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    • 专利摘要:
    ABSTRACT The present invention relates to a thruster assembly for a spacecraft. Thethruster assembly comprises a first set of at least four thrusters, configured to providethrust forces in the Z direction of the spacecraft, wherein each thruster is configuredto provide an adjustable tilt angle relative the Z direction, such that an adjustablethree-axis torque can be created. The thruster assembly further comprises a secondset of at least three thrusters being configured to provide thrust force in the directionof the center of mass in +/-Y direction, +/-X direction, and -Z direction of thespacecraft. Publication figure: Fig. 1.
    公开号:SE1450438A1
    申请号:SE1450438
    申请日:2014-04-09
    公开日:2015-10-10
    发明作者:Camille Chasset
    申请人:Ohb Sweden Ab；
    IPC主号:
    专利说明:

    A THRUSTER ASSEMBLY FOR A SPACECRAFT TECHNICAL FIELD The present invention relates to a thruster assembly for a spacecraft, and inparticular the invention relates to a thruster assembly that provides control of sixdegrees of freedom to a spacecraft.
    BACKGROUND The interest in Active Debris Removal (ADR) missions in space has recentlyincreased significantly due to the ever increasing amount of debris in orbit around theearth. This debris constitutes a real danger for other missions and spacecraft (S/C).The ADR missions are complex and require more powerful attitude and orbit controlcompared to regular missions. A solution to this problem is to utilize a set of ReactionControl Thrusters (RCTs), providing the following functions: Three-axis orbit control capability. The S/C needs to be able to modify its orbitalong any axis for large orbit transfers (from the launch vehicle insertion orbitto the target orbit, and later on from the target orbit to the final disposal orbit) or for small orbit manoeuvres (rendezvous phases).
    Three-axis attitude control capability when the desired torque cannot behandled by Reaction Wheels (RWs). This situation occurs in particular: During large orbit transfers, During Angular Momentum Management (after Launch Vehicle separation, for RW off-loading, or in Safe Mode), ln case no RW are used at all (RCTs are then the only actuators used for attitude control).
    A complete set of thrusters needs to be defined and accommodated on the spacecraft in order to provide the desired 6-degrees-of-freedom (6-dof) capability.
    A known thruster configuration for ADR missions comprises 24 RCTs. ThreeRCTs are provided in the “corners” of the spacecraft _ This configuration poses anumber ofdisadvantages. First and foremost this configuration utilizes a largenumber of RCTs, resulting in high mass and cost penalties. Secondly, the RCTs arenot configured in cold-redundant pairs. lf any thruster fails, then the force and torquecapabilities are divided by a factor of two. Compared to the baseline solution, thismeans that the thrust level required of each thruster must be doubled. Once againthis adds costs and mass. Finally, such a thruster configuration is fully symmetric anddoes not take into account the specific force and torque demands in the different directions.
    Therefore, there exists a need for an improved thruster configuration that atleast obviates some of the above mentioned problems.
    SUMMARY lt is an object of exemplary embodiments of the invention to address at leastsome of the issues outlined above. This object and others are achieved by thethruster assembly according to the appended independent claims, and by theembodiments according to the dependent claims.
    An exemplary embodiment provide a thruster assembly for a spacecraftcomprising a first set of at least four thrusters. The first set of at least four thrusters isconfigured to provide thrust forces in the +Z direction of the spacecraft. Each thrusteris configured to provide an adjustable tilt angle relative the Z direction such that athree-axis adjustable torque can be created. The thruster assembly further comprisesa second set of at least three thrusters being configured to provide thrust force in thedirection of the center of mass in +/-Y direction, +/-X direction, and -Z direction of the spacecraft.
    An advantage of exemplary embodiments is that an improved thruster assembly is provided.
    An advantage of certain embodiments is that the number of RCTs can bereduced and that the torque and force capabilities better fit the force and torque demands.
    BRIEF DESCRIPTION OF THE DRAWINGS ln the following description of embodiments of the invention, reference will be made to the accompanying drawings of which: Fig. 1 is a schematic perspective drawing of a spacecraft illustrating anembodiment of the invention with 7 RCTs; Fig. 2 a) and b) are schematic drawings of the spacecraft in a XZ plane, illustrating force directions from the first set of thrusters; Fig. 3 is a is a schematic drawing of a spacecraft in a XZ plane, illustrating an embodiment of the invention with 7 RCTs; Fig. 4 is a schematic drawing of the spacecraft in a XZ plane, illustrating an embodiment of the invention with 7 RCTs; Fig. 5 is a is a schematic perspective drawing of the spacecraft illustrating anembodiment of the invention with 8 RCTs; Fig. 6 a)-c) are schematic drawings of the spacecraft in the XY plane, ZYplane, and XZ plane, respectively, illustrating an embodiment of the inventionwith 8 RCTs; Fig. 7 is a is a schematic perspective drawing of a spacecraft illustrating anembodiment of the invention with 9 RCTs; Fig. 8 a)-c) are schematic drawings of the spacecraft in the XY plane, ZYplane, and XZ plane, respectively, illustrating an embodiment of the inventionwith 9 RCTs; Fig. 9 is a schematic perspective drawing of a spacecraft illustrating anembodiment of the invention with 10 RCTs.
