FIELD OF TECHNOLOGY

[0001] The present invention relates to deployable booms and in particular but not solely to an apparatus for deploying and in some embodiments selectively retracting a boom. Such booms may be implemented on spacecraft such as satellites and more particularly small satellites or nanosatellites, such as cube satellites (CubeSats). The boom may be utilised to deploy payloads such as optics or other sensors or may be utilised as part of other apparatuses.

BACKGROUND

[0002] Remote sensing, earth observation, and monitoring of satellites make up a significant portion of the missions that earth satellites undertake. These activities provide important data and images on the earth's environment and satellites. There is a need to continue to provide images and data for such missions.

[0003] There has been a big shift towards launching smaller satellites such as CubeSats into space for missions or operations. Such small satellites take up less space in a launch vehicle, meaning they are cheaper to launch, and multiple satellites can be launched in a single launch.

[0004] As such, there is an increasing need for satellite systems and instruments to fit into the confined space of a CubeSat.

[0005] Deployable booms may be used in orbit however to deploy payloads such as instruments away from the satellite. Deployable coilable booms are an example of extendible boom structures which may be used in situations in which low mass, a simple and reliable deployment mechanism, and a small storage volume are desirable. They may be utilised in spacecraft structures such as antennas, solar sails, and solar panels. These booms can also be used in terrestrial applications.

[0006] Deployable booms are usually coiled on a central hub and deploy much like a carpenter's tape. A variety of coilable booms with different deployed cross-sections have been developed to match various bending and torsional stiffness requirements.

[0007] Much of the early work in designing and modelling deployable coilable booms focused on isotropic materials. In recent years, booms manufactured using composite laminate materials, such as carbon fiber and glass fiber, have been developed due to their higher specific properties and design flexibility. However, the deployment process of such booms is commonly highly energetic and can become chaotic. Thus, complex mechanisms are required to control the deployment, adding to the system mass and risk of deployment failure.

[0008] A deployment failure mode that can occur is called 'blossoming', in which the boom unwinds and extends within the deployment mechanism. This can jam the mechanism and damage the boom or mechanism. As such, mechanisms are needed that closely control the boom and reduce the risks of blossoming.

SUMMARY

[0009] It is an object of the disclosure to provide an improved deployable boom apparatus which addresses or ameliorates one or more disadvantages or limitations associated with the prior art, or at least to provide the public with a useful choice.

[0010] Additionally or alternately, it may be an object of the disclosure to provide a spacecraft comprising one or more deployable boom apparatuses.

[0011] Additionally or alternatively, it may be an object of the disclosure to provide a payload deployment assembly that is optionally re-stowable, the payload deployment assembly including a boom having a payload interface and a boom deployment apparatus.

[0012] Additionally or alternatively, it may be an object of the disclosure to provide a reduced mass and/or volume deployment and stowage apparatus for a boom for a spacecraft.

[0013] Additionally or alternatively, it may be an object of the disclosure to provide a deployable boom apparatus which is capable of repeated deployments and retractions of a boom and is inherently stable against blossoming failure. The boom may be stable against blossoming failure during both deployment and during optional retraction of the boom. The boom may be intrinsically stable against blossoming failure during both deployment and retraction of the boom.

[0014] Additionally or alternatively, it may be an object of the disclosure to provide a deployable and retractable boom mechanism where a motor of the mechanism is driven only in a first direction during both a deployment and a retraction of the boom.

[0015] In a first aspect, the disclosure provides a deployable boom mechanism comprising: a boom drum and a boom windable thereon, the boom drum rotatable in a deployment direction to deploy the boom, a drive element drum and a drive element, wherein a first portion of the drive element is associated with the drive element drum and is windable thereon and a second portion of the drive element is associated with the boom drum and is windable thereon radially outside of boom, and an effector operable to rotate the drive element drum in a deployment direction to wind the drive element onto the drive element drum from the boom drum and so rotate the boom drum in its deployment direction and deploy the boom.

[0016] The boom comprises an elongate sheet which is flat across a width of the elongate sheet when wound about the boom drum.

[0017] The boom comprises an elongate sheet which is curved across its width when not wound about the boom drum.

[0018] The deployable boom mechanism further comprises supports located above and below the elongate sheet where the boom unwinds from the boom drum, and the supports act to support an unwound portion of the elongate sheet. [0019] At a distal end of the boom the elongate sheet is fixed in a curved shape across its width.

[0020] The drive element drum has a smaller diameter than the boom drum and the drive element is provided in the form of a spring windable between the drive element drum and the boom drum and biased towards being wound about the drive element drum, wherein the spring is the effector and is operable to rotate the drive element drum in its deployment direction and deploy the boom.

[0021] When the boom is in a retracted state the spring is at least partially wound about the boom drum.

[0022] The effector comprises a motor and the deployable boom mechanism further comprises a bias arrangement configured to rotationally bias the boom drum away from rotation in its deployment direction.

[0023] The mechanism is operable to rotate the boom drum in its deployment direction to deploy the boom and thereafter selectively to rotate the boom drum in a retraction direction opposite to its deployment direction to retract the boom.

[0024] The bias arrangement provides a substantially constant bias during rotation of the boom drum.

[0025] The bias arrangement comprises a clock spring.

[0026] The clock spring is located internally of the boom drum.

[0027] The bias arrangement comprises a spring motor having a spring wound between a major spool associated with the boom drum and a minor spool, the spring being biased to wind towards the minor spool.

[0028] A reversibly drivable gearing arrangement is provided between the motor and drive element drum, such that a) the boom may be deployed by energising the motor to overcome an influence of the bias arrangement and drive the drive element drum and rotate the boom drum in its deployment direction, and b) the boom may be retracted, under the influence of the bias arrangement and causing an unwinding of the drive element from the drive element drum, by a deenergization of the motor such that the influence of the bias arrangement is not overcome.

[0029] During a retraction of the boom the motor is energised to control the unwinding of the drive element from the drive element drum and maintain tension on the drive element between the drive element drum and the boom drum.

[0030] The mechanism is configured to passively retract the boom from a deployed state under the influence of the bias arrangement when the motor ceases to be driven.

[0031] During retraction of the boom the motor is completely de-energised, such that it does not provide active resistance to the unwinding of the drive element from the drive element drum. [0032] When the boom is deployed and electrical power is not provided to the motor, the boom is passively retracted under the influence of the bias arrangement.

[0033] A non-reversibly drivable gearing arrangement is provided between the motor and drive element drum, such that a) the boom may be deployed by energising the motor to drive the drive element drum and overcome the influence of the bias arrangement to rotate the boom drum in its deployment direction, but b) the boom does not passively retract when the motor is not energised to overcome the influence of the bias arrangement.

[0034] The non-reversibly driveable gearing arrangement comprises a worm drive gear set, and cylindrical gear of the worm drive gear set is associated with the motor.

[0035] When the boom is deployed and electrical power is not provided to the motor, the boom remains in its deployed state.

[0036] The effector comprises a spring motor, the spring motor configured when released to rotate the drive element drum to wind the drive element thereon and so rotate the boom drum and deploy the boom.

[0037] The spring motor comprises a spring wound between a minor spool associated with the drive element drum and a major spool, and when released the spring motor is configured to wind from the major spool onto the minor spool.

[0038] The deployable boom mechanism further comprises a bias arrangement configured to rotationally bias the boom drum away from rotation in its deployment direction and a drive arrangement configured to selectively drive major spool of the spring motor to wind the spring thereon and so unwind the drive element from the drive element drum and allow the retraction of the boom by its winding onto the boom drum under the influence of the bias arrangement.

