Spacecraft having a dual reflector holddown for deploying multiple reflectors in a single release event

A spacecraft having nested reflectors that are released and deployed during a single release event using one or more dual reflector holddowns. The nested reflectors are held in place prior to release by the holddowns and are released during the single release event. The nested reflectors are secured to the body of the spacecraft by hinges attached to respective reflector backup structures and are releasably secured to the body using the one or more dual reflector holddowns. The reflector backup structures are secured by reflector interface brackets of the respective holddowns. An exemplary holddown has a separable tubular housing that is longitudinally secured together between an end cap and a release device. A threaded shaft 28 extends through the tubular housing, the end cap and the release device. A retraction spring is disposed around the exterior of the housing. The reflector interface brackets are secured to the outer and inner housings that attach the plurality of reflectors to the holddown.

BACKGROUND
 The present invention relates generally to spacecraft, and more
 particularly, to a dual reflector holddown for use in supporting and
 deploying nested reflectors disposed on a spacecraft.
 The assignee of the present invention manufactures and deploys spacecraft
 that have reflectors (communication antennas) disposed on the spacecraft
 body that are used to reflect communication signals. Heretofore, nested
 reflectors have not been used on any spacecraft developed by the assignee
 of the present invention. Single reflectors are supported and released by
 commonly available holddowns. Part numbers E008080-01 and E028600-01
 manufactured by the assignee of the present invention are examples of such
 commonly available holddowns. However, it would be desirable to provide
 for the use and deployment of nested reflectors on spacecraft.
 Accordingly, it would be advantageous to have a dual reflector holddown for
 use in supporting and deploying nested reflectors disposed on a
 spacecraft.
 SUMMARY OF THE INVENTION
 The present invention provides for a spacecraft having nested reflectors
 that are released and deployed during a single release event. One or more
 dual reflector holddowns are provided that support and deploy the nested
 reflectors. The nested reflectors are held in place prior to release by
 the one or more dual reflector holddowns and then released using a ground
 command during the release event.
 The spacecraft has a body to which the nested reflectors are secured using
 the one or more dual reflector holddowns. Reflector backup structures are
 secured to rear surfaces of the reflectors. The reflector backup
 structures each comprise a generally triangular tubular structure
 connected to a hinge and to the rear surfaces of the respective
 reflectors. The reflector backup structures are secured to the dual
 reflector holddowns by means of reflector interface brackets that are part
 of the dual reflector holddowns located adjacent vertices of the
 triangular tubular structure. The dual reflector holddowns releasably
 secure the reflector backup structures to the body.
 An exemplary dual reflector holddown comprises a separable tubular housing
 which may include an outer housing, an outer insert, a middle insert, and
 inner housing and an inner insert longitudinally secured together, using a
 single (tensioned) rod. An end cap and a release device are disposed on
 opposite ends of the tubular housing. The rod extends axially through the
 end cap, the tubular housing and the release device. The rod is secured by
 a nut at the end cap and a ball retained by the release device. A
 retraction spring is disposed around the exterior of the housing adjacent
 to the end cap. Reflector interface brackets are secured to the housing
 that attach the plurality of reflectors to the holddown.
 The one or more dual reflector holddowns may be used to support the
 reflectors during launch and orbit raising of the spacecraft. The single
 release event separates components of the outer reflector holddown from
 the components of the inner reflector holddown, and components of the
 inner reflector holddown from interfaces on the spacecraft. The reflectors
 are then free for deployment.
 The various housings of the dual reflector holddown are mutually threaded
 and hence adjustable along the axis of the holddown. The dual reflector
 holddown also has three rotational degrees of freedom due to the
 construction of the interface brackets and the manner in which they are
 attached to their respective housings. Furthermore, the dual reflector
 holddown also has zero, one or two translational degrees of freedom due to
 the adjustable floating interfaces at the holddown attachments to the
 reflector backup structure.

DETAILED DESCRIPTION
 Referring to the drawing figures, FIG. 1 is a front view of an exemplary
 spacecraft 10 employing two dual reflector holddowns 20 in accordance with
 the principles of the present invention. The spacecraft 10 comprises a
 body 11 and one or more engines 12. The exemplary spacecraft 10 is shown
 having two nested reflectors 13, 14 (inboard and outboard reflectors 13,
 14) secured to the body 11 by means of the two dual reflector holddowns
 20. The two nested reflectors 13, 14 are released and deployed during a
 single release event.
