Key Point: For a "smart" round, it had a lot of dumb problems.
In the 1990s, the U.S. Army was developing a new series of tank ammunition for the Abrams main battle tanks. The new round, designated XM943 Smart Target Activated Fire and Forget (STAFF), was to have lethality far beyond what was possible with conventional ammunition: it would fly over enemy tanks and detonate above them, projecting an explosively formed projectile through the top armor to destroy them. Some reports suggest that the round could have an astounding 11.5:1 kill ratio against an enemy armor force.
But the program fell victim to post Cold War budget cuts and was canceled in the early 2000s. It begs the question: why was such a theoretically amazing round canceled? Could it be as effective as it was predicted to be on the modern battlefield against newer tanks?
The STAFF round was envisioned to be the Army’s first “smart” tank round. A “smart” tank round was defined as a round that could identify, acquire, maneuver to, and kill targets. These rounds differ from traditional gun launched ATGMs in that they are meant to be fired at the same velocity as standard tank rounds, making them much harder to intercept and detect. It also meant that the guidance and seeker mechanisms had to be hardened far more than those in traditional ATGMs.
The STAFF round achieved the goals of the identification and target selection via a miniaturized radar seeker in the head of the round. Maneuvering is achieved by rotating the explosively formed penetrator (EFP) warhead on the same axis of the round's flight. Thus the STAFF doesn't change the flight path but rather aims a secondary EFP projectile which is meant to destroy the tank.