The drones are coming! The drones are coming! But this time they're not armed with hellfire missiles. These drones are packing a new kind of heat: steaming pizzas, fresh tacos and cold beer.

Drones - the popular term for a wide range of unmanned aerial vehicles that are autonomous, semi-autonomous, or totally remote controlled - are not just limited to military use.

Even though drones rightfully call up images of large, ominous, lethal, all-seeing machines, their smaller cousins are breaking into the civilian world of consumer products and business operations.

And they're doing so in a variety of strange ways that may change the face of modern transportation - from how late-night munchies arrive at your doorstep to how equipment and medicine is delivered to remote regions.

Some of the proposed everyday uses of drones fully embrace the bizarre. Early last year, the announcement of a new start-up called Tacocopter started plenty of buzz.

By using a smartphone app, you, the hungry consumer, could punch in an order for tasty Mexican fare and soon a quadcopter drone laden with tacos woul­d be on its way to your house or office - no tip necessary.

Stephen Colbert lampooned the idea on his show: "Thanks to the imagineers at Tacopter, now, wherever I am, by sending my cellphones GPS co-ordinates I can call in a surgical flavour strike that will level my hunger with significant collateral deliciousness."

However, much to the dismay of many tech writers, Tacocopter and its convincing website ended up just being a product concept that was announced to gin up interest rather than an actual start-up.

The dreams of drone-delivered dinners don't end there, though.

Two engineers from Yelp are working on a project they call the "Burrito Bomber" that would shuttle around the taco's big brother.

Domino's pizza is also getting a piece of the action.

The company recently revealed the "DomiCopter", which uses an octocopter drone - it needs more blades than a Tacocopter because pizzas are heavier than tacos - to fly a payload of up to two large pizzas to customers.

In a video of the proof-of-concept run, you can watch the remote-piloted drone navigate rural terrain and reportedly traverse six kilometres in 10 minutes, with pizzas in tow. But don't expect the DomiCopter to be coming to a neighbourhood near you anytime soon.

There are plenty of logistical, technological and legal barriers to overcome before the system can be successfully operationalised.

One restaurant in Britain does have immediate plans for using a drone waiter that will serve up dishes on a quadcopter they call the "iTray".

The YO! Sushi restaurant chain explains in a video showing the iTray in action that it is trialling the drones in the company's Soho location, and it hopes to roll them out in other locations around Britain.

Similarly, at OppiKoppi Music Festival, taking place this August in South Africa, attendees will have the opportunity to use an app to call in a drone that will parachute a cold brew to their GPS co-ordinates on the festival grounds.

The co-founder of Darkwing Aerials, the company running the drone service, said in an interview with Billboard that the technology works well, but "it's more of a PR thing for the festival than trying to get beer out to the masses."

Using drones for mundane tasks such as delivering food, while popular, is not exactly revolutionary.

For now, the benefit comes just from enjoying the novelty of these high-tech marketing stunts. Chances are our skies won't be swarming with drones zipping around with dinner orders, nor are they likely to replace waiters and bartenders.

If we want to understand how drones might actually have a significant impact on transportation - particularly in the delivery of things - we should think about the Pony Express.

That's right, the speedy (for its time) mail delivery system.

It was composed of relay stations in which riders could exchange their horses for fresh ones - that way the beasts were always galloping at full speed.

Now think of the Pony Express, but with drones. That's the basis for what two companies, Matternet and ARIA (Autonomous Roadless Intelligent Array), are currently working on.

The concept is simple: specially designed drones would be loaded with a package; they would fly from one relay station to another; and their batteries would be swapped out with a fully-charged replacement. The process would repeat until they reach their destination and deliver their packages.

The founder and chief executive of Matternet believes his team has "stumbled upon something that can be the next paradigm for transportation, initially in small goods, and later on, of heavier and heavier goods.

The key application can be in medical delivery and also for transportation in places that are very, very congested." While "next paradigm" is a high aspiration, the drone relays could prove to be an innovative way to quickly send crucial items to locations that are lacking infrastructure or are surrounded by treacherous terrain.

The initial investment to get such a system up and running looks to be within reason, too.

"A case study of the Maseru district of Lesotho put the cost of a network of 50 base-stations and 150 drones at US$900,000, compared with US$1 million for a 2-kilometre, one-lane road," reported the Economist.

However, the upkeep and maintenance of a drone network would require expertise and resources that are likely to be hard to come by in the remote, underdeveloped regions where these systems would be implemented.

There are more complicated barriers to overcome than just economic costs.

You may have noticed that none of these drones - DomiCopter, iTray, or the relay system - are being rolled out within the US.

This is because there are strict laws and licensing procedures for commercial drone operation, which are enforced by the Federal Aviation Administration (FAA).

"The FAA intends to announce a plan for commercial operators to seek certificates of authorisation in September of 2015, but that does not mean that drones will be able to fly right away," says Ryan Calo, a law professor at the University of Washington who specialises in robotics.

While the proper authorising paperwork may become easier to obtain, drone operators will also have to consider other laws.

In particular, Calo pointed to the fact that "although trespass law no longer grants ownership rights 'to the heavens', land owners still own the air rights above their land that they can reasonably use.

Thus, drone-based delivery systems will have to take care not to fly too close - whatever that means - to private property".

Last month, National Geographic photographer George Steinmetz was arrested for flying a paraglider over a feedlot. Brian Palmer points out that the airspace rights on private property probably extend to an altitude of 80 to 500 feet (25 to 150 metres).

It should be no surprise that a flying robot would ignite worry and confusion about traditional concepts of property and privacy.

Therein lies another reason why something like the drone network has much more potential in other countries where legal restrictions aren't as stringent.

The military uses drones for more than armed strikes and surveillance.

The K-MAX may look like a normal helicopter, but in reality this "aerial truck" is an unmanned vehicle that can fly up to 2700 kilograms of cargo into war zones, all without a flight crew taking on a dangerous mission.

And then there's the massive drone known as "Phantom Eye", which has a wingspan of 150 feet (45 metres), space for a payload of 200 kilograms, and which can stay in the sky for five days. One crucial element that makes this drone unique is that it's powered by liquid hydrogen.

The creator, Boeing, thinks this will make the machine three times more energy efficient. For now, Boeing is pitching Phantom Eye as an airborne mobile tower, but it's not much of a stretch of the imagination to see how a modified version could be used to transport cargo long distances and in an environmentally friendly way.

At this point, though, drones, and especially non-military ones, are still an immature technology.

There are many ethical concerns that drone-based transportation systems will have to confront before they become anything like a viable mode of delivery. Dangerous malfunctions are a realistic hazard, for instance, and the risks have to be seriously considered before we jump on board with this new innovation.

"Given the rate of gravity, it doesn't take much height for a dropped item - or a plummeting robot itself - to be harmful or lethal, whether intentional or not," said Patrick Lin, Director of the Ethics + Emerging Sciences Group at California Polytechnic State University.

"A hot pizza falling from the sky could also burn a person, like cheesy napalm." Lin said he finds it hard to see why, at this point, any business would want to take on that kind of risk and liability just to deliver things to people in a novel way.

One of the biggest drone-transportation obstacles is the general distaste for anything drone-related.

As US General Stanley McChrystal said, "They are hated on a visceral level, even by people who've never seen one or seen the effects of one."

This loathing is likely to put the brakes on drone delivery in the near future.

But that gives us time to contemplate the ill effects of using drones in this way, and maybe we can pre-emptively avoid a future where we have to dodge meteoric drones.

Slate