When it comes to delivery-by-drone, one of the main limiting factors is battery life. After all, the aircraft would have to fly from a warehouse to a client's home and then back again, all on a single battery charge. Well, a recently-unearthed patent filed by Amazon addresses that issue. It proposes using airships as "airborne fulfillment centers" (AFCs) that would essentially drop cargo-carrying drones toward the buildings below.

The patent suggests that the AFCs – which could be autonomous or have a human crew – would maintain an altitude of about 45,000 feet (13,716 m), above commercial airline routes. Each airship would be stocked with an inventory of commonly-ordered goods, along with a fleet of unmanned aerial vehicles (UAVs).

The idea is that when an Amazon Prime Air order was placed, a computer system would check if the item was aboard an AFC in the client's general vicinity. If it was, it would be attached to a UAV multicopter drone (seen below), which would then be released from the AFC. Using a built-in mono-wing and the force of gravity, the UAV would proceed to glide down towards its target. As it got closer, it would start up its motors, allowing it to hone in on its destination more like a helicopter.

Once the delivery was made, the UAV would not fly back up to the AFC – that would require too much power. Instead, it would proceed to a ground station where it would be loaded onto a shuttle aircraft. Possibly taking the form of smaller airships, these shuttles would make periodic flights up to the AFCs, replenishing them not only with UAVs but also with inventory and fuel. They could also take away cargo such as overstock inventory.

This means that the AFCs themselves could remain aloft almost indefinitely. Although they wouldn't change location for each individual delivery, they could move to areas in which a demand for services was anticipated.

So, will we be seeing Amazon airships anytime soon? Quite likely not, although there was a time when the same thing was being said about the company's drone delivery service itself, which has now begun operations.

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