylindrical shape with an outer diameter D1 and an inner diameter D2. The outer diameter D1 and the inner diameter D2 may be selected based on a diameter of the magnetic element 172. Additionally, the radial position of the magnetic element 172 relative to the longitudinal axis 100A is based on the diameter of the magnetic element 172. As such, the diameter may be selected based on positioning the magnetic element 172 radially closer to or farther from the longitudinal axis 100A.
In addition, the magnetic element 172 has a thickness T. The thickness T is the difference between the outer diameter D1 of the structure 174 and the inner diameter D2 of the structure 174. As such, the outer diameter D1 and the inner diameter D2 may also be selected based on the thickness T of the magnetic element 172.
Still further, the plurality of magnetic elements 172 may be one or more permanent magnets positioned radially relative to the longitudinal axis 100A. As such, the structure 174 may be configured to retain the one or more permanent magnets.
The plurality of magnetic elements 172 are collectively configured to produce an independent magnetic dipole moment and counteract the HET magnetic dipole moment produced by the magnetic field sources 140A-140C and the magnetic field flux guide material 130, without significantly disrupting the magnetic field within the discharge chamber 150 and the discharge area 158 (i.e., affecting the overall shape of the magnetic field or the orientation of the magnetic field flux lines proximate the first end 128). In particular, the magnitude and direction of the magnetic dipole moment of the magnetic elements 172 is selected for reducing the absolute value of the magnetic dipole moment of the HET 110 by a certain amount, one example of which may be a predetermined percentage (%) in a direction along the longitudinal axis 100A, which in some applications may result in a near-zero net magnetic dipole moment (A-m2) for the system. In other embodiments, the absolute value of the magnetic dipole moment of the HET 110 may be reduced by a set numerical value (e.g., value having unit A-m2). Accordingly, the plurality of magnetic elements 172 may be referred to as null magnetic elements 172 or compensating elements 172 configured to compensate for the HET magnetic dipole moment of the HET 110. The magnetic dipole moment of the magnetic elements 172 may be based on one or more of the following: the type of magnetic elements 172, the number of magnetic elements 172, the size (e.g., diameter, thickness) of the magnetic elements 172, and/or the radial position of the magnetic element 172 relative to the longitudinal axis 100A. The magnetic elements 172 produce the compensating magnetic dipole moment.
In some embodiments, the plurality of magnetic elements 172 is configured to reduce the HET magnetic dipole moment of the HET 110 by between forty and ninety-five percent. In other embodiments, the plurality of magnetic elements 172 is configured to reduce the HET magnetic dipole moment of the HET 110 by between fifty and ninety-five percent. In yet other embodiments, the plurality of magnetic elements 172 is configured to reduce the HET magnetic dipole moment of the HET 110 by between sixty and ninety-five percent. In yet still other embodiments, the plurality of magnetic elements 172 is configured to reduce the HET magnetic dipole moment of the HET 110 by between seventy and ninety-five percent. For example, in the illustrated embodiment, the magnetic element 172 is configured to reduce the HET magnetic dipole moment of the HET 110 from about 3.5 A-m2 (±) to about 0.4 A-m2 (±) such that the HET magnetic dipole moment is reduced by about ninety percent.
The mount assembly 460 is adjacent to the housing 420. The mount assembly 460 includes a body 464. The illustrated body 464 is positioned proximate a second end 424 of the HET 410, opposite the first end 428. In the illustrated embodiment, the body 464 is coupled directly or indirectly to the plate 432 of the HET 410 (e.g., such as by fasteners). For example, the plate 432 or the body 464 includes a plurality of apertures, each aperture configured to receive a respective bolt for coupling the plate 432 and the body 464 together. In other embodiments, the body 464 may be coupled to the HET 410 by other securement means such as welding, and/or may be coupled at other locations of the HET 410 (e.g., magnetic flux guide material, magnetic field sources, etc.). Accordingly, the second end 424 of the HET 410 is coupled to a first side 468 of the body 464.
With particular reference to
The mount assembly 460 (i.e., the body 464) is formed of non-magnetic material (e.g., aluminum). In addition, the mount assembly 460 is configured to support the HET 410 and is configured to securably retain the HET 410 to the spacecraft. The body 464 further includes a plurality of protrusions 498 extending away from the circumferential surface 496 proximate the second surface 494. The protrusions 498 are configured to securably retain the HET 410 to the spacecraft. In the illustrated embodiment, the protrusions 498 are integral with the body 464; however, in other embodiments, the protrusions 498 may be separate but secured to the body 464. Still further, in other embodiments, the mount assembly 460 may include other structure that support the protrusions 498 or replace the protrusions 498 (e.g., mounting ring, brackets, etc.) for securably retaining the HET 410 to the spacecraft.
