They were the mischievous creatures blamed for causing mechanical failures and faults on aircraft during World War Two and later the destructive monsters in a hit film franchise.

So Gremlins might not seem like the first choice for a fleet of robotic aircraft being developed by the US military.

But the US Defense Advanced Research Projects Agency is developing swarms of re-usable drone aircraft that can work together to perform a mission, which it has called the Gremlins program.

Darpa said the program has been deliberately named Gremlins after the imps that British pilots during Wold War Two adopted as their good luck charms.

The idea is to replace the expensive and increasingly vulnerable multi-function combat aircraft which currently perform a range of different missions.

Instead they propose deploying from the air smaller unmanned aircraft, each with different capabilities, to perform a mission before retrieving them mid-air so they can be used again.

HYPERSONIC MISSILES MAY REVOLUTIONISE AIR TRAVEL Air Force bosses have revealed they hope to have hypersonic missiles capable of crossing countries in minutes within five years. Several tests of hypersonic projectiles have already been carried out. Now the timelines for the first systems have been revealed. Carrying a small, conventional warhead, a hypersonic weapon could be used as a stand-off missile, so the military could strike targets at a safe distance without putting pilots and aircraft at risk. Experimental unmanned aircraft developed for the U.S. Air Force have already gone hypersonic during tests off the Southern California coast, flying at more than five times the speed of sound. The Air Force said Friday the X-51A WaveRider flew for more than three minutes under power from its exotic scramjet engine and hit a speed of Mach 5.1 last year. The test marked the fourth and final flight of an X-51A by the Air Force, which has spent $300 million studying scramjet technology that it hopes can be used to deliver strikes around the globe within minutes. The Advanced Hypersonic Weapon is part of a program to create a missile that will destroy targets anywhere on Earth within hours - travelling at speeds in excess of 3,500 miles-an-hour or Mach 5. Advertisement

Not only would the concept remove the risk to pilots by keeping them out of the front line but it would also drastically reduce the cost of each aircraft.

Darpa said the program has been deliberately named Gremlins after the imps that British pilots during Wold War Two adopted as their good luck charms.

This is because they are hoping to the 'feasibility of conducting safe, relatable operations with multiple air-launched unmanned drones'.

Dan Patt, program manager at Darpa, said: 'Our goal is to conduct a compelling proof-of-concept flight demonstration that could employ intelligence, surveillance and reconnaissance (ISR) and other modular, non-kinetic payloads in a robust, responsive and affordable manner.'

Darpa says the Gremlin drones would have a lifetime of around 20 uses, fitting somewhere between missiles and conventional aircraft.

The Gremlins would be launched in mid-air from larger aircraft and then retrieved in the same way.

The agency is hoping to build on its automated mid-air refuelling technology alongside the sea based platforms for capturing drones as they come into land.

Mr Patt said: 'We wouldn't be discarding the entire airframe, engine, avionics and payload with every mission, as is done with missiles.

'But we also wouldn't have to carry the maintainability and operational cost burdens of today's reusable systems, which are meant to stay in service for decades.'

Darpa is now inviting military engineers and academics to suggest solutions that will allow the drones to be launched and recovered mid-flight along with navigation and flight control systems.

In its briefing, the agency said it hopes that by using cheap drone aircraft it would be possible to overwhelm the increasingly sophisticated defences of enemies.

Darpa said the program has been deliberately named Gremlins after the imps that British pilots during Wold War Two adopted as their good luck charms, and were inmportalised in the film of the same name.

It said: 'As part of a future concept of operations, it is envisioned that instead of using conventional, monolithic systems to conduct missions in denied environments, multiple platforms with coordinated and distributed warfighting functions can be employed to saturate adversary defenses while achieving mission objectives.

'Within this concept of operations, a Gremlins system would provide options for delivering small Intelligence, Surveillance, and Reconnaissance (ISR) and other non‐kinetic payloads to the battlespace in a manner that is robust and responsive.

THE 'AIRCRAFT CARRIER IN THE SKY' The project forms part of a larger attempt to create flying 'aircraft carriers'. Military air operations typically rely on large, manned, robust aircraft, but such missions put these expensive assets—and their pilots—at risk. While small unmanned aircraft systems (UAS) can reduce or eliminate such risks, they lack the speed, range and endurance of larger aircraft. 'These complementary traits suggest potential benefits in a blended approach—one in which larger aircraft would carry, launch and recover multiple small UAS,' said DARPA. The project forms part of a larger attempt to create flying 'aircraft carriers'. 'Such an approach could greatly extend the range of UAS operations, enhance overall safety, and cost-effectively enable groundbreaking capabilities for intelligence, surveillance and reconnaissance (ISR) and other missions.' 'We want to find ways to make smaller aircraft more effective, and one promising idea is enabling existing large aircraft, with minimal modification, to become 'aircraft carriers in the sky',' said Dan Patt, DARPA program manager. 'We envision innovative launch and recovery concepts for new UAS designs that would couple with recent advances in small payload design and collaborative technologies.' Advertisement

'Responsiveness is achieved through the use of conventional aircraft hosts to transport and launch a volley of gremlins from stand‐off ranges.