Solar Craft Flies Through Two Nights

An anonymous reader writes "A solar-powered, unmanned craft has flown for 54 hours — a record for both unmanned aerial vehicles and solar craft. None before has managed to store enough solar energy to fly through more than one night. There is also a video showing the 18m carbon fiber wing craft being launched."

more

[stoolpigeon]

This BBC article has good info. [bbc.co.uk]
 
It should not be a surprise that the Global Hawk record did not stand. Look at the two craft. If a global hawk hit the zephyr it probably wouldn't even notice.

Re:

[stoolpigeon]

global hawk is a lot more than an r/c. my understanding is that when it made the 20 hour or so flight to Australia - it did so without direct input once it left the ground.

Re:

[DustyShadow]

You are correct. It is fully autonomous, from take off to landing. Pilots can give it waypoints but don't actually fly it to those points. It does it all on its own.

engouh solar energy

[InvisblePinkUnicorn]

From Wikipedia:

"Engouh Solar Energy (ESE) is a newly-discovered form of solar energy capable of lighting even the darkest parents' basement to the point where the average nerd can neither see his keyboard nor the inevitable typos he'll make on internet discussion boards."

Glass houses...

[billbaggins]

Looked at your /. username lately?

Re:

[InvisblePinkUnicorn]

"Looked at your /. username lately?"

The i is not missing, it is simply invisible, out of reverence for Her Holy Horn (H^3).

Either that, or the full username was already taken and this looked the most like that.

What constitutes Solar Power?

[mweier]

Obviously solar panels feed it to maintain energy stores; however since it must store this energy in a battery of some sort, is it required that the batteries be empty when launched? If not, what's to stop someone with a major pile of pre-charged solar-rechargeable batteries from tacking one solar panel on top & calling it a solar vehicle even if it could never fully charge those during use? Not accusing these folks of doing that but just curious about how they classify solar vehicles...

Re:

[TheRaven64]

I'm not sure why going two nights is such an achievement. Surely you charge the batteries in the first day, discharge them the first night, and then repeat on the second day and night. Unless the batteries are not fully discharged for takeoff, as you say.

Re:

[QuantumG]

There's these things called clouds right, and they obscure the thing called the Sun which the solar power comes from.. and, as such, no two days are the same.

Re:

[Somegeek]

Not many clouds above 50,000 ft. That's where this thing flies.

Re:

[mr_matticus]

That would require that the craft generate enough solar power to charge the batteries AND power the craft at the same time. The loss of energy in transferring from solar cells to batteries and drawing from batteries again is not inconsiderable, and the motors need to run in daylight, too.

At 20% overall efficiency (assuming arbitrary battery losses from a 30% solar cell), you need to be able to collect ten times the operational requirements of your vehicle in order to pull off what you describe. That's qui

Re:

[TheRaven64]

Right. I understand why flying through the night is impressive, but why is flying through a second night impressive? If on day 1 you can generate enough power to fly through night 1, why is it hard to generate enough power on day 2 to fly through night 2? Unless, of course, the battery is charged prior to take off, at which point calling it solar powered is not really accurate; solar assisted might be better.

Re:

[Eivind]

Your hunch is correct; the plane is charged prior to take-off, which it needs to be because on the first day it has *two* tasks, one is to charge the batteries, the other is to gain 15-18000 meters of altitude. It would be unable to do both, but manages to do one of the two.

And that's why *2* nights is interesting -- on the first day/night cycle the plane demonstrates that it can climb to altitude without using the batteries, and that it can survive the night on batteries-only.

On the second day/night cycle

Re:

[larkost]

There is a natural limiter here: batteries are very heavy and a battery-powered (heavier-than-air) aircraft is unlikely to ever get close to this record. That is something that is unlikely to change before things change enough to make this sort of record meaningless anyways.

Re:

[Jartan]

There is a natural limiter here: batteries are very heavy and a battery-powered (heavier-than-air) aircraft is unlikely to ever get close to this record. That is something that is unlikely to change before things change enough to make this sort of record meaningless anyways.

Why use batteries though? What about miniature flywheels and what not? Batteries would be the last type of energy storage I'd look at for this sort of application.

Re:

[jtcm]

Why use batteries though? What about miniature flywheels and what not?