[0039] The bias arrangement comprises a second spring motor, a major spool of which is associated with the boom drum.

[0040] Tension applied to the drive element by the drive element drum applies a radial pressure to the boom on the boom drum, constraining the boom from uncoiling from the boom drum.

[0041] A payload interface configured to mount a payload thereon is provided at a distal end of the boom, such that a deployment of the boom comprises a deployment of the payload.

[0042]

[0043] When the drive element is maximally wound onto the drive element drum, an angle subtended between a deployed portion of the boom and a portion of the drive element between the drive element drum and the boom drum is less than about 45 degrees. [0044] When the drive element is maximally wound onto the drive element drum, an angle subtended between a deployed portion of the boom and a portion of the drive element between the drive element drum and the boom drum is less than about 30 degrees.

[0045] When the drive element is maximally wound onto the drive element drum, an angle subtended between a deployed portion of the boom and a portion of the drive element between the drive element drum and the boom drum is less than about 20 degrees.

[0046] When the drive element is maximally wound onto the drive element drum, an angle subtended between a deployed portion of the boom and a portion of the drive element between the drive element drum and the boom drum is less than about 10 degrees.

[0047] When the drive element is maximally wound onto the drive element drum, an angle subtended between a deployed portion of the boom and a portion of the drive element between the drive element drum and the boom drum is from about 0 degrees to about 5 degrees.

[0048] When the drive element is maximally wound onto the drive element drum, the drive element between the boom drum and the drive element drum is substantially in contact with a deployed portion of the boom.

[0049] One of the first and second portions of the drive element is one end of the drive element, and the other of the first and second portions of the drive element is another end of the drive element.

[0050] In another aspect, the disclosure provides a deployable dragsail comprising a plurality of the deployable boom mechanisms of claim 1 or 2 and a dragsail, wherein the boom of each of the plurality of deployable boom mechanisms is associated with the dragsail such that a deployment of the boom of each of the deployable boom mechanisms deploys the dragsail.

[0051] The deployable dragsail is provided as a releasable payload appended to the boom of another deployable boom mechanism of claim 1 which is provided as part of a spacecraft.

[0052] In another aspect, the disclosure provides a deployable boom mechanism comprising: a first drum and a boom windable thereon, the boom drum rotatable in a deployment direction to deploy the boom, a second drum, and an effector, the effector windable between the first drum and the second drum and biased towards being wound onto the second drum, wherein the bias of the effector is operable to rotate the second drum in a deployment direction to unwind the effector and boom from the first drum and so deploy the boom.

[0053] In another aspect, the disclosure provides a deployable and retractable boom mechanism comprising: a boom drum and a boom windable thereon, the boom drum rotatable in a deployment direction to deploy the boom, a bias configured to resist the rotation of the boom drum in its deployment direction, a drive element drum and a drive element, wherein a first portion of the drive element is associated with the drive element drum and is windable thereon and a second portion of the drive element is associated with the boom drum and is windable thereon radially outside of boom, and an effector drivable in a first direction to both: a) rotate the drive element drum in its deployment direction to overcome the bias and so deploy the boom, and b) resistively be overcome by the bias and so retract the boom.

[0054] The effector comprises a motor and during the retraction of the boom a driving force of the motor is less than a force provided by the bias, and the drive element is unwound from the drive element drum and the boom and drive element re-wound together onto the boom drum.

[0055] One of the first and second portions of the drive element is one end of the drive element, and the other of the first and second portions of the drive element is another end of the drive element.

[0056] In another aspect, the disclosure provides a deployable and retractable boom mechanism comprising: a boom drum and a boom windable thereon, a bias configured to resist a deployment rotation of the boom drum, a drive element having a first portion windable with and radially outside of the boom on the boom drum and a second portion windable on a drive element drum, and a motor operable to be driven in one direction only during both a deployment of the boom and in which the drive element is wound onto the drive element drum and a retraction of the boom in which the drive element is unwound by the bias from the drive element drum.

[0057] The deployable boom mechanism as described herein for use as a component of a spacecraft and more particularly a satellite.

[0058] In another aspect, the disclosure provides a method of assembly of a satellite, the method comprising the steps of: providing a deployable boom mechanism as described herein, and assembling the deployable boom mechanism with a body of the satellite.

[0059] In another aspect, the disclosure provides a space launch vehicle comprising a satellite comprising a deployable boom mechanism as described herein.

[0060] In another aspect, the disclosure provides a method of controlling a deployable boom mechanism as described herein when provided as a component of a satellite in space, the method comprising the steps of: transmitting from Earth to the satellite a command, wherein the command comprises one or more of: a command to release a retainer retaining the deployable boom mechanism in a retracted state, a command to sever a burn wire retaining the deployable boom mechanism in a retracted state, a command to operate the effector to deploy the boom, and a command to operate the effector to retract the boom.

[0061] One of the first and second portions of the drive element is one end of the drive element, and the other of the first and second portions of the drive element is another end of the drive element.

[0062] In another aspect, the disclosure provides a deployable boom mechanism comprising: a boom drum and a boom windable thereon, a drive element drum, a drive element having a first portion windable about the drive element drum and a second portion co-windable with the boom about the boom drum, wherein a winding of the drive element onto the drive element drum rotates the boom drum and deploys the boom, and wherein when deployed, a deployed portion of the boom is located between the boom drum and the drive element drum.

[0063] One of the first and second portions of the drive element is one end of the drive element, and the other of the first and second portions of the drive element is another end of the drive element.

[0064] In another aspect, the disclosure provides a deployable boom mechanism that deploys a boom from a housing or apparatus, the boom stowable in position about a boom drum, the deployable boom mechanism comprising: a drive element co-coiled with the boom on the boom drum, where an end of the drive element is stowed on a ribbon drum positioned to align with the boom drum, a motor connected to the ribbon drum, an operation of the motor driving the deployment and controlling a stowing of the boom, and a constant torque spring that resists a deployment rotation of the boom drum, and so tensions the drive element during motor driven deployment of the boom.

[0065] During a stowing of the boom, the torque spring retracts the boom, while the motor is driven to provide resistance to the stowing of the boom by way of tension on the co-coiled drive element.

[0066] The drive element on the ribbon drum is located on an outside of the boom.

[0067] If motor power is lost during a deployment of the boom, the torque spring will passively retract the boom so that it returns to its stowed position.

[0068] The boom is made from a composite laminate material, such as carbon fiber or glass fiber.

[0069] A wire is co-coiled with or within the composite laminate material, to power a payload to be located at a distal end of the boom.

[0070] In another aspect, the disclosure provides a spacecraft comprising: a deployable elongate boom, driven by a deployable boom mechanism to extend out from the spacecraft and return in to the spacecraft, at least one camera located at a distal end of the boom, the camera controlled by a controller to take images of the spacecraft and its surrounds, in use in space, wherein the deployable boom mechanism comprises: a drive element co-coiled with the boom, where the drive element is stowable on a ribbon drum positioned to align with the boom drum, wherein a stowing of the co-coiled drive element on the ribbon drum causes the boom to deploy, a motor connected to the ribbon drum, the motor driving deployment and controlling stowage of the boom and drive element by operation of the ribbon drum, and a constant torque spring that resists a deployment rotation of the boom drum, hence tensioning the drive element during deployment.

[0071] During a stowing of the boom the torque spring retracts the boom, while the motor provides resistance to the retraction. [0072] The spacecraft is a satellite and more particularly a CubeSat.

