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Around the World in a Solar Plane
Coati writes "Bertrand Piccard, the guy that flew around the world in a balloon, wants to do it again, this time in a solar plane."
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If you had clicked the article link, you'd see a picture of it flying at dusk, right on the front page!.
Also from the press release
The Solar Impulse aircraft will have an extremely long wingspan, advanced aerodynamics, and a revolutionary structure in order to capture and store sufficient solar energy during the day and to be able to maintain itself in flight during the night.
According to the wikipedia, Jean-luc Picard was named after Dr. Jean Piccard, another balloonist!
"Backups are for wimps. Real men upload their data to an FTP site and have everyone else mirror it." -- Linus Torvalds
An aircraft of this type will certainly be cruising above the clouds, and will be steering well clear of any convective activity (thunderstorms) for safety reasons. The real power storage challenge is to get through the night.
This is the reason you don't see all that many solar-powered UAVs, never mind piloted aircraft. The economics of solar flight would change radically if battery technology improved.
You need to make 700mph to fly arround the world in complete sunlight, starting at sunrise on the equator, and taking 36 hours arriving at your departure point at sunset the next day.
Ah ha! Found the relevent paragraph of the website! They do indeed expect to stay aloft overnight, several in fact, which means enough power stored in batteries to keep the aircraft aloft during the shorter summer nights. I can't see any mention on whether they plan on gliding and using the propellers as required or not though.
UNIX? They're not even circumcised! Savages!
Solar Powered Helios Plane Destroyed in Test Flight... coincidence?
Auguste Piccard was a Swiss while J-L Picard is a Scot actor playing a French dude. I am certain the Star Trek NG writers had in the back of their mind that A. Piccard was a famous explorer, and they wanted their J-L Picard to be more the Swiss Explorer than the Captain Cook-like J.T. Kirk. If they knew about A. Piccard, they may have changed the name and nationality to make it simpler for TV viewers.
Cook definitely was the inspiration for Kirk, both as an explorer and as a shoot-from-the-hip military man, while I think that J-L Picard was meant to be more science and less militarism. Remember, STNG was kind of like a Total Quality Management, Fan Focus Group, New and Improved Star Trek, and one of the criticisms of Star Trek was putting the captain in harms way all the time. Captain Cook put himself in harms way and was killed in a skirmish in Hawaii, but some dweeb critics thought the captain of the Enterprise was too important to get into hand-to-hand combat with aliens every other episode, so Picard was supposed to be kept safe by Worf, and Riker was supposed to tangle with the aliens and get beat up. But as episodes went on, we learned from Q that Picard had an artificial heart because he was more hot-headed than he let on, and by the time he has turned into Locutus, he was fighting aliens and proved to be a scrappier fighter than Kirk (or the time he single-handedly thwarted a hijacking of the Enterprise by terrorists when the crew was gone on leave in a thin ripoff of Stephen Segal's "Under Siege" -- while Navy Seal Segal was "only a cook" because he was busted in rank, Captain Picard was "only the barber" because I suppose with his shaved head that was real funny).
well ive already mentioned the factors involved in earth shadow. now we must consider the energy requirements and aerodynamics.
solar energy 1.4KW m^2 outside earth atmosphere.
atmospheric radiation dissipation due to various phenomena in clear sky conditions below tropopause 0.11KW/KM
so we should have 03KWm^2 of top surface area.
we can throw in some basic guestimates that the wing area will be ~= 20m^2. a moderate flying speed of around 200knots. and NACA aerofoil efficiency of around 0.83.
now taking the STP at flight level 50 of 700hectopascals and an average rho value into rayleighs formula average viscosity constants,
a drag of 420N/m^2
to achieve 200knots a thrust force of around 840Kg/s would be required.
it can be seen that it is fairly easy to achieve solar powered flight.
although i have no idea how efficient modern galium arsenide solar cells are?
Who is Jean-Luc Piccard anyway?
Bertrand is the son of Jacques and the grand-son of Auguste. See his biography.
"His grandfather, Auguste (1884-1962), [...invented] the principle of the pressurised cockpit and the stratospheric balloon. In making the first exploration of the stratosphere [...] in 1931, he [...] became the first man to see the curvature of the earth's surface with his own eyes."
"His father, Jacques, continued the work of Auguste [...] the world's deepest dive (-10916 metres in the Marianas Trench, the greatest known ocean depth)."
Those interested in efficient flight should read about Paul MacCready (and many others) who have been involved in the American human/solar powered flight movement: More with Less: Paul MacCready and the Dream of Efficient Flight.
First entomology, then virology, and finally bioinformatics systems. Bugs follow me wherever I go.
The EPFL explains much more about the technological aspects. It's in French of course: here.
:-), they also have nice pictures
But for those who cannot read
One technological aspect is that by flying very high, they can take advantage of the cold (-55C), which can improve efficiency of electro-magnetic motors.
There are other interesting bits. I guess the page will be translated in English in a few days. (Forget computer translations, unless you want a cheap laugh)
The Helios Solar Airplane probably could have flown around the world. But with a cruising speed of only about 40 km/hr it would have taken 1000 hours (41 days). Such a long duration flight is fine for an unmanned aircraft, but poses severe challenges for manned flight. Carrying weeks worth of food, water, and oxygen represents additional payload that such a vehicle can ill afford. Onboard recycling/extraction systems could reduce the need for consumables, but they add weight also.
..... SIGH!
But without a person in the cockpit, the venture won't get much media attention. And without media attention, the project won't attract much sponsorship.
Two wrongs don't make a right, but three lefts do.
As long as he can design a solar plane which can fly at mach 2, this shouldn't be a problem.
Nahh, 700 mph is all he needs. If he flies with the sun, night will gain on him at a velocity of v_s - v, where v_s is the speed of the light's edge and v is his speed. If he takes off at dawn, and flies along the equator, he has to get all the way around (25,000 miles) before night, which starts out at 12,500 miles away, catches up.
So, he has to achieve a velocity v that satisfies both:
and
where t is the travel time and c is the circumference of the earth. Isolating t in each and setting them equal gives:
c / [ 2 (v_s - v) ] = c / v==> 2 (v_s - v) = v
==> 2 v_s = 3 v
==> v = 2/3 v_s
Plugging in the numbers, that means he needs a velocity of about 694 mph, assuming the earth's circumference is 25000 miles.
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Remember Physics 101, and that little thing you might have learned about the conservation of energy? If all we used was solar power, then yes, that energy would not /directly/ be heating the surface of the earth. But our panels collect that energy, and it gets used to heat homes, to power transportation, whatever. All that energy will eventually be converted back to heat. All of it. The earth won't miss one bit of it.
To debunk the metaphysicist, one needs only to take him outside and throw a rock at his head. If he ducks, he's a liar.