Originally Posted by
KenV
If it runs on hydrogen as indicated, the only emissions will be water vapor, which should be politically correct as it contains no carbon.
If you ignore the fact that most current hydrogen production comes from natural gas.
The SR71 was originally going to be hydrogen-powered, but I forget exactly why. They dumped that idea because they just couldn't make it work; amongst other things, it would have been a much larger vehicle, just to support the tanks required for the low-density fuel.