With particular reference to
As shown in
As discussed with respect to the assembly of the first HET 110, the plurality of magnetic elements 472 of the HET 410 is configured to produce the compensating magnetic dipole moment. In particular, the magnitude and direction of the magnetic dipole moment of the magnetic elements 472 is selected for reducing the absolute value of the magnetic dipole moment of the HET 410 by a certain amount, one example of which may be a predetermined percentage (%) in a direction along the longitudinal axis 400A. In other words, the compensating magnetic dipole moment is configured to reduce the HET magnetic dipole moment toward the near-zero net magnetic dipole moment (A-m2). In other embodiments, the absolute value of the magnetic dipole moment of the HET 410 may be reduced by a set numerical value (e.g., value having unit A-m2). The plurality of magnetic elements 472 are configured to counteract the HET magnetic dipole moment produced by the magnetic field sources and the magnetic field flux guide material 430, without significantly affecting the magnetic field within the discharge chamber 450 and the discharge area 458 (i.e., affecting the overall shape of the magnetic field or the orientation of the magnetic field flux lines proximate the first end 428).
In operation, with reference to the embodiments of the first HET 110, and its corresponding example of an HET 410 as shown in
The mount assembly 260 includes a body 264 coupable to the magnetic field flux guide material 230/magnetic field sources 240A-240C. More specifically, the body 264 includes a first side 268 and a second side 270 spaced from the first side 268. A second end 224 of the HET 210 opposite the first end 228 is coupled to the first side 268 of the body 264. The mount assembly 260 is formed of non-magnetic material (e.g., aluminum). The mount assembly 260 is configured to support the HET 210 and is configured to securably retain the HET 210 to the spacecraft.
The HET assembly 212 further includes a shield assembly 276. In the illustrated embodiment, the shield assembly 276 includes a housing 280 having a first portion 284 and a second portion 286 extending axially therefrom relative to the longitudinal axis 200A. The first portion 284 has an inner surface 288 in facing relationship with a side 270 of the body 264. The first portion 284 further includes an outer surface 290. The second portion 286 radially surrounds the HET 210 and the mount assembly 260 relative to the longitudinal axis 200A. Although not shown, portions of the mount assembly 260 may extend through the first portion 284 of the housing 280 for coupling the mount assembly 260 to the spacecraft.
The housing 280 is formed by material having high permeability (i.e., soft magnetic material such as iron, ferrite, Mu-metal, Hyperco®, etc.). The housing 280 is configured to shield the magnetic field sources 240A-240C and the magnetic field flux guide material 230 for reducing the absolute value of the HET magnetic dipole moment of the HET 210 by a predetermined percentage (%) in a direction along the longitudinal axis 200A. In other words, the housing 280 is configured to reduce the HET magnetic dipole moment toward the near-zero net magnetic dipole moment (A-m2). More specifically, the housing 280 is configured to inhibit or reduce interaction of the magnetic field generated by the magnetic field sources 240A-240C and the magnetic field flux guide material 230 with other magnetic fields (e.g., Earth's magnetic field) without significantly affecting the magnetic field within the discharge chamber 250 and the discharge area 258 (i.e., affecting the overall shape of the magnetic field or the orientation of the magnetic field flux lines proximate the first end 228). Accordingly, the shield assembly 276 may be referred to as a shield configuration. The shielding capabilities of the shield assembly 276 may be based on one or more of the following: the type of material, the thickness of the first and/or second portions 284, 286, respectively, and/or the radial position of the second portion 286 relative to the longitudinal axis 200A.
In some embodiments, the shield assembly 276 is configured to reduce the HET magnetic dipole moment of the HET 210 by between thirty and seventy percent. In other embodiments, the shield assembly 276 is configured to reduce the HET magnetic dipole moment of the HET 210 by between forty and sixty percent. For example, the shield assembly 276 is configured to reduce the HET magnetic dipole moment of the HET 210 from about 3.5 A-m2 (±) to about 1.9 A-m2 (±) such that the HET magnetic dipole moment is reduced by about fifty percent.
In operation, with reference to
The mount assembly 360 includes a body 364 coupable to the magnetic field flux guide material 330/magnetic field sources 340A-340C. More specifically, the body 364 includes a first side 368 and a second side 370 spaced from the first side 368. A second end 324 of the HET 310 opposite the first end 328 is coupled to the first side 368 of the body 364. The mount assembly 360 is formed of non-magnetic material (e.g., aluminum). The mount assembly 360 is configured to support the HET 310 and is configured to securably retain the HET 310 to the spacecraft.