[0073] In another aspect, the disclosure provides a method of deploying a boom from a spacecraft as herein described.

[0074] In another aspect the disclosure provides a deployable boom mechanism, that deploys a boom from a housing or apparatus, the boom stowed in position about a boom drum, the deployable boom mechanism comprising: a drive ribbon (or drive element) co-coiled with the boom, where the drive element is stowed on a ribbon drum positioned to align with the boom drum, causing the drive element to deploy with the boom and apply pressure on the boom, a motor connected to the ribbon drum, the motor driving and controlling deployment and stowage of the boom and drive element, a constant torque spring that resists the rotation of the ribbon drum, hence tensioning the drive element during deployment.

[0075] Preferably in use, during the stowing phase of the boom, the roles of the motor and spring are reversed such that the torque spring retracts the boom, while the motor provides resistance.

[0076] Preferably the drive element deploys on the outside of the boom.

[0077] Preferably if motor power is lost during a deployment of the boom the torque spring will passively retract the boom so that it returns to the stowed position.

[0078] Preferably the mechanism is for deploying the boom from a spacecraft, such as a satellite, and more particularly a CubeSat.

[0079] Preferably, the boom is made from a composite laminate material, such as carbon fiber or glass fiber.

[0080] Preferably a wire is co-coiled with the boom laminate material, to power the load at the distal end of the boom. In other configurations the wire may be embedded with or within the boom.

[0081] Preferably the boom is made from fiber reinforced polymer (FRP) composites.

[0082] In another aspect, the disclosure provides a spacecraft comprising: a deployable elongate boom, driven by a drive mechanism (or deployable boom mechanism) to extend out from the spacecraft and returning in to the spacecraft, at least one camera located at the distal end of the boom, that is controlled by a controller to take images of the spacecraft and its surrounds, in use in space, wherein the deployable boom mechanism comprises: a drive ribbon (or drive element) co-coiled with the boom, where the drive element is stowed on a ribbon drum positioned to align with the boom drum, causing the drive element to deploy with the boom and apply pressure on the boom, a motor connected to the ribbon drum, the motor driving and controlling deployment and stowage of the boom and drive element, a constant torque spring that resists the rotation of the ribbon drum, hence tensioning the drive element during deployment. [0083] Preferably in use, during the stowing phase of the boom, the roles of the motor and spring are reversed such that the torque spring retracts the boom, while the motor provides resistance.

[0084] Preferably the spacecraft is a satellite and more particularly a CubeSat.

[0085] In another aspect, the disclosure provides a method of deploying a boom from a spacecraft as herein described.

[0086] In another aspect, the disclosure a deployable boom mechanism, that deploys a boom from a housing or apparatus, the boom stowed in position about a boom drum, the deployable boom mechanism comprising: a drive ribbon co-coiled with the boom, where the drive ribbon is stowed on a ribbon drum positioned to align with the boom drum, causing the drive ribbon to deploy with the boom and apply pressure on the boom, a motor connected to the ribbon drum, the motor driving and controlling deployment and stowage of the boom and drive ribbon, a constant torque spring that resists the rotation of the ribbon drum, hence tensioning the drive ribbon during deployment.

[0087] Preferably in use, during the stowing phase of the boom, the roles of the motor and spring are reversed such that the torque spring retracts the boom, while the motor provides resistance.

[0088] Preferably the drive ribbon deploys on the outside of the boom.

[0089] Preferably if motor power is lost during a deployment of the boom the torque spring will passively retract the boom so that it returns to the stowed position.

[0090] Preferably the mechanism is deploying a boom from a spacecraft.

[0091] Preferably the spacecraft is a satellite.

[0092] More particularly, the satellite is a CubeSat.

[0093] Preferably, the boom is made from a composite laminate material, such as carbon fiber or glass fiber.

[0094] Preferably a wire is co-coiled with the boom laminate material, in order to power the load at the distal end of the boom.

[0095] Preferably the boom is made from fiber reinforced polymer (FRP) composites.

[0096] In another aspect, the disclosure provides a spacecraft comprising: a deployable elongate boom, driven by a drive mechanism to extend out from the spacecraft and returning in to the spacecraft, at least one camera located at the distal end of the boom, that is controlled by a controller to take images of the spacecraft and its surrounds, in use in space, wherein the drive mechanism comprises: a drive ribbon co-coiled with the boom, where the drive ribbon is stowed on a ribbon drum positioned to align with the boom drum, causing the drive ribbon to deploy with the boom and apply pressure on the boom, a motor connected to the ribbon drum, the motor driving and controlling deployment and stowage of the boom and drive ribbon, a constant torque spring that resists the rotation of the ribbon drum, hence tensioning the drive ribbon during deployment.

[0097] Preferably in use, during the stowing phase of the boom, the roles of the motor and spring are reversed such that the torque spring retracts the boom, while the motor provides resistance.

[0098] In another aspect , the disclosure provides a deployment mechanism for a boom, the mechanism comprising: a boom drum and a boom windable thereon, the boom drum rotatable in a boom drum deployment direction to deploy the boom; and a drive element drum and a drive element, wherein a first portion of the drive element is associated with the drive element drum and is windable thereon and a second portion of the drive element is associated with the boom drum and is windable thereon radially outside of the boom, the drive element drum being rotatable in a drive element drum deployment direction to wind the drive element onto the drive element drum from the boom drum and to rotate the boom drum in the deployment direction to deploy the boom.

[0099] The mechanism further comprises an effector operable to rotate the drive element.

[0100] In another aspect, the disclosure provides a mechanism for boom deployment comprising: a boom drum and a boom deployable with a rotation of the boom drum; and a drive element drum and a drive element associating rotation of the boom drum with rotation of the drive element drum.

[0101] As used herein the term "and/or" means "and" or "or", or both.

[0102] As used herein "(s)" following a noun means the plural and/or singular forms of the noun.

[0103] For the purpose of this specification, where method steps are described in sequence, the sequence does not necessarily mean that the steps are to be chronologically ordered in that sequence, unless there is no other logical manner of interpreting the sequence.

[0104] The term "comprising" as used in the specification and claims means "consisting at least in part of." When interpreting each statement in this specification that includes the term "comprising," features other than that or those prefaced by the term may also be present. Related terms "comprise" and "comprises" are to be interpreted in the same manner.

[0105] This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

[0106] To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims. The disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting.

[0107] Other aspects of the invention may become apparent from the following description which is given by way of example only and with reference to the accompanying drawings.

[0108] The present application claims priority to the provisional patent applications NZ 792506 filed 16 September 2022, and NZ 792557 filed 19 September 2022, the entirety of which are herein incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

[0109] Preferred embodiments of the invention will be described by way of example only and with reference to the drawings, in which:

[0110] Figure 1 A shows a spacecraft that may utilise the deployable boom mechanism.

[0111] Figure 1 B shows a close-up view of the spacecraft of Figure 1 A.

[0112] Figure 2 shows a configuration of the spacecraft of Figures 1 A and 1 B in which the boom is deployed, and a distal end of the boom includes a boom end assembly.

[0113] Figure 3 is a view of the deployable boom mechanism.

[0114] Figure 4 is a view of the deployable boom mechanism.

[0115] Figure 5 is a view of the deployable boom mechanism.

[0116] Figure 6 is a rear view of the deployable boom mechanism.

[0117] Figure 7 is a cross-sectional side view of the deployable boom mechanism taken through the section A-A of Figure 5 which bisects the drive element, showing the deployment rotational direction and the retraction rotational direction of both the boom drum and the drive element drum.

