Mechanisms denoted restraint/ release/deployment-initiation (RRDI) devices have been invented to enable the rapid, reliable, one-time deployment of panels that have been hinged together and stowed compactly by folding them together at the hinges. Although the RRDI devices were originally intended for use in deploying the solar photovoltaic panels that generate electric power for a spacecraft, they are also suitable for deploying other, similarly hinged panel arrays (including solar photovoltaic panels) in terrestrial applications. The RRDI devices overcome the disadvantages (shock and the consequent potential for damage) of explosive release devices as well as the disadvantages (slowness and high power demand) of electrically actuated thermal release devices.
Figure 1 depicts an array of panels in the stowed and deployed states in the original spacecraft application. During stowage, the RRDI devices clamp the panels together, at their hinged edges, against brackets attached to the main body of the spacecraft. At the time of deployment, the RRDI devices cease to clamp the panels. The hinges are typically of a strain-energy type: they carry little load during stowage, but when the clamping forces are removed, they spring open from the folded condition to assist in deploying the panels.
Figure 2 presents an exploded view of an RRDI device. During stowage, the panels are stacked and clamped between the upper bracket and a base. The edge of each panel at the clamping location is fitted with a U-shaped bracket. Serrations on the U-shaped bracket of each panel mate with the serrations on the U-shaped bracket of the adjacent panel, base, or upper bracket; these serrations serve to keep the panels from shifting from their desired stowage position as long as they remain clamped.
The clamping force (compressive preload) applied by each RRDI device is applied by torquing the adjustment bolt. The outermost panel (see upper bracket) is held in place by a separation bolt, which is secured (preloaded) in the separation-nut assembly. The separation-nut assembly is a commercially available nonexplosive electromechanical device. At the time of deployment, the separation-nut assemblies of all the RRDI devices are electrically energized to make them release their separation bolts. Once the separation bolt has been released, strain energy accelerates the bolt into the bolt catcher, and the spring ferrule and coil spring assist in quickly withdrawing the separation bolt from the separation-nut housing. The spring ferrule and coil spring further insure that the separation bolt remains in the bolt catcher. The bolt catcher is basically a closed-end cylinder that contains a small piece of crushable material inside to absorb the kinetic energy of the bolt. A spring-loaded contact element (within the base) protrudes through the base and pushes the panels outward for positive deployment. A long leaf spring located on the side of the separation- nut housing acts as a bumper and guides the panel stack-up during deployment.
This work was done by Michael T. Izumi of TRW, Inc., for Goddard Space Flight Center.
This invention has been patented by NASA (U.S. Patent No. 5,810,296). Inquiries concerning nonexclusive or exclusive license for its commercial development should be addressed to
the Patent Counsel
Goddard Space Flight Center; (301) 286-7351.
Refer to GSC-13931.