A Plane Just Flew Around the World Without a Single Drop of Fuel | Hacker News Reader

A Plane Just Flew Around the World Without a Single Drop of Fuel

huffingtonpost.com

94 pointswnm40 comments

Manned flight doesn't seem to be a good application for solar aircraft given the weight and speed limitations. Solar drones seem a much better fit. Airbus seems furthest along with their Zephyr [0], it has stayed aloft for 14 days (!). They are targeting the military as a customer and are marketing it as an alternative to a satellite, that is, an indefinite surveillance capability.

Facebook has a similar program, Aquila, which is aimed at providing internet access. They just recently had first flight of a full scale version [1].

[0] https://airbusdefenceandspace.com/our-portfolio/military-air...

[1] http://arstechnica.com/information-technology/2016/07/facebo...

To a large extent it would seem the Solar Impulse team agrees with you:

> What we are working on now [...] is to build an airplane which has no pilot. [...] an unmanned version which could fly six months, maybe one year

[1] http://videos.usatoday.net/Brightcove2/29906170001/2016/01/2... 0:47 onwards

> Solar drones seem a much better fit

Does that mean you could have a drone permanently hovering just above the clouds, taking constant video or photo surveillance, periodically sending data to whomever, all of this powered entirely by the sun without ever needing to come down or stop?

Solar aircraft at this stage (large, slow) have to stay in the sun, are sensitive to wind, and require periodic maintenance. In principle what you describe is basically the goal; aviation equivalent of a nuclear submarine that can stay in flight for weeks, months, or more.

Yes, that's what Facebook is aiming for with their Aquila project, for example:

https://code.facebook.com/posts/268598690180189

(Except they want to provide wireless internet, not surveillance.)

* they want to provide wireless internet for surveillance.

Facebook's raison d'etre is to surveil you.

Short answer, yes. In practice they would probably switch off with another drone after some period of time (months?) to do a maintenance check.

What about the mushy on board computer powered by glucose?

Having a person on board cost several hundred pounds where the electronics would have been under 1. AKA, the person was closer to cargo, than necessary.

Pardon if this is out of sorts but this will probably be the funniest thing I read today, and I salute you for pointing out the sticky-wicket of talking about 'fuel' in this case.

Things get interesting when we cross the inflection point of having an abundance of lift.

Once you can achieve X+Y lbs of indefinite lift, where X is the necessary weight and Y is the excess, then maintaining Y*C aloft indefinitely becomes simply a matter of scaling the number of crafts to contribute the requisite excess lift (aerodynamics aside for the time being).

What affect will indefinitely floating object, barges, buildings (living, restaurants, business), etc... have on society where fuel isn't a factor? (e.g., Facebook's global internet, cheaper flying transports, cars and eventually domiciles)

You're absolutely right, above a certain ratio of surface area to mass it becomes downright hard to keep a structure on the ground.

I'm experimenting with kites and the Magnus effect to eventually build exactly what you describe: infrastructure in the sky. (Note the absence of "cloud" puns, that is deliberate.) With computer control I see no reason why we couldn't have flying buildings.

My concern is that we will need to be able to fly to pass through the current mass extinction. I was looking at birds one day and realized that the dinosaurs that made it could fly. One way or another we are going to need to move lots of people and things rapidly over great distances.

I want to make swarms of cellular kite robots that can reconfigure themselves and combine to create vast lifting bodies.

----

Should mention Bucky Fuller's discovery: An aluminium geodesic sphere of one-half mile or greater diameter will float.

Sunlight reflecting internally from the metal heats the air which expands. Above the critical size the mass of the air displaced from the sphere by thermal expansion exceeds the mass of the aluminium shell. If you sealed the sphere (even if it leaked a bit) it would remain aloft overnight.

Bucky called them "Cloud Nine" and wanted to build cities in them.

Next step would be building it emission free and without use of any products that use the same fossil resources for the plastics?

Why? Then you would have 1 experimental solar plane that uses 0 fossil fuels anywhere it the supply chain.

It's not necessary to make everything use 100% renewable but rather solve some big problems that'll make a difference in reducing green house gases. Solving only 1% of a problem by reducing it to 0 means global disaster.