[0118] Figure 8 is a view of the deployable boom mechanism with the boom end assembly removed.

[0119] Figure 9 is a view of the boom end assembly.

[0120] Figure 10 is an angled bottom view of another configuration of the deployable boom mechanism in which the deployable boom mechanism includes a worm drive.

[0121] Figure 11 is a view of another configuration of a deployable boom mechanism.

[0122] Figure 12 is a view of another configuration of a deployable boom mechanism.

[0123] Figure 13 is a view of an application of the deployable boom mechanism for stereoscopic vision.

[0124] Figure 14 is a view of a deployable drag sail mechanism employing a configuration of the deployable boom mechanism.

[0125] Figure 15 is a view of a spacecraft having a deployable boom mechanism which is in its deployed state, and the distal end of the boom comprises a dragsail. DETAILED DESCRIPTION

[0126] The disclosure provides for various configurations of a deployable boom mechanism and various applications of such deployable boom mechanisms.

[0127] Figure 1 A shows a CubeSat spacecraft 10 on which a boom deployment mechanism (elsewhere deployable boom mechanism) according to the disclosure may be utilised. Figure 1 B shows a partial view of spacecraft 10. As seen in Figure 1 B the spacecraft 1 has dragsail 20, a deployable boom mechanism 100 to deploy the boom 110, and a camera assembly 270 as the payload 185 of the boom 110. Another section of the spacecraft 10 contains thermal sensors 255 and an imaging payload 260. The spacecraft 10 may include solar panels 30 for providing electrical power to the spacecraft.

[0128] A deployable boom mechanism 100 may include a flat elongate member (a boom) that is capable of being deployed from a housing or apparatus. In spacecraft applications, the housing or apparatus may be or be part of the spacecraft. The boom may be capable of holding or supporting a payload, such as a payload that is connected to and powered by electronics/a battery in the housing or apparatus. The housing encloses the boom in an undeployed state, preferably rolled into a coil. The deployment of the wound boom is controlled by a deployable boom mechanism.

[0129] In a preferred form, the boom 110 may be made from a carbon fibre material. The boom 110 may be made from a carbon fibre laminate material. The carbon fibre may be a reinforced polymer (CFRP) material. The carbon fibre may include a wire formed within it, to power the payload. The carbon fibre may include more than one wire formed within it, to power and/or communicate with the payload. In one preferred form the load is a camera or set of cameras fitted at the tip of the boom. When deployed the boom (and camera(s)) move away from the body of the spacecraft.

[0130] The deployable boom mechanism 100 may be operable to selectively deploy a boom 110. In the case of implementation on a spacecraft 10, a distal end 115 of the boom 110 when deployed may be spaced away from the spacecraft. Because the deployable boom mechanism 100 may deploy a boom from a retracted or stowed state within the spacecraft, the deployable boom mechanism may allow the corresponding deployment of a payload 185 that may be associated with the distal end 115 of the boom 110.

[0131] In some configurations the deployable boom mechanism may be operable once the boom has been deployed to retract the boom partially or fully to a retracted or stowed state within the spacecraft.

[0132] Figure 2 shows the spacecraft 10 of Figure 1 A where boom has been at least partially deployed so that the distal end 115 of the boom 110 is deployed from the spacecraft 10. The boom 110 used with the deployable boom mechanism 100, for the example a CubeSat spacecraft 10 application, may have a total length of about 2m. This may for example provide a deployable length of about 1 .8m, so that the payload can be placed about 1 .8m from the spacecraft. Limiting the deployment length may allow some length of the boom to remain on the boom drum to reduce the risk of overextension. Connected to the distal end 115) of the boom 110 is the payload 185. The payload may be, for example, at least one camera 270.

[0133] Two major challenges faced in the design of the deployment mechanism were electrically connecting the cameras on the tip of the boom with the electrical power system (EPS) and preventing the boom from blossoming during deployment or return.

[0134] Solving the challenge of a wired electrical connection had two principal problems. The first problem was to design a system that would allow the wires to be deployed and retracted freely with the boom. Given the long length of the boom and the limited space inside the spacecraft, the wire would either have to be co-coiled with the boom or stored on a separate spool or drum. Either option then raised the issue of maintaining an electrical connection between the stationary EPS and motor driver board and the rotating end of the wire. Co-coiling the wires with the boom was the preferred and chosen option to limit the number of moving parts and to make efficient use of the volume within the spacecraft. This is particularly a consideration in highly volume- constrained applications such as satellites and more particularly CubeSats. Combining the boom carbon fiber element with electrical wires is one option for co-coiling.

[0135] Preferably, the boom is bistable over the whole length (BOWL), which means that a restraining structure is not required to keep the boom on the boom drum, which is a different challenge from the phenomenon of blossoming. If the wires to connect the camera load with the EPS and on-board computer or otherwise a controller are combined with the boom length a cocoiled deployment becomes easier.

[0136] To maintain the electrical connection between the rotating proximal end of the boom on the boom drum and the stationary electronics elsewhere on the spacecraft, either slip rings and a clock spring ribbon cable arrangement may be utilised.

[0137] Addressing the second major challenge, prevention of blossoming of the boom, was achieved through the design of the deployable boom mechanism. Blossoming of deployable booms occurs during deployment when the end of the boom is resisted while the motor or other deployment effector continues to turn the boom drum. For example, blossoming could occur with the deployable boom mechanism 100 of Figures 3-5 if the movement of the boom end assembly 170 was restricted as the boom drum 120 rotates to deploy the boom 110. Continued rotation of the boom drum 120 in the deployment direction combined with a restriction of movement of a part of the boom 110 that is not wound on the boom drum 120 may cause the wound layers of the boom to unwind or unfurl about the boom drum 120, rather than unwinding away and projecting away from it. Such an unwinding or unfurling may result the boom 110 jamming the deployment mechanism or some other element of the spacecraft.

[0138] Typically, blossoming of a boom occurs in dragsail or solar sail mechanisms where the sail gets caught on surrounding structure or has difficulty unfolding, but it can also occur due to friction of the boom's supports. To mitigate blossoming, a solution that utilises the deployer mechanism has been designed to keep pressure on the outer surface of the boom during stowing and deployment. This pressure is applied by a drive element 130. In addition or alternatively, the deployable boom mechanism may be configured to maintain tension on the boom at least at the point at which the boom is wound onto the boom drum.

[0139] This solution involves the co-coiled drive element 130, that preferably includes with the boom 110 a constant torque spring or bias arrangement 150 attached to the boom drum 120. This is shown, for example, in Figures 3-5.

[0140] The position of the drive element drum underneath the boom 110, adjacent to the motor 140 (see for example Figure 5 or Figure 7), means that the drive element 130 is on the outside of the coiled deployable boom 110 when deployed. Therefore, putting tension on the drive element 130 applies a radial pressure to the boom 110 so that it is pressed on to the drum 1 . The motor 5 and constant torque spring work together to maintain tension in the drive element 130. During the deployment phase the motor 140 rotates the drive element drum's shaft while the constant torque spring resists this rotation and hence tensions the drive element 130. During the stowing phase the roles are reversed, the torque spring retracts the boom 110 while the motor 140 provides the resistance.

[0141] In various configurations, the motor 140 is connected only to the ribbon drum via the gearing system, whereas the boom drum is connected to the motor only through the drive element. The bias arrangement is connected directly to the boom drum.

