For novel ideas about building embedded systems (both hardware and firmware), join the 40,000+ engineers who subscribe to The Embedded Muse, a free biweekly newsletter. The Muse has no hype and no vendor PR. Click here to subscribe.

By Jack Ganssle

Why the Towers Fell

Published 9/10/2002

They didn't die. Thousands of them escaped the inferno; thousands of families were not shattered. Structures designed merely as office spaces absorbed planes, burned, and stood for a time as their denizens made their way to safety. An engineer's work, so boring to most people, saved so many lives.

This week we'll remember the horrific events of a year ago. The nation and the world will celebrate the rescue workers' bravery and mourn the dead. Like so many others I watched the towers burn, aghast. During that hour never in the deepest recesses of my mind did I imagine they would collapse. Yet raging fires ignited by cruelly deployed jet fuel softened steel and snapped connections till the structures could stand no longer.

Sales of the Koran and books about Islam jumped as the nation sought understanding rather than ethnic condemnation. I felt proud to be an American as we groped for insight rather than lashing out in revenge.

And I felt proud again this week, watching Why The Towers Fell, a NOVA program ( broadcast on PBS channels. The show described the investigation into the engineering of the buildings. It showed clearly the steps leading to their collapse, without a hint of accusation or blame. No scapegoats were sought, no malfeasance exposed other than that of the sick perpetrators.

As engineers we're trained to examine problems dispassionately, yet this show was hardly that. Poignant, painful images again seared the soul, tempered with interviews with the designers and forensic engineers.

The central character: Leslie Robertson, the World Trade Center's structural engineer, the man who designed the buildings over 30 years ago. The haunted look in his eyes shouted a tale of personal agony more clearly than words. The producers treated Robertson gently, maybe even heroically, showing how his design saved many lives. If the buildings had been knocked over, whole swaths of Manhattan would have been leveled; instead, they pancaked straight down despite the awesome sideways force imparted by the impacting aircraft. The buildings stood, absorbing the fires, until many thousands evacuated.

A horrible failure, certainly, but one tinged with elements of success.

But a failure nonetheless. Everything can fail. There is no way to design a structure or an embedded system that's immune from any imaginable or unimaginable insult. America often deals poorly with failures. I remember the hysteria surrounding Challenger's explosion (, another awful event that now seems like a shadow of happier times. Reporters asked NASA officials how they could ensure such a calamity would never reoccur. What a dumb question! Anything flung into space atop 6 million pounds of explosives is a disaster held at bay by perfect engineering, unstinting QA and perpetually-enlightened management. Though the unethical behavior of Thiokol's program managers was the proximate cause of the explosion (, things fail, for both technical and human reasons. Perfection is too high of a standard for mere humans to attain.

Build it, and it will break. Challenger was a total failure consuming her entire crew, as was the Apollo 1 fire so many years earlier. The World Trade Center was a total failure, too, but one mediated by a design that gave a bit of desperately-needed time to the occupants.

I salute Leslie Robertson. Though the program showed a man who appeared riddled with guilt, tormented by the imperfections in his creation, his work saved thousands. That's the legacy of heroes.