Solar Plane Completes 24-Hour Flight

asukasoryu writes "An experimental solar-powered plane landed safely Thursday after completing its first 24-hour test flight, proving that the aircraft can collect enough energy from the sun during the day to stay aloft all night. The record feat completes seven years of planning and brings the Swiss-led project one step closer to its goal of circling the globe using only energy from the sun. The team will now set its sights on an Atlantic crossing, before attempting a round-the-world flight in 2013." We ran a story about the flight's departure yesterday.

Comments

Uses

[IflyRC]

I think that this technology will show up in military drones before we'll ever see it in general aviation. It sounds great for smaller drones that can stay aloft without ever needing to refuel. Speed is also going to be a huge factor. Most drones, I would think, do not need to fly that fast as most can be launched near the location in which they need to patrol.

Re:Uses

[kg8484]

What ever happened to Helios, the NASA solar powered "atmospheric satellite"?

I think you answered your own question:

They had some kind of failure that resulted in a crash

More info on Wikipedia.

Re:bah

[Anonymous Coward]

Yesterday's story was about how they were attempting the flight and had taken off. Today's story is about how they succeeded.

Hybrid Planes

[COMON$]

Which makes me wonder, can enough energy be gathered to help offset the cost of jet fuel in existing commercial planes? You are above the clouds so you have a steady supply of power, but I dont know anything about the amount of energy a jet plane needs. Perhaps solar cells just aren't efficient enough yet? If that is the case, how efficient would they need to be?

Re:Hybrid Planes

[gurudyne]

If solar cells were 100% efficient, they might be able to gather enough energy to power the entertainment electronics on commercial aircraft.

Yes, you have a steady supply of power but you would be lucky to gather one (1) kw per square meter on cells oriented 90 degrees to the Sun. Since that would probably not be optimally aligned to the flight direction, your collection would be less.

Re:Hybrid Planes

[wagnerrp]

You are above the clouds so you have a steady supply of power, but I dont know anything about the amount of energy a jet plane needs.

Going off some numbers for a (relatively old and inefficient) 747, you burn through ~5gal of kerosene per mile, at 550mph. That's about 6lbs of fuel per second, or around 120MW of thermal output. Using average efficiency available for commercial solar panels, you're looking at a half square kilometer array to power a single aircraft at cruise conditions. If you were to replace the turbine powered ducted fan engines for electric powered ones, you would cut that power consumption in about half.

Re:Hybrid Planes

[BlackPignouf]

Assuming that the solar irradiance you get on top of the atmosphere is 1360W/m2, 1 square meter worth of solar panel with 20% efficiency (e.g. the best SunPower crystalline silicon modules) would generate 270W of electricity.

Airbus claims that the A380 consumes 3l/100km.passenger of fuel.
At Mach 0.85 (~250m/s at 10km altitude), this represents 27l/h.passenger.

Assuming 10kWh/l of fuel energy content and 50% efficiency of the turbofans (pulled out of my ...), that amounts to 135kW of mechanical power needed for every single passenger.

Assuming an electrical motor with 100% efficiency, you would need 500m2 of solar panels for every passenger to generate the required electricity, but only during the day.

The plane from TFA seems to have 200m2 of solar panels with 12% efficiency. It can get away with it because it is much lighter and flights much slower.

Conclusion : The orders of magnitude just don't match, even with 100% efficiency => Commercial flights as we know them & photovoltaics are incompatible.

Re:How about winter flight

[eln]

You're right. The original Wright Flyer barely made it off the ground in optimum conditions, there's no way it would have made it in poor weather, and it certainly wouldn't get me across the country in a reasonable amount of time. Clearly this whole heavier-than-air flight nonsense is wildly impractical and we should stop trying to make it work.

Solar powered flight is evolving just like any technology, and it's currently in its infancy. It may or may not ever prove to be practical, but abandoning it just because an experimental craft has shortcomings we don't think a fully mature product should have would be silly.

Probably not

[gsgriffin]

Um, maybe not. Huge wing span and slow? Perfect target. Not a useful payload. Hugh amounts of electronics needed by a drone and....the military doesn't care about the costs of fuel or operation. Land it. Fuel it up. Send it out again. This is not a military technology.

We'll see this improve over time where costs will come down and eventually people that like to fly gliders, or hang glide or whatever (and have tons of money) will have items like this for play. We'll probably also have the technology begin to pop up in other areas, but military...I really don't think so.

Re:Probably not

[Chibi Merrow]

Um, maybe not. Huge wing span and slow? Perfect target. Not a useful payload. Hugh amounts of electronics needed by a drone and....the military doesn't care about the costs of fuel or operation. Land it. Fuel it up. Send it out again. This is not a military technology.

Disclaimer: I work with the FAA on UAS system integration into the NAS, so my opinions are a bit coloured by my experiences.

I don't think you're imaginative enough about the types of missions our military wants to fly. Yes, a slow moving large UAS is not useful for low altitude fast turnaround tactical type missions, but that's what a Raven is for.