[0142] The bias arrangement 150 may be any arrangement to bias the boom drum 120 away from rotation in its deployment direction 300, towards the retraction direction 301. The bias arrangement 150 may be a torque spring or spring motor, such as is illustrated in the configuration of Figures 3-5. Where the bias arrangement 150 is in the form of a torque spring, it may be configured to be a constant or substantially constant torque spring. Where the bias arrangement 150 is in the form of a torque spring it may also be referred to as a spring motor.

[0143] Where a torque spring or spring motor is utilised in a deployable boom mechanism it may preferably be configured to provide an at least substantially constant bias during the deployment and/or retraction of the boom.

[0144] The bias arrangement 150, such as a constant torque spring or spring motor illustrated in Figures 3-5, also has a secondary function. If power is lost during a deployment, causing the motor to be de-energised, the torque spring will passively retract the boom so that it returns to the stowed position while the electrical system is diagnosed and rebooted. If the boom remained deployed during such an event, then it would be harder for the control system of the spacecraft to reorientate the spacecraft to maximise battery recharging in a safe mode.

[0145] Figures 3 and 4 show further detail of a configuration of the deployable boom mechanism 100. The deployable boom mechanism 100 includes a boom 110. The boom 110 is able to be wound about a boom drum for storage and is able to be unwound from the boom drum 120 for deployment. As seen in Figure 3, the boom 110 is wound about the boom drum 120.

[0146] The drive element 130 may be utilised to rotate the boom drum 120 to deploy the boom 110. One end of the drive element 130 is associated with a drive element drum 135 and is windable thereon by rotation of the drive element drum 135.

[0147] In prior art satellites and space missions, either a passive payload is deployed, ora single deployment is made of an active payload. However, in at least some configurations the deployable boom of the present disclosure can extend (or deploy) and retract multiple times, so as to move the payload, for example an active camera payload, multiple times as needed.

[0148] In some preferred embodiments, a camera payload is oriented to look back at the housing or apparatus (but in preferred forms the spacecraft, and more particularly, a CubeSat) and deploy from a zenith face of the spacecraft, to enable the capture stereoscopic imagery and video of the CubeSat. The cameras themselves may be Raspberry Pi cameras, but other small or miniature cameras appropriate for the particular application as needed may be used.

[0149] Figure 3 shows an illustration of the drive mechanism or deployable boom mechanism 100 of the present invention that will deploy the boom 110. The drive mechanism includes a deployment drum 120, stiffening rods 190, boom 110, mounting plate 200, to which the drum is mounted, a stepper motor 140 and motor driver control board 210. At the tip (distal end) of the boom is the boom tip assembly 170, that includes the load (in this example, at least one camera). Elsewhere herein the drive mechanism 100 may be referred to as a deployable boom mechanism 100, the deployment drum 120 as a boom drum 120, the mounting plate 200 as a chassis 200, the stepper motor 140 may simply a motor 140, and the motor driver control board 210 as a controller 210, and the boom tip assembly 170 as a boom end assembly 170.

[0150] While described as stiffening rods 190, the parts 190 may additionally or alternatively perform other functions. For example, they provide a support for routing of cables.

[0151] As shown in Figure 3, the deployable boom mechanism 100 has a boom 110 which is wound about a boom drum 120. The boom 110 may be provided in the form of an elongate sheet, which as seen in Figure 3 is able to at least in part be wound about the boom drum 120. The boom has a first face 111 (illustrated in Figure 8) which is faces away from the boom drum when the boom is wound on it, and a second face 112 which faces the boom drum when the boom is wound on it. [0152] When wound onto the boom drum 120, the boom 110 may be flat across its width. Wound, or co-wound, with the boom 110 is a drive element 130. One end of the drive element 130 is associated with the boom 110 and/or boom drum 120. As seen in Figure 3 the drive element 130 is wound with the boom 110 on the boom drum 120 such that the drive element 130 is radially outside of the boom 110. The boom 110 and drive element 130 may be wound multiple times about the boom drum 120, but the drive element 130 will remain the outermost layer wound on the boom drum 120. As shown in Figure 3 the deployable boom mechanism 100 is configured so that the boom is in a retracted state.

[0153] In the retracted state the distal end of the boom 110 projects from the boom drum 120 and is associated with the boom end assembly 170. A payload 185 is associated with the boom end assembly 170 by a payload interface 180.

[0154] The deployable boom mechanism 100 is operable to deploy the boom 110 to a deployed state. In the deployed state the boom end assembly 170 and any payload 185 associated with it may be moved away from the remainder of the deployable boom mechanism 100. Where the deployable boom mechanism 100 is provided as part of a spacecraft, for example by mounting of a chassis 200 of the deployable boom mechanism to the spacecraft, the deployment of the boom 110 can operate to displace a payload 185 away from the body of the spacecraft.

[0155] The deployment of the boom 110 entails the unwinding of the boom 110 from the boom drum 120. The deployment of the boom 110 is affected by tension on the drive element 130. As previously described, the drive element 130 is wound on the boom drum 120 on top of the boom 110. One end of the drive element 130 may be connected to the boom drum and/or to the boom. The other end of the drive element is associated with and windable onto a drive element drum. By rotation of the drive element drum, the drive element 130 may be wound thereon. This winding onto the drive element drum increases tension on the drive element 130 and may as a result cause the drive element 130 to be unwound from the boom drum 120 as it is wound onto the drive element drum. The unwinding of the drive element 130 from the boom drum 120 causes a rotation of the boom drum 120. Because the drive element 130 and boom 110 are wound together in the same direction on the boom drum 120, the unwinding of the drive element 130 causes a simultaneous unwinding of the boom 110 from the boom drum. The unwound boom 110 may be caused to deploy outwardly of the remainder of the deployable boom mechanism, as will be described.

[0156] While respective ends of the drive element may be described as being associated with the boom and/or boom drum and drive element drum, it will be appreciated that the association may not be at the most distal ends of the drive element. The association may otherwise be characterised as being with a first portion and second portion respectively of the drive element.

[0157] In some configurations, the deployable boom mechanism 100 may be configured to deploy the boom 110 from its retracted state to its deployed state, without being configured to retract the boom from the deployed state. The boom 110 may be deployable under the influence of an effector, for example a motor 140. In other arrangements, the boom may be passively deployable.

[0158] In other configurations, the deployable boom mechanism 100 may be configured to both deploy the boom 110 from its retracted state to its deployed state, and then also to operate the boom back to the retracted state.

[0159] The operation of the deployable boom mechanism to deploy the boom 110 may be under the action of an effector. The effector may be configured to rotate the drive element drum on which the drive element is windable, therefore unwinding and deploying the boom 110.

[0160] Where booms are deployed from a wound state on a drum, the unwinding of the boom during deployment may introduce the potential blossoming, where the rate of deployment at the distal end of the boom does not match the rate of unwinding of the boom from the boom drum. Where this happens, the boom may become unfurled about the boom drum and may jam other parts of the deployment mechanism. At its worst, this may disable the boom from being either further deployed or being retracted.

[0161] The configuration of the deployable boom mechanism 100 where the drive element 130 is wound on top of the boom 110 about the boom drum may aid in preventing such a failure mode during deployment, as the tension on the drive element 130 may act to retain the boom 110 on the boom drum 120, preventing it from unfurling about the boom drum.

