U.S. patent application number 15/366646 was filed with the patent office on 2017-03-23 for deployable root stiffness mechanism for tubular slit booms and method for increasing the bending and torsional stiffness of a tubular slit boom.
The applicant listed for this patent is Deployable Space Systems, Inc.. Invention is credited to Mark Douglas, Brian R. Spence, Stephen F. White.
Application Number | 20170081046 15/366646 |
Document ID | / |
Family ID | 58056763 |
Filed Date | 2017-03-23 |
United States Patent
Application |
20170081046 |
Kind Code |
A1 |
Spence; Brian R. ; et
al. |
March 23, 2017 |
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.
Inventors: |
Spence; Brian R.; (Solvang,
CA) ; White; Stephen F.; (Ventura, CA) ;
Douglas; Mark; (Santa Barbara, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Deployable Space Systems, Inc. |
Santa Barbara |
CA |
US |
|
|
Family ID: |
58056763 |
Appl. No.: |
15/366646 |
Filed: |
December 1, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14738860 |
Jun 13, 2015 |
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15366646 |
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62012574 |
Jun 16, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B64G 1/10 20130101; B64G
1/222 20130101; B64G 1/443 20130101; B64G 1/66 20130101 |
International
Class: |
B64G 1/22 20060101
B64G001/22; B64G 1/44 20060101 B64G001/44; B64G 1/10 20060101
B64G001/10 |
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
RELATED APPLICATIONS
[0001] This is a continuation of U.S. application Ser. No.
14/738,860 which was filed on Jun. 9, 2015, which claimed priority
to U.S. application Ser. No. 62/012574 which was filed on Jun. 16,
2014 for which applications these inventors claim domestic
priority, and which applications are incorporated in their
entirety.
BACKGROUND OF THE INVENTION
[0002] The present invention generally relates to deployable space
structures and booms and more specifically provides a mechanism
which provides structural support to tubular open-section boom
systems.
[0003] Spacecraft systems, which include earth and planetary
orbiting satellites and deep space probes, often incorporate
deployable systems which include deployable structures, deployable
solar arrays, deployable antennas, and other deployable subsystems.
These deployable systems must be configurable between a storage
configuration that enables the entire spacecraft system, inclusive
of the deployable structure, to fit within the small volume
constraints of a launch vehicle, and a deployed operable
configuration that enables the spacecraft to function in a desired
manner once in space.
[0004] Once the spacecraft is in space, the spacecraft is typically
configured for use by deploying an assembly of extendable
deployable components. For example, the assembly of extendable
components may comprise an extended solar panel or blanket array
that is used to convert collected solar radiation into electrical
energy. In another example, the assembly of extendable components
may comprise an extendable antenna assembly that is used to
transmit and receive electromagnetic signals to and from a
plurality of earth-based installations. In yet another example, the
assembly of extendable components may comprise an extendable boom
assembly that is used as a platform for a critical sensor, such as
a magnetometer or electric field sensor.
[0005] The deployable boom assemblies are required to compactly
stow into a small volume and then reliably deploy in a known
kinematic manner to form a rigid and strong appendage of the
spacecraft. The boom assemblies must also be lightweight so they
can be launched into space, and low cost so they can be affordable
to the program. Further complicating the design of these devices,
emerging space missions require deployable systems of increased
size and load-carrying capability while minimizing program
costs.
[0006] One type of deployable boom assembly comprises a metallic
tubular slit boom. Metallic tubular slit booms have been used in
the space industry to deploy sensors and in some cases as
structural elements within a larger deployable system. Due to the
open-section nature of the tubular slit boom accompanied by the
characteristic base mounting of the tube to the spacecraft, a
linear or near-linear pattern of fasteners opposite the tube slit
have been typically used for applications with lower loads and
orbital accelerations. Recently, slit booms of composite reinforced
construction have been developed that offer increases in deployment
force, torque and thermal stability. However, the thin-wall nature
of the metallic or composite reinforced slit tube and localized
bending of the tube forward of the conventional base mount limits
the bending load-carrying capability of the slit tube. In addition,
the standard boom mounting allows the free edges of the slit boom
to translate relative to each other when a torsional load is
applied to the boom tip significantly reducing the torsional
stiffness of the boom.
[0007] Various approaches have been utilized to address these
issues. At the system level, slit booms may be used effectively in
pairs so that they are loaded primarily in bending due to the low
torsional stiffness of each individual boom. For higher load
applications, open lattice, articulated or potentially telescoping
booms are used. These boom types are comprised of multiple and
complex deploying elements that are arranged in a repetitive manner
to form a boom of desired length. However, the open lattice,
articulated and telescoping boom technologies are high cost and
labor intensive to manufacture. They consist of a large number of
moving parts that may inherently reduce the deployment reliability
of the boom system. As increasingly advanced types of spacecraft
are being developed, it has become apparent that currently utilized
boom technologies are insufficient for meeting emerging
applications in terms of cost, reliability, stiffness and
strength.