    DETAILED DESCRIPTION OF EMBODIMENTS The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodiments of theinvention are shown. This invention may, however be embodied in many differentforms and should not be construed as limited to the embodiments set forth herein;rather, these embodiments are provided so that this disclosure will be thorough andcomplete, and fully convey the scope of the invention to those skilled in the art. ln thedrawings, like reference signs refer to like elements. ln Fig. 1 an embodiment of the invention is disclosed. ln Fig. 1 a spacecraft(S/C), generally designated 100, is schematically illustrated as a box. The S/C has acenter of mass, designated CoM within the S/C 100. The center of mass CoM is alsoan origin of a coordinate system fixed to the S/C 100, with a Z axis 101 in the mainvelocity direction of the S/C 100, the X axis 102 pointing downwards, and the Y axis103 pointing out of the drawing.
    The S/C 100 comprises a first set of thrusters 104, comprising at least fourthrusters 105a, 105b, 105c, and 105d. The first set of thrusters 104 are arranged inthe XY plane and are mainly aligned with the Z direction so that it provides largetorque components about the +/-X and +/-Y directions.. The first set of thrusters 104are configured to be tiltable relative the Z axis 101 , such that a torque component inthe +/-Z direction can be generated. ln Fig. 2a the first set of thrusters are tilted such that thrust force components are generated in the X and Y directions which creates torque about the +/-Z direction.
    The thrust force from the first thruster 105a provides X and Y force components 108,the second thruster 105b provides X and Y force components 110, the third thruster105c provides X and Y force components 109, and the fourth thruster 105d providesX and Y force components 111. ln some cases it is preferable if no X force components are generated andthis is illustrated in Fig. 2b, wherein the first set of thrusters are tilted such that thrustforce components 112, 113, 114, 115 are created in the Y direction by thecorresponding thrusters 105a-d.
    Now with reference made to Fig. 1 again. The S/C 100 further comprises asecond set of thrusters 106. ln one embodiment the second set of thrusterscomprises three thrusters 107a, 107b, 107c being configured to provide thrust forcein the direction of the center of mass in +/-Y direction 102, +/-X direction 103, and -Zdirection 101 of the S/C 100. Each thruster of the second set of thrusters 106 pointstowards the center of mass CoM, whereby the attitude control is not disturbed upon activation.
    The first set of thrusters 104 and the second set of thrusters 106 providescontrol of the desired six degres of freedom (6-DOF). The first set of thrusters 104provides full control of the torque and provides force in the +Z direction. Since, thefirst set of thrusters does not provide control of 6-DOF it is necessary to provide thesecond set of thrusters in order to provide control of 6-DOF.
    An embodiment of a second set of thrusters 106 that provides control isfurther illustratated in Fig. 1. This embodiment of the invention utilizes a second set ofthree thrusters. A first thruster 107a of the second set 106 is arranged along the Zaxis on the upper panel of the spacecraft at a distance from the CoM. The thrustforce from this first thruster 107a is directed towards the CoM. A second thruster107b of the second set 106 is arranged along the bottom edge of the S/C 100 thatextends in the Z direction. The thrust force from the second thruster 107b is alsodirected towards the CoM. A third thruster 107c is arranged on the edge opposite thesecond thruster 107b, of the S/C 100. The thrust force from this third thruster 107calso is directed towards the CoM of the S/C 100. ln Fig. 3 a schematic drawing of the S/C 100 in the XY plane is disclosed.The thrust force components are angularly separated in the XY plane as can be seenin Fig. 3. ln Fig. 3 the second set of thrusters 106 are arranged such that the thrustforces from the thrusters 107a-c are symmetric in the XY plane, about the CoM. ln the embodiment disclosed in Fig. 3, the second set of three thrusters 106 may bearranged with an intermediate angle (d) being equal to 120 degrees in the XY plane. ln Fig. 4 a schematic drawing in the YZ plane of the S/C 100 is disclosed.The thruster force from the thruster 107a of the second set 106 is directed towardsthe CoM at an angle (ß). ln Fig. 5 another embodiment of a thruster assembly according to theinvention is disclosed. This embodiment of the invention utilizes a second set of fourthrusters. The S/C 100 comprises a first pair of thrusters having thrust forces 502,504arranged in the YZ plane at a distance from the CoM. The S/C 100 further comprisesa second pair of thrusters with thrust forces 501 ,503 arranged in the XZ plane at a distance from the CoM.
