Board Thread:Warhammer 40k General Discussion/@comment-25618639-20150604030859/@comment-6078851-20150608175434

if a journey to another galaxy was to be made fuel/power would definitely be an issue, but given such real world tech as the ion drive i think fuel for the journey could be easily taken care of.

a sleeper ship may not need a generation ship alongside it (although generation ships are also a means of intergalactic travel): if using stasis the crew can simply take skeleton-shifts of a year per-awake-cycle, or 5 years, or 10, or 20 etc, to provide ship maintainance, check supplies/power, correct any deviations in course etc, and with a suitably large crew such a vessel could reach another galaxy (obviously a relatively close one) with the original crew that set out.

obviously the imperium could do with substantial upgrades for intergalactic travel, i'm just saying that they have the minimal requirements for such an undertaking, it would be somewhat on a relative technological par with the 1st moon landing.