Deployable Root Stiffness Mechanism for Tubular Slit Booms and Method for Increasing the Bending and Torsional Stiffness of a Tubular Slit Boom

Abstract

A deployable root stiffness mechanism and method increases the bending and torsional stiffness and strength of a tubular slit boom while allowing the slit boom to be flattened and rolled to a compact stowage volume. The slit booms may be flattened and rolled into a compact cylindrical stowage volume and once released, elastically and immediately deploy from the rolled stowed configuration to the final structural tube shape. An embodiment of the disclosed apparatus comprises a base member which is engaging contact with a bottom surface of the tubular slit boom and a reaction member which translates along the base member as the tubular slit boom transitions between the storage configuration to the deployed configuration and between the deployed configuration to the storage configuration. The reaction member provides an opposing reactive force to a load conveyed through the thin-wall construction of the boom. The method provides a means for increasing the bending and torsional stiffness and strength of a tubular slit boom by reacting external loads through the boom walls into a structure which generally conforms to the shape of the boom as it is deployed.

Claims

1. In a spacecraft having a tubular slit boom attached to the spacecraft by a structural interface, wherein the tubular slit boom comprises a thin-wall construction and the tubular slit boom has a storage configuration in which at least a first portion of the tubular slit boom is flattened and configured into a stowage volume and wherein the tubular slit boom has a deployed configuration in which at least a second portion of the tubular slit boom is extended to assume a tubular shape, a root stiffness mechanism comprises: a base member which is engaging contact with a bottom surface of the tubular slit boom; and a reaction member which provides an opposing reactive force to a load conveyed through the thin-wall construction of the tubular slit boom as the base member as the tubular slit boom transitions from the storage configuration to the deployed configuration.

2. The stiffness mechanism of claim 1 wherein the reaction member comprises a first side plate and a second side plate wherein an end of the tubular slit boom is captured between the first side plate and the second side plate as the tubular slit boom achieves the deployed configuration.

3. The stiffness mechanism of claim 2 wherein the first side plate and the second side plate are deployed into a position in which the first side plate and the second plate are tangentially disposed against the end of the tubular slit boom after the tubular slit boom achieves the deployed configuration.

4. The stiffness mechanism of claim 2 wherein a biasing mechanism urges the first side plate and the second side plate against the end of the tubular slit boom as the tubular slit boom transitions into the deployed configuration.

5. The stiffness mechanism of claim 2 wherein the first side plate and the second side plate each comprise a lower edge, wherein each lower edge is constrained with respect to the base member.

6. The stiffness mechanism of claim 5 wherein the base member comprises slots and the lower edge of the first side plate and the lower edge of the second side plate each comprise an outwardly extending pin, each outwardly extending pin disposed within a corresponding slot of the base member, each outwardly extending pin translatable within its corresponding slot.

7. The stiffness mechanism of claim 1 wherein the at least second portion of the tubular slit boom comprises a longitudinally extending strip attached to an inner wall of the tubular slit boom.

8. The stiffness mechanism of claim 1 wherein the reaction member translates long the base member as the tubular boom slit transitions from the storage configuration to the deployed configuration.

9. In a spacecraft having an onboard system wherein the onboard system has a stowage configuration and a deployment configuration and deployment of the onboard system is achieved, at least in part, by a tubular slit boom attached to the spacecraft by a structural interface, wherein the tubular slit boom comprises a thin-wall construction and has a storage configuration in which at least a first portion of the tubular slit boom is flattened and configured into a stowage volume and wherein the tubular slit boom has a deployed configuration in which at least a second portion of the tubular slit boom is extended to assume a tubular shape, a method of increasing the bending and torsional stiffness of the tubular slit boom comprises the following steps: initiating deployment of the tubular slit boom so that the at least second portion boom transitions into the tubular shape; capturing an end of the tubular slit boom within a structure having a reaction member which provides an opposing reactive force to a load realized by the tubular slit boom during a transition of the onboard system from the stowage configuration into the deployment configuration; and completing deployment of the tubular slit tube boom into the deployed configuration, the end of the tubular slit boom remaining captured within the structure.

10. The method of claim 9 wherein the structure comprises a first side plate, a second side plate, and a base member wherein the end of the tubular slit boom is captured between the first side plate, the second side plate and the base member during a transition of the onboard system from the stowage configuration into the deployment configuration.

11. The method of claim 10 wherein the first side plate and the second side plate are deployed into a position in which the first side plate and the second plate are tangentially disposed against the end of the tubular slit boom after the tubular slit boom achieves the deployed configuration.

12. The method of claim 10 wherein a biasing mechanism urges the first side plate and the second side plate against the end of the tubular slit boom as the tubular slit boom transitions into the deployed configuration.

13. The method of claim 10 wherein the first side plate and the second side plate each comprise a lower edge, wherein each lower edge is constrained with respect to the base member.

14. The method of claim 13 wherein the base member comprises slots and the lower edge of the first side plate and the lower edge of the second side plate each comprise an outwardly extending pin, each outwardly extending pin disposed within a corresponding slot of the base member, each outwardly extending pin translatable within its corresponding slot.

