Still waiting for someone to come up with "Rods from God lite" - smaller projectiles launched from lower altitudes.
An MQ-9 Reaper drone will happily reach 30,000 feet or so. A broomstick sized projectile made out of tungsten would weigh around 10kg. This means that the aforementioned drone would be able to carry over 100 of them with ease.
Travelling at the speed of sound, more than achievable for a streamlined dense projectile dropped from that height, it would have an impact energy of around 400,000 ft lbs - that's more than a 40mm cannon shell carries at the muzzle, and concentrated on a point of less than half the area. This means it would slice through the top armour of even the most heavily protected battle tank like a hot knife through butter.
Since it's only being dropped and not performing atmospheric re-entry, the guidance system doesn't need to be particularly hardened and indeed an existing kit used for JDAMs and the like can be easily adapted.
Upping the ante and using something like the Global Hawk flying at 60,000 feet would increase projectile energy while increasing system survivability, most targets would never know what hit them.
For area targets, you could have a projectile composed of say a hundred 100 gram darts which bursts open a given distance above the ground. Each individual dart would still have more than enough energy to go through the roof and floor of a pickup truck together with the occupants inside.
Something like the the flechette warheads carried by the
CRV-7 rocket:
Further study into this effect led to the WDU-5002/B FAT warhead, Flechette Anti-Tank, containing five tungsten-reinforced steel flechettes that could penetrate a T-72's side and top armour at a distance of 10,000 feet (3,000 m). It was also found to be a useful warhead for use against medium and light armoured vehicles. Further development led to the WDU-500X/B "General Purpose Flechette" for use against personnel, some light armour, thin skin vehicles and helicopters which releasing 80 tungsten flechettes that can penetrate 1.5 inches of roll-hardened armor.
Precise targeting would result in minimal collateral damage, and there would be no explosive ordnance either stored at the base, carried on the aircraft or left on the battlefield as a dud.
The CBU-107 passive attack weapon is a step in the right direction but going higher and adding guidance seems to be the way to go to do more damage with less.
