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What I've Learned
In 1999, the $125 million Mars Climate Orbiter was lost because British scientists who built the Orbiter calculated how many miles the craft needed to fly to reach Mars and how many pounds of thrust its engines required. Meanwhile, NASA scientists calculated kilometers of flight and newtons of thrust. The wrong figures were entered into the navigational computer, miles instead of kilometers and pounds instead of newtons. As a result, the Orbiter hit the Martian atmosphere at the wrong angle. At first it was thought the satellite had crashed into the surface, but later data suggested that it bounced off the atmosphere and disappeared into space. Either way, it was a disaster.
A hundred years from now, no one will believe this. In 2099, some know-it-all will look back and swear it was impossible.
"By 1999," he'll say, "men had long since walked on the moon. This was not the early days of space flight. There is no way, by that date, scientists would have confused imperial measurements with metric."
There's no way. Nevertheless, they did.
Which brings me to this. If you were steering a boat that had a long handle (a tiller) attached directly to the rudder, which way would you move the handle to turn the boat left?
Picture it. To make the boat go left (or to port, if you will), you push the handle right. Why? Because the rudder that's attached to the other end is moved in the opposite direction, to the left. Water hits the rudder, slowing down the left side of the boat. If the left side is trying to go slower than the right, the boat turns to the left.
Sail boats used to have steering wheels (called helms) attached to rudders in such a way that to steer left, you'd turn the wheel to the right and to steer right (or to starboard, if you will) you'd turn the wheel to the left, just as if a tiller were attached directly to the rudder.
To avoid confusion about what was wanted, orders were given, not concerning which way to turn a ship, but which way to turn the wheel. These were called Tiller Orders. If a captain wanted to turn to port, he'd tell the helmsman, "hard a starboard," meaning turn the wheel sharply to the right. This would cause the rudder to swing left and the ship to go left.
When steam ships came along, this changed. To turn the ship left, you steered left and to turn right, you steered right, just like you do now when driving a car. Wheel orders, however, continued to be given as Tiller Orders, with the understanding that they now meant the opposite of what they used to. If an officer wanted a ship to turn to port, he'd give the order, "Starboard Helm." On a sailing vessel, the helmsman would have responded to this by turning the wheel right. On a steam ship, he would respond by turning the wheel left.
In time, Tiller Orders were replace by Rudder Orders, which did away with this backward situation. "Port Helm," meant turn the wheel to port. "Starboard Helm," meant turn the wheel to starboard.
It has recently been suggested that a confusion over Tiller Orders and Rudder Orders is what caused the Titanic to hit the iceberg that sank her.
When First Officer William Murdoch spotted the iceberg, he ordered "hard a-starboard." This was a Tiller Order. What he wanted was for the ship to turn left, to port, to steer around the iceberg. But the helmsman, Quartermaster Robert Hitchins, responded by following the order literally and turning the wheel to starboard. By the time the mistake was realized and a correction made, it was too late for the ship to avoid disaster.
This idea is getting press right now because the granddaughter of one of Titanic's officers claims she was told it by her grandmother.
Know-it-alls mock the revelation. They say, "This couldn't have happened. The change from Tiller Orders to Rudder Orders happened years before. There is no way in 1912 that a helmsman would have mistakenly spun the wheel to starboard."
Oh really? Well there's no way in 1999 that scientists working on a 10-year, $125 million space project would have confused miles and kilometers. But they did.