But once technicians had prized the segments of the motor apart, the engineer noticed unmistakable signs of burning across an inch-long section of the primary Viton ring inside the forward field joint of one rocket—and more in the seal of the nozzle joint of the other. This was alarming news: it meant that the O-ring erosion discovered in 1981 was no longer an isolated exception, but a recurring issue. And this time it had happened in two places on the same flight.
