Urban centres have increasingly become sites of conflict and locating threats amongst innocent people is essential. With their ability to see people through certain materials like plasterboard an adverse weather, mm-waves have useful military applications for imaging in such situations.
Millimetre-waves have had much success in the area of missile guidance. Conventional missile guidance systems use lasers for guidance but these are not useable in bad weather. With the capability to see through fog, rain, smoke and dust, missile guidance systems at mm-wavelengths provide an alternative. Millimetre-wave systems can only operate at distances of a few kilometres and so can only be used for short range missiles or when the missile is almost at its target to give precision aiming.
The military have also adapted mm-waves into weapons themselves. The US Government has developed VMADS (Vehicle Mounted Active Denial System) which they plan to use as a non-lethal weapon in conflict. VMADS fires intense mm-waves at the target person which heats their skin to temperatures up to 55°C causing them pain comparable to getting a blast from an oven. The pain ends when the target moves out of the line of site of the instrument, and so could potentially be used to disperse crowds or on the front line to deter the enemy.
This new technology has met with some criticism. The main concern is that the effects intensify on sweaty skin and may produce harmful hotspots as a result of a radiation build up. This has brought up debate of how functional the weapon would be in hot or humid conditions. There has been no report on whether the system is eye-safe. VMADS has not yet been deployed and is undergoing further testing. If VMADS proves to be safe and effective then they say it would provide a useful half way point between verbal deterrents and shooting.