Kevlar can fend off bullets traveling at hundreds of meters per second no problem, but the supertough synthetic fiber is no match for debris hurtling through outer space at several kilometers per second. In June, engineers at the Fraunhofer Institute for High-Speed Dynamics in Germany ran a space-debris simulation to test the fiber. Small meteoroids and other space flotsam can hit resupply vessels to the International Space Station, so the vessels have shields. Those shields are made up of an aluminum wall covering a layer of Kevlar and Nextel, a ceramic fiber. In the simulated impact, the engineers fired a 7.5-millimeter-diameter aluminum bullet from a specialized gun at a model shield. Traveling at about seven kilometers per second, the bullet punched a fist-sized hole through the Kevlar-Nextel fabric. Despite the damage, this shield did its job: dissipating the energy of the bullet and so protecting the inner walls.
This article was originally published with the title "What Is It?" in Scientific American 311, 3, 26 (September 2014)