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."

Comments

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

[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:An idea

[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: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 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: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

[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.

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.

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, 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.

Re:What the?

[cuantar]

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

Re:An idea

[Daedone]

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

AC Propulsion did this a while back

[Thagg]

Check out this press release.

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

Thad Beier