A shock tube apparatus may include a plenum to hold a volume of gas. The plenum may include a hollow chamber having a first end and a second end located opposite one another along a longitudinal axis, the first end of the chamber defining a shock egress opening. A valve assembly may be positioned at the first end of the chamber to seal the shock egress opening. A piston may be positioned within a recess located at the second end of the chamber. The piston may separate a first volume located between the piston and the first end of the chamber from a smaller second volume located between the piston and the second end of the chamber. A tension supporting rod may connect the valve assembly to the piston. A release valve may be in fluid connection with the second volume and a switch may be operable to open the release valve to release gas from the second volume and trigger opening of the valve assembly to generate a shock wave through the shock egress opening.