You're right, flywheels can store the same energy using less mass, and can be more efficient. I suspect, though, that heavey flywheels on a light airframe would make for some difficult gyroscopic effects.

In fact, see this page with a Flywheel vs Battery Energy Storage [axeonpower.com] comparison. It's just past halfway down the page:

Flywheels are preferred over conventional batteries in many aerospace applications because of the following benefits

Fl

Re:

[petermgreen]

The other big problem with flywheel batteries is failure. If the complicated superconducting bearing and vacum systems fail the energy could be released very rapidly. Add to that the fact that for maximum energy density the flywheel is probablly on the brink of flying apart and the potential for carnage is obvious.

Re:

[salec]

You can mount the flywheel in gyroscope gimbals, thus decoupling it from the airframe (and you also get a gyroscope for free :P )

Re:

[agingell]

The record in question actually has nothing to do with solar power. It is purely an endurance record for longest flight time under continuous power. The Global Hawk is actually powered by a turbojet engine and normal Jet A1 fuel.

Solar powered aircraft have been quite successful for some time for instance the Pathfinder and Helios aircraft by NASA the biggest issue is to get through the night on battery power. I believe the NASA aircraft had to resort to gliding and soaring which this aircraft does not.

Re:

[XaXXon]

Charge as many batteries with as much power as you want - you have to get them off the ground. The problem is that right now batteries are heavy and not efficient enough. It's the same problem with getting rockets into space. You have to carry the energy you want to use later.

This is something that will get solved - the only interesting part is 'when'. The fact that it's happening now is what's interesting.

Re:

[Eivind]

Nothing prevents that. But a battery doesn't contain even nearly enough energy to fly for 2 nights and 3 days. So if you did this, your plane would come back down once the battery was empty, after a few hours at best.

The endurance-record for not-collecting-energy is the Global Hawk, it uses jet-fuel which has a lot more energy relative to weight compared to batteries, and it still manages "only" max 30 hours.

I'm guessing the max for a batteries-only plane would be in the single-digit-hours, indeed for this

Re:

[LoudMusic]

It still has to heft those batteries. In my solar-uneducated-opinion, if it made it through one night and was able to recharge and make it through the next it should be able to do that indefinitely. Assuming optimal conditions. It could also take advantage of flying west in the sunlight and east in the darkness to pick up a few extra minutes of Sunlight.

I'm wondering if there are plans to put these things in motion with cameras equipped for continual updating of surface images in populated areas. A team of

Innovative solution to the nighttime problem

[Anonymous Coward]

A series of halogen lights mounted along the wings are illuminated at night to power the solar array.

Re:

[XaXXon]

Too bad it's not metal.. you could just put a magnet in front and above the plane to keep it up and and moving.

Re:

[Yvanhoe]

Brilliant !

What the?

[veganboyjosh]

enouhh

What the hell kind of spelling mistake is that? Come on editors, at least READ the edited summary...

Re:

[greg_barton]

No furking shyte. Wish I had mod points.

Re:

[MobileTatsu-NJG]

"No furking shyte. Wish I had mod points."

Why? So you could mod up the post bitching about a frivilous typo instead of working to lower the signal-to-noise-ratio?

Re:

[coldmist]

They did! They changed it from 'enuf' to 'enougg' for us.

Re:

[cuantar]

The best part is, when the story was first posted, it was "engouh" until it was corrected to read "enouhh."

Re:

[HTH NE1]

Indeed, engouh is enouhh!

Re:

[Kelz]

I'd imagine some editors actually have a sense of humor and like to poke fun at grammar/spelling trolls.

Question?

[SnarfQuest]

Does this bring us closer to personel flying cars, that have been promised to us for decades?

What if it flew in the opposite direction of sun

[CrazyJim1]

During the day, it flys with the sun, to get a longer day. Then during the night, it flys in the opposite direction in order to achieve a shorter night.

Re:What if it flew in the opposite direction of su

[Ogive17]

While I understand your point, anything moving that slow will wind up just a few miles from the origin if you fly west with sunlight and east in the dark.

Tipping Point

[Doc Ruby]

This is the watershed performance for solar powered vehicles. If it can go through 2 nights, it can go through any number of them. Though we're still on the sunny side of the equinox (2 weeks prior), so there is a little more time charging in the sunshine than discharging in the darkness.

