Solar Impulse is back in the air
April 23, 2016 8:55 AM Subscribe
Flying around the world on solar power has proven challenging. 2007: "Meanwhile in Switzerland, development continues on the Solar Impulse, which has a goal of flying around the world, manned(!), by 2010." 2010: "The Solar Impulse took flight today... with the goal of flying around the world in 2012." 2015: "The Solar Impulse... is currently in the midst of the longest leg in its pioneering round-the-world journey — China to Hawaii." Today: Watch a live stream of the Hawaii to California flight. Things are going okay so far.
The biggest problem is that an A320 making a cross country flight uses the equivalent of about 175,000 kWh of kerosene (4500 gal = 639900MJ = 177750kWh and the propulsive efficiency of a jet engine is almost 100%). Solar Impulse 2 has a peak generation capability of 45kW. If you used Tesla battery packs (544kg per 85kWh) as a baseline you would need 1100 tons of batteries which is 50% more than the MTOW of said A320.
It's an impressive achievement but sadly, we are still multiple orders of magnitude away from electrical propulsion being a practical reality.
posted by Talez at 9:36 AM on April 23, 2016 [4 favorites]
It's an impressive achievement but sadly, we are still multiple orders of magnitude away from electrical propulsion being a practical reality.
posted by Talez at 9:36 AM on April 23, 2016 [4 favorites]
My bad, SI2 is 66kW and SI1 is 45kw. But it's still a couple of orders of magnitude short.
posted by Talez at 9:40 AM on April 23, 2016
posted by Talez at 9:40 AM on April 23, 2016
Well, yeah. This is more of a technology demonstrator though, rather than a competitor to commercial airliners? I don't think this project is a failure if it doesn't result in airlines immediately scrapping their jet fleets in favor of solar planes; that's really not the point. I'm pretty sure the idea here is for a couple of Swiss billionaires to have some aristocratic-adventurer-style fun while also showcasing what recent engineering advances have made possible in terms of ultralight, ultra-efficient, solar-powered transportation.
In a few years we'll probably see stuff like this showing up in the form of long-range drones, aerostats, things like that. The underlying technologies will see use in aerospace, consumer electronics, photovoltaics, electric cars, and many other things. Lithium-sulfur batteries are particularly promising, and this will have been the signature achievement to date for that technology. The stuff that makes Solar Impulse possible will get repackaged, improved, and become part of the fabric of our lives.
That would have happened anyway, but this is an excellent demonstration and generates some great bragging rights for Borshcberg and Piccard. They could certainly have found worse uses for their money.
posted by Anticipation Of A New Lover's Arrival, The at 10:14 AM on April 23, 2016 [9 favorites]
In a few years we'll probably see stuff like this showing up in the form of long-range drones, aerostats, things like that. The underlying technologies will see use in aerospace, consumer electronics, photovoltaics, electric cars, and many other things. Lithium-sulfur batteries are particularly promising, and this will have been the signature achievement to date for that technology. The stuff that makes Solar Impulse possible will get repackaged, improved, and become part of the fabric of our lives.
That would have happened anyway, but this is an excellent demonstration and generates some great bragging rights for Borshcberg and Piccard. They could certainly have found worse uses for their money.
posted by Anticipation Of A New Lover's Arrival, The at 10:14 AM on April 23, 2016 [9 favorites]
Talez: It's an impressive achievement but sadly, we are still multiple orders of magnitude away from electrical propulsion being a practical reality.
There's one major factor to add in to your calculations: Power required is approximately proportional to velocity cubed. (Plus induced and transonic drag, but let's not make this too complicated. ☺) So a couple of those orders of magnitudes can be shaved off by going slower, as the Solar Impulse is doing.
posted by clawsoon at 10:16 AM on April 23, 2016 [1 favorite]
There's one major factor to add in to your calculations: Power required is approximately proportional to velocity cubed. (Plus induced and transonic drag, but let's not make this too complicated. ☺) So a couple of those orders of magnitudes can be shaved off by going slower, as the Solar Impulse is doing.
posted by clawsoon at 10:16 AM on April 23, 2016 [1 favorite]
So a couple of those orders of magnitudes can be shaved off by going slower, as the Solar Impulse is doing.
