To avoid clouds
Swiss adventurer Bertrand Piccard today moved one step closer to fulfilling his ambition to fly a solar-powered aircraft round the world as his Solar Impulse completed its first full-fat test flight. The Solar Impulse The Solar Impulse boasts a wingspan as wide as a Boeing 747, with 12,000 solar cells powering four electric …
Don't know what it's cruising altitude will be, but 10,000 feet puts you above most of the thick stuff over low-altitude land, and light high overcast still lets plenty of light through for solar cells (which are happy with diffuse illumination).
10,000 feet is also low enough that one can breathe comfortably without pressurisation.
I don't get the point of it - if it is for a persistent surveillance platform, it will need to be faster to be able to maintain position against winds > 50 mph, which you certainly get at 30K feet.
So it would be unmanned - no problem, but if it can't maintain position, it won't be much use, unless you had a series of them being blown around on the trade winds, and using their power for data transmission.
There's a wheel at the base of the tail, two very long retractable wheels on the wings and a retractable nose-wheel. The 'dolly' looks to be access steps for the pilot, and probably some maintenance/monitoring stuff.
Looks good fun though. I'd love a go in it :)
Assuming the 44mph figure was a ground speed, and assuming that they stuck to the equator which is 24000 miles (of course it wont be with the equator, they will want to be over land as much as possible so flight distance would be longer)
I make that a little short of an 18 month journey, but the article seems to be saying the journey will be less than a month (5 day legs x 5 legs).
Are they traversing the global just a little south of the north pole and hence covering 360 degrees but only actually flying 500 miles?
Not entirely sure how you came to this figure, missed a multiplication somewhere or something?
The equator's about 25,000 miles..
At 44mph average speed, theyll complete an average of 1,056 miles per day (44 x 24 = 1056)
Theyre planning on upto 5 legs of 5 days each, a total of 25 flying days. 1056 x 25 = 26,400 miles they can potentially cover in this 25 days at an average of 44mph.
Recent reckonings give us approximately 24 of them hour thingies every day so that's 24 x 44 = 1056miles per day x 5 = 5280miles per leg x 5 = 26,400 miles comfortably making a trip around the world with maximal landfall (sic) I surmise the previous poster was using 44miles per DAY to get 18 months.
If this beast is a sailplane with additional electric power then it could conceivably stay up for a very long time, especially if it got some altitude. Sailplanes can travel quite fast -- at least as fast as a light plane -- and in the right conditions can stay up all day (or until the pilot gets bored) and attain serious altitude (20,000feet+).
The whole purpose to staying up is to end up with an unmanned plane you can send up and tell to loiter for the next month or two. Its cheaper than launching satellites. (As for any human needs -- find out how glider pilots cope.....)
"Flying around the world is flying around the world, no matter how many stops you make. Are you saying I didn't fly from Florida to Arizona because Delta made a connecting stop in Colorado?"
Correct, you flew from Florida to Colorado, then from Colorado to Arizona, not from Florida to Arizona. It probably doesn't make a big difference when going on vacation, but when you're trying to brag about your awsomeness it does make a difference. What this guy is doing is hard, but I'll be even more impressed by the guy who does it nonstop.
-Bounty "I've gone 10,000 hours without eating" (just not consecutively) Hunter
Definitely. Replace the human pilot with a robot and a bunch of comms gear, get the endurance up from days to months, and you have a cheap and quasi-stationary replacement for satellites to bring 21st-century communications to rural areas. (They'd need to increase the cruising altitude, but with no human pilot that might not be too hard).
Actually, better than satellites, for which speed-of-light latency is a nuisance or worse.
You might care to ponder how many "essentials" of a modern car were invented and developed for racing or rallying, and might never have been developed at all if motor-sports had not been pushing at the envelope.
It seems obvious that this is a test for a long endurance UAV where they put in a pilot during the test phase as they need the flexibility that a pilot gives during development.
This I buy.
However, I am not sure it will be able to remain circling around one point for a long time if the wind gets up. If you can only go 44mph, and the wind is > 44mph, you will start to drift off.
What they need is more power, and hence solar cells that are more efficient for the same mass (check out their website). They would also like better batteries (as would the whole EV world).
They may be in luck with the batteries as loads of people are working on this, it is likely to happen sooner or later. The solar cells are another matter. Lots of people are working on solar cells, but I have not heard of anyone working on very LIGHT ones. This they will have to pioneer themselves.
Then there is the ultimate efficiency of solar cells. These seem to top out at about 38% at present for very expensive ones. They are using 12% ones (for lightness), and we could imagine they could get to say 18% with a little work.
This is still only 50% more power, which might allow them fly 25% faster - say 55mph - this is still too slow to hold position in many stratospheric zones.
You can buy 18%-effficient panels to go on your roof today. The gap between best and cheapest will narrow for solar cells, just as it has for CPUs.
For light weight, one wants a thin film solar panel, rather than thick(ish) slices of silicon assembled into an array. Then integrate the thin film into the flight surfaces of the UAV. You can probably do that with CdTe or CIGS, and the technology of thin-film solar cells is rapidly advancing.
It might not be the end of the world if one could not do stratospheric position-holding, though it would require some diplomatic effort to allow a large number of high-altitude unmanned communications platforms to "orbit" the planet in the stratosphere. Manouvering ability sufficient to avoid being blown over a few paranoid states like North Korea might suffice, if China, Russia, the major emerging economies and the West agreed to allow a worldwide UAV communications system.
Air is much thinner at high altitude - doesn't that reduce the amount of power needed to fight a headwind?
While this is cool, to me this seems much less promising than other technologies. Consider this:
They also have a flying prototype. And their craft is faster, flies higher, is safer, wouldn't be affected by cloud cover, and most importantly can actually carry a useful load. I think the future of solar powered aircraft is more likely to take a shape like this than a heavy aircraft that can not lift anything.
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