AGM-136 Tacit Rainbow

AGM-136 Tacit Rainbow was a Cold War attempt to combine cruise-missile, anti-radiation, and unmanned loitering concepts. Designation-Systems.net describes the program's AGM and BGM designations, while FAS presents it as an air- or ground-launched system intended to suppress enemy air defences. The key idea was persistence: instead of flying directly to a known radar, the missile could reach a target area, loiter, and attack when hostile emitters appeared.

Tacit Rainbow was not just a faster HARM-style missile. Its design aimed to patrol a preplanned area and then home on radar emissions, making it an early ancestor of modern loitering-munition logic. That required an airframe with enough endurance, guidance autonomy, and seeker capability to wait for enemy radars that might switch on only briefly. The resulting system promised saturation attacks against integrated air defences, but also introduced cost, reliability, and program-management challenges.

Tacit Rainbow did not become an operational weapon. FAS notes program controversy and cancellation-era problems, and the weapon remained an example of ambitious Cold War technology that outran its acquisition environment. Its service legacy is therefore conceptual rather than numerical. Modern militaries now routinely discuss loitering munitions, autonomous targeting, and distributed suppression of air defences, all of which make Tacit Rainbow look less like an oddity and more like an early expression of a later trend.