[0162] Figures 4 and 5 are further views of the deployable boom mechanism 100 of Figure 3. The deployable boom mechanism 100 can operate to deploy the boom 110 then also to selectively to retract the boom 110 and wind it back onto the boom drum 120. In Figure 4 the drive element 130 is shown wound on top of the boom 110 on the boom drum 120. As seen in Figure 5 the drive element 130 extends from the boom drum and is attached to the drive element drum 135. The effector operable to rotate the drive element drum 135 in a deployment direction to deploy the boom 110 is the motor 140. The motor 140 acts on the drive element drum 135 by a gearing arrangement 220. As illustrated in Figure 5 the gearing arrangement may be a set of spur gears. Operation of the motor 140 rotates the drive element drum 135 in its deployment direction through the gearing arrangement 220. As the drive element drum 135 rotates in its deployment direction, the drive element 130 is wound onto the drive element drum 135. Under sufficient driving force from the motor 140, the rotation of the drive element drum 135 in its deployment direction results in the rotation of the boom drum 120 as the drive element 130 is unwound from it and wound onto the drive element drum 135.

[0163] In other configurations the motor 140 may be arranged to directly drive the rotation of the drive element drum 135, without an intervening gearing arrangement 220. [0164] A bias arrangement 150 is provided to the deployable boom mechanism 100. As seen in Figures 4 and 5, the bias arrangement 150 is operable to bias the rotation of the boom drum 120. In the configuration of Figures 4 and 5, the bias arrangement 150 has a spring 151 which is windable between a major spool 160 and a minor spool 165. The major spool 160 is rotatable with the boom drum 120. The spring 151 is configured so that it is biased towards being wound onto the minor spool 165. The configuration of the bias arrangement 150 in Figures 4 and 5 may be referred to as a spring motor.

[0165] As the drive element 130 is wound onto the drive element drum 135 causing the boom drum 120 to rotate in its deployment direction, the spring 151 is wound from the minor spool 165 onto the major spool 160. In doing so, the spring 151 acts to resist the deployment rotation of the boom drum 120.

[0166] The bias arrangement 150 may be configured to provide an at least substantially constant bias against the rotation of the boom drum 120 in its deployment direction across the entire deployment of the boom 110.

[0167] It will be appreciated that the configuration of the spring may be varied such that the spring is biased towards being wound onto the major spool 160. In this case, the location of the major spool 160 and minor spool 165 may be switched.

[0168] While illustrated in Figure 4 and 5 as being a spring motor, the bias arrangement 150 may be provided in other forms. For example, the bias arrangement 150 may be a clock spring. The clock spring may be located inside of the boom drum.

[0169] Further detail of the operations of the drive element drum 135 and boom drum 120 during the deployment and optionally retraction of the boom 110 are now described with reference to Figure 7, which shows a cross-sectional view through the lines A-A of the rear view of the deployable boom mechanism 100 of Figure 6.

[0170] The cross-section of Figure 7 is taken through the drive element 130. The operation of the motor 140 through the gearing arrangement 220 may rotate the drive element drum 135 in the direction 311 , causing the drive element 130 to be wound onto the drive element drum 135, provided that the drive force provided by the motor 140 is sufficient to overcome the bias provided by the bias arrangement 150. The winding of the drive element 130 onto the drive element drum 135 causes the rotation of the boom drum 120 in its deployment direction 300. As the boom drum 120 rotates in the deployment direction 300 the boom 110 and drive element 130 are both unwound from the boom drum 120.

[0171] To enhance the effectiveness of the overwound drive element 130 at resisting blossoming failure of the boom during deployment, the boom drum 120 may be located so that an angle 302 subtended between the deployed portion of the boom 110 and the drive element 130 between the boom drum 120 and the drive element drum 135 may be minimised. The angle 302 as illustrated in Figure 7 may be less than 45 degrees, or about 30 degrees.

[0172] The deployable boom mechanism 100 may be configured so the angle 302 less than about 90 degrees. The deployable boom mechanism 100 may be configured so the angle 302 is less than about 45 degrees. The deployable boom mechanism may be configured so the angle 302 is less than about 30 degrees. The deployable boom mechanism may be configured so the angle from about 0 degrees to about 5 degrees when the drive element 130 is maximally wound onto the drive element drum 135.

[0173] In some configurations the deployable boom mechanism 100 is configured to optionally retract the boom after it has been deployed. The retraction of the boom may be conducted only under the driving influence of the bias arrangement 150. In some configurations the retraction of the boom may be conducted under the driving influence of the bias 150, while the motor 140 acts resistively to control the retraction of the boom.

[0174] During a retraction of the boom 110, the drive element drum 135 rotates in the direction 310, unwinding the drive element 130 from the drive element drum. Under the influence of the bias arrangement 150, the boom drum 120 then rotates in the retraction direction 301 , winding the boom 110 onto the boom drum and the drive element 130 also on to the boom drum, on top of the boom 110.

[0175] The winding of the drive element 130 on top of the boom 110 during retraction of the boom may aid in ensuring the boom is tightly re-wound onto the boom drum.

[0176] Where the deployable boom mechanism is able to retract the boom following its deployment, the potential for blossoming failure may be introduced by blossoming of the drive element 130. This failure mode may occur where the drive element drum 135 unwinds the drive element 130 faster than the bias arrangement 150 acts to wind the drive element 130 onto the boom drum 120. Should this relative difference in unwinding and re-winding of the drive element occur, the drive element could become jammed. This could jam the deployable boom mechanism against further retraction of the boom. It could also jam the deployable boom mechanism against later deployment of the boom.

[0177] The risk of blossoming failure of the drive element during retraction of the boom may be provided by ensuring that the rate of unwinding of the drive element 130 from the drive element drum 135 does not exceed the rate at which it is wound onto the boom drum 120.

[0178] In the configuration of Figure 7 this function may be provided by providing resistance to the unwinding rotation of the drive element drum 135 by the motor 140. For example, the motor 140 may be driven so that it resists but is overcome by the rotational force exerted on the boom drum 120 by the bias arrangement 150. [0179] By the described configuration a repeatably deployable and retractable boom may be provided, in which the risks of blossoming failure are ameliorated. The boom may be deployable and retractable by the active operation of an effector, for example the motor 140, in only one direction during both deployment and retraction.

[0180] When unwound from the boom drum 120, the boom 110 may be caused to project outwardly of the remainder of the deployable boom mechanism. When wound on the boom drum, the boom 110 may be flat across its width. As the boom 110 is unwound, assume a non-flat shape across its width in order to stiffen the boom 110.

[0181] The boom may be deformed so that it is not flat across its width. As illustrated in Figure 8, where the boom 110 deploys from the boom drum 120 a guide assembly 240 may be provided. The guide assembly may be located at one or both of the first face 111 and second face 112 of the boom 110.

[0182] As illustrated in Figure 8, the guide assembly 240 causes or allows the boom 110 to assume a concave shape across its width, similarly to a tape measure as it deploys. As shown in Figure 8 the deployable boom mechanism does not include a boom end assembly 170.

[0183] In some examples, the boom may at rest be flat across its width, and during deployment it may be caused to assume a concave shape by the guide assembly 240.

[0184] In other examples, the boom may at rest have a concave shape across its width and may be caused to be flat across its width when it is wound onto the boom drum 120, particularly under tension applied to the drive element 130. Particularly where the boom naturally assumes a concave shape when unwound from the boom drum, the guide assembly 240 may function to locate the proximal end of the deployed portion of the boom. This may increase the structural integrity of the deployed boom and any payload that depends from it.

