The US Air Force has smashed the world speed record for a vehicle aided by magnetic levitation, or "mag lev." The 846th Test Squadron at the Holloman Air Force Base broke the milestone twice -- first hitting 513MPH, then topping 633MPH a few days later. The team's sled is levitated with super-conducting magnets cooled with liquid helium. Rockets then power the contraption along a 2,100 foot-long track, with an acceleration close to 928 feet per second. Although maglev transportation isn't unique -- trains have used it to top 370MPH -- this particular setup is one of a kind.