บท 786: Chapter 744 Hanging by a Thread

In 1960, three years after the launch of humanity's first artificial satellite "Sputnik" into space, NACA launched a very special satellite, "Echo 1."

The essence of Echo 1 was a giant balloon made from a polyester film only 0.08 millimeters thick and coated with a 0.013-millimeter-thick layer of aluminum foil.

It was folded during launch, and benzoic acid material had been placed inside beforehand. Once Echo 1 entered space and the benzoic acid was heated by the sun, it would vaporize, causing the balloon to gradually inflate to a diameter of about 30 meters.

This enormous inflatable metal sphere was the first-generation passive communication satellite, and its principle was exceptionally simple:

A signal sent from point A on Earth to Echo 1 would be reflected by its metal surface and return to point B on Earth, thus achieving satellite communication.