When a vehicle can go 24h on only 12h prior charge, that will be the next major milestone. Still not enough for uninterrupted travel past a latitude where nights are longer than a whole couple of days (depending on the battery - a yearlong discharge battery would be good anywhere with current performance).

The next parallel milestone is automated rechargers leaving ground charging stations to recharge the permanently aloft vehicle in flight.

After that, there's not a lot more demand for improvement, except overall efficiency for carrying heavier loads and more demanding equipment.

Like a network of these permanently in high atmosphere propelling solar sails through the solar system and down to blimp spaceports.

Re:Tipping Point

[XaXXon]

Mathematically that's not quite true. If it had some amount of initial charge it could be using some percentage of that in order to make it through each night. Perhaps that number is 50% each night :)

I don't know if that is the case here.. just saying that it doesn't necessarily follow that the plane can stay up indefinitely.

Re:

[Doc Ruby]

That's an interesting idea: use excess daytime solar power to gain altitude, storing power in the entire craft gravitationally, rather than in a battery. Perhaps using some small amount of power (while the sunlight is available) to change the wing shape from whatever best suits the primary application into one that glides farther (falls slower). Gravitational storage rather than battery means the entire vehicle is lighter, therefore more efficient, if a minimum of mass is dedicated to accommodating the nigh

Helios was cooler

[iiii]

Helios was way cooler. It was headed for continuous flight several years ago. Unfortunately it met an untimely end. I think NASA should rebuild it and continue the work. Some of the, um, pundits, on this thread don't seem to have the faintest about how it could work, but it is an awesome concept: solar panels collect all day, generating enough power to fly and to charge the hydrogen fuel cells, which power the craft all night. And it can fly high enough to be above the weather, so the sunshine will be

Talk about doing it the hard way

[Colin Smith]

Replace the wings with an envelope and you can stay up for weeks.

 

Re:

[Eivind]

True, but you're less maneuvrable. A compromise may be worthwhile, building a plane like this, but seal it and fill it with helium. Dunno if the volume is enough that the added lift would outweigh the extra mass for sealing it though.

Re:

[afidel]

There's that whole problem of speed, I assume even an ultralight plane like this can make better headway then even the fastest semi rigid airships like the Zeppelin NT @ 125 km/h.

Grousing about submissions

[kwerle]

Not only did I submit this story with no type-o's, last night, but I also made reference to the previous solar powered flight that lasted 2 nights [acpropulsion.com], which this submission implies never happened before.

Though the previous one also did gliding/non-powered flight part of the time. Still, up for 48 hours.

AC Propulsion did this a while back

[Thagg]

Check out this press release. [acpropulsion.com]

AC Propulsion said that they could do it indefinitely, but their pilots got worn out.

Thad Beier

Re:AC Propulsion did this a while back [2yrs ago!]

[Thagg]

I hadn't read the article -- I remember it when it was done, but I had thought it was just recently.

This was done by AC Propulsion two years ago.

Thad

Attaining altitude

[drwho]

Like many space and exotic aircraft, it must have to expend a lot of energy to get to its cruising altitude. Once that's done, conditions should become easier. Would it be considered 'cheating' to launch such a perpetual flying machine with an assistance device? That could be either disposable batteries that are jettisoned when discharged, or some chemcal rocket engine, or a jet engine, or have it launched from an aircraft.

Insolation is going to me much better at high altitudes. I just hope the photovoltaic cells are designed to take advantage of the increased amount of energy available in the UV spectrum. How about filling the free space in the wings with hydrogen? That might help lift a little, at least from the ground. However, there would have to be some way of dealing with the reduced pressure at operational altitude.

There's been a lot of interesting improvements in PV efficiency lately. However, most of these seem to only happen when the cell is operated at insolation far above normal. These are obtained by focusing the sunlight. Unfortunately, all of the technologies I know of which could do this are heavier than simply adding more, less efficient cells which operate at normal insolation or the slight improvement that high-atmosphere flight provides.

Re:

[jeti]

I think the ultimate goal is not to establish a record, but to
use these planes as communication links or surveillance platforms.
So who cares how you get the bird up as long as you can do it on
short notice and with acceptable costs?

