Patent Number: 047626623
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the sole FIGURE of the drawing, there is shown a trigger device 10 comprising a closed vessel 11 containing a piston 12 slideably mounted in the vessel to divide it into two compartments 14 and 16. A pressurized fluid, preferably an inert gas, is contained within each of the compartments at substantially the same pressure. A connecting rod 18 is operatively connected to the piston 12, its other end being connected to an actuator means 28 so that movement of the piston 12 will activate the actuating means. A piston seal 20 acts to minimize fluid leakage between compartments 14 and 16 during activation of piston 12. A bellows arrangement 22 prevents leakage of the fluid from the system while allowing movement of the rod 18. A pipe 24 serves as vent means communicating with compartment 14. The pipe is normally closed by having a sealed tip 26 at its outward end. EXAMPLE The following example is set forth to more fully illustrate the preferred embodiment of the invention, but it is not intended as a limitation thereof. The cylinder 11 may vary in size, a large cylinder being pressurized at a lower pressure than a small cylinder. The pressure inside this cylinder conveniently varies from 100 to 1000 psi. Typically for use in a nuclear space reactor 30 the cylinder 11 will be from 6 to 12 inches in length and have a diameter of about 2 to 4 inches. The connecting rod 18 will typically be about 3 ft in length. Helium or argon is particularly preferred for use as the pressurizing gas. The reactor is equipped with beryllium or beryllium oxide reflectors about 10 inches on its inside, 18 inches on its outside and 14 inches high. About five pipes 24 are distributed throughout various parts of the spacecraft. These pipes are all connected to compartment 14 and each has a rupturable tip 26 at the end thereof. Upon reentry into the earth's atmosphere, a temperature of about 1650.degree.-2200.degree. C. (3000.degree.-4000.degree. F.) is encountered. The stainless steel tips at the end of tube 24, which are located for reentry burnoff, melt and rupture at temperatures above about 1400.degree. C. (2600.degree. F). Thereby compartment 14 is opened to vacuum, and piston 16 and rod 18 move in the direction of the arrow because of the difference in pressure created between compartments 14 and 16. Conveniently the motion of the connecting rods either introduces a beryllium carbide poison into the reactor or moves the reflectors away from the nuclear core. Either of these events will render the reactor subcritical. Although the invention has been described in terms of a preferred embodiment and a specific illustration, it will be obvious to those of ordinary skill in the art that various modifications and adaptations of the invention are possible without departing from the spirit and scope of the invention as claimed hereinbelow. For example, the thermally activated trigger device is not limited for use with any particular nuclear space reactor, but it is clear that the invention has applications in a wide variety of nuclear space reactors such as those useful for weather observation, communications, and surveillance, as well as for other apparatus and process applications.