A Candle in the Dark

A look on science, politics, religion and events

This is why you should use SI units

with one comment

The recent initial success of NASA’s phoenix lander has led to a lot of attention and excitement about space exploration, and rightly so! However, things haven’t always been this peachy for NASA.

In December of 1998, NASA launched a spacecraft whose primary mission was to monitor the climate of mars from orbit, which was aptly titled the ‘Mars Climate Orbiter’. The total cost of the project was around 300 million dollars. As you’d have probably guessed by now, the mission ended in failure. As the spacecraft approached Mars, it received instructions to power its main engines in order to insert itself into the required orbit. In fact, as the NASA mission page documents, this is what should have happened.

The Mars Climate Orbiter will arrive at Mars on September 23, 1999. As it nears its closest point to the planet coming in over the northern hemisphere, the spacecraft will fire its 640-newton main engine for 16 minutes 23 seconds to brake into an elliptical capture orbit. The spacecraft will loop around Mars roughly once every 12 to 17 hours. The period of the capture orbit will increase if launch takes place on a later date, due to an increasing arrival velocity. If launch takes place at the end of the launch period in late December, the capture orbit period would be approximately 20 hours.

However, the orbiter never reemerged from behind Mars, and all contact was lost. What happened?

Amazingly, NASA messed up the units.

The peer review preliminary findings indicate that one team used English units (e.g., inches, feet and pounds) while the other used metric units for a key spacecraft operation. This information was critical to the maneuvers required to place the spacecraft in the proper Mars orbit.

Wow.

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Written by parseval

May 30, 2008 at 1:07 am

Posted in engineering, history

One Response

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  1. Hil…arious!

    N

    July 17, 2008 at 8:28 pm


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