Aeronautics and astronautics – Spacecraft – Spacecraft formation – orbit – or interplanetary path
Reexamination Certificate
1999-02-18
2001-10-09
Swiatek, Robert P. (Department: 3643)
Aeronautics and astronautics
Spacecraft
Spacecraft formation, orbit, or interplanetary path
C244S173300
Reexamination Certificate
active
06299105
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to deployable structures and more particularly to a spacecraft body having a deployable structure held in a stowed state by a holding device which is responsive to an environmental circumstance and is operative to release the deployable structure after the holding device is exposed to the environmental circumstance for a preselected criterion.
Deployable structures such as solar arrays and antennas are frequently used in spacecraft applications where a compact structure is required during a first stage and is deployed to a larger size in a second stage. Typically the first stage occurs when the spacecraft is coupled to a launch vehicle during the launch stage where the spacecraft is confined to a compact space. The second stage occurs when the spacecraft decouples with the launch vehicle in the deployment stage and subsequently expands in size by deploying the spacecraft' deployable structures such as antennas, booms, sensors, solar panels, and the like.
During the launch stage, deployable structures are positioned in a stowed state and secured in that stowed state with a holding device which has sufficient holding force to prevent the deployable structure from deploying until the desired time. At the desired time, an electrical signal is typically sent to the holding device instructing the holding device to release the deployable structure.
Clamps, bolts and gimbals are typically used as the holding device where the clamp opens, the bolt explodes or the gimbal moves in response to the electrical signal. Typically, the electrical signal used to release the holding device is generated by a human located in a ground control unit and is sent to the spacecraft. The drawback in this type of a system is that it is dependent on the spacecraft having the ability to receive and correctly process the electrical signal. If the spacecraft is oriented such that the electrical signal cannot be received, or, if the receive system is not functioning properly, the spacecraft will not receive the electrical signal and will subsequently not release the deployable structure which can be fatal to the spacecraft mission. In the case of deployable solar array, the solar arrays cannot deploy and the spacecraft will not be able to recharge the batteries resulting in a dead spacecraft. In the case of an antenna, the antenna cannot deploy limiting the communications capability of the spacecraft.
One method known to address this drawback is to provide an on-board spacecraft processor which is programmed to generate the electronic signal at a preselected time and send that signal to the holding device. The holding device releases the deployable structure in response to the signal thereby negating the need for ground control. However, this type of system is dependent on the processor to generate the electronic signal at the appropriate time which is in turn dependent on the reliability of the components within the processor. The components or processor can become damaged or fail such that the electronic signal is not generated.
What is needed therefore is a holding device which would release at a preselected time free of dependence on a human generated or electronically generated signal.
SUMMARY OF THE INVENTION
The preceding and other shortcomings of the prior art are addressed and overcome by the present invention which provides, in a first aspect, a spacecraft comprising a deployable structure having a stowed state and a deployed state. A holding device is coupled to the deployable structure and holds the deployable structure in a stowed state during a first operative stage. The holding device is responsive to a preselected environmental circumstance present during a second operative phase. The holding device is operative to release the deployable structure after being exposed to the preselected circumstance for a preselected criterion. A deployment mechanism is operative to deploy the deployable structure after the holding device releases the deployable structure.
For a first aspect of the invention, the holding device is fabricated of a material or a plurality of materials which are responsive to a preselected environmental circumstance, such as a presence of atomic oxygen, radiation, temperature or thermal cycles which occurs in the second operative phase. Prior to exposure to the environmental circumstance, the holding device has sufficient holding strength to hold the deployable structure in the stowed state. Upon exposure to the preselected environmental circumstance for a preselected criterion, such as time, total dosage or a number of thermal cycles, the holding device loses said sufficient holding strength to hold the deployable structure in a non-deployed state thereby releasing the deployable structure.
For a second aspect of the invention, the holding device is comprised of an energy generating device and a releasable clamping mechanism. The energy generating device is responsive to a preselected environmental circumstance such that upon exposure to the preselected environmental circumstance for a preselected criterion, the energy generating device generates a preselected amount or level of energy. The releasable clamping mechanism is responsive to the energy generated by the energy generating device and is operative to release the deployable structure from the stowed state upon exposure to the energy.
REFERENCES:
patent: 3268184 (1966-08-01), Biggar et al.
patent: 5027892 (1991-07-01), Bannon et al.
patent: 5060888 (1991-10-01), Vezain et al.
Kaller Robert W.
Swiatek Robert P.
TRW Inc.
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