It sounds crazy, when you think about it.

It's starting to look a little less crazy.

Hyperloop Transportation Technologies announced today that it has signed agreements to work with Oerlikon Leybold Vacuum and global engineering design firm Aecom. The two companies will lend their expertise in exchange for stock options in the company, joining the army of engineers from the likes of Boeing and SpaceX already lending their time to the effort.

"It's a validation of the fact that our model works," says Dirk Ahlborn, CEO of Hyperloop Transportation Technologies. "It's the next step."