Re:

[mks113]

Hang it under a balloon to get it to altitude. You'd lose a bit of altitude when it launched at zero forward speed though...

Props are not counter-rotating?

[mnemotronic]

In the video, the props both appear to turn CCW (viewed from behind the craft) and turn very slow. I wonder why they didn't go with props that turn in opposite directions?

First 2 night Heavier than Air Craft

[Maximum Prophet]

Better check the record books. I'm sure that this is the first heavier-than-air craft to do this. Unmanned ballons have stayed up for much longer and I sure a remote controlled Zepplin could stay up much longer.
The article says that it landed 54 hours later, but didn't specify where. If this thing doesn't have enough power to keep up with the winds above a city, it won't be much use as a satellite replacement. However if it can keep up and fly in circles above the weather it'd make an ideal replaceme

Re:

[corsec67]

At a high enough altitude, sure.....

Huh???

[Gription]

I think the quantity of energy that it takes to go over 1000 miles an hour is going to be pretty hard to collect in a solar powered plane.

Re:

[BigDogCH]

Well, at least they should travel in that direction, adding maybe an hour to their day. Then, at dusk, turn around, reducing the length of the night. They could even then land where they started....after enough days anyway.

I assume the problem is pilots, so this one would have to be automated.

Re:An idea

[dartboard]

Sure if it could go 1000 mph, that would work fine. It might be tricky to break the sound barrier with a solar-powered craft though.

Re:An idea

[everphilski]

Depending on the time of year it wouldn't have to do that... you could have it do loops around the north or south pole at a much higher latitude and still get sunshine 24/7 (or damn near close) and not have to travel as fast as they would near the equator to keep up with the sun.

Re:

[gomoX]

You don't get any power from the sun at high latitudes. It's not just about the sun being there, it's also about the angle of incidence its rays have.

Re:

[salec]

But, planes control their roll. Couldn't a plane be flown in horizontal flight, keeping direction, tilted toward one side?

Re:

[Eivind]

It depends though, the closer you are to a pole, the shorter a distance you need to fly to go troug all time-zones.

I wonder if anyone has been flying for like a week in northern latitudes during midnight-sun. It should help a lot to have 24 hours of sunshine, but the problem is that sunshine comes in almost horisontally, so it's a lot harder to make use of it if your solar-cells are mounted ontop of the wings as is customary.

Re:An idea

[dougmc]

Or even better go a bit further than that during mid summer and then it makes no difference how fast you go because you'll be in 24 hour sunlight.

The problem with that idea is that as your latitude goes up, the angle of the sun goes down. It approaches 90 degrees at the equator, but it's much lower above the arctic circle. So solar cells on top of your plane will be *much* less efficient. You might be able to make a second giant `wing' of solar cells that you can adjust the angle of (but it generates no lift, so you still need your main wing), so it's nearly vertical to catch that sun at midnight above the arctic circle, but in that case you've greatly increased the weight and drag of the plane, and even then the sun you're picking up is greatly reduced in intensity because it's gone through lots and lots of atmosphere.

Storing energy is the key. You might be able to store it in batteries like these people have done, or store it in your altitude and just let it glide down at night -- but that would require a really efficient plane. This looks to be a really efficient plane, but it's obviously not quite efficient enough to do that.

That would be cool if they'd try to fly it across the Atlantic -- it would be the first electric plane to do so, and the first solar powered plane to do so. TAM 5 [plannet21.com] took 39 hours to cross the Atlantic, and this plane was up longer than that -- but it's a lot slower too. TAM 5 averaged about 48 mph, and I'll bet this plane is less than half that.

Re:

[CastrTroy]

But because you would have perpetual sunlight, you wouldn't have to carry batteries that needed to hold a charge (or would need considerably fewer batteries). Judging by the weight of most batteries I've seen, this could cut the weight considerably.

Re:

[dougmc]

Yes, but it's perpetual crappy sunlight. Above the arctic circle, the sun never gets very high above the horizon, especially at night. And so it may go through many hundreds of miles of atmosphere, which makes it weaker -- compared to the dozens of miles it goes through near the equator -- and most of the atmosphere is hit in the last six or so miles.

