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.

How about winter flight

[SpacePunk]

Ok, it works fine on one of the days of the year that has the longest period of daylight, but how well does it work on a day that has the shortest period of daylight? Just because something works in optimum conditions doesn't make it noteworthy.

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

[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.

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:This is a *long* way from being a commercial je

[Anonymous Coward]

From the article:

But while the team said this proves that emissions-free air travel is possible, it doesn't see solar technology replacing conventional jet propulsion any time soon.
Instead, the project's overarching purpose is to test and promote new energy-efficient technologies.

Re:This is a *long* way from being a commercial je

[Anonymous Coward]

I think the goal of the project is more to 'promote solar energy' rather than to develop a commercial airliner.

If they wanted to produce a useful airplane, they would probably use solar power to split water into hydrogen and oxygen on the ground, and use the hydrogen as fuel for some kind of jet/prop engine. This would be far more practical than using 400kg of Lithium-ion polymer batteries to store the energy and they would probably end up with a plane that can to some degree compete with todays planes in terms of capacity and speed.

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: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? :)