A single-action discharge valve for discharging a vessel's contents. The valve has a valve body with a passage therethrough through which the contents are discharged, a frangible seal held within the valve body and sealing the passage while the seal is intact, and a solenoid including an armature moveable from a first to a second position. As the armature moves, pins or teeth impact and break the frangible seal. Magnets hold the armature in the first position until the solenoid is actuated. The armature is substantially exterior of the passage so that discharge is unimpeded. In one embodiment, the pins reciprocate radially when cammed by the armature and impact the sidewall of a frangible dome seal. In other embodiments, teeth on the armature, or pins in the armature's path, reciprocate parallel to the armature's movement and impact a frangible disk.