And also the plane would have to fly at approximately right angles to the sun -- if not, the solar panels would be at an angle, and power would drop eve

Re:

[account_deleted]

Comment removed based on user account deletion

Re:

[DieByWire]

I didn't do the math, so this is more a question than a statement:

A + B = C + D

A hours good sunlight + B hours crappy sunlight < C hours good sunlight + D hours NO sunlight ?

The reason is doesn't work is that rate climb is a function of excess power. (i.e., power in excess of what's required for level flight.)

Let's say an electric aircraft (powered glider, really) requires 10 watts for level flight. If it gets 9 watts for 24 hours, it will never have enough power to sustain level flight. Launch it, it lands.

Give it 18 watts for 12 hours, and it will climb for 12 hours. (The rate of climb will depend on the weight of the aircraft - just turn 9 watt-hours into poetntial

Re:

[DieByWire]

...just turn 9 watt-hours..

D'oh! 18 - 10 = 8 in most places. Make that 8 watt-hours.

Re:

[dougmc]

One problem is that above the arctic circle, it's more A hours crappy sunlight (during the `day') + ( 24 - A ) hours *really* crappy sunlight (during the `night'), thanks to the sun being so low on the horizon, even at high noon -- even if you do have the fancy second rotatable wing with all the solar cells on it so they can always face the sun as much as possible, while the main wing is always level (unless turning, of course, but when you want efficiency, you turn as little as is possible.)

Now, what

Re:

[dougmc]

In space, you'd be correct though.

If you could get the plane up to 50+K feet, that might be close enough to space to make it work, and yet close enough to Earth to have some atmosphere to fly in? Perhaps aerotowing with another plane could get it up to altitude, then let the solar panels and motors take over, as they'd produce more power up there?

Helios [nasa.gov] came pretty close to 100K feet. Our `Polar flyer' would be a lot less efficient, as the solar cells would have to be on a second, rotatable by almost 90 degrees, wing, adding lift a

Re:An idea

[LWATCDR]

There are some problems with that idea.
That would work only in the summer.
That would be handy only if you needed that aircraft over the polar region during the summer months.
Then you have the really big problem...
The solar panels are mounted on the wings... The sun at the poles never climbs very high in the sky so the panels would have to be mounted on the sides of the aircraft. That would limit your collecting area a lot and or produce a lot of drag.

So the idea while interesting at first glance really is far from practical.

Re:An idea

[flyingsquid]

So the idea while interesting at first glance really is far from practical.

I have an idea- how about mounting some LEDs on the wings which could help boost the amount of light the solar panels recieve? You could keep going for like, forever.

Re:

[Daedone]

Lisa, in this house we OBEY the laws of thermodynamics!

Re:An idea

[Manhigh]

Sure, if it's fast enough. Solar powered aircraft tend to be driven by large, slow-turning propellers. Even commercial jet aircraft typically can't beat the Sun from the eastern US to the west, so I doubt we'll be seeing such a solar powered aircraft anytime soon.

Re:

[Gadgetfreak]

In case you don't want to do the rough math, the Earth is a little less than 25,000 miles around at the equator. So you'd have to go about 1040 MPH to maintain your position with the sun. Less if you're away from the equator, but still way faster than solar craft are flying now.

Re:

[CastrTroy]

Just as a reference point, the Concorde [wikipedia.org] has a cruising speed of 1350 mph. However I'm wondering if we have to change the distance around the earth, since the circumference is measured from the surface of the earth, Actually, never mind, just checked, if you assume flying at an altitude of 30,000 ft (5.68 miles), then you only increase the distance around the earth by about 100 miles. So, if the Concorde can beat the sun around the earth, can it go back in time? Isn't that how superman did it?

Re:

[fractoid]

Faster than daylight is quite a trick. ;) Good point about the latitude, at 45 degrees you only have to travel about 0.7 times as fast to keep up with sunlight. Also, remember that when a plane is taking off, the altitude gain can cause the sun to re-rise even if the forward motion of the plane would be too slow to produce such an effect on its own.

Re:

[stoolpigeon]

they probably can't go that fast. then there is weather, wind, what not.

Re:

[SatanicPuppy]

Wind sure, but not weather. The thing cruised at 18,000 meters, solidly in the Stratosphere; not much up there but ozone. Even the wind wouldn't be that big a deal; the stratosphere is so called because it sits in layers (strata), and as long as you're not climbing or descending, your environment should stay pretty much the same.