SUMMARY OF THE INVENTION
[0008] Embodiments of the present invention address the problems
identified above. Embodiments of the present invention provide a
stowable and deployable root stiffness mechanism which maximizes
the structural performance of a slit boom.
[0009] Embodiments of the present invention will provide a
deployable mechanism which captures the base of the rollout boom
during deployment as the rollout boom transitions from a flat
rolled configuration to an extended tubular configuration. An
embodiment of the root stiffness mechanism may comprise: (1) a
baseplate that serves as a structural interface of the boom
assembly to the spacecraft or other system level structural
component; (2) side plates that interface both the base plate and
boom side walls; (3) boom attachment strips that help distribute
the loads applied to the boom into the side plates; and (4) spring
elements, or other biasing mechanisms, attached to the lower edge
of each side plate which elements erect and preload the side plates
as the boom deploys from a flattened, rolled state to a tubular
state.
[0010] In one embodiment, the base plate may have integral slotted
features that interface with the deployable side plates. The slit
boom may be attached to the base plate opposite the slit using a
series of fasteners arranged in a linear or near-linear pattern.
The lower edges of the side plates interface the base and are
constrained so as to translate within the slots of the base plate.
The upper surface of each side plate will typically contact the
outer surface of the slit boom at approximately mid-level. It is to
be appreciated that the base plate and side plates serve to conform
to the changing geometry of the slit boom as it deploys, thus
capturing and supporting the end of the slit boom.
[0011] In another embodiment, a boom attachment strip may contact
the inner surface of the slit boom directly opposite the
corresponding side plate. The boom attachment strip may be bonded
to the inner surface of the slit boom as required. Redundant
mechanical fasteners may pass through each side plate and
corresponding holes in the boom wall, threading into the boom
attachment strips to secure each side plate to the boom wall.
Springs, constant force or other, or other biasing mechanisms
(collectively referred to hereinafter simply as "springs") are
fixed to the base plate and apply a load to the lower edge of each
side plate. In this embodiment, with reference to the orientation
generally depicted in the figures, the springs deploy the side
plates to a vertical orientation (i.e., generally perpendicular to
the base plate) as the boom deploys, as a result of the boom's
stored strain energy, from a flattened state to a tubular state.
The springs preload each side plate against the end of the
corresponding base plate slot. If additional latching is desired,
other latching mechanisms may be employed, such as simple leaf
spring latches which may be attached to the base plate to preload
and latch the lower edge of each side plate once the side plate
reaches its deployed upright position.
[0012] The unique kinematics of the root stiffness mechanism allow
the side plates to stow neatly behind the slit boom as the boom is
flattened and rolled from the boom tip to a compact cylindrical
configuration. During boom deployment the side plates, activated by
the springs or other biasing mechanisms, achieve a vertical
orientation and preload against structural stopping mechanisms in
the base plate, such as slots.
[0013] The root stiffness mechanism greatly increases the bending
stiffness and strength of a slit boom over conventional boom
mounting methods by reacting external loads through the boom walls
into the side plates and the base plate. In addition, the root
stiffness mechanism increases the torsional stiffness of the boom
by resisting shearing of the boom free edges adjacent to the slot.
The root stiffness mechanism may be used in conjunction with any
number of closeout methods of the boom edges and boom tip to
further enhance the boom system structural performance.
[0014] An embodiment of the disclosed method comprises the steps of
increasing of the bending and torsional stiffness and strength of a
tubular slit boom by the reacting of external loads through the
boom walls into a capturing structure, such as one having deploying
side plates and an associated base plate as the boom is deployed,
or other structural supports which provide the reacting of the
external loads through the booms walls into a capturing structure,
where the capturing structure generally conforms to the geometry of
the tubular slit boom as it changes from a stowed flat sheet
structure in a rolled configuration to a deployed tubular
structure.
[0015] Emerging space missions require deployable systems of
increased size and load-carrying capability while minimizing
program costs. By implementing the root stiffness mechanism
described herein, metallic and composite reinforced tubular slit
booms may be used to meet stringent mission structural
requirements. Tubular slit booms offer cost savings, reduced
complexity and higher reliability over the existing open lattice,
articulated and telescoping boom technologies. An embodiment of the
disclosed base mechanism allows tubular slit booms to be used for
higher load and stiffness applications reducing costs and providing
structural enhancements over existing boom technologies.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 depicts an example of a spacecraft having an onboard
system--solar panels in the case of this example--in 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.
* * * * *