Alan MacDonald, The Man Who Didn’t Want The Challenger To Take Off | Science


Just over 35 years ago, the shuttle Challenger It was destroyed in a massive explosion, 73 seconds after takeoff, in sight of the world and some relatives of the seven astronauts, whom NASA had explicitly invited to follow the launch from the VIP platform at the Kennedy Center. It was a tragedy that people can hardly recover from. Unfortunately, it wasn’t entirely unexpected. Of the hundreds of engineers and technicians supporting the launch, at least two bore a doom and gloom.

The night before launch (January 28, 1983) was unusually cold. Temperatures have dropped to eight degrees below zero, a figure unheard of in the Florida climate. Long icicles hang from the service tower body. The launch date was set shortly before noon. The weather should improve somewhat, but the thermometer won’t get much higher than zero. Under the circumstances, two Thiokol technologists – Roger Boychol and Alan MacDonald – expressed their reluctance to continue the countdown.

Thiokol was the company in charge of the shuttle accelerators, the two huge Pencils They are located either side of the plane to help lift it during the first minutes of the flight. It was the largest of all: 45 meters long and three and a half in diameter. Inside, they stored about 500 tons of propellants with a central star-shaped tunnel running from top to bottom. At the time of launch, the flamethrower at the upper end caused simultaneous ignition of the entire surface and the combustion gases sought to escape through the nozzle at the bottom.

The missile consists of five cylindrical parts stacked one on top of the other. When it was triggered, the pressure inside was tremendous which is why the joints between the sections are equipped with double rubber rings to ensure tightness. It was precisely those rings that bothered Thiokol’s technicians. Low temperatures can make them brittle and a leak in any of them can have serious consequences.

NASA officials disagreed with those concerns. It is true that the night was cold, but conditions will improve when the sun rises. So the countdown continued. MacDonald, as the engineer in charge of the accelerators, refused to sign the conformity document.

MacDonald has always had a vague sense of guilt for not insisting more on putting off this release

What no one remembered at the time was that the large ventral fuel tank had been filled with liquid oxygen and hydrogen for at least six hours before launch. At temperatures around 200 degrees below zero. The wind blew from the same direction for most of the night. First it hit the port throttle, licked the main fuel tank, to cool it further, and finally it destroyed the right overhead missile. The rubber gaskets have been exposed to much more cold rain than weather reports indicated.

The rest is a story that I remember thousands of times. At the time of takeoff, the right throttle was slightly bent, the rubber gasket could not withstand the effort and a jet of flame, almost a torch, carried out from there, cutting off the lower support of the rocket. After a minute and a half, the throttle was released from its grip, turned sharply, and its arch broke the upper dome of the central tank. The explosion of millions of liters of hydrogen and oxygen fragmented the shuttle (although the astronaut capsule continued to rise as a single piece for a few minutes before crashing into the sea). Seven crew members were killed in the collision, including Christa McAuliffe, the first teacher to fly through space.

In the investigation that followed, MacDonald was instrumental, stating that Thiokol had warned of the dangers of landing in such severe weather. Incidentally, the O-rings, as designed, were not completely reliable. As the tragic truth has just proven.

Thiokol did not interact well with this testimonial. MacDonald was demoted from his position. Senator Edward Markey was shocked to learn of such retaliation, which extended to other workers, by issuing a decree banning NASA from entering into new contracts with the company. Thiokol reconsidered his decision, McDonald is promoted and made responsible for redesigning the new boards. The new model will henceforth equip all phrases.

MacDonald continued to work at Theokol until his retirement. He always had a vague feeling of guilt for not insisting more on delaying that launch. This was reflected in a book Truth, lies, and episodes In which he smoothly defended ethical analysis in decision-making.

Alan MacDonald died a few days earlier, following a home accident. He was 83 years old. He used to repeat: “Time reduces regret for the things we did. But regret for what we did not do is unbearable.”

Raphael Clemente He is an industrial engineer and founder and first director of the Barcelona Science Museum (now known as CosmoCaixa). He is the author of “A Small Step into” [un] Man (Books Dome).

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