Sebesta was part of an effort in the late 1990s to redesign the Shuttle tires to make them significantly stronger and able to withstand greater speeds and crosswinds, and that project included designing an upgraded pressure sensor for the new tires. Instead, the Shuttle engineers relied on extensive pre-flight ground testing to mimic flight conditions over long periods of time and learn the rate at which the tires lost air, so they could prepare the tires with enough margin to be safe during landing. There was an externally mounted strain gauge, he says, but it only gave a very rough estimate of pressure-enough to know if the tire had completely gone flat but not accurate enough to alert pilots if the pressure was simply low. Luckily, he says, “in the history of the program, we only ever had one tire go flat, and it happened when we were almost completely stopped.” That was in the 1980s, Sebesta recalls, before there was really any way to monitor tire pressure during flight. You’d be yawing to the right or left, toward the side that had the tires no longer inflated, and eventually roll right off the runway. “Then you’d roll on the rims until they were destroyed. “If one was flat, the other tire on that side would blow, then you would have two blown tires,” he explains.
The Shuttle had four rear tires, two under each wing, and if even one was low on air during landing, it would be a “very bad day,” says Steve Sebesta, a Kennedy Space Center flight engineer. The fanciest models can even give a real-time pressure reading for each tire.īut the earliest versions of those sensors had a much bigger purpose: ensuring the tires on the Space Shuttles were fully inflated and safe for landing.
It’s something that should be happening less these days, thanks to tiny sensors that light up a dashboard warning whenever the tire pressure is off. How many people can think of a time when they got to their destination only to realize one of their car tires was dangerously low on air? Or they heard an ominous pop on the highway, only to realize an undetected slow leak had turned into a blowout?
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