 Inboard and outboard reflector backup structures 15, 16 are secured to rear
 surfaces of the respective reflectors 13, 14. The inboard reflector 13 is
 beneath the outer reflector 14 and is shown along with the hidden portion
 of the inboard reflector backup structure 15 by means of dashed lines. The
 inboard and outboard reflector backup structures 15, 16 each comprise a
 generally triangular tubular structure connected to a hinge 17 and to the
 rear surfaces of the respective reflectors 13, 14, respectively.
 The inboard and outboard reflector backup structures 15, 16 are secured to
 the body 11 by the respective hinges 17. The inboard and outboard
 reflector backup structures 15, 16 are also secured to the two dual
 reflector holddowns 20 by means of reflector interface brackets 21 that
 are part of the dual reflector holddowns 20 located adjacent vertices of
 the triangular tubular structure that are distal from the hinge 17.
 FIG. 2 is a side view of the spacecraft 10 shown in FIG. 1. FIG. 9 shows
 the inboard and outboard reflectors 13, 14 in their respective stowed
 positions (solid lines) prior to the release event, and in their
 respective deployed positions (dashed lines) after the release event. The
 curved arrows indicate motion of the reflector backup structures 15, 16
 and reflectors 13, 14 from their stowed positions to their deployed
 positions.
 The two dual reflector holddowns 20 each comprise two reflector interface
 brackets 21 (shown in phantom) that are respectively secured to the
 inboard and outboard reflector backup structures 15, 16. This is shown in
 more detail in FIG. 3, for example. Also, the two dual reflector holddowns
 20 are secured to the body 11 of the spacecraft 10 using respective
 attachment members 22.
 FIG. 3 is a perspective view of the dual reflector holddowns 20. FIG. 4
 shows a front view of one reflector interface bracket 21. FIGS. 5 and 6
 show side and front views of the dual reflector holddown 20. FIG. 7 is a
 cross-sectional side view of the dual reflector holddown 20 attached to
 one of the reflector backup structures 15, 16. FIG. 8 is an enlarged view
 of the interface between the reflector backup structures 15, 16 and the
 reflector interface bracket 21. FIG. 9 is an enlarged top view of the
 reflector interface bracket 21 shown in FIG. 4.
 As is shown in FIGS. 3, 5, 6 and 7, the dual reflector holddown 20
 comprises a separable tubular housing 30, which may be cylindrical, having
 an end cap 31 and a release device 40 disposed on respective ends thereof.
 The exemplary tubular housing 30 is comprised of an outer housing 23, an
 outer insert 24, a middle insert 25, and inner housing 26 and an inner
 insert 27. The housings 23, 26 and inserts 24, 25, 27 are threaded with
 internal and external threads to provide for axial adjustability, are
 secured to each other by means of a plurality of snap rings 35, and this
 assembly is longitudinally held together under compression by means of a
 threaded tensioned rod 28. The essence of the separable tubular housing 30
 is that its separable components separate upon initiation of the release
 event so that the reflector backup structures 15, 16 and reflectors 13, 14
 are free to deploy.
 The end cap 31 and release device 40 each have a central hole disposed
 therein. The threaded tensioned rod 28 extends through the end cap 31 and
 release device 40 and protrudes outside of the dual reflector holddown 20.
 The release device 40 is secured to the spacecraft 20 by means of the
 attachment member 22. A spring retaining nut 29 threaded over the threaded
 tensioned rod 28 retains a retraction spring 34 and end cap 31.
 As is shown in FIG. 7, the retraction spring 34 is disposed around the
 outermost portion of the exterior of the outer housing 23 which is
 retained between the end cap 31 and a retainer 39 and is secured by means
 of the spring retaining nut 29. Rhea inner end of the tensioned rod 28 is
 held by the release device 40. The release device 40 is actuated by means
 of a ground command.
 An outboard reflector-holddown separation interface 36 is formed at the
 juncture between the outer insert 24 and the middle insert 25. An inboard
 reflector-holddown separation interface 38 is formed at the juncture
 between the inner insert 27 and the attachment member 22.