Something like this, though, would be invaluable for long duration surveillance type missions, like monitoring borders in Iraq and Afghanistan for weapons smuggling. Stick something like this at high altitudes to do autonomous surveillance and deploy more agile solutions on an as-needed basis to check out potential targets the high altitude UAS detects. The plans for UAS systems are very layered approaches, with room for little soldier-deployable RC craft, short ranged attack/reconnaissance craft, and high altitude, long-range, long duration surveillance craft.

You might think that the military will just "land and refuel" a UAS when necessary because money is no object, but that implies the existence of established airbases in the theater the UAS will be operating in, or long travel times to and from its mission which further reduce their loiter time. So, no, it's not as simple as "money is no object".

Honestly, the period that UASes are most at risk is on landing and take-off, both from hostile ground fire and just simple things like wind gusts dashing them against the ground or knocking them over. Having a UAS system that rarely has to land and take off would immensely improve their reliability and life expectancy.

So in summary, yeah, I think the military would be very interested in this type of technology.

Re:Probably not

[DerekLyons]

the military doesn't care about the costs of fuel or operation.

I'm guessing all those times I spent at the end of a fiscal quarter or a fiscal year hoping I had enough budget to buy my spares and consumables were figments of my imagination. The same goes for the gradual accumulation of ships at the piers towards the end of a quarter, after all they didn't have a quarterly fuel budget... (And this was at the height of the Cold War!)
 
Or, IOW, bovine exhaust. The military does care about the costs of fuel and operations as they don't have a blank check.
 

Land it. Fuel it up. Send it out again

The military also cares deeply about endurance and cycle time - because the shorter they are, the more units you need to maintain coverage. All else being equal (and taking budget into account) they'll chose the system with maximum endurance and minimum cycle time consistent with minimal life cycle costs.

Imperial vs metric hours

[Anonymous Coward]

The flight took 26 metric (Swiss) hours.
Wasn't aware of imperial hours existence :-)

Re:How about winter flight

[blackfrancis75]

you're still not talking anything remotely practical for commercial use.

If such a plane can be made to carry even small amounts of cargo across the earth - slowly, but faster than terrestrial speeds - and it's operating costs are negligible, wouldn't that have a variety of commercial applications?

An unmanned variant might someday even has some military and civilian uses

Contradicts first statement.

it's never going to replace our chemically powered, high speed transportation aircraft.

Possibly true, but irrelevant.

Re:bah

[Jawnn]

(Obligatory...)
Whooosh!

How much juice was left?

[tomhath]

What they proved is that they can make it through the night with fully charged batteries. What they didn't say in the article is whether the batteries would be charged back up by tonight if they had stayed aloft.

Still an impressive feat, but I'll be even more impressed when they can show that it fully recharges while in flight.

Re:How much juice was left?

[jklovanc]

Check out http://www.solarimpulse.com/nightFlights/charts.php. Notice that it took 6.5 hours to go from 46% charge to 100%charge. By extrapolation it should take about 12 hours to get a full charge though that may not be true as the solar cell efficiency seems to decrease as the cells cool below 0 degrees. Here are a few other interesting points from the graph.

1. They need a more accurate speed and altitude sensor. There are quite a few spikes in the charts. Some of them have "disappeared". They were probably fixed in the data by averaging.
2. They started with the battery 69% charged.
3. The low point in battery level was 46%
4. It took 7.5 hours to get to full charge.
5. When air temp decreased below 0 the efficiency of the solar cells also decreased dramatically.
6. For a 2.5 hour period when the engine power was at 4% with 0% solar charging the battery charge did not decrease; strange.
7. When the battery was used, it drained at about 10% per hour.
8. The airspeed was about 23kmph most of the time. That is probably the minimum sink speed for the aircraft.

Re:vanes

[wagnerrp]

im kinda suprised they didnt make the wings longer from back to front, for more solar panel area.

Larger chord length would result in lower aspect ratio, higher induced drag, and lower efficiency. They could put propellers out on the wingtip to counter induced drag...

That's cool and all but

[ThatsNotPudding]

all I read are the precursors to an affordable, 24/7, domestically deployed Panopticon system. Gotta think of the children, and if you have nothing to hide...

Re:That's cool and all but

[Chibi Merrow]

They already do this sort of stuff with helicopters and aircraft for law enforcement purposes--at least UASes are a cheaper way to do it with less risk to human life. If a UAS crashes oh well we're out some money, if a police chopper smashes into a news chopper, it's bad times all around...
Never mind the law enforcement implications, the immense benefit for things like tracking/coordinating responses to wildfires, cataloguing herds of wildlife, providing communication to remote settlements... Isn't Slashdot the home of 'just because it can be used for something bad doesn't make it wrong!' type arguments? :)

Not entirely a terrible thing

[Uniquitous]

The military spends the money to perfect it, or at least bring it to a generally useful stage. At the point that commercial interests get their hands on it, most of the major bugs in the core functionality have been worked out, allowing the erstwhile vendors to spend their money adding bells & whistles. By the time we consumers get our grubby paws on it, the major pitfalls have been addressed.

Re:Why is parent 'troll'?

[COMON$]

looks like someone had mod points and went down the thread marking troll. This is what we refer to as someone abusing their mod points. One of the more blatant ones I have seen.