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Lilium electric aircraft is a VTOL order

Concept drawing of the Jet. Source - Lilium Aviation

German start-up Lilium promises your very own electric aircraft by 2018 – with no runway required

In almost every vision of future transportation, the flying car is a prominent feature. These would carry millions of drivers away from congested roads and into the (equally congested) sky, as commuters rushed to work at the robot factory, or spaceport.

Unfortunately, while the future arrived, the flying car is still to take off.

But do not despair, as a new solution may be on the horizon: German start-up Lilium Aviation has designed the world’s first electric jet capable of vertical take-off and landing (VTOL) for personal use. With help from the European Space Agency’s incubation unit, the firm’s two-seater aircraft “will open the door to a new class of simpler, quieter and environmentally friendly planes available from 2018.”

Lilium’s expectations are not small. Its website outlines a vehicle capable of reaching top speeds of 400km/h (250 mph) and with 500 km (300 miles) of range. The “Lilium Jet” has a reported 320 kW of power at its disposal, sent to an undetermined number of ducted fan engines – these also allow it to perform VTOL.

The increased power-to-weight ratio of electric engines compared with conventional ICEs means that, in principle, they are an sound choice for flight – provided one has access to a suitable amount of electric power. At present, there are no details as to the size or design of the aircraft’s battery, likely the greatest hurdle to getting this innovation off the ground. ElecTrans reached out to the company for more information, and we’ll update you as we have it.

We do know that the max take-off weight will be 600kg, including a 200kg max payload, and that it will be fly-by-wire, with computer-assisted VTOL. Landing requires a clear space of 15 metres by 15 metres, with the developers suggesting that its low space requirement, VTOL capability and quieter electric engine will make it ideal for use in urban spaces.

The aircraft is intended for “recreational flying” under a Light Sport Aircraft rating, in good weather conditions and up to an altitude of 3km (10,000 feet). Unfortunately, that might rule out a winter morning commute.

Close-up of the ducted fan design. Source - Lilium Aviation
Close-up of the ducted fan design – Lilium Aviation

Staying grounded

The principle behind the craft looks fairly sound – indeed, the design very much echoes Aurora Flight Sciences’ hybrid-electric VTOL-capable LightningStrike, a demonstrator model of which was recently commissioned by the US’ Defense Advanced Research Projects Agency (DARPA). But in terms of how exactly this will be executed, the company isn’t quite as clear.

According to the ESA, Lilium has already proved the concept with several small-scale 25kg prototypes and is now developing the first, full-sized (but unmanned) aircraft. Test flights of this model are scheduled to begin over the summer, with manned experimental flights in 2017. Certainly the company has come a long way since its founding in February 2015 by four engineers and doctoral students from the Technical University of Munich.

Yet the lack of detail which has been provided casts doubt over its production schedule – especially given the 20 months or within which they will begin to “rollout.” Licensing the aircraft alone – a feat which has held back AgustaWestland’s VTOL-capable TiltRotor for years – could present a major hurdle for the developers, before full production could even begin.

Nevertheless, Lilium is confident that you can probably afford one, stating that: “The retail cost will be far less than similar-sized aircraft of today and with much lower running costs.” CEO Daniel Wiegand notes that: “In the longer term, our target is to build an aircraft that not only the super-rich can afford, and that can make private air transportation possible for a much wider number of people. With the concept of taking off and landing almost everywhere, we could see that one day our plane will be used for quick and daily transportation almost like a car today.”

 

I want to believe

The past month has seen the concept generate a lot of internet traffic, but there remain a great deal of unanswered questions. Battery size and density in particular is the greatest hurdle to electric aircraft – even visionary Elon Musk doesn’t believe we’re there yet – meaning Lilium would have to make an incredible leap forward in the next 12 months to meet its production schedule.

To put that into numbers, you’d need around 60 kWh to get the aircraft off the ground, if we assume around 20 minutes of 320-kW motor use at nearly full power. Even with using much lower power once airborne – say 25% power for 90 minutes – is another 120 kWh. With additional power needed for landing and some in reserve, Lilium would need something like a 280-kWh battery pack.

To meet Lilium’s payload restrictions, that battery system would also need to weigh less than 100kg – maybe as little as 80kg – requiring more than a tenfold increase in specific energy density (from under 0.3 kWh/kg to over 3 kWh/kg). We do not anticipate such a breakthrough in technology within the next 18 months.

We’d love to see these made available as soon as possible, but at present Lilium looks like a cool concept waiting for a viable technology. Without such a breakthrough, pigs may well fly before the Jet does.

 

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One comment

  1. Yes. Their KWH and hence battery density numbers don’t add up.

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