mike wightman
SOC-14 10K
My first thought was for the exodus to be renegade Nobles and Admirals from Lucan's fraction too
Recognising the hoplessness of their situation they made plans to refit a mothballed fleet and to get as many scientists, engineers etc. as they could.
How far do you want to stretch the "physics" of the backstory?
How about the exodus fleet making use of a one off jump portal - one of Lucan's special projects - to get them 36 parsecs away in the first jump.
They sabotaged the portal to prevent anyone following, but mysteriously some of the ships were lost.
The exodus fleet then proceeds by jump after jump until they have left the Imperium far behind.
Their route would take them coreward/trailing, taking them through the lesser rift. This would require sometimes travelling STL, adding five to six years to a journey that could have taken only a few months, if only the fleet could have had jump 6 engines for every ship.
Their target worlds are a quadrant of worlds cut off by jump 4 rifts from surrounding systems.
The exodus fleet took with them the very best in robotic construction machinery, the full Imperial technical database, and enough supplies and equipment to rapidly build a colony on a human compatible world.

Recognising the hoplessness of their situation they made plans to refit a mothballed fleet and to get as many scientists, engineers etc. as they could.
How far do you want to stretch the "physics" of the backstory?
How about the exodus fleet making use of a one off jump portal - one of Lucan's special projects - to get them 36 parsecs away in the first jump.
They sabotaged the portal to prevent anyone following, but mysteriously some of the ships were lost.
The exodus fleet then proceeds by jump after jump until they have left the Imperium far behind.
Their route would take them coreward/trailing, taking them through the lesser rift. This would require sometimes travelling STL, adding five to six years to a journey that could have taken only a few months, if only the fleet could have had jump 6 engines for every ship.
Their target worlds are a quadrant of worlds cut off by jump 4 rifts from surrounding systems.
The exodus fleet took with them the very best in robotic construction machinery, the full Imperial technical database, and enough supplies and equipment to rapidly build a colony on a human compatible world.