Shuttle flight rules get lost in translation

James Oberg NBC News space analyst

HOUSTON - NASA mission manager LeRoy Cain had a tough translation job on his hands Thursday night when he tried to explain how his team could proceed to launch the space shuttle Atlantis — under the very same circumstances that aborted a launch attempt earlier that day.

He seemed to be using ordinary terms such as “flight rules” and “rationale” and “decision.” But such terms are tricky when you're telling journalists that a new policy of tolerating previously forbidden hardware problems could really be as safe as the zero-tolerance approach.

To an outsider, it may have looked as if NASA was cutting corners on safety once again. But take it from a former insider: Cain's approach makes perfect sense.

It all comes down to what the meaning of the word “rule” is, and why it may be justifiably different in space from what it is back on Earth.

These aren’t ironclad laws that incur civil punishment if broken, or rote checklists that must be followed like some tax form’s flow chart. A rule for spaceflight guides decisions in much the same way that Mission Control guides the spacecraft: It gives you a planned path — but when certain conditions are met, detours are allowed.

An explosive subject
In this case, the rules deal with a literally explosive subject, the propellant in the shuttle’s giant external tank. More critically, the rules deal with that critical phase near the end of the ascent when the propellant is nearly but not quite exhausted.

Back on Earth, when driving cross-country, a gas gauge that reads "nearly empty" when the tank actually runs dry leaves you stranded and embarrassed. On a spaceflight, it can mean death.

During Thursday’s aborted countdown, two of the four fluid sensors in the shuttle’s main hydrogen tank indicated that they would report "wet" — that is, "not yet empty" — even if the tank actually went dry. Under certain conditions, if those sensors don’t accurately report that the tank is running empty, there could be disastrous consequences to the shuttle and its crew. If either the oxygen or the hydrogen feed stops while the other feed continues, the fire in the engines can go disastrously out of control.

To permit the launch to proceed, NASA currently requires that three of the four fuel tank sensors be operational. So when Cain was suggesting it might be safe enough to decide that only two working sensors might be adequate, was he lowering the level of safety?

My own years in Mission Control told me that he wasn't. He was describing a classic NASA practice of making sure you and your equipment are ready for every emergency. His logic was impeccable, safety was being preserved, and yet the message failed to get across to his audience because he wasn’t actually speaking ordinary English, as most listeners assumed.

Flight Rules with capital letters
In the Mission Control Center, a “flight rule” is a capitalized, well-defined concept. These Flight Rules, or FRs, are compiled in a book that is the first reference for rapid decision-making during situations that don't follow the norm. It is by no means a mindless cookbook for automatic obedience. Nor is it merely a list of suggestions that can be followed or not by whim.

Essentially, it’s the product of “worrying in advance” about possible failures, or combinations of failures, and what the best reactions to them are. These reactions are developed based on analysis, on testing, on complex mission simulations and real flight experience.

As a veteran of Mission Control myself, I didn’t learn this from a book, or from being lectured. All this practical theory was drilled into me when, in 1979, NASA flight director Neil Hutchison asked me to be the panel secretary for his new project: composing the very first Flight Rules for a space shuttle launch.

Hutchison headed the "Silver Team" — the men and women tasked to conduct the first-ever space shuttle blastoff (and when it happened, on April 12, 1981, I was there in Mission Control as a member of that team). Even though the team drilled and drilled to think fast, Hutchison realized from experience that most choices could be defined and described in advance.

System by system — propulsion, power, communications, life support, the works — the panel reviewed the kinds of failures that might occur, how they would manifest themselves, what could be done about them, and how soon the advice had to be acted upon. I chronicled the debates, collected the draft rules and the logic behind them, distributed the notes and collated the critiques. Gradually, a workable reference book emerged.

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