Board Thread:Warhammer 40k General Discussion/@comment-24821739-20140604204305/@comment-6078851-20140717142545

when emps dies and the astronomican goes humans will definitely still have the capacity for intersteller travel, but in comparison to astronomican aided travel it would be like comparing the pace of a snail to the pace of a jet.

the warp could still be traversed but it would be an exceptionally risky mode of travel - without the astronomican the majority of ships entering the warp would never return to realspace, or if they did return they would have spent so long in warpspace that they would be completely insane at best, and utterly corrupted/mutated at worst.

the imperium wont survive without the astronomican, it's too galactically widespread for sub-warp travel to maintain. there would still be mini-empires (for a little while at least), but because warp-travel wouldn't be safely accessible then such empires wouldn't really be feasible beyond a few neighbouring systems. and even systems that were relativelly close together would be a long time away from each other in terms of travel time.

communications would suffer as well from the astronomican going out, and while communications would always be faster than actual travel it would still be a fraction of what it was with the astronomican.