On approximately Stardate 54700, the USS Voyager detected a series of energy discharges 5.9 light years ahead of the ship. Long range sensors showed subspace radiation and metallic debris throughout the area, without revealing any apparent cause. The ship proceeded on course, but on reaching the area the crew encountered a series of guided weapons emerging from subspace and exploding all around. The detonations were extremely powerful, producing level 9 shock waves which damaged Voyager's warp drive even from hundreds of thousands of kilometres away.Initially the crew feared a new and powerful adversary, but soon afterwards a warning beacon was discovered which was transmitting a message stating that the area was a "subspace munitions range" being used for target practice. Voyager attempted to communicate with the owners of the beacon but the warheads seemed able to travel over tremendous distances, perhaps dozens of light years, and there was no way to find those who had fired them. Seven of Nine and Icheb were able to recalibrate the astrometrics sensors to detect the minor gravimetric distortion caused when the warheads approached the subspace barrier, giving some warning of their emergence. However, when the ship engaged warp drive a warhead accidentally locked onto it from some twelve million kilometres away. Captain Janeway attempted to destroy the device with a spread of photon torpedoes, but the warhead fired some form of protective cloud ahead of itself and destroyed the weapons. Scanning revealed that the warhead was equipped with a proximity resonance detonator operating at 4.84 GigaHertz, but as soon as an anti resonance pulse was tried the system rotated the frequency to avoid jamming. No contact was ever made with the makers of the subspace warheads, nor were there any further encounters with these powerful weapons.