15. The method of claim 9 wherein the at least second portion of the tubular slit boom comprises a longitudinally extending strip attached to an inner wall of the tubular slit boom.

16. The method of claim 9 wherein the reaction member translates long the base member as the tubular boom slit transitions from the storage configuration to the deployed configuration.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG. 1 depicts an example of a spacecraft having an onboard systemsolar panels in the case of this examplein which the onboard system is deployed by tubular slit booms.

[0017] FIG. 2 shows a perspective view of an embodiment of a fully deployed tubular slit boom.

[0018] FIG. 3 shows a perspective view of an embodiment of a partially deployed tubular slit boom.

[0019] FIG. 4 shows a detailed perspective view of an embodiment of the deployable root stiff mechanism in the deployed position.

[0020] FIG. 5 shows a series of three perspective views showing how an embodiment of the disclosed apparatus closes in preparation for stowed of the boom in a flattened and rolled configuration.

[0021] FIG. 6 shows a perspective view of an embodiment of a partially deployed tubular slit tube boom with an embodiment of the disclosed apparatus attached at the boom base.

[0022] FIG. 7 shows a perspective view of an embodiment of a near fully stowed deployed tubular slit boom with an embodiment of the disclosed apparatus attached at the boom base.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] Referring now to the Figures, FIG. 1 shows an example of a spacecraft 10 which deploys an onboard system, such as solar panels 12, which are deployed on tubular slit booms 101. FIG. 2 shows a perspective view of an embodiment of a fully deployed tubular slit boom 101. Tubular slit boom 101 is an elastically deployable, thin-walled, metal or composite reinforced tubular boom with a slit 102 along its length to allow the boom to be flattened and rolled from one end into a cylindrical stowage volume.

[0024] FIG. 3 shows a perspective view of an embodiment of a partially deployed tubular slit boom 101. The tip of the boom 101 has been flattened and rolled to achieve a cylindrical stowed boom segment 103. The slit 102 allows the boom 101 to be flattened and subsequently rolled back into a stowable configuration.

[0025] FIG. 4 shows a detailed perspective view of an embodiment of the deployable root stiffness mechanism 104. The root stiffness mechanism 104 greatly enhances the bending and torsional stiffness and strength of the deployed boom 101, while embodiments of the device will generally have the added advantage of stowing neatly and compactly behind the boom 101 as the boom is flattened and rolled into a compact cylindrical stowage volume such as generally depicted in FIG. 7. The root stiffness mechanism 104 comprises a base plate 105 which serves as the structural interface of the boom assembly to the spacecraft or other system level structural component.

[0026] The root stiff mechanism 104 may also comprise side plates 106 which interface the base plate 105 and the side walls of the boom 101. Boom attachment strips 107 may function as part of the system by helping to distribute the loads applied to the boom 101 into the side plates 106. The root stiff mechanism may also comprise biasing mechanism, such as spring elements 109 which may be attached, among other locations, to the lower edge of each side plate 106, there the spring elements 109 erect and preload the side plates as the boom 101 deploys from a flattened, rolled state, as generally depicted in FIG. 6. As indicated in FIG. 4, the lower edges of the side plates 106 are generally constrained with respect to base plate 105 as the boom 101 and root stiffness mechanism 104 are flattened during storage. Such constraint may be achieved by the side plates comprising pins 110 which translate within slots 108 of the base plate 105.

[0027] FIG. 5 shows a series of three perspective views showing how an embodiment of the root stiffness mechanism 104 stows neatly and compactly behind the boom 101 as the boom is stowed.

[0028] FIG. 6 shows a perspective view of an embodiment of a partially deployed tubular slit boom 101 with the root stiffness mechanism 104 attached at the boom base. The tip of the boom 101 has been flattened and rolled to achieve a cylindrical stowed boom segment 103.

[0029] FIG. 7 shows a perspective view of an embodiment of a near fully stowed deployed tubular slit boom 101 with the deployable root stiffness mechanism 104 attached at the boom base. The boom 101 has been flattened and rolled to achieve a cylindrical stowed boom segment 103. The roof stiffness mechanism 104 is fully collapsed achieving a low profile, compact, volume.

[0030] A method increasing the bending and torsional stiffness and strength of a tubular slit tube boom 101 is provided by embodiments of the disclosed root stiffness mechanism 104. This method comprises the steps of the reacting of external loads through the boom walls into a capturing structure, such as one having deploying side plates 106 and an associated base plate 105 as the boom is deployed, or other structural supports which provide the reacting of the external loads through the walls of the tubular slit tube boom 101. In this this method, a capturing structure generally conforms to the geometry of the tubular slit boom 101 as it changes from a stowed flat sheet structure in a rolled configuration to a deployed tubular structure. Generally, the capturing structure will have reaction plates, such as side plates 106, which, as the boom assumes the tubular structure, the reaction plates will be disposed against the outside wall of the boom, typically such that the reaction plates are tangential to the outside facing wall of the slit tube boom 101 when it achieves the deployed tubular structure.

[0031] While the above is a description of various embodiments of the present invention, further modifications may be employed without departing from the spirit and scope of the present invention. Thus the scope of the invention should not be limited according to these factors, but according to the following appended claims.