I already wrote here about the Lilium Jet. The sheer specifications that this electric private jet promises, arouses my enthusiasm : vertical takeoff and landing, 300 km range at a speed of 300 km/h. That would mean connecting cities like Paris and London in less of an hour, taking off and landing from areas the same size of a tennis court. It will be a great complement for a private jet. It could hop from any airport to any destination in crowded cities in a matter of minutes. It could become available for location in the airports. Just look at the video below to notice how stable and elegant it looks. It fluctuates in the air with an awesome handling.
But there is a big question
Batteries seem to heavy and not enough powerful to allow Lilium jet the kind of performances it promises.
At Lilium Jet, they seem quite optimistic, though
With a broad chest and a lot of PR, the startup Lilium is celebrating its Lilium Jet flight taxi as the means of transport of the future. But a lot of what you hear from Lilium just sounds too good to be true. An engineer has now calculated – and comes to a sobering result.
The numbers that Lilium trumpets from its headquarters in Weßling near Munich sound quite impressive: The Lilium Jet is said to fly 300 kilometers in one go, in just 60 minutes. The flight taxi should offer space for five people – and transport its passengers at a price that does not significantly exceed that of a normal taxi ride. The Lilium Jet is scheduled to go into service as an air taxi in 2025 and begin its triumphal march in the world’s metropolises.
Bearer of hope or imposter?
So much for the vision of the Lilium founders around CEO Daniel Wiegand. Former Chancellor Helmut Schmidt already knew that visions should be better seen by a doctor, but on the other hand the mobility industry is also feeding on the ideas and concepts of supposed spinners who leave the beaten path and venture into new spheres. However, these people are also subject to the limits of physics – and this is exactly where the major weakness seems to be in Lilium’s PR construct: In the German aerospace magazine Aerokurier, an expert is now reporting massive doubts about the technical basics of the Lilium Jet. In a detailed calculation, the specialist, who is not mentioned by name, comes to the conclusion that the postulated performance data for the flight taxi are simply not feasible. Instead of 300, the Lilium Jet’s conceptual critique only covered 18 kilometers. The specialist calculates the maximum possible hovering duration – i.e. the flight condition at take-off and landing, which eats up a lot of energy – for the flight taxi driven by 36 jacket propellers, as only 67.7 seconds. His assessment: “This is scary short”. The energy density of the current batteries, up to 240 watt-hours per kilogram, is too low for better results. The expert’s conclusion is correspondingly negative: “The promise of a range of 300 kilometers and a flight duration of up to one hour is not achievable for the fully weighted, five-seater concept aircraft with the latest battery technology.” And not even if you look at the parameters the calculation in favor of Lilium: more than 29 minutes of flight time and 145 kilometers of range are therefore not possible – with only 60 seconds of hover, without reserves. If the Lilium Jet had to hover a minute longer, for example due to the applicable regulations, this would mean that the range would be 50 kilometers less, the engineer says.
If it is up to the will of the Lilium founders, their “jet” should revolutionize passenger transport on a grand scale by 2025. However, it is questionable whether airspace regulations and infrastructure have reached this point by then.
At Lilium you naturally see it very differently. Faced with the results, the company reacts evasively. The calculations were based on inaccurate parameters, and Lilium also refers to a flight video that shows the Lilium Jet hovering for two minutes. In addition, the company is already experimenting with new batteries with an energy density of 300 watt-hours per kilogram. These are “readily available”, as Lilium press officer Oliver Walker-Jones explains to the Aerokurier. But if you follow the concept criticism published by the magazine, even these batteries could not solve the basic problem of the Lilium Jet. This would require batteries with an energy density of 398 to 650 watt-hours per kilogram – and, according to the author of the calculation, lithium-ion technology cannot deliver them.
Communication made of PR bubbles?
Colleagues agree with the unnamed author: Aeronautical engineering professor Erol Özger from the TH Ingolstadt even considers the accepted data of the concept criticism to be “surely still too optimistic.” Mirko Hornung from the TU Munich accused Lilium, “with his claims and the highly professional PR, nothing other than an illusory world “. “With the current state of technology, the aircraft cannot achieve the postulated performance data,” Hornung is certain.
Investor Frank Thelen counters
It is quite possible that word has got around among the project investors. At least one of them responds to aerokurier’s inquiries about the Lilium Jet with a fairly thin skin: Frank Thelen, known from the TV show “Die Höhle der Löwen”, finances Lilium with his company Freigeist Capital – and considers the criticism from the experts to be typically German : “We are the people of concern. Instead of supporting innovative, young companies and visionary founders, we nip their innovative ideas in the bud with our skepticism. ”It remains to be seen whether Thelen and the“ visionary founders ”will ultimately prevail despite criticism. Lilium has the ball. But there are doubts.
Are the announced performance values for the Lilium Jet too good to be true? It almost looks like this. In any case, it will be exciting to see whether the Bavarian startup will really get closer to its ambitious goals by 2025 – or whether the “doubters” are right. One thing is clear: The limits of physics, PR or not, also apply to Lilium.