Aeronautics and astronautics – Spacecraft – With payload accommodation
Utility Patent
1999-06-21
2001-01-02
Poon, Peter M. (Department: 3644)
Aeronautics and astronautics
Spacecraft
With payload accommodation
Utility Patent
active
06168116
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to orbiting spacecraft with deployable lightweight panels. More particularly, the present invention relates to an automatically releasing shear tie device which couples the lightweight panels together into a rigid structure. The shear tie device automatically releases the panels to achieve their operating position upon reaching orbit.
2. Description of the Related Art
Orbit-type spacecraft are commonly equipped with a set of deployable panels, such as solar panels, radar panels, or antenna panels. During the launch phase of the spacecraft, the panels are folded over one another in an accordion-like fashion so that the panels form a compact stack. The stack of panels is then attached to the side wall of the spacecraft using a tie-down device that extends through the center of the stack. After the spacecraft reaches orbit, the stack of panels is released and unfolded so that the panels align edge-to-edge within a common plane.
The individual panels desirably have certain structural qualities. The panels are desirably thin and lightweight so that the panels do not overly increase the payload weight of the spacecraft or consume too much space within the spacecraft cargo bay. However, while it is highly desirably for the panels to be thin and lightweight, they should also be sufficiently strong to survive the rigorous loads that are often encountered during launch. The panels should also be thick enough to avoid coupling with the low-frequency excitation of the launch vehicle, which may cause the panels to buckle. Unfortunately, thinner and lighter panels have lower resonant frequencies and lower strengths which increases the likelihood of the panels coupling with the low-frequency excitation of the launch vehicle and deforming during launch.
The Applicant has observed that this problem may be overcome by binding or tieing the panels together during the launch phase so that the stack of panels functions as a single, thick structure that is capable of absorbing and withstanding the launch loads. There is therefore a need for a device that may be used to easily and reliably distribute the shear force between adjacent panels during launch. Desirably, the device automatically releases the panels upon reaching orbit with a reduced likelihood of jamming during such release.
SUMMARY OF THE INVENTION
The aforementioned needs are satisfied by the present invention which relates to a shear tie device for coupling together deployable panels on a satellite. The shear tie device provides a tight fitting shear tie through the launch phase of the spacecraft and automatically releases on orbit with little or no risk of jamming. The mechanism of release advantageously provides a smooth separating force between the panels to reduce the likelihood of harming the satellite during separation. Advantageously, the triggering mechanism for the release is a change in environmental or ambient conditions, such as the environmental state change that occurs as a result of achieving orbit.
One embodiment of the shear tie device comprises a post disposed on one panel. The post is initially secured within a ring of fingers located inside a cavity in an adjacent panel. This configuration is preferably maintained throughout the launch phase of the satellite. The fingers are preferably sufficiently stiff so that when the post pushes against the fingers in a transverse direction, the fingers will inhibit movement of the post and provide the requisite shear coupling between the panels. However, the fingers are sufficiently flexible so that when pressure is applied to an underside thereof, the fingers will bend up and away from the post, providing axial freedom for the post.
A partially deflated annular bladder resides in the cavity beneath the fingers. As the ambient pressure decreases to below a threshold value, the bladder preferably inflates and exerts a force against the underside of the fingers. Upon reaching orbit, the annular bladder preferably inflates sufficiently to cause the fingers to flex upward and away from the post. As the fingers flex away from the post, the post is free to move away from the cavity along the longitudinal axis of the post. Advantageously, the fingers also exert a separating force between the panels as the fingers flex upward. In an alternate embodiment of the device an annular wall separates the post from the annular bladder.
When the bladder expands, the annular wall prevents the bladder from contacting the post.
In one aspect of the invention, there is disclosed an apparatus for coupling a first panel to a second panel. The apparatus comprises at least one male member extending outwardly from a surface of the first panel and at least one female member extending into a surface of the second panel. The female member is positioned to receive the male member when the first panel is juxtaposed with the second panel. The apparatus additionally comprises at least one finger extending radially into the female member. The finger defines an aperture sized to receive the male member. A bladder is positioned within the female member. The bladder consumes a first volume when exposed to a first ambient pressure and a second volume when exposed to a second ambient pressure below the first ambient pressure. The bladder exerts a force on the finger sufficient to deform the finger and increase the size of the aperture when the bladder is at the second volume.
In another aspect of the invention, there is disclosed an apparatus for coupling a first panel to a second panel. The apparatus comprises at least one post on the first panel and at least one cavity on the second panel which is configured to receive the post. The apparatus additionally comprises a plurality of radial fingers coupled to the cavity. The radial fingers desirably have edges that form an aperture dimensioned to receive the post.
The apparatus additionally comprises means for deflecting at least one of the plurality of fingers to increase the size of the aperture.
In yet another aspect of the invention, there is disclosed a spacecraft, comprising a first panel defining a front surface and a second panel defining a front surface. The first and second panels are configured to move between a folded position wherein the front surfaces are juxtaposed and a deployed position wherein the first and second panels are aligned within a common plane. At least one male member is on the front surface of the first panel and at least one female member is on the front surface of the second panel. The female member defines an aperture configured to receive the male member therein when the first and second panels are in the deployed position. The size of the aperture increases as ambient pressure decreases.
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patent: 559911 (1896-05-01), Sheridan
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patent: 3458052 (1969-07-01), Kann
patent: 3537736 (1970-11-01), Kroopp
patent: 3672710 (1972-06-01), Kroopp
patent: 4540873 (1985-09-01), Kester
patent: 4988060 (1991-01-01), Janson et al.
patent: 1426294 (1966-04-01), None
patent: 197421 (1923-05-01), None
patent: 403207 (1966-06-01), None
Marks Geoffrey W.
Renshall James T.
Knobbe Martens Olson & Bear LLP
Palo Francis T.
Poon Peter M.
TRW Astro Aerospace
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