 The outer and inner reflector interface brackets 21 are secured to the
 outer and inner housings 23, 26 respectively. Details of the outer and
 inner reflector interface brackets 21 are shown more clearly in FIGS. 3,
 4, 5 and 7. As is shown in FIGS. 3, 4, 5 and 7, the outer and inner
 reflector interface brackets 21 comprise a generally flat surfaced
 H-shaped member with a central opening therein. Outer ends of the surfaced
 H-shaped member have holes 43a therein that are used to secure the outer
 and inner reflector interface brackets 21 to the reflector backup
 structures 15, 16. The inboard and outboard reflector backup structures
 15, 16 may be secured to the reflector interface brackets 21 using a
 plurality of machine screws, for example.
 The outer and inner reflector interface brackets 21 comprise a bearing
 housing 43 which houses a spherical bearing 44 that is retained therein by
 means of a bearing retainer plate 45. The outer and inner reflector
 interface brackets 21 comprise a threaded shaft 42 that extends laterally
 outward from the surface of the housing 30. The H-shaped reflector
 interface brackets 21 are secured to the threaded shaft 42 by means of two
 locking nuts 47 on either side of the bearing 44 mounted on the reflector
 interface bracket 21.
 The position of each H-shaped reflector interface bracket 21 relative to
 the housing 30 is thus adjustable along the axis of the threaded shaft 42.
 The angular orientation of each H-shaped reflector interface bracket 21 is
 also adjustable because the spherical bearing 44 allows freedom for
 angular rotation. The radial boss 41 is respectively disposed on the outer
 and inner housings 23, 26 which secures the outer and inner reflector
 interface brackets 21 to the housing 30 by means of the threaded shafts
 42.
 The two nested reflectors 13, 14 are held in place prior to release by the
 dual reflector holddowns 20 and are released during a single release
 event. The functioning of the dual reflector holddowns 20 during the
 release event to deploy the reflectors 13, 14 is as follows.
 Referring to FIG. 8, it is an enlarged view of the interface between the
 reflector backup structures 15, 16 and a reflector interface bracket 21.
 The threaded shaft 42 is secured into a threaded interface 41a in a radial
 boss 41. The spherical bearing 44 is secured to the threaded shaft 42 by
 mean of the axial locating nuts 47. The spherical bearing 44 is thus
 adjustable along the length of the threaded shaft 42. By sizing the sleeve
 42a, the bearing 44 can slide back and forth on the sleeve 42a, therefore
 providing an axial degree of translational freedom. The reflector
 interface bracket 21 interfaces to the spherical bearing 44 by means of a
 slot 48 that allows the bearing 44 to slide relative to the bearing
 housing 43 (into and out of the plane of the drawing). The spherical
 bearing 44 allows three degrees of rotation which is not locked. The
 spherical bearing 44 provides for adjustment resulting from angular
 misalignment. Therefore, the holddown-to-reflector interface provides
 three rotational and two translational degrees of freedom.
 FIG. 9 is an enlarged top view of the reflector interface bracket 21 shown
 in FIG. 4. Two threaded set screws 51 extend through opposite sides of the
 reflector interface bracket 21 and are secured by set screw locking nuts
 52. These set screws 51 may be used to lock the bearing 44 to prohibit
 axial sliding, if required.
 In operation, the dual reflector holddown 20 is actuated by a ground
 command, which releases the (restrained) ball end of the tensioned rod 28
 secured by the release device 40. Upon release of the tensioned rod 28,
 the retraction spring 34 pulls the rod 28 out of the assembly and holds it
 behind the outboard reflector. Once the rod 28 is retracted, each
 reflector is free to be driven out using an electric motor and gear train
 mechanism designed into the hinge assembly. In essence, the hinge assembly
 acts as a motor. Therefore, using the ground command, the outboard
 reflector is driven out and positioned in its deployed position. Then, the
 inboard reflector is driven out to its deployed position using the other
 hinge and motor.
 In summary, the present invention provides for a holddown 20 for use in
 securing dual nested reflectors 13, 14. The nested reflectors 13, 14 are
 released using a single command and single release device. Components of
 the dual reflector holddown 20 are tensioned together using a single
 tensioned rod 28. The holddown-to-reflector interface provides three
 rotational and two translational degrees of freedom. The holddown 20 is
 adjustable in length by incorporating threaded tubes, or the like.
 Thus, a dual reflector holddown for use in supporting and deploying nested
 reflectors disposed on a spacecraft has been disclosed. It is to be
 understood that the described embodiment is merely illustrative of one of
 the many specific embodiments that represent applications of the
 principles of the present invention. Clearly, numerous and other
 arrangements can be readily devised by those skilled in the art without
 departing from the scope of the invention.