At that point wouldn't a blimp be more effective?
posted by Talez at 10:39 AM on April 23, 2016 [1 favorite]
At that point wouldn't a blimp be more effective?
posted by Talez at 10:39 AM on April 23, 2016 [1 favorite]
I'm someone who is fascinated by completely impractical things like human-powered helicopters, so take what I say with a grain of salt. It's enough for me that this is interesting.
But, blimps: They have to have so much drag-producing surface area that 70mph appears to be the fastest speed ever for a blimp, and I suspect it required a lot of propulsion power to get to that speed. The sweet spot for an efficient plane might be 100mph, where it's going to be 5^3 = 125 times more efficient than a jetliner which cruises at 500mph. (There'll be less efficiency gain than that given induced drag and Reynolds number effects. But I digress again.)
However, there doesn't seem to be much of a market for mid-speed transport off land, as various hovercraft and ground effect vehicle inventors have discovered. People want to take light loads fast (on jetliners), or heavy loads slow (on ocean liners), but no-one is really interested in taking light loads at moderate speeds unless it's in a car on a highway.
posted by clawsoon at 11:05 AM on April 23, 2016 [1 favorite]
But, blimps: They have to have so much drag-producing surface area that 70mph appears to be the fastest speed ever for a blimp, and I suspect it required a lot of propulsion power to get to that speed. The sweet spot for an efficient plane might be 100mph, where it's going to be 5^3 = 125 times more efficient than a jetliner which cruises at 500mph. (There'll be less efficiency gain than that given induced drag and Reynolds number effects. But I digress again.)
However, there doesn't seem to be much of a market for mid-speed transport off land, as various hovercraft and ground effect vehicle inventors have discovered. People want to take light loads fast (on jetliners), or heavy loads slow (on ocean liners), but no-one is really interested in taking light loads at moderate speeds unless it's in a car on a highway.
posted by clawsoon at 11:05 AM on April 23, 2016 [1 favorite]
A friend of mine has been working on a more practical alternative for the past couple of years. Things seem to be picking up speed. His company is called Faradair.
posted by Cobalt at 11:18 AM on April 23, 2016 [1 favorite]
posted by Cobalt at 11:18 AM on April 23, 2016 [1 favorite]
At that point wouldn't a blimp be more effective?
The problem with blimps is that helium isn't an infinite resource. It mostly comes from gas wells in the American mid-West, the result of bilions of years of Alpha radiation happening in uranium deposits. It leaks constantly from a gasbag, so a blimp has to be recharged regularly. If we were to convert a substantial part of our air travel to blimps, we'd run out of helium fairly soon. And all the other gases which can be used in a blimp are flammable, if not outright explosive. (Would you ride in a blimp that was full of acetylene?)
Hot-air blimps would be the only real approach that makes sense, but that means they would be burning propane to stay in the air. At that point, what exactly are you saving compared to regular aircraft?
posted by Chocolate Pickle at 11:22 AM on April 23, 2016 [1 favorite]
The problem with blimps is that helium isn't an infinite resource. It mostly comes from gas wells in the American mid-West, the result of bilions of years of Alpha radiation happening in uranium deposits. It leaks constantly from a gasbag, so a blimp has to be recharged regularly. If we were to convert a substantial part of our air travel to blimps, we'd run out of helium fairly soon. And all the other gases which can be used in a blimp are flammable, if not outright explosive. (Would you ride in a blimp that was full of acetylene?)
Hot-air blimps would be the only real approach that makes sense, but that means they would be burning propane to stay in the air. At that point, what exactly are you saving compared to regