Bofors (of Sweden) is working on a low-cost anti-aircraft solution known as Abraham. This is a 120mm rocket-powered shell, fired from a launch tube on smaller vehicles, which costs 1/10 as much as an anti-aircraft missile. There is some possibility that Bofors could adapt the system to be fired through the barrel of a tank cannon. The 25kg shell spins at high speed during its 10km flight, and uses a high frequency laser radar to scan for aircraft. If an aircraft is directed within 90 meters, the computer brain of the shell fires the directional warhead the next time the spin of the shell brings it facing the target (a tiny fraction of a second). The 10 kilogram charge expels steel balls at high speed, with a good probability of a hit. --Stephen V Cole