The World’s Fastest Electric Airplane and GM Invests in Electric Boat Technology

This Week in Engineering explores the latest in Engineering from academia, government and industry.


Episode Summary:

Aviation industry stalwart Rolls-Royce has announced that a joint program of the UK Aerospace Technology Institute, the Department for Business, Energy & Industrial Strategy and Innovate UK called ACCEL, has set new records for speed and time to climb for electric powered aircraft. The single seat aircraft called ”Spirit of Innovation” travelled a 345 mph for 3 km, achieving a peak speed of 387 mph. The records were set with a bespoke 6000 cell triple battery pack built by electric aviation specialist Electroflight and a 500 hp axial flux motor developed by automotive EV supplier YASA. 

Electrification of cars and trucks is ongoing, but electric watercraft are only now developing. This may accelerate as General Motors has announced a 25% stake in Seattle-based Pure Watercraft, a maker of electric outboard motor systems. Pure watercraft’s current technology uses a 50 hp equivalent power unit mounted on a conventional transom, powered by one or more modular batteries that can be fitted anywhere in the hull of most recreational watercraft. GM expects to help Pure Watercraft scale production with the automaker’s assembly line expertise and supply chain management knowledge. 

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Transcript of this week’s show:

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Segment 1: While the race for all electric transportation naturally focuses on cars and trucks, the same technology is making waves in the aviation industry. Rolls-Royce’s “Spirit of Innovation” test aircraft has set a new world speed record for electrically powered airplanes: 555.9 km/h (345.4 mph) over 3 kilometres, breaking the current record by 213.04 km/h (132mph). 

Tested at the UK Ministry of Defence Boscombe Down aircraft test centre, the sleek single seater also achieved 330 miles an hour over 15 km, 182 miles an hour faster than the previous record and also set a new mark in time to climb to 3000 m at 202 seconds, a full minute faster than the current record. Peak speed achieved was 623 km/h (387.4 miles per hour). According to Rolls-Royce, this performance makes the Spirit of Innovation the world’s fastest purely electric vehicle. 

The aircraft was built under a joint program funded by the Aerospace Technology Institute, the Department for Business, Energy & Industrial Strategy and Innovate UK. Called ACCEL, for ”accelerating the electrification of flight”, powerplant and battery technology was provided by Electroflight and British axial flux motor pioneer YASA. The propeller is actually driven by three axial flux motors that deliver 500 hp combined with 90% energy efficiency. Typical internal combustion engines operate with a typical thermodynamic efficiency limit of 37%, but in practice operate around 20%. The pinnacle of internal combustion engine technology, Formula One racing cars, can approach 50% efficiency. 

The battery pack is the densest ever installed in aircraft, containing 6,000 cells with a custom cooling system to reject the considerable heat generated during record runs. Flown for endurance rather than speed, the aircraft could fly 200 miles on a single charge. The 6,000 cells are divided into three battery packs for redundancy, and the entire system weighs 300 kg, approximately 40% of the overall aircraft weight. Battery developer Electroflight is using technology developed for the record breaker on regional airliner development projects. 

The next step? Official FIA certification of the record runs. How much has technology advanced? The original prototype Supermarine Spitfire achieved a top speed of 335 mph, and used a 990 hp Rolls-Royce Merlin internal combustion engine to achieve it. 

Segment 2: With electrification of transportation on the ground and now emerging in the air, what about the water? Battery electric tech is appearing there too, and General Motors has announced that it has acquired a 25% ownership stake in Seattle-based Pure Watercraft to develop the company’s electric boating solutions. 

The plan is to integrate GM EV technology, supply chain expertise and assembly line knowledge to allow Pure Watercraft to move their systems into mass production. Pure Watercraft currently markets converted production powerboats from established hull manufacturers, as well as outboard systems to repower existing boats. Their electric outboard is 50 hp equivalent and mounts on a standard transom. Connection is similar, with two power cables replacing the fuel line. 

Battery packs are modular, and sit in the hull, allowing the weight to be positioned at the owner’s discretion, simplifying or eliminating trim or center of gravity issues. Battery packs can be added to increase range, and systems are water resistant to the IP 67 standard of the International Electrotechnical Commission, the IEC. This standard is equivalent to a National Electrical Manufacturers Association NEMA Type 6 enclosure for electrical equipment, meaning the batteries are tested to be stand up to immersion in water half a metre deep for 30 minutes, which should be more than adequate for recreational boating applications. Battery packs can be charged on a 240 V system from half full to full in 90 minutes, or five hours per battery pack on a standard 120 V circuit. The motor unit weighs 112 pounds, while each battery pack weighs 118 pounds. 

According to the company, a two-battery pack system installed on a bass boat will deliver three hours and 45 minutes of propulsion over approximately 20 miles during a typical Saturday of fishing with a 15% charge reserve remaining. Current pricing for a single battery system is $16,500. Can GM’s mass production expertise bring that price down? In all likelihood, yes, and it will be interesting to see how traditional internal combustion engine makers in the recreational watercraft industry respond. 

Written by

James Anderton

Jim Anderton is the Director of Content for ENGINEERING.com. Mr. Anderton was formerly editor of Canadian Metalworking Magazine and has contributed to a wide range of print and on-line publications, including Design Engineering, Canadian Plastics, Service Station and Garage Management, Autovision, and the National Post. He also brings prior industry experience in quality and part design for a Tier One automotive supplier.