[0185] The guide assembly 240 may include one or more sliding elements to help reduce friction between the boom 110 and the guide assembly 240 as the boom is deployed or retracted past the guide assembly 240. The sliding elements may for example be rollers. In other examples the sliding elements may additionally or alternatively be fixed elements configured to support the boom but allow low-resistance sliding of the boom across them.

[0186] Figure 9 shows a view of a boom end assembly 170 and a payload 175 connected to it. The boom end assembly 170 may be configured to maintain the deployed end of the boom 110 in its desired shape, for example the concave shape illustrated in Figure 8. To this end the boom end assembly 170 may include one or more boom attachment fixtures 171.

[0187] One or more burn wires may be provided to different components of the deployable boom mechanism 100 to ensure it remains in its retracted state until a spacecraft on which it may be utilised is in space and ready to deploy the boom. A burn wire loop 173 is shown as part of the boom end assembly 170. The burn wire loop may have a burn wire passed through it, to retain the boom end assembly 170 until after launch of the spacecraft.

[0188] To ensure that the boom end assembly is aligned with the remainder of the deployable boom mechanism during launch and when it is retracted after deployment, one or more alignment elements 176 may be provided between the boom end assembly 170 and another part of the deployable boom mechanism. For example, as illustrated in Figure 8 the chassis 200 includes a mating vee 172, which is able to receive an alignment element 176, thereby aligning horizontally the boom end assembly 170 and the remainder of the deployable boom mechanism 100.

[0189] As previously described, in some configurations the deployable boom mechanism 100 for the deployable boom 110 is driven by the motor 140. Preferably the motor has a single spur gear set 16 to step up the output torque. A constant torque spring is attached to the boom drum 120 so that the motor has to overcome the spring to deploy the boom 110. In contrast, during the stowing or retraction phase the motor 5 acts to control the movement of the boom so that it slows down against the torque of the spring.

[0190] An encoder may be attached to the minor spool 165 of the constant torque spring to provide deployment position data to a controller. The deployment position data may be calibrated at, for example, 6 ° per pulse, which may in some examples correspond to approximately 2 mm of extension of the boom 110 per pulse. The distance per pulse is variable throughout deployment and stowing operation due to the variation of active diameter of the minor spool 165 and major spool 160 of the spring.

[0191] A rapid-prototype development model of the deployer mechanism has been constructed as an initial proof of concept. In the prototype, the material of the drive element is a Kapton film that was preferably 25 pm thick. However, other appropriate materials can make up the ribbon, or other appropriate thicknesses. The constant torque spring was manufactured from 301 stainless steel and preferably provided a near-constant torque of 73 ± 7.3 mNm. With a 3:1 spur gear ratio combined with a further geometric gear ratio between the drive element drum and the boom drum diameters, the system has been tested to deploy using an off-the-shelf NEMA 8 stepper motor that is rated to 30 mNm. Prior to testing with the motor a deployment torque test was conducted to quantify the required deployment torque and, therefore, the margin with the geared system. Table 2 shows the results of the deployment torque tests. Critically, tests were conducted with and without the boom present on the boom drum. This was because the boom has, despite being bistable, a slight tendency to actively deploy due to the tip of the boom being in the stress-free configuration, which reduces the required deployment torque. With the amount of time the boom will be stowed it is likely to stress relieve, therefore, characterising the system without this assisting torque was important. The tests were conducted with a torque driver and an early development model.

Table 2: deployment tests of the deployable boom mechanism with and without the deployable boom present

[0192] With the motor attached, 25 deployment tests were conducted to a nominal working distance of 0.7 m. In addition, more challenging tests have been successfully conducted in which the boom was deployed against gravity, to increase the load on the motor.

[0193] As illustrated in Figures 3-5, 7, and 9, the gearing arrangement 220 between the motor 140 and the drive element drum 135 is a gearing arrangement that is able to be driven in either direction. More particularly, the gearing arrangement 220 of the deployable boom mechanism 100 of Figures 3-5, 7 and 9 is illustrated as a pair of spur gears. The spur gears may be driven by the motor 140 during deployment of the boom. Under normal operation, the spur gears may be driven during retraction by the bias arrangement 150, while resistance is provided by the motor 140. However, in the case of a power outage or other conditions where resistance is not provided by the motor 140, no resistance may be provided and the bias arrangement 150 may still tension the drive element and rotate the drive element drum 135 and spur gears.

[0194] Arrangements such as this where the deployable boom mechanism in the absence of power to the motor 140 will passively retract may be desirable as a fail-safe.

[0195] In other arrangements, it may be desirable that the boom does not passively retract in the absence of power to the motor 140. This configuration may be provided by a gearing arrangement 220 which is not passively driveable in one or both directions.

[0196] For example, the deployable boom mechanism 100 of Figure 10 has a gearing arrangement 220 that includes a worm gear set 221. The worm gear set 221 is configured so that the motor 140 can drive the rotation of the drive element drum 135, but the rotation of the drive element drum 135 cannot rotate on its own, without the operation of the motor 140. This arrangement may be desirable to provide a boom which can remain passively deployed, and which will not retract passively under the absence of power to the motor 140.

[0197] Where the effector is a motor and it is driven to deploy the boom, it may remain energised in order to hold the deployed position of the boom.

[0198] In other configurations, a locking mechanism may be provided to retain the boom in a deployed state without requiring the motor to remain energised.

[0199] While configurations of a deployable boom mechanism have been described here the boom is deployable under the driving action of a motor, such as the motor 140, other effectors may be utilised.

[0200] An example of a configuration utilising a non-motor effector 145 is shown in Figure 11. This configuration may be utilised where the boom is only needed to be deployed once and is not required to be retracted. This arrangement may provide a simplified and lighter weight deployable boom mechanism than that of other configurations, for example the configurations of Figures 3-9 which include a motor 140.

[0201] In Figure 11 the effector 145 that is provided to drive the deployment of the boom by rotating the boom is a spring motor. The spring motor has a spring 141 that is wound between a major spool 142 and a minor spool 143. As shown in Figure 11 , the spring 141 is biased towards being wound on the major spool 142. The minor spool 143 is associated with the drive element drum 135. The spring motor may be wound so that the spring 141 is wound onto the minor spool 143 and in this state the spring motor is associated with the deployable boom mechanism, with the boom 110 in its retracted state. The boom may be maintained in its retracted state until deployment is desired, for example by a burn wire or a mechanical stop which operates to prevent operation of the spring motor and more particularly the minor spool 143 of the spring motor in the configuration of Figure 11 .

[0202] When the restriction on the spring motor is released, the spring 141 may spool from the minor spool 143 to the major spool 142, and so cause the drive element 130 to be wound onto the drive element drum 135 and the boom 110 to be deployed.

[0203] A deployable boom mechanism 100 as described in relation to in Figure 11 may include a bias arrangement 150 that acts on the boom drum 120 to bias it against rotation in its deployment direction.

[0204] In other configurations to increase the simplicity and decrease the weight and/or volume of the deployable boom mechanism, the deployable boom mechanism as described in relation to Figure 11 may not include a bias arrangement that acts on the boom drum 120.

[0205] In such configurations a bias against rotation of the boom drum, to aid in preventing blossoming of the boom during deployment, may be provided by increasing the frictional resistance to the rotation of the boom drum. [0206] In other configurations, the components of a spring motor 145 may be integrated in place of the drive element and drive element drum in order to provide a further simplified deployable boom mechanism which is capable of one-way deployment of a boom. Figure 12 illustrates such a configuration.

