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# SI Mass and Weight Units

## Measurements that represent matter or the force of gravity related to an object.

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How to Crash a Space Vehicle

### How to Crash a Space Vehicle

Credit: NASA
Source: https://commons.wikimedia.org/wiki/File:Mars_Climate_Orbiter_during_tests.jpg

The Mars Surveyor '98 Climate Orbiter was intended to survey the atmosphere of the planet Mars over a two-year period.  Plans for the vessel included monitoring of atmospheric dust and water vapor as well as observing seasonal changes on the planet’s surface.  Due to an error more commonly committed by freshman chemistry and physics students, the space vehicle burned up in the atmosphere.

#### Amazing But True!

• The common units of scientific measurement are the metric system, first developed in France.  This system is used throughout the world for any expression of scientific data.
• The English (sometimes referred to as “imperial”) system of units is still commonly employed by the United States, Liberia, and Burma (with some use still in Great Britain, India, and Malaysia).
• The Mars Climate Orbiter was assembled at two different sites in the U.S.  The Lockheed Martin engineers responsible for the propulsion unit normally determined force in pounds.  Scientists at the Jet Propulsion Lab (who put together other components of the system) used metric units for force.
• Credit: NASA
Source: http://en.wikipedia.org/wiki/File:Mars_Climate_Orbiter_2.jpg

What the orbiter would have looked like in Martian orbit[Figure2]

• Nobody remembered to tell the computers to convert from one system to the other and no checks were made of the entire craft to see that all the parts worked together.  The result was a very expensive (\$125 million) mistake.  Oops!

#### Explore More

1. What was supposed to be the measurement system for all NASA projects?
2. What other Mars vessel disasters were mentioned in the Congressional investigation?
3. Were there early warning signs that a problem existed?
4. Have there been any successful missions since these disasters?

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