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NASA flying-car man designs electric VTOL podcraft

'Puffin' tailsitter offers just 6 minutes' hover, though

Only 6 minutes' hover before flat battery - or just 3 if you want to go somewhere

So cunning is this design that Moore reckons just 45 kilowatts of power will suffice to lift the Puffin and its pilot off the ground. Unfortunately, while electric motors are great they generally mean the use of batteries - which aren't great at all, even today. The Puffin has just 45kg of them, which with present-day lithium phosphate technology means only 4500 watt-hours of juice: in other words the machine can hover for about six minutes before its batteries run flat.

Moore has told the press that the Puffin could fly in tipped-over plane mode for 20 minutes, achieving a range of 80 km. Previous remarks of his have suggested energy consumption of around 7.5 kW in the cruise for such aircraft, indicating that there'd also be juice for around 90 seconds' hovering at each end of such a journey - not much time for dithering, certainly.

As it stands, then, the Puffin is pretty marginal as a means of flying from place to place: though it could make an impressive glider, the more so as its props would be able to act as turbines in forward flight, recharging the batteries as the Puffin glided down. Electric motors don't lose performance with height, but propellors do: however the machine - if not its pilot - would be theoretically capable of reaching 30,000 feet, reportedly.

Even so, in the current state of battery tech the Puffin is no more than a curiosity. Moore and his colleagues hope to have a scaled-down prototype flying within months, and have suggested that military customers might like the design as it stands - it would be no noisier "than a conversation", apparently, and having no exhausts would boast low infrared signatures.

But the Puffin isn't vastly more capable than existing jetpacks or minicopters, and the military has conspicuously failed to embrace them. Hopeful commentary along the lines of "let's not forget who put men on the Moon" is out of place here, too - NASA has shown quite clearly that it is uninterested in PAVs.

Even so, there's hope for aspiring electric hover-pod pilots yet. Moore believes that battery energy densities could triple in coming years, which would make Puffin-style craft much more useful. ®

*Puffins genuinely can't fly in winter, when they moult their flight feathers and become groundbound. Hopefully not an omen. (The puffin is environmentally friendly, according to Moore, "because it hides its poop".)

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