[0207] As seen in Figure 12, the deployable boom mechanism 100 is simplified so that the effector that is operable to rotate the drive element drum is a spring motor 145. However, the spring 141 of the spring motor 145 is provided in the place of the drive element 130 of other configurations. The spring 141 is co-wound with the boom 110 about the boom drum 120. The other end of the spring 141 connected to and able to be wound about a minor spool 143, which takes the place of the drive element drum 135. In this arrangement the boom drum 120 performs the function of the major spool 142 of the spring motor 145. When the spring motor 145 is released, the bias of the spring 141 towards the minor spool 143 will cause it to be wound onto the minor spool and unwound from the boom drum 120, simultaneously deploying the boom 110.

[0208] The deployable boom mechanism may be used to deploy any desired payload. This may include payloads associated with the operation of the spacecraft that the deployable boom mechanism is part of, or operations associated with another spacecraft - for example as subsequently described in relation to Figure 15.

[0209] In one example, a camera payload 270 of Figure 9 may be associated with the boom of a deployable boom mechanism. The camera payload 270 of Figure 9 is configured to direct the field of view of the camera or cameras back at the spacecraft. The deployment of the boom may thus enable in-situ imagery to be obtained of the spacecraft, such as the spacecraft with earth in view. Such a camera payload 270 may additionally or alternatively be utilised for monitoring of the spacecraft, such as for monitoring active operations by it or for inspection to visually assess damage or faults.

[0210] The ability to deploy the payload away from the spacecraft, and optionally retract it back into it, may also be desirable for other types of payloads. For example, the payload may include one or more remote sensors. These remote sensors may include sensors the functioning of which is improved by separation from the spacecraft, for example magnetometer sensors or radio sensors.

[0211] Figure 13 shows another example of an application of the deployable boom mechanism. It may be desirable in various space operations to utilise stereoscopic vision, for example to give depth perception to a person conducting some task remotely using a spacecraft. Figure 13 illustrates a deployable boom mechanism 400. Two booms 410a and 410b are wound around a central boom drum 420. Two camera payloads 185a and 185b are provided at the distal ends of each of the booms 410a and 410b. While not shown, at least one or preferably two drive elements, drive element drums, and an effector may be provided. Similarly, a bias arrangement may be provided to bias the boom drum against its deployment rotation direction 300.

[0212] The camera payloads 185a and 185b may be arranged so that they have aligned fields of vision 401 a and 401 b. By the deployment of the booms 410a and 410b in the respective directions 402 and 403, the stereoscopic depth of the images from the two camera payloads 185a and 185b may be varied.

[0213] A deployable boom mechanism 400 may preferably be configured to be able to deploy and retract the booms. While it is exemplified by the use case of the deployable boom mechanism 400 but equally applies to other implementations of a deployable boom mechanism, the mechanism may be configured to only partially deploy and/or only partially retract. For example, the camera payloads 185a and 185b of Figure 13 may be partially deployed to obtain a desired stereoscopic perspective, then the perspective may be fine-tuned by successive further deployment increments and/or retraction increments.

[0214] While the boom and mechanism of some illustrated configurations are used to deploy cameras, this system could be used to deploy sensors, optical payloads, or other payloads.

[0215] An example of an application of the deployable boom mechanism is illustrated in Figure 14, which shows a mechanism 320 for deploying a dragsail, as part of a deployable dragsail 400.

[0216] The mechanism 320 combines multiple deployable booms and boom deployment mechanisms to provide for the deployment of a dragsail.

[0217] Each of the deployment mechanisms of the mechanism 320 are of the simplified form previously described in relation to the deployable boom mechanism 100 of Figure 12, where the drive element is provided as a spring, which is biased to wind from the boom drum onto a smaller drive element drum, which performs the role of the minor spool of a spring motor described elsewhere herein.

[0218] The mechanism 320 has a chassis 322 to which the other components of the mechanism are mounted. A central boom drum 335 is rotatably mounted to the chassis 322. Four booms 330 (330b-d are shown) are wound with each other about the boom drum 335. Wound on top of each of the four respective booms are four corresponding drive elements 323 (323a-c are shown). The outer ends of the drive elements 323 are each associated with a respective drive element drum 324 (324a-c are shown).

[0219] A dragsail (not shown) may be provided within the dragsail housing 340. As illustrated in Figure 14, the dragsail may be provided in four portions, one within each of the housing sections 341 (where 341 b and 341 c are shown). The corners of the dragsail may be connected to the distal ends of each of the booms 330. For example, the dragsail portion housed within the dragsail housing section 341 b may be associated with the boom 330b, and the dragsail portion housed within the housing section 341 c may be associated with the boom 330c.

[0220] The drive element drums 324 may be able to be driven to rotate to wind the respective drive elements onto them. For example, one or more motors may be provided to drive the rotation of the drive element drums.

[0221] In other configurations, the drive element drums 324 may be configured to passively rotate and deploy the booms 330 and thus the connected dragsail. To passively deploy the booms, the drive elements 323 may be provided as springs, such as the springs of a spring motor. The boom drum 335 acts as the major spool of the spring motor, while each drive element drum acts as the minor spools. A release element or mechanism, such as a burn wire, may be provided to retain the mechanism 320 in its non-deployed state. When this is released, the mechanism 320 may passively deploy each of the booms 330, so as to deploy an attached dragsail.

[0222] The deployable dragsail 400 may be retained in a non-deployed state until deployment is required. In the arrangement of Figure 14 the deployable dragsail 400 may be retained in the non-deployed state by a locking member which prevents rotation of the boom drum 335. A compression spring 350 is operable when it extends to cause the locking member to retract from its engagement with the boom drum, so that the boom drum may rotate, and the booms may be deployed. The compression spring 350 may be retained in its compressed state until deployment is required. For example, the compression spring 350 may be held in place by a release mechanism and/or a burn wire.

[0223] Figure 14 shows a deployable boom mechanism 100 where the boom 110 has been deployed. A payload 185 is provided at the distal end of the boom. As seen in Figure 14, the payload 185 is a mechanism 320 in combination with a dragsail. The deployable dragsail may be able to be deployed when the boom 110 is in its deployed state. Alternatively, the deployable boom mechanism 100 may be used for emplacing the deployable dragsail onto another spacecraft, for example a satellite that is to be deorbited.

[0224] Where the dragsail payload 185 is to be emplaced onto another spacecraft, the payload interface 180 at the distal end of the boom 110 may include a release mechanism for deploying the dragsail payload 185 from the boom. The operation of such a release mechanism may be controlled by a controller of the deployable boom mechanism 100 and/or by a controller of a spacecraft which includes the deployable boom mechanism 100.

[0225] The deployable boom mechanism of the disclosure may be utilised with a boom of any known configuration which is able to be wound about a drum and deployed therefrom.

[0226] While an example implementation of the deployable boom mechanism has been described as having a boom that when fully deployed extends approximately 2 m, it will be appreciated that the deployable boom mechanism is not limited to use with booms of this size and may be utilised in either shorter or longer applications, as required for the particular use case and as allowed for by available boom technologies.

[0227] For example, a carbon fibre laminate boom may be configured to provide a deployment length of about 5 m.

[0228] Although embodiments have been described with reference to a number of illustrative embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the preferred embodiments should be considered in a descriptive sense only and not for purposes of limitation, and also the technical scope of the invention is not limited to the embodiments. Furthermore, the present invention is defined not by the detailed description of the invention but by the appended claims, and all differences within the scope will be construed as being comprised in the present disclosure.

[0229] Many modifications will be apparent to those skilled in the art without departing from the scope of the present invention as herein described with reference to the accompanying drawings.