Communications: radio wave antennas – Antennas – Antenna components
Reexamination Certificate
2000-01-07
2001-11-27
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
Antenna components
C343S912000, C343S882000, C343S880000, C052S111000
Reexamination Certificate
active
06323827
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to perimeter truss structures for space borne antennas. In particular, the present invention relates to a deployable perimeter truss structure that folds into a compact volume for launch.
Industry has continued to improve space deployable reflector antennas for over 30 years. In the past, reflector antenna designs included a cantilever radial rib structure that supported an elastic shaped mesh. However, the radial rib structure required elaborate manufacturing, assembly, and alignment techniques, while the elastic mesh required a great deal of time, labor, and expense to attach. Because the rib structure had an inherently high weight, some past reflector antennas attempted to substitute a labyrinth of expensive caternaries including radial and cross cords to develop the density of control points required to shape the elastic mesh properly. A common difficulty associated with these past approaches, however, was that the resulting structures suffered from high weight and large stowed volume.
Space borne antennas, of course, reach orbit in a launch vehicle. Launch vehicles are extremely expensive, and any reduction in payload size and weight generally results in reduced launch cost. Past radial rib structures in particular, however, required very large volume inside a launch vehicle shroud. As a result, larger shrouds and larger launch vehicles were required.
The cost difference between launch vehicles can be enormous. As one example, a satellite launched by an ATLAS rocket incurs an approximately $185 million launch cost, while a satellite with an antenna that requires a larger TITAN launch vehicle incurs an approximately $400 million launch cost. Thus, although large antennas are generally desirable, the large stowed size and weight of such antennas, in the past, presented an enormous launch and manufacturing cost hurdle.
A need has long existed for a cost effective, lightweight, large aperture antenna support structure that folds into a compact volume for launch.
BRIEF SUMMARY OF THE INVENTION
One aspect of the present invention is a folding perimeter truss structure suitable for deployment in outer space.
Another aspect of the present invention is a folding perimeter truss structure that occupies less stowed volume than previous folding perimeter truss structures.
A further aspect of the present invention is a folding perimeter truss structure that uses translating joints to allow the truss structure to collapse into a volume much smaller than previous antenna structures.
One feature of the present invention is a folding perimeter truss structure that may be used to support traditional parabolic reflectors.
An attribute of the present invention is a folding perimeter truss structure that optionally includes extension spars above and below deployable bays to support a reflector surface.
Another attribute of the present invention is a folding perimeter truss reflector formed from individual bays sharing common structure, and in which certain bay support members are disposed on opposite sides of the truss reflector to allow the reflector to fold into a very compact volume without interference between the support members.
A preferred embodiment of the present invention provides a perimeter truss structure that may be used, for example, to support an RF reflector. The truss structure includes multiple deployed bays arranged in a ring. Each deployed bay includes a first upper horizontal support member attached to a first vertical support member and collapsible on a first joint translating on a second vertical support member, as well as a first lower horizontal support member attached to the second vertical support member and collapsible on a second joint translating on the first vertical support member.
The first and second vertical support members define a ring inside and a ring outside. The first upper horizontal support member is disposed on one ring side (e.g., the outside), while the first lower horizontal support member is disposed on the opposite ring side. The horizontal support members (which are oriented vertically in the stowed position) are thus non-interfering in the stowed position.
The truss structure optionally includes extension spars that extend out of the ring from above, below or both above and below the deployed bays when the ring is deployed. Adjacent bays may share support structure. Thus, for example, the perimeter truss structure may further include a third vertical support member, a second upper horizontal support member attached to the third vertical support member and collapsible on the first translating joint on the second vertical support member, as well as a second lower horizontal support member attached to the second vertical support member and collapsible on a third translating joint on the third vertical support member.
Each deployable bay may include supporting shear lines cross connected between the first upper horizontal support member and the first lower horizontal support member. Additionally, the truss structure preferably includes, for each bay, cross connected extension spar guy lines connected between the downwardly extending extension spars and the upper horizontal support members and cross connected extension spar guy lines connected between the upwardly extending extension spars and the lower horizontal support members.
A ring tension line is optionally provided around the inside of the ring to add additional stiffness to the truss structure. The tension line may be coupled to each of the deployable bays through a tension line truss structure. As an example, the tension line truss structure may form a pyramidal tension line truss structure connected to each bay.
Another preferred embodiment of the present invention provides a deployable perimeter truss structure. The deployable truss structure includes collapsed bays arranged in a ring, the collapsed bays including at least first, second, and third vertical support members. The vertical support members delineate a first bay and a second bay with the second vertical support member shared between the first bay and second bay.
The first bay includes a first upper horizontal support member attached to the first vertical support member and collapsed on a first joint translating on the second vertical support member as well as a first lower horizontal support member attached to the second vertical support member and collapsible on a second joint translating on the first vertical support member. Similarly, the second bay includes a second upper horizontal support member attached to the third vertical support member and collapsed on the first joint translating on the second vertical support member and a second lower horizontal support member attached to the second vertical support member and collapsed on a third joint translating on the third vertical support member.
In the deployable truss structure, the vertical support members define a ring inside and a ring outside. In the stowed position, the first and second upper horizontal support members are disposed in a vertical orientation. Similarly, the first and second lower horizontal support members are disposed in a vertical orientation opposite the first and second upper horizontal support members.
Multiple pulleys are employed that either ride with the joints or that are attached at ends of the vertical support members. A deployment cable runs over and under certain of the pulleys associated with the upper horizontal support members. A winder may then activate to pull in the deployment cable to lift the first joint into a deployed position. Because the collapsed bays are connected to one another around the ring, the winder action not only lifts the first joint into place, but also every other joint in the deployable truss structure. A redundant deployment cable may be provided for the lower horizontal support members.
In addition, redundant synchronization cables may be connected between the upper horizontal support members and the lower horizontal support members. The synchronizati
Gereau John C.
Gilger L. Dwight
Thomson Mark W.
Alemu Ephrem
McAndrews Held & Malloy Ltd.
TRW Inc.
Wong Don
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