After receiving an information packet from Earth containing supposed improvements to their engines the flotilla captains met and agreed to wait; additional information -- possibly contradictory -- could have been on its way, and more time would allow the individual crews to examine the technical data in more detail. Unfortunately, one year later, when Sky Haussmann was three, the Islamabad was destroyed with all hands (and all passengers). The explosion caused minimal damage to the four remaining ships, as well as killing its crew members currently outside their hulls. The explosion was assumed to have been caused by an attempt to implement the engine modifications.
However, after Titus Haussmann was killed in an attempt at sabotage by a fanatical planted aboard before the fleet's departure, Sky Haussmann theorized that the Islamabad's untimely end was the result of another such individual; one who managed to succeed in their mission.
Unknown to all but Sky Haussmann, the destruction of the Islamabad would have vast repercussions for humanity, the galaxy, and quite possibly the universe (as the end result of the greenfly could be on that scale). When it detonated a sixth ship was affected, a grub ship. Named the Caleuche by its human visitors, it had begun to tail the interstellar colonists to gather information about their potential to draw Inhibitors to local space; it was in the process of determining whether to make peaceful contact and explain the existential threat or to begin systematically destroying human civilization. This "void warren" was severely damaged by the blast, and ultimately boarded and destroyed by Sky Haussmann. As such, humanity's contact with other sentient species -- and their technology -- as well as their knowledge of the Inhibitor threat was delayed by centuries.