[FPSPACE] msnbc (Oberg): Remembering the shuttle's scary start
joberg at houston.rr.com
Wed Apr 12 22:53:46 EDT 2006
msnbc (Oberg): Remembering the shuttle's scary start
Remembering the shuttle's start
April 12, 2006
The very first space shuttle mission, on April 12, 1981, almost ended soon after it began. Fortunately, the unexpected problem was not observed when it occurred, so the crew and mission control didn't know how frightened they should have been.
"I recall that my team saw nothing of the problem, either. My duty station was a console in the 'Staff Support Room' for the 'Propulsion' console in the main mission control center room, and our responsibility was monitoring the engines and tanks associated with the Reaction Control System (the RCS, the 42 small jets on Columbia's nose and tail) and the Orbital Maneuvering System (the OMS, the two midsized engines at Columbia's back end). The front-room position's call sign was 'Prop,' my experienced partner's call sign was 'OREO' (we made that up to be cute - it stood for OMS/RCS Engineering Officer), and I answered to the handle 'Consumables' - I watched the gas gauges.
"We all knew that nobody had ever flown this kind of spaceship before, and that it hadn't been tested - it hadn't even been designed to allow it to be tested - in an unmanned shakedown launch. We had designed numerous emergency 'outs,' and the crew had an ejection seat and a pressure suit originally designed for SR-71 spy planes. But the whole team was energized by the proper mix of controlled fear and quick-thinking ingenuity, and by a hunch that it might be barely enough to make this actually work.
"Unlike television dramatizations of space launches, we didn't watch a televised view of the launch - that was forbidden as too distracting. We watched, instead, TV screens with tables of numerical and graphical data, as well as alert light panels - red, yellow, green - that indicated discrete events and conditions of concern. And we had practiced for two years to recognize signs of trouble that would require a rapid change of plans for the astronauts aboard the spaceship. Part of the training had been to pare away any extraneous data inputs that would only distract us from what we needed to know.
"What we didn't see - and, fortunately, what the crew didn't see, either - was exactly what happened when the shuttle's three main engines lit up, and then its two massive solid-rocket boosters, or SRBs, fired to push it up into the air. Nobody had ever test-fired all these engines together, in a simulated launch pad or any other test stand. Nobody took seriously what then actually happened.
"The SRB ignition threw flames down into the space beneath the launch pad, where heat-armored sloping surfaces channeled the flow off to the side - there to catch unlucky birds and other creatures whose quick-fried body parts would provide feasts for other scavengers in the days to come. But the flames didn't all get deflected safely.
"In the initial burst of flame there also were grains of unburned solid fuel, scraped loose by the ignition. Unlike traditional gunpowder skyrockets that usually burn from the bottom to the top, SRBs have a long central passageway from nose to tail, and incendiary mortars fire at the nose, downward, to ignite the entire inner surface of that cylinder. This ignition swept some debris out with the first burst of flames.
"Those grains, surrounded by flame, immediately ignited - in the 'flame pit' directly below the shuttle. A concussive shock wave from this unexpected explosion blew in all directions, including upward towards the tail of the slowly receding spaceship.
"That blast wave smashed into the shuttle, hitting the tiled protective shields around the engines and other aft structure. The forces were about five times higher than predicted - but then, the shuttle had been built with a safety factor at least twice the expected stresses and strains of flight. The tail structure momentarily strained, and held.
"The blast wave also swept over the trailing edge of an aileron-like hinged panel that was a flush extension of the shuttle's underbelly, called the 'body flap.' Tilting it up or down during atmospheric flight gave the spaceship control over its nose up-down rotation (its 'pitch'). The flap is driven by hydraulic force from lines that are pressurized by their own generator.
"As we later - fortunately, much later - learned, the blast shoved the body flap out of position, forcing it against its own internal hydraulic pressure to bend through an angle clearly visible in pad television views (and in on-board telemetry). Pre-flight estimates had suggested that it was an angle much too large for safe operation. The compression of fluid in the flap's hydraulic lines might have been enough to crack or rupture them..
"After the flight, mission commander John Young was shown those videos. His reaction was severe. 'Had I known the body flap had been deflected so far off position,' he told associates, 'I'd have concluded the hydraulic lines had been ruptured and the system was inoperative.'
"Without a working body flap, a controlled descent and landing would have been extremely difficult if not impossible. The pitch control thrusters might or might not have been enough to provide control. The shuttle might have tumbled out of control and disintegrated at very high speed and altitude. There was one and only one option available to him to save his life and that of his co-pilot, Bob Crippen.
"'I'd have ridden the vehicle up to a safe altitude,' he later stated, 'and while still in the ejection envelope [the range of speed and altitude for safely firing the ejection seats] I'd have pulled the ring.' The two men would have been thrown clear, and Columbia would have been destroyed a few seconds later by a range safety officer's command to the onboard explosive charges.
"His thinking may have been that waiting much longer would have brought him into flight regimes where he couldn't get back down to low enough altitudes for ejection, if the body flap was later confirmed failed. There would have only been a few dozen heartbeats in which to make the 'save-my-life' decision - if he had been aware of the extent of the actual deflection.
"It would have been years before the next shuttle - Challenger - would have been ready to fly, if the U.S. had ever gotten up the nerve to try again. And the recovered debris may not have been in good enough shape to determine that the ejection had been commanded based on a mistake. The hydraulic lines were not damaged, and they functioned perfectly.
"For the next two days, the flight crew and Mission Control kept careful eye on the performance of the spaceship. It ticked along like the proverbial watch. When it came time to return to the atmosphere, I was off duty, but at my office listening to the air-to-ground conversations that confirmed that a safe entry had been achieved.
"Only later did we learn that all of our margins, and all of our planning, had only just barely been enough to succeed on that launch day. We also learned that we had definitely not been aware of all factors affecting split-second safety decisions. These were sobering lessons, and the experience provided a recipe for future flight safety - if it had been followed. History would later teach us, alas, that it was a recipe we let ourselves forget.
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