Leonardo da Vinci is usually credited with conducting the first systematic study of friction in the late 15th century, a subfield now known as tribology that deals with the dynamics of interacting surfaces in relative motion. Da Vinci's notebooks depict how he pulled rows of blocks using weights and pulleys, an approach that is still used in frictional studies today, as well as examining the friction produced in screw threads, wheels, and axles. The authors of this latest paper used an experimental setup similar to da Vinci's.
But what if it’s not fine? Even back in 1996, before a single component of the ISS was launched into orbit, NASA foresaw the possibility of an even worse worst-case scenario: an uncontrolled reentry. The crux of this scenario involves multiple systems failing in an improbable but not completely impossible cascade. Cabin depressurization could damage the avionics. The electrical power system could go offline, along with thermal control and data handling. Without these, systems controlling coolant and even propellant could break down. Unmoored, the ISS would edge slowly toward Earth, maybe over a year or two, with no way to control where it is headed or where its debris might land. And no, we could not save ourselves by blowing the station up. This would be extremely dangerous and almost certainly create an enormous amount of space trash—which is how we got into this hypothetical mess in the first place.
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