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Solar-Powered Flight For 81 Hours: a New Endurance World Record
Hallie Siegel writes: A team of researchers from ETH Zurich have just set a new endurance record for solar powered flight of an unmanned autonomous aircraft, achieving over four days of solar-powered flight in a range of weather conditions. Being able to demonstrate more than 24 hours of endurance is important because overcast skies can inhibit recharging and poor weather or high winds can effect power consumption. Nice achievement for this class of aircraft.
This isn't big news for solar or batteries.
Just 2316 km over 81.5 hours is more like floating than flying, and the main advance came from the reduction in mass, not improved solar/battery tech.
It's 6.5 kg while the prior record holder was 13 kg. If you look at the thing, it's not much more than a really large wing.
The records it took were for longest flight among aircraft under 50 kg and longest flight for low-altitude, it doesn't have the overall longest flight, nor longest unmanned flight.
Um, no. The cells were 23% efficient, which is not exceptional, and the batteries had an energy density of 243W h kg1, which again is scarcely cutting edge.
I think this project demonstrates maturity in the technologies used, not progress as such.
Perhaps OP was thinking of what they promised (a 5-year flight), or perhaps my quick googling is insufficient... I was able to find a 14-day unmanned solar-powered flight in 2010 from Qinetiq's Zephyr craft.
Following the link to the article (I know, I know, this is slashdot, we don't do that here), there's an important qualifier missing from the summary; this is a record for an aircraft *in its class*. Specifically, that class is aircraft under 50 kg total mass. They do cite the Zephyr (now as an Airbus property) as the longest UAV flight, and Solar Impulse 2 as a longer flight by a (manned) solar airplane. It is also notably different than the Zephyr because it is a "low-altitude" vehicle. From one of the research papers on their website (OK, I realize this is getting out of hand... I mean, following the link is one thing, but doing a google search for the company involved???), it looks like they're staying below 1,000 meters. The Zephyr is intended to fly between about 60,000 and 70,000 feet, where winds are weaker and there is less drag. On the other hand, apparently this craft has an IR camera to help it find thermals that it can ride to help reduce the power requirements.
That said, given the additional requirements of transporting a human, I give the award for most impressive achievement to the Solar Impulse team. Their pilot outweighs not only the payload of the AtlantikSolar and Zephyr crafts (0.8 kg and 2.5 kg, respectively), but probably also the whole UAV itself (6.8 kg/15lb and 53kg/117lb, respectively - I'll assume that their pilots don't have a second job as a jockey). Add to that about 5 pounds of food and 7 pounds of water/drinks *per day*, plus some bottled oxygen so the pilot can breathe at 40,000 feet... And apparently the sensor and data downlink package from Solar Impulse consumes up to 50W - that's as much as the craft in this article uses for all its needs, including propulsion. There's a lot of stuff required to keep us silly humans alive.
I'll grant them that it's an impressive feat in a small package - but I still think the bigger package with the bigger payload (a human) is more impressive.