From the image, there doesn't appear to be any vacuum. The tunnel is filled with air, which blows around the loop like a circular wind tunnel. I don't know any

From the image, there doesn't appear to be any vacuum. The tunnel is filled with air, which blows around the loop like a circular wind tunnel. I don't know anything about fluid mechanics, but wouldn't there be some serious friction between the fast moving air and the tunnel wall? I'd be surprised if that resulted in less energy loss than a fast moving vehicle through static air, but perhaps someone with expertise about such things could chime in...