A Protocol 17 failure is the worst case for any soul bearing vessel in space. For any ship operating under regulated commission, occupant safety is the primary concern. Above profit, above efficiency, by law. To pass inspection, each ship must have 16 independent, publicly accountable fail-safes for each life-critical system. Backups, generators, parallel deployments, and all sorts of ingenious redundancies and buffers gave breathing room for any sort of disaster, often quite literally. For each of these, an untampered status report was required to be available to the public on demand. It's one thing to trust your pilot not to go too fast and use up all the fuel, it's another to simply know the speed and see the course projections in real time.
Protocol 17 is what happens when all of those systems fail independently. It is a last ditch effort to create some sort of livable space and get it to a livable place for rescue. It's the one of the few proprietary secrets on each vessel, in order to keep it secure against sabotage. The finer mechanics are the stuff of engineering grad school legends, being entrusted with designing "sacrifice systems" was an honor only the most distinguished shipwrights were afforded. But the only real evidence is found in the logs of the worst wrecks. They are systems that only operate once, with little regard to repair and reuse, so the changes they enforced could be quite dramatic.
The SS Prime Frequency was one tragic example. The few recovered black boxes tell the story of a vessel bumping across some sort of sudden, extreme gravitational anomaly with all sorts of nasty radiation. The power systems lost three backups, the oxygen supply was fully on reserve supply, but the ship wasn't fully doomed until the HVAC systems all collapsed, one by one. Severe magnetic flux ruined all of the primary turbines, something blew out the vacuum core, and a novel interaction with the calibration fluids in the barometer array led to a serious of serious errors in pressure distribution. This in turn literally fanned the flames of the melting auxiliary drives and ultimately caused a fatal eruption that sent a good third of the ship scattering out into the black.
Of the 11,217 souls that embarked on that fateful journey, a mere 177 survived it. The finer details of how Protocol 17 engaged are mostly lost to catastrophe, but a few details are clear. At some point, the build up in pressure in the starboard life shaft was ignited to effect a hard turning maneuver. Whether that cost more lives to fire or to g-force is a question debated with grim curiosity at best. Three engines were salvaged with partial capacity after emergency fabrication repairs, and a habitable section was atmospherically stabilized in the forward section. For roughly 300 hours, a contingent of nearly 3,000 survivors hunkered down and persisted on careful rations dictated and enforced by the Protocol. But all of that was only a precursor to the true tragedy of the Prime Frequency. After all available emergency repairs were complete, and the limited capability of what was left of the ship was understood, the trajectory laid bare a grim future.
Perhaps it is for the best that we don't know how Protocol 17 made its decisions, lest we get caught up in the emotions and ethics of death. But after working so hard to keep a few thousand living souls alive, warm and fed, it had to make it's hardest choices. It had to engineer yet another detonation, severing a small section of the craft at a critical apex to send it on a safe arc to a nearby shipping lane for rescue. But to do that, it would have to leave the bulk of the ship behind, and in fact convert a fair amount of it into reactive fuel. Including the 2,642 people who would not fit on the detaching compartment. How the Protocol picked between the survivors, selecting some to persist and others to burn, is a questions few seek answers too, and perhaps none truly know. But the logs are clear, and the mass of couple dozen hundred souls were torched in a final, macabre sacrifice.
Among the survivors, most shy away from talking about what happened. The differing stories told by the few that speak up publicly rarely provide much clarity but serve to sell a lot of powerful books and autobiographical holodramas. The 177 that survived speak of their former shipmates with a haunted reverence, daring not to tempt fate with a lack of gratitude. But one thing holds true in every telling, those that were lost in that final burn knew it was coming. Not all were willing, but at the very least, all knew that their sacrifice wasn't in vain.