The up to 18km/s is from the linked shield. Up to 0.1c is from the interstellar spaceship competition "cruise" speeds (also used 0.01c) as presented in their d

The up to 18km/s is from the linked shield. Up to 0.1c is from the interstellar spaceship competition "cruise" speeds (also used 0.01c) as presented in their deck. They're a few orders of magnitude difference. Also, there's plenty of resources around on interstellar travel that shows interstellar dust/debris is going to be a huge problem. For example Atomic Rockets, which has a bunch of good reference materials (albeit poorly organized), or the Astronomy Cafe https://sten.astronomycafe.net/at-what-speed-does-the-interstellar-medium-become-lethal-to-high-speed-flight/ https://sten.astronomycafe.net/at-what-speed-does-the-inters...