All human beings make mistakes, and NASA is no exception. It is important to learn from this mistake that highlighted the importance of physical units and how they can affect our real life. This is the story of one of the failed mission of NASA.
On December 11, 1998, a rocket took off from Cape Canaveral, Florida, bound for Mars. On board was the Mars Climate Orbiter, the first meteorological satellite to be sent to another planet. The mission of that small probe was to analyze the Martian atmosphere. The spacecraft was due to arrive on Mars in September 1999. At that time, the satellite would begin to orbit the red planet about 150 kilometers high, collecting data and sending it to Earth. But it never happened because of a stupid reason that nobody noticed until it was too late.
Things began to twist long before they reached Mars. In all the missions, the controllers correct the trajectory of the spacecraft from Earth. This is called TCM (Trajectory Correction Maneuver), and it is a routine. This time, however, several navigators noticed something strange. The spacecraft was too far off its route. They corrected the trajectory, but the spacecraft was diverted again, for no apparent reason.
The navigators gave the alarm to their superiors; something was altering the course of the ship, and they had no idea what could be. The response they got from their superiors was .... none at all. As astonishing as it may seem, nobody investigated anything, no one checked anything. Months later, NASA justified it by saying that navigators had not made use of the "formal process" to voice their concerns.
As the spacecraft approached Mars, the navigators, increasingly worried, continued to readjust trajectory. It did not help. On September 23, 1999, after a nine-month voyage, the ship disappeared from the screens of the California Institute of Technology without a trace and without anyone knowing why. The $300 million invested in the mission had evaporated somewhere, very close to Mars. But the worst news for NASA was yet to come.
An almost inconceivable errorIn the following weeks, a commission of inquiry was organized to clarify what had happened. And after numerous reports, surveys and interviews, the conclusion could not have been more humiliating for the US space agency: they had made a mistake in the units of measurement.
The navigation team used the metric system (SI unit) in its calculation, while the spacecraft is designed to carry out the calculations in the English system (FPS). Thus, each time the controllers make spacecraft to change its course, they sent some data in newtons that the spacecraft interpreted as if they were pounds. One pound equals 4.45 newtons, so each path correction caused a greater deviation. When the navigation team decided to place the orbiter at an altitude of 110 kilometers, it was already burning in the Martian atmosphere, just over 50 kilometers above the surface. (80 kilometers is the minimum altitude that Mars Climate Orbiter was thought to be capable of surviving during this maneuver).
The Mars Climate Orbiter mission continues to be today, the most stupid mistake in the history of space exploration. An example of how the most complex systems can fail in the most absurd and unforeseen way.