The distant roar of the engines never ceased. It was one of those sounds which had long ago dropped below the threshold of consciousness for the crew. Indeed, I considered, it would be a reason for immediate concern, perhaps even panic, were the drone of the drives to suddenly stop.
According to the Endurance technical reporting service, our current acceleration was 27.3 gravities. This had been stable for months now, and so we were asymptotically approaching the speed of light. For a long time now we had been at velocities where relativistic effects came into play, so our flight would be measured in months of subjective time for us travellers, but many decades for those left behind.
Of course those left behind would be able to see us well enough for half of that time. The blazing plasma emitted from our engines would make us one of the brightest stars in the night sky back on Earth, at least until we performed our turnaround manoeuvre. After that, we would be pointing our engines at our destination rather than our origin and decelerating at approximately the same rate to arrive in the Tau Ceti system where, as it had been known for decades, planets existed which might just resemble Earth.
Not that we were really expecting to make a planetary landing any time soon after our arrival. What we were really looking for were icy bodies like those in the Kuiper Belt or the Oort Cloud; indeed, very much like the body we currently inhabited, the one we had extemporised into an inter-stellar spacecraft in our retreat from Earth's system. The exodus had been forced upon us; our objective to try and make a home elsewhere in the galaxy was not welcomed by the governments of Earth, and we had nearly lost a war of survival for our pains. Now, we sincerely hoped, we were one of a handful of expeditions to nearby systems intent on establishing a colony entirely away from the Earthy interference.
The chunk of ice that had become our ship had a mass of well over a hundred million tonnes, and the triumvirate of reactors between them had an output measured in hundreds of gigawatts, at least two-third of which was directed to inertia management or, in everyday language, artificial gravity. Our actual accommodation areas, now much less cramped thanks to continual expansions and refitting, were in the centre of the body, so as to be shielded from the radiation of the reactors at the rear and the effects of cosmic particles - hydrogen atoms, mainly - impacting at near light speed at the front.
Drive Engineering kept the apparent gravity to around 110% of that of Earth, a level chosen to be reasonably comfortable: everybody could move around without hindrance, with a sizeable minority claiming that couldn't tell the difference compared with the natural planetary standard. Besides, to a man and woman, we were extremely fit and healthy; everybody selected for this particular mission - and therefore the opportunity to carry on living - had to pass a series of rigorous physical and genetic tests.
The care and feeding of the inertia field suppressors were my specific worry. It was my duty - my pleasure too, even my calling - to look after the vast complexities and extreme energies of these immense devices. Truly, it was a huge responsibility: our acceleration was quite enough to squish us all to a thin red paste if the suppressors were to fail for even a fraction of a second.
It was the pinnacle of our technology, one of the few things which had eventually given us an edge over the reactionary Consolidationalists with their Earth-centric viewpoint, the antagonists in a punishing civil war from which we had escaped. The suppressors themselves were generally thought to be highly reliable and actual failures were extremely rarely observed. The problem was that, if even a transient failure were to occur, subjecting any human or even mechanical observer to that failure, would result in rapid and permanent death, which would tend not to leave them in a position to made either an accurate or favourable report.
So, I found myself spending endless hours immersed in augmented reality poring through the mathematics of non-Euclidian warped space and the quantum Hamiltonian functions which made the engineering possible, or applying myself to the models and simulations of inertial suppressor systems behaviour, all the time looking for errors which could manifest themselves as sudden and unavoidable death for us all.