Yeah, you'd do far better by trying to improve the fuel efficiency for super freighters by half a percent, or less.

oh yeah if they would already enforce current regulations on emissions of these big ship (freighters, cruise, all of them) in international waters. Now they only have to be efficient, low emission near ports for example.

Ships must abide by flag country laws in international waters. There are treaties that cover most states. Compliance is an issue now though to say the least.

I was merely asking the question if that would/could be the next goal for them. Not so much wondering about a why. Or if it would even be something we should want.

This is less a plane, and more of a battery with wings. The amount of cargo a solar plane could carry is minuscule.

Limits to battery energy density means that we can't improve very much on this.

Batteries are (in theory) optional and irrelevant for solar planes. The 747 uses about 80MW of power on takeoff, and maybe half that for cruising. The 747 has 525 m^2 of wing surface area. The sun blankets the earth with 1kW per square meter.

Solar cell efficiency is the limiting factor, if you are willing to fly only at day. No batteries needed. And it will never be enough with current designs, since 500kW is well under 40MW.

Of course a solar plane can cruise much higher since it doesn't need oxygen for the motors. And it gets more range traveling westward. At a fast enough speed (tantalizing "easy" mach 1.4) a plane on the equator could cruise under high noon forever. Wing size tends to go down with speed, so I doubt that design will ever be possible.

Edit: You were originally off by three orders of magnitude.

Solar flux at 1 AU is ~1.3 KW/m^2. At sea level, due to atmospheric absorbtion, it is between 1 KW/m^2 and 500 W/M^2.

And yeah, 500 KW of power is probably enough to get a Cessna off the ground... Not so much a useful aircraft.

Sorry, I think I fixed it while you were typing out your post?

Atmosphere conditions are usually a bit better at 9km up than at sea level. If the numbers weren't quite so bad there would be a case for detachable JATO units to get a solar plane off the ground, which then fly back to the airport to launch the next plane.

... and I forgot the speed of sound gets slower at altitude. It would need to do mach 1.6 to stay under the sun.

What limits?

The ones to the battery energy density

My bet for carbon-neutral aviation is not batteries, it's synthetic hydrocarbon fuels.

A factory that can make kerosene out of atmospheric carbon and electricity at a reasonable cost seems like a smaller stretch than an exotic new battery with orders of magnitude better energy density.

Yep. If only we can make it work economically, carbon-neutral oil will be a complete win.

I think that hydrogen may be a practical alternative. Hydrogen seems vastly inferior for cars but I think the economics are very different for large aircraft.

Hydrogen is low energy density and next to impossible to contain or transport without lossage. These are major barriers to commercial adoption absent a breakthrough, laying aside the problem of generation.

Hydrogen has low energy density by volume, but very good energy density by weight. The overhead of the volume might be offset by the gains from the reduced weight, which is especially important for aircraft.

Lossage is certainly a problem, but I think once your aircraft is airborne, you can basically burn any hydrogen as it outgasses.

This.

But storage is currently a problem for most airplane sizes, and hydrogen would really shine if coupled with fuel cells, not turbines.

That is, airplanes would really gain from all those useless gadgets companies used to push into cars.

I was thinking carbon-neutral oil, because we have all the infrastructure already.

I wonder if the plane had a small backup generator of some type in case they had total power loss over water, or was there a chase plane?

There's a chase plane. https://twitter.com/solarimpulse/status/574875287986507776

Was not there just a parachute for the pilot?

You still need someone to pick up the pilot before they drown.

For the heck of it, I compared this to what it would have taken to ship the SI2 via container ship. Apparently, a container ship can move a ton of cargo 500 miles on a gallon of fuel, so to ship the SI2 the entire distance of it's trip would take about 120 gallons of fuel.

The container ship would have been significantly faster, taking 50 days to complete the trip, versus over 500.

SI2 was the first time a trip around the world without chemical fuel was attempted.

Container ships move much more than that, leveraging the scale of cargo transport.

When the same amount of cargo is moved by non-chemical means, I'd be interested to compare the two.

but the solar plane does not need 100 million years to replace its fuel...

That pic over the pyramids is stunningly beautiful. Hopefully this achievement opens more eyes.

Except the fuel used to create the airplane ;)

Reply on news.ycombinator.com