The mount assembly 360 includes a plurality of magnetic elements 372 (e.g., electromagnetic coils or permanent magnets). In the illustrated embodiment, the plurality of magnetic elements 372 includes one element 372 positioned proximate and spaced from the second side 370 of the body 364. The element 372 is a single, cylindrical magnet positioned concentrically with the longitudinal axis 300A. In other embodiments, the plurality of magnetic elements 372 may be one or more discrete magnets positioned at a selected radial location relative to the longitudinal axis 300A. These discrete magnetic elements may each be formed by an arc-shaped segment, rod-like shaped segment, box-like shaped segment, etc., positioned at predetermined radial positions relative to the longitudinal axis 300A. Still further, the plurality of magnetic elements 372 may be one or more electromagnetic coils positioned radially relative to the longitudinal axis 300A. The plurality of magnetic elements 372 is configured to produce a magnetic dipole moment.
The HET assembly 312 further includes a shield assembly 376. In the illustrated embodiment, the shield assembly 376 includes a housing 380 having a first portion 384 and a second portion 386 extending axially therefrom relative to the longitudinal axis 300A. The first portion 384 defines an inner surface 388 in facing relationship with the magnetic element 372. The first portion 384 further includes an outer surface 390 in facing relationship with the second side 370 of the body 364. The second portion 386 radially surrounds the magnetic element 372 relative to the longitudinal axis 300A. Although not shown, portions of the mount assembly 360 may extend around or through the shield assembly 376 for coupling the mount assembly 360 to the spacecraft.
The housing 380 is formed by material having high permeability (i.e., soft magnetic material such as iron, Mu-metal, Hyperco®, etc.). The magnitude and direction of the magnetic dipole moment of the plurality of magnetic elements 372 is selected for reducing the absolute value of the magnetic dipole moment of the HET 310 by a certain amount, one example of which may be a predetermined percentage (%), in a direction along the longitudinal axis 300A. In other embodiments, the absolute value of the magnetic dipole moment of the HET 310 may be reduced by a numerical value (e.g., value having units A-m2). Accordingly, the plurality of magnetic elements 372 may be referred to as null magnetic elements 372 or compensating elements 372 configured to compensate for the HET magnetic dipole moment of the HET 310. The housing 380 is configured to shield the HET 310 from the magnetic element 372 for reducing or constraining the effect of the compensating elements 372 on the magnetic field (i.e., the flux lines) proximate the first end 328 while facilitating the reduction of the absolute value of the HET magnetic dipole moment of the HET 310 by a predetermined percentage (%) in a direction along the longitudinal axis 300A. In other words, the compensating magnetic elements 372 are configured to reduce the HET magnetic dipole moment toward the near-zero net magnetic dipole moment (A-m2), while the housing 380 is configured to reduce or constrain the effect of the compensating magnetic elements 372 on the magnetic field of the HET 310 proximate the first end 328. The combination of the plurality of magnetic elements 372 and the shield assembly 376 is configured to counteract the HET magnetic dipole moment produced by the magnetic field sources 340A-340C and the magnetic field flux guide material 330, without significantly affecting the magnetic field within the discharge chamber 350 and the discharge area 358 (i.e., affecting the overall shape of the magnetic field or the orientation of the magnetic field flux lines proximate the first end 328).
In some embodiments, the plurality of magnetic elements 372/shield assembly 376 is configured to reduce the HET magnetic dipole moment of the HET 310 by between forty and ninety-nine percent. In other embodiments, the plurality of magnetic elements 372/shield assembly 376 is configured to reduce the HET magnetic dipole moment of the HET 310 by between fifty and ninety-nine percent. In yet other embodiments, the plurality of magnetic elements 372/shield assembly 376 is configured to reduce the HET magnetic dipole moment of the HET 310 by between sixty and ninety-nine percent. In yet still other embodiments, the plurality of magnetic elements 372/shield assembly 376 is configured to reduce the HET magnetic dipole moment of the HET 310 by between seventy and ninety-nine percent. For example, the magnetic elements 372/shield assembly 376 is configured to reduce the HET magnetic dipole moment of the HET 310 from about 3.5 A-m2 (±) to about 0.0156 A-m2 (±) such that the HET magnetic dipole moment is reduced by about ninety-eight percent.
In operation, with reference to
Thus, the disclosure provides, among other things, an HET assembly 112, 212, 312, 412 configured to have a near-zero net magnetic dipole moment without significantly affecting the magnetic field within a discharge chamber 150, 250, 350, 450 and the discharge area 158, 258, 358, 458, respectively. Specifically, the HET assembly 112, 212, 312, 412 includes compensating elements 172, 372 and/or a shield assembly 276, 376 for achieving the near-zero net magnetic dipole moment. The compensating elements 172, 372 and/or the shield assembly 276, 376 may reduce or inhibit the interaction between the HET magnetic dipole moment of the HET 110, 210, 310, 410 and magnetic dipole moments generated by other magnetic fields such that torque applied to a spacecraft may be lowered.
Although the disclosure has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the scope and spirit of one or more independent aspects of the disclosure as described.
Various features of the disclosure are set forth in the following claims.
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/US2020/026420 | 4/2/2020 | WO | 00 |