    The thrust forces 501-504 are further disclosed in Fig. 6 a) in which the XYplane of the S/C 100 is shown. ln Fig. 6 b) the YZ plane of the S/C 100 is disclosed.ln this plane the first pair of thruster forces 502, 504 each forms a first angle (ßx) to the Z axis. ln Fig. 6 c) the XZ plane of the S/C 100 is disclosed. ln this plane the secondpair of thruster forces 501, 503 each form a second angle (ßy) to the Z axis. ln one embodiment of the thruster assembly may the first angle (ßx) and the second angle (ßy) be equal.
    This embodiment has the advantage of decoupling the orbit control on the Xand Y axes. Orbit control about -Z can be performed by actuating 2 thrusters only. ln Fig. 7 an embodiment of the present invention is disclosed. This embodiment of the invention utilizes a second set of five thrusters. A first thruster isarranged to provide a thrust force 701 in the +Y direction towards the CoM, a secondthruster is arranged to provide a thrust force 702 in the +X direction towards theCoM, a third thruster is arranged to provide a thrust force 703 in the -X directiontowards the CoM, and a fourth thruster is arranged to provide a thrust force 704 in the -Y direction towards the COM. Finally, a fifth thruster is arranged to provide athrust force 705 in the -Z direction.
    This embodiment is further elucidated in Fig.8 a)-c) in which different planesand corresponding thrust forces are disclosed. ln Fig. 9 an embodiment of the invention is disclosed. This embodiment utilizes a second set of six reaction control thrusters. A first thruster in thisembodiment provides a thrust force 901 in the +Y direction, a second thrusterprovides a thrust force 902 in the +X direction, a third thruster provides a thrust force903 in the -X direction, and a fourth thruster provides a thrust force 904 in the -Ydirection. The remaining two thrusters are arranged along the +Z axis at positive andnegative Y coordinates, respectively, such that the corresponding thrust forces 905,906 are directed toward CoM.
    This embodiment provides a solution that has the advantage of not thrustingdirectly toward the Target in case of close operations with an approach along +Z(reduced plume impingement effects).
    Even if some embodiments of the present invention are perfectly adapted toActive Debris Removal missions, it is not the only case when it could be suitable. lt is also adapted to the following kinds of missions: Missions which include a rendezvous with uncooperative (rotating) targets.The target can be another satellite, an asteroid or any other type of body.
    Missions which includes both large orbital manoeuvres (orbit transfers) usinga large/ powerful orbit control thruster, and precise rendezvous /formation flyingorbit control. ln the drawings and the specification, there have been disclosed typicalpreferred embodiments of the invention and, although specific terms are employed,they are used in a generic and descriptive sense only and not for purposes oflimitation, the scope of the invention being set forth in the following claims.
    权利要求:
    Claims (1)
    [1] 1. _ A thruster assembly for a spacecraft (100), comprising: a first set (104) of at least four thrusters (105a-d), configured to providethrust forces in the Z direction of the spacecraft (100), wherein eachthruster is configured to provide an adjustable tilt angle relative the Z direction, such that a three-axis adjustable torque can be created; and wherein the thruster assembly comprises a second set (106) of at leastthree thrusters (107a-c) being configured to provide thrust force in thedirection of the center of mass (CoM) in +/-Y direction (102), +/-Xdirection (103), and -Z direction (101) of the spacecraft. _ A thruster assembly for a spacecraft (100) according to claim 1, wherein the second set (106) of thrusters are arranged such that the thrust forces aresymmetric in the XY plane, about the Z axis (101 )_ _ A thruster assembly according to claim 2, wherein the thrust force components of the second set (106) are angularly separated in the XY plane. _ A thruster assembly according to claim 3, wherein the second set (106) of thrusters comprises three thrusters (107a-c) arranged with an intermediate angle (d) being equal to 120 degrees in the XY plane. _ A thruster assembly according to claim 2, wherein the second set (106) is configured to provide a first pair of thrust forces pointing towards the CoM inthe ZY plane, each thrust force forming a first angle (ßx) with the Z axis. _ A thruster assembly according to claim 5, wherein the second set (106) further is configured to provide a second pair of thrust forces, pointing toward theCoM in the ZX plane forming a second angle (ßy) with the Z axis. _ A thruster assembly according to claim 6, wherein the first angle (ßx) and the second angle (ßy) are equal.
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    同族专利:
    公开号 | 公开日
    SE539081C2|2017-04-04|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
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    申请号 | 申请日 | 专利标题
    SE1450438A|SE539081C2|2014-04-09|2014-04-09|Propulsion device composition for a spacecraft|SE1450438A| SE539081C2|2014-04-09|2014-04-09|Propulsion device composition for a spacecraft|
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