The promise of 3D printing has finally taken off with the development of a drone that takes just a week to create
Under darkening skies on a grass airstrip in the UK's Wiltshire Downs, north of Stonehenge, I am watching half a dozen aeronautical engineers rushing to assemble an uncrewed aircraft before the weather takes a turn for the worse. They are hoping to show how 3D printing will revolutionise the economics of aircraft design – by flying the world's first fully "printed" plane.
Led by Andy Keane and Jim Scanlan of the University of Southampton, the team believes that 3D printing will soon allow uncrewed aircraft known as drones or UAVs to go from the drawing board to flight in a matter of days. No longer, they say, will one design of UAV be repeatedly manufactured on a production line. Instead, designers will be able to fine-tune a UAV for each specific application – whether it be crop spraying, surveillance or infrared photography – and then print a bespoke plane on demand.
3D printing has come on in leaps and bounds since its origins as an expensive prototyping tool over two decades ago. It uses laser-assisted machines to fabricate plastic or metal objects, building up the item layer by layer, each slice just 100 micrometres thick.
To do this, the 3D printer first slices up an object's computerised design into hundreds of easily printable layers. Each layer is then "printed" by training a laser beam on a bed of polyamide plastic, stainless steel or titanium powder – depending on the object being created – tracing out the entire 2D shape required for that layer. The laser's heat fuses the particles together at their boundaries. Once each layer is complete, more powder is scattered over it and the process repeated until a complete artefact is produced.
What the printer spits out is a powdery "cake" from which the desired object can be retrieved simply by pulling it out, like a child yanking a buried toy from a sandpit
To create a stronger object that can withstand higher loads and stresses, an electron beam can be used in place of a laser to melt the powder particles completely. And because 3D printing involves no cutting or grinding of metal, it offers vast design freedom.
This is a huge deal for aircraft designers. Some of the best ideas in aviation history have involved designs which proved too pricey and tough to make. The Supermarine Spitfire, for example, was among the most manoeuvrable fighter aircraft of the second world war because its wings were of an ultra-low-drag elliptical design. But it was a nightmare to produce, requiring complex machinery and production expertise.
"With 3D printing we can go back to pure forms and explore the mathematics of airflow without being forced to put in straight lines to keep costs down," says Keane.
So Keane's team set out to see how quickly they could design a 1.5-metre-wingspan, super-low-drag UAV, print it and get it airborne. A UK-based 3D-printing firm, 3T RPD of Greenham Common, Berkshire, joined the venture, agreeing to print the UAV out of hard nylon.
"We designed in printable hinges that would let the ailerons move," says 3T RPD spokesman Stuart Offer. "And we decided where to split the fuselage so the nose could be snap-jointed to the fuselage easily."
The budget for the Southampton University Laser Sintered Aircraft (Sulsa) was £5000, which imposed a number of design constraints. The aircraft would have no undercarriage to keep complexity and weight down, necessitating the use of a launch catapult – and a belly landing. It would be electric-motor-powered to eliminate the need for starting equipment and heavy fuel. And it would have a V-shaped tail rather than the usual upside-down-T, so that only two parts had to be printed instead of three.
Cost savings here meant that the plane could have Spitfire-style elliptical wings, as well as a strong geodesic airframe – another expensive second world war-era design, this time from the stout Vickers Wellington bomber, which was extraordinarily resistant to anti-aircraft fire.
Back at the airstrip, two wings, a nose cone and a fuselage with a built-in V-shaped tail have been ripped from nylon cakes, dusted down and delivered. Sulsa's airframe designers Jeroen van Schaik and Mario Ferraro, both grad students at the University of Southampton – which launches a UAV masters course in September – are assembling the aircraft after stuffing it with electronics, servos and batteries.
Nearby, Matthew Bennett of autopilot-maker SkyCircuits is discussing with the aircraft's ground-based pilot, Paul Heckles, how to hand manual control to the ARM-microchip-based autopilot once the plane is airborne.
Soon it's flight time. Sulsa twitches like a giant, grounded butterfly flexing its wings as ailerons and rudders are tested. Then the powerful launch catapult is cranked back. As soon as Sulsa clears the rail, Heckles punches the throttle – and the plane takes to the sky.
