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The most expensive mathematical error

Remember all the times you lost marks because you forgot to specify the units? Every now and then, it just so happens that you calculate a value in centimetres but write the units as metres instead, or don’t convert grams into kilograms. Ever felt the frustration of losing ONE MARK because of an asinine mistake? Well, take that and amplify it a few million times because that’s how the rocket scientists at NASA felt losing a spacecraft worth $125 million to a mindless error!

This incident did in fact happen in the December of 1998, when the world’s state-of-the-art space agency, boasting the most ingenious of scientists and programmers, made a simple math mistake! In 1994, the US administration had launched a panel, informally called ‘Faster, Better, Cheaper’, setting new guidelines for NASA to conduct cheaper but innovative space missions in a relatively shorter timeframe. The first mission under this program, launched in 1996, was the Mars Global Surveyor – to probe the red planet. Its immense success led to another mission – the Mars Climate Orbiter (MCO). Unfortunately, little did they preconceive that this would turn out to be one of the ‘biggest blunders in the history of rocket science’.

The MCO, intended to be the first-ever interplanetary weather satellite, was launched on 11th December 1998 to study climate on Mars. It was also meant to act as a relay station for the Polar Lander, which launched a few weeks after the MCO’s launch. The 9-month travel from Earth to Mars’ orbit was smooth except for a few minor hitches that got rectified. 8th September 1999 was the fateful day. The Orbiter couldn’t be put into the orbit of Mars. The scientists on the ground had expected a signal loss from the probe when it went behind Mars. But this happened 49 seconds earlier than expected. Communication couldn’t be re-established with the orbiter, and it was lost forever.

Scientists observed that the spacecraft was almost 100 miles closer to the Martian surface than expected. At such close proximity to the Martian atmosphere, it probably would have incinerated due to friction.

So, what went wrong? After analysis, the Jet Propulsion Laboratory (JPL) discovered that the company that built the Spacecraft – Lockheed Martin, had used Imperial unit of measurement, whereas NASA had used the metric system. Simply put, while the spacecraft sent signals in miles, NASA analysed it in kilometres, when it meant pounds, NASA read it as kilograms, and when it meant pound-Newtons (Imperial unit of force), NASA read it as Newtons (metric unit of force).

For reference, 1 pound-newton is equivalent to 4.45 metric newtons. While this is inconsequential for us earthen physics students, who simply use these units to solve numericals, when dealing with lightyears in space and millions in dollars, it’s unfathomable to overlook such minor, albeit monumental, detail.

Innumerable scientists, software developers and engineers worked together in this mission, and not a soul rechecked the calculations. This careless math mistake caused an insurmountable loss for the space industry. It’s futile to cry over spilt milk, and the prudent thing to do is to learn from the events of history. To sum it up (pun intended), never forget to write units because one small flub for man can be one giant blunder for mankind.

Tagged in : mars climate orbiter, NASA, Metrics,