Get ready to put that dilapidated VW bus out to pasture hippies, because Reaction Engines’s A2 concept promises to reach speeds as high as Mach 5 on hydrogen fuel. That is around 2x the speed of the now defunct Concorde with zero carbon emissions. That means you could be out with Greenpeace bitching about Apple products on one side of the country, and back in your hometown on the other side well inside an hour—without feeling like you have harmed mother Earth.