The military unmanned delivery aircraft are all tail sitters (500 pound payloads). I hope Google's drafting behind all the existing R&D there. The military stuff out there is crazy - hummingbird-size ornithopters, 2 ounce helicopters that can fly for 30 minutes with an encrypted HD video uplink, etc.,
> The only reason for tilt-rotors is when you need to keep the main body of the aircraft level.
Actually, a tilt-rotor can be manipulated to make the aircraft go where you want it to. The same idea explains how helicopters make their way across the landscape.