Magazine article Science & Spirit

Slinging Mailbags Back to Earth

Magazine article Science & Spirit

Slinging Mailbags Back to Earth

Article excerpt

A group of engineering students from universities around the world will attempt to bring a payload of "space mail" from a satellite back to Earth on a string--the longest device ever deployed in space. If the string is successful, the project may open the way for a simple and cheap mechanism to fling packages home from a spacecraft.

The string, which is thirty kilometers (18.6 miles) long, will hang like a tether from the Russian research satellite Foton M3 after it is launched into orbit in September. The satellite will orbit between 260 and 300 kilometers (between 160 and 186 miles) above the Earth. Using the slingshot effect of the moving satellite, the rope will fling a six-kilogram (13.2 pounds) parcel into the Earth's atmosphere, where gravity will pull it down to its delivery site in Russia--if the plans work.

"The tether is made of Dyneema," said Marco Stelzer, an engineer from Germany. "It is the same material used by kite surfers to surf through the waves on the end of their kite. Strong stuff." Although the string is only half a millimeter in diameter, its length and ability to reflect sunlight will make it visible at night in South America and Eastern Russia.

Five hundred students worldwide worked on the project, called the Young Engineers Satellite. The student effort is sponsored by the European Space Agency (ESA), which also will use Foton M3 to test how a string hanging from a satellite could be used to control its orbit without resorting to rocket engines.

So far, more than twenty experiments have tested using a tether in space, either for navigation, propulsion, or transportation. The past tests have tried tethers as long as twenty kilometers (12.4 miles), and the students are using the longest tether yet. With this string, they hope to, for the first time, fling a re-entry capsule back to Earth. …

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