Swiss start-up Sirius Aviation is targeting 2025 for a first flight of a demonstrator of its planned hydrogen fuel cell-powered electric vertical take-off and landing (eVTOL) aircraft.
Called the Sirius Jet, the design is being readied for planned service entry in 2028, says Sirius Aviation founder and chief executive Alexey Popov.
Sirius revealed the design of the jet at the turn of the year, following that up with an event on 17 January at Payerne airport in Switzerland to highlight the fuel cell propulsion system.
Popov says it is the powertrain that sets the Sirius Jet apart from its battery-powered eVTOL rivals, delivering significant speed and range advantages.
Marketing literature claims the Sirius Jet will be able to fly up to 566nm (1,050km) in its five-passenger Millennium Jet guise, or 1,000nm as a three-passenger business jet.
That compares with ranges of around 100nm for aircraft using lift-and-cruise configurations, or 117nm for the Lilium Jet, which employs a similar ducted fan architecture.
Although the Lilium and Sirius aircraft have a strong resemblance to each other, Popov says the likeness between the two designs was inevitable as it is the “only architecture to address regional air mobility”.
Externally the two aircraft are similar but not identical. Besides two fewer ducted fans – the Sirius Jet uses 28 versus 30 on the Lilium Jet – and the way they are moved, the Swiss aircraft also features a V-tail.
However, at the subsystem and powertrain level “these are two completely different products”, he says.
It is the powertrain that confers the real advantage, Popov argues. Liquid hydrogen is used in fuel cell stacks – from Swiss EH Group – generating electricity to run the motors. However, this is augmented by batteries which provide a short-term power boost for take-off and landing.
Sirius is keeping details of the power output from the system close to its chest, but the 28 electric motors are each sized at 85kW, suggesting a total requirement in excess of 2MW.
In all, the powertrain – including 300kg (660lb) of cryogenic tank – accounts for around 850kg of the aircraft’s 3,000kg maximum take-off weight, says Popov.
While certain elements of the design have been developed in house – notably the electric motors – other components are sourced externally; Leonardo, for example, will build the composite fuselage and wings.
The electric motors, however, are also being supplied to third parties. First deliveries are expected next year, says Popov, providing a valuable additional revenue stream to help fund the aircraft development.
Thermal management of the fuel cell system is provided by parent company FED – a Ukraine-based business with a long history of aerospace manufacturing.
Popov says Sirius Aviation is comfortable funding the jet’s development internally but could ultimately seek strategic partners as it moves to production.
“We are open to investors and will be precisely choosing among those who would be willing to partner with us at later stages,” he says.
Aircraft for European customers will be built in Switzerland, while those for the US market will be assembled locally via subsidiary Sirius Jet Inc.