Riding Rockets

As the seismic wave of Abbey’s announcement was tearing apart the TFNGs, we were blissfully ignorant of another 9.0 wave moving through the system. Five months earlier, one of the eight O-rings on STS-2’s recovered right-side booster had shown heat damage. This discovery had shocked the SRB engineers. Since the boosters were twelve feet in diameter, had a hollow center, and burned from the inside toward the outside, the perimeter-installed O-rings were far from the 5,000-degree gas throughout most of the burn. The unburned propellant served as an insulator. (In the final seconds of the burn, other insulation material at the walls kept the heat from the O-rings.) The O-rings should never show heat damage. And in seven ground tests and one mission (STS-1), involving a total of sixty-four primary and sixty-four backup O-rings, no heat damage had ever been recorded. The fact that an O-ring inside STS-2’s right-side booster had been damaged was an indication that, at some point in flight, it had not held the nearly 1,000-pounds-per-square-inch pressure inside the tube and a finger of fire had worked between the segment facings to touch it. This suggested a serious problem with the joint design. But no consideration was given to stopping shuttle flights and conducting more ground tests. The NASA PR machine had promised Congress and the American public a rapid expansion of the shuttle flight rate with a vehicle turnaround time measured in a few weeks.Schedule had become the 800-pound gorilla in shuttle operations. Nobody wanted to wrestle with it. Instead, engineers at Thiokol and NASA searched for a way to continue operations in spite of the STS-2 anomaly. So they intentionally damaged an O-ring to a much greater degree than the damage they had observed on STS-2, put it in a laboratory test article, and pressurized it to three times the pressure developed by a burning SRB. The damaged O-ring held the pressure. Armed with these impressive results the Thiokol engineers endorsed their product as flight worthy. Lost in this process, however, was the fact something never expected and not completely understood had been accepted.

No astronaut was aware of the SRB O-ring problem. In fact, most of us were ignorant of the entire SRB design. There was only a single indication of SRB performance available in the cockpit of a launching shuttle. As the tube pressure fell to less than 50 pounds per square inch, a message flashed on the computer screens giving a warning that burnout and separation were near. Since we had little insight and no control over a burning SRB, we didn’t waste our time in studying its design. We had too many other things into which we did have insight and over which we did have control (the liquid-fueled engines, hydraulics, electrical system, etc.). We devoted our time to learning the design and operation of these systems. We were convinced the SRBs were just big, dumb skyrockets, as safe and reliable as a hobby store model rocket. It was the SSMEs, which periodically blew up in ground tests, that we feared most.

The Thiokol and NASA SRB engineers were buoyed when STS-3’s boosters returned with no O-rings damaged. It was full speed ahead with the shuttle program.

And the program shifted into overdrive on July 4, 1982. It was then that President Ronald Reagan and the First Lady celebrated Independence Day at Edwards AFB by personally welcoming Ken Mattingly and Hank Hartsfield back from space after their successful STS-4 mission. Reagan called attention to the latest orbiter to join the shuttle fleet,Challenger. Fresh from the nearby Rockwell factory, that vehicle was mounted atop its 747 carrier aircraft ready to take off for Florida as soon as the president finished his comments. It was an incredibly intoxicating sight.Columbia sat on the cracked dirt of the lakebed looking every bit the veteran of four spaceflights, with her nose and fuselage streaked with soot from four blazing reentries.Challenger sparkled in her virgin newness. It was the perfect backdrop as the president continued his speech and declared the space shuttle program “operational.”