Patent ID: 7922236

Claim:
A method of operating a volume-filling structure, comprising: sensing an impact event; and expanding the volume-filling structure from a non-expanded state to an expanded state upon the sensed impact event, wherein the volume-filling structure comprises an open celled material, a first end cap connected to one end of the open celled material and a second end cap connected to a second end of the open celled material, and an activation mechanism regulating expansion of said open celled material from said non-expanded state to said expanded state in response to an activation signal, wherein the activation mechanism comprises an actuator interfaced with the first and second end caps, wherein expanding the volume-filling structure comprises triggering the activation mechanism, wherein triggering the activation mechanism comprises an explosive discharge of a pyrotechnic device to force the second end cap from the first end cap and expand the open celled material, and wherein the pyrotechnic device is in operative communication with one or more tethers, wherein the one or more tethers have one end attached to the second end cap and another end attached to a movable mass, wherein explosive discharge of the pyrotechnic device moves the movable mass such that the one or more tethers force the second end cap from the first end cap and expands the open celled material.