Star Trek: 10 Classified Starfleet Secrets
1. The Omega Directive
In the late 23rd century, a Federation scientist named Ketteract made a very dangerous discovery: the Omega molecule.
Ketteract created an Omega molecule using boronite ore, but, lacking proper containment, the molecule became unstable and exploded, killing everyone aboard their secret research base and devastating the Lantaru sector. The worst effect of the explosion was the destruction of subspace, which rendered warp travel and subspace communications impossible across lightyears of space.
Starfleet determined that Omega was too dangerous to be allowed to exist, as a few mere particles were thought to be enough to destroy subspace across an entire quadrant. All information regarding them was classified, and only Starfleet Captains and Flag Officers were briefed on its existence, for the sole purpose of destroying it at any cost, should any molecules be detected.
Voyager encountered a large number of Omega molecules in the episode The Omega Directive. Alone in the Delta Quadrant, Janeway was forced to inform the crew about Omega, and with the help of Seven of Nine, successfully destroyed the molecules, damaging only a small area of space.