A rather harrowing idea in WH40k, but what are the consequences of the dreaded order 'abandon ship'?
Clearly, one should not even contemplate doing this in the warp. Even if escape craft could be shielded from the dread inhabitants of the immaterium, they would be lost forever, waiting till their coccoons ran out of air. The only slim -and very, very slim- chance would be a shielded stasis pod, hoping you'd be picked up. But the chance is so minimal that we can safely assume this will never be a ready to use emergency option. So, as far as the travel through the warp goes, I think we can decide that within the immaterium there is no hope of escape.
That leaves us the void. The vast universum where chances of survival seem minimalistic. Why spend resources on safety measures if the only result will be a slow death far away in the endless void? Although this is absolutely true, there are some mitigating factors.
Firstly, most void travel takes place in systems, many of which are highly advanced. I think we can even say that most basic void travel takes place in advanced systems, as they have the greatest need of interstellar communications. Feudal worlds with a subsistence economy will not see the traffic of a Forge World. The combination of these two facts increases the chance that in case of a mishap there is still a chance of aid being directed to the survivors.
Secondly, most fights and battles also take place in systems. These are the spots worth fighting for and these are the spots where ships have a fair chance of finding each other. This means that ship abandoned in battle will mostly be found close to other ships and in inhabited star systems, often with a decent technological base.
Combining these two elements, we can conclude that there is a very good chance that when ship has to be abandoned it sails in an area where there is a chance of rescue, So, what are the chances? And how can a ship (and of course, the players) increase their chances?
I fear that we have to admit that saving most of the crew of a starship will be impossible without outside help. With a crew of 60,000 you would need no less then 600 craft each capable of holding 100 men...clearly impossible. Nor will there be enough vaccuum suits -not that they will help much- for the crew. So, if there are rescue craft, they will be for the lucky few, the Rogue Trader and his trusted entourage, possibly extended to his trusted officers and guards (i.e. the people he has to command to stop other people getting in his escape module). Logically, these rescue craft would be close to the command decks, on the higher spires of the ship, easy to acces for the bridge staff. One might envision rescue 'balls' of sorts being shot away, or even a whole part of the spire detaching itself to form a great rescue craft, and anything in between. Obviously, getting away from the ship fast would be vital, as it won't help a lot getting of a disintegrating cruiser only to be blown to bits by a plasma explosion or ripped to shreds by the warp drive imploding. Once 'safely' drifting into space, there is the manoeuvrability question. Can these craft cross reasonable parts of system space (interstellar is obviously a nono)? Can any of these craft make planetfall (which will add considerably to the complexity of the craft)?
Of course, a better option might be to rush for your flight decks or lighter bay and try to grab your private gun cutter, but that would be an adventure on its own. Getting there from the bridge through a panicking crew and a ship that is falling apart as you speak would be a harrowing experience, disregarding even the problems of launching it from the disintegrating ship. Droppods would be a fair bet too, when close to a planet. Slightly cheating the odds would be using a teleporter to enter another ship or habitable planet.
In each case, it is a good thing to consider both as a GM and as a player as to what you would do if the ship starts taking catastrophic damage, there are orks aboard and the Master Enginseer has told the Lord Captain he can hold the reactor room for another half hour at the most, when he will blow up the ship...
Friedrich van Riebeeck, Navigator Primus, Heart of the Void