Re:

[stoolpigeon]

Thunderstorms can get taller than that - and I'd imagine even if one were a bit lower, the disturbance would extend above.

Re:

[caramelcarrot]

It'd have to be flying at supersonic speeds to follow the sun, and that thing certainly isn't flying at supersonic speeds. As you go faster, you're wasting more energy on air resistance, at which point it'd be even less feasible to use solar power.

Re:

[rleibman]

Speed of sound = 1225 km/h.

I am going to be pedantic and point out that the speed you give is at sea level, looking this up in wikipedia I read that the speed of sound in air is not heavily dependent on air pressure but more on temperature (it is slower as you go up since it gets colder).

At 29,000 the speed of sound is merely 1083 km/h.

Ann Rice's vampires do this

[peter303]

The more powerful vampires are able to follow the night and and be awake for the perpetual night.

Re:

[ScrewMaster]

Yes, but then again vampires aren't exactly solar powered. Unless you count the motivation to avoid the Sun as a power source.

Re:

[Dirtside]

Yes, but then again vampires aren't exactly solar powered.

As it happens, Solar Powered Vampires is opening at the Whisky a Go Go tomorrow night.

Re:

[Spy der Mann]

Couldn't a solar craft just follow the sun around the earth, indefinitely?

Until the next solar eclipse, that is. :)

Re:

[msevior]

Well for 6 months at least if was at the North or South Pole :-) I guess sit would have to work out some tricky aerodynamics to keep the solar cells facing the sun though.

Re:

[ChrisA90278]

"Couldn't a solar craft just follow the sun around the earth, indefinitely?"

Have you done the math? How big is the Earth? It would have to fly all
the way around once every 24 hours. It works out to just over 1000 miles
per hour. Millitary jet fighters can do this speed for short sprints but you
can't really do that with an electric driven propeller.

Re:What good is it?

[stoolpigeon]

it's good for learning things to be used in later vehicles that will accomplish, you know, stuff

Re:

[Amouth]

it is called a step in the right direction....... if you cant' see that then please open your eyes

Re:

[forkazoo]

it is called a step in the right direction....... if you cant' see that then please open your eyes

He can't open his eyes right now -- too much solar energy.

Re:What good is it?

[Dunbal]

Can this thing seriously carry any cargo that is worthwhile?

      Well if you're in the used battery business, this thing is a gold mine!

what is it good for?

[symbolset]

Recon

Re:

[isaac]

Surveillance package. It's gonna be made by Rockwell [rockwellcollins.com], for Rockwell [wikipedia.org].

Re:

[TheRaven64]

Wireless access points. Even at LEO, satellites add latency (not to mention a great deal of expense) to connections. Something like this could be used over rural communities to provide wireless access without satellite latencies. If it can stay up more or less indefinitely, then it can relay signals to an exchange somewhere. Fitting them with point-to-point communications lasers could allow them to be deployed in a mesh configuration, which might be a lot cheaper than deploying cell phone towers in a lo

Re:

[kimvette]

Yes, but how are we going to get the swallow to carry the coconut?

It could grasp it by the husk?

Re:

[Chapter80]

engouh
What the hell kind of spelling mistake is that? Come on editors, at least READ the summary...

I read it as "enough". Then again, I read this article [slashdot.org] earlier.

Re:What the...?

[Gertlex]

engouh

What the hell kind of spelling mistake is that?

A typo?

Re:

[Dunbal]

I, for one, welcome our [can't think of a damn thing witty] overlords.

      Robotic, solar powered flying overlords?

Re:

[Opportunist]

Darn memes. Engouh already!

Re:

[kd5ujz]

How often does landing gear fail during takeoff? (French aircraft aside)

Re:

[petermgreen]

Afaict the time when landing gear tends to fail is deployment. when the plane is on the ground the gear is already deployed and holding the weight of the plane.

Re:

[fractoid]

I'd guess you lock the props horizontal and perform a water landing? Something that light has got to float. Hell, it could probably land on wet grass with no damage.

Re:

[Farmer Tim]

What would be really useful is a solar powered blimp to replace satellites.

There's Billions waiting for something like that.

They're already advertising [weebls-stuff.com].