Fig. 3. Heuvelman IA17, 2cm Infantry
Powergun with magazine tube waiting to be loaded (John Treadaway)
Gold is for the mistress – silver for the maid –
copper for the craftsman cunning at his trade.
'Good!' said the Baron – sitting in his hall,
'But Iron – Cold Iron – is master of them all.'
– Kipling
The most effective weapons of the late 3rd Millennium were powerguns. They worked on the principle that metallic atoms of a fixed linear magnetic orientation could be converted directly into energy by the application of heat, pressure and intersecting magnetic fields. Powerguns used cartridges of copper-cobalt aligned in a wafer of microporous polyurethane. Powerguns released a flash of energy and plasma that struck in straight lines at light speed. Short iridium barrels were used to protect the firer from scatter. The barrels were cooled with liquid nitrogen but even so had limited life spans.
Powerguns came in all sizes from 1-2 cm infantry weapons to 15-25 cm heavy tank guns. Starships and planetary defence systems used similar weapons of up to 100 cm diameter. Quick-firing guns of 1-3 cm could be manufactured and these were commonly grouped into multi-barrelled, anti-personnel and air defence weapons, gatlings or calliopes. One tactical quirk is that powergun shots released all their energy on the first thing they hit, even soft cover could be protective to a target, at least for the first shot. Powerguns were expensive and difficult to manufacture but were the standard Terran military weapon.
High intensity lasers were utilised in much the same way. They had less destructive power than powerguns, were expensive to manufacture, and were more delicate but they had one major advantage for colonial warfare in that they did not require ammunition.
Kinetic energy weapons of various sizes, from infantry weapons to heavy tank guns, and various levels of sophistication were still employed. There were too many variants to discuss here but they break down into simple, cheap, solid propellant ammunition, the more effective wire-fired liquid propellant rounds, and complex electromagnetic rail or coil guns that fired penetrators at flat hypervelocities. The most sophisticated versions of the latter fired osmium fletchettes down squeeze cone-bore barrels made from a single synthetic diamond crystal. These hypervelocity guns had higher penetration than powerguns but less destructive impact. They were not cheap and could only be manufactured by technically advanced cultures such as the Gorgon Cluster.
Artillery weapons, which includes guns, rockets and missiles, could fire a wide variety of ordinance over considerable distances. Loads included anti-personnel cluster rounds (firecrackers), anti-armour rounds with seeker heads, ground penetrators (bunker-busters), biochemical warfare rounds, nuclear warheads (if the enemy was foolish enough not to be protected by nuclear suppresser fields), electronic warfare rounds, reconnaissance rounds and even good old high explosive & shrapnel. Artillery was truly devastating if it penetrated the opposition's air defences.
Artillery was such a potentially puissant weapon that competent armies carried air defence guns that could shoot artillery shells out of the air before they deployed their bomblets. A variety of small to medium sized multi-barreled gatlings or calliopes were used in conjunction with sophisticated automatic detectors and targeting devices.
Some remarkably simple weapons were in common use even in the most sophisticated forces, for examples grenades, grenade launchers and buzz bombs. Buzz bombs were simple, unguided, short range, anti-armour rockets of a wide variety of designs. They were an infantryman's personal artillery and could penetrate any armour. They gave tankers sleepless nights as they could not be decoyed or shot down. An armoured vehicle's only hope was to prevent the infantryman getting close enough or to use automatic strip mines. These were claymore-type devices positioned along the sides of armoured vehicles that sprayed shotgun–like blasts of shrapnel. They could be set to fire automatically if the vehicle sensors detected infantry or incoming buzz bombs. Hypervelocity unguided rocket-penetrators were used in the anti-tank role precisely because they were too fast to intercept either by gunfire or stripmines but these weapons required stable launch bases of greater mass than an infantryman's shoulder.
Military combat vehicles could be wheeled, tracked or hover craft. Wheeled vehicles were by far the simplest and cheapest to manufacture and maintain. Their disadvantages were limited all-terrain ability and limited weight capability, which precluded anything other than light armour although surprisingly large weapons could be fitted, provided the recoil was not too high. Light weight limited designs to armoured personnel carriers and armoured cars. Wheeled combat vehicles were always horribly vulnerable to mines.
Tracked vehicles offered considerably better terrain capability than wheeled and could carry considerably more weight. Their disadvantages lay in complexity and cost. Tracks could also be an endless maintenance problem. The most sophisticated tracked vehicles used electromagnetic suspensions that floated the body independently of the transmission but the cost and sophistication of such armoured fighting vehicles was not much less than a hover vehicle.
The elite armed forces used hover transmission vehicles. These required large power supplies, usually fusion motors, but could carry high weights allowing heavy armour. They were expensive, sophisticated vehicles with complex computer controlled tiltable multi-fans pressurising a plenum chamber. They had excellent terrain crossing ability, the lighter vehicles had sufficient power to weight ratio to cross open water and some with no armour could even fly (should the driver be tired of life).
A variety of armour types was employed. The most common heavy armour was cast iridium, which gave a good all round performance. Various steel and sapphire composite heavy armours were also used. These sacrificed some protection against kinetic energy penetrators for robustness to powerguns and shaped charges. High tech lighter armours included ceramic-iridium composites and titanium-aluminium alloys. Some armies still made do with steel, which at least had the virtue of being cheap and usually could be manufactured locally.
It is worth noting that no combat aircraft were seen over late 3rd Millennium battlefields. Sophisticated automatic detection and targeting systems coupled through AIs to heavy hypervelocity and light speed long-range weapons made an airman's lot a very unhappy one. Heavily protected hyperspeed aerospace fighters were used to deliver ordinance from low orbit but these are best considered to be a form of strategic artillery.