Common knowledge is what rules our daily life. But once a while something you read or see will just smash your common sense in to the wall, then stood beside it and laugh. Something I know this week does exactly that to me involved a satellite, also a phenomenon performed by a term which we will refer it to our life every single day: metal.

Normally, when you put two metal block which made of identical material, nothing interesting should happened. However, if you recreated this environment in space, you will get a completely different result: they will become one chunk and can not be split again. Sounds unbelievable, isn’t it? This phenomenon is as known as “Cold Welding”, which is a very cool thing that could happened in vacuum. Because when two chunk of metal were place against each other in vacuum, there was absolutely nothing between them, hence, they will recognize them as a unity. Quote from Richard Feynman, one of the most humor scientist in the world, “The reason for this unexpected behavior is that when the atoms in contact are all of the same kind, there is no way for the atoms to “know” that they are in different pieces of copper. When there are other atoms, in the oxides and greases and more complicated thin surface layers of contaminants in between, the atoms “know” when they are not on the same part.”

But why will this has anything due to a space mission of a satellite? In matter of fact, it almost destroys a muti-billion space operation. In Oct,9th, 1989, NASA launch a spacecraft name “Galileo”in to the space, which has a primarily use of gathering data of Jupiter. Because the distance between the earth and the Jupiter is so far, the scientist in NASA design a special antenna for the spacecraft in order to complete the mission. This “High-gain Antenna” could transmit about 80k per second back to the earth when it’s functional, and it was elaborately design into an umbrella structure to maintain a small size in order to transport. After one and a half years sailing in to the space, the “Galileo” arrived Jupiter at April 10th, 1991. However, the scientists can’t be able to launch the Antenna. After thousands of speculation, the scientists narrow it down to a very simple but lethal malfunction: the main mobile structure was stick together because of the cold welding phenomenon, and at last they end up using the low-gain Antenna, which has 0.01% efficiency of the original Antenna. Sad story.

http://esmat.esa.int/Publications/Published_papers/STM-279.pdf

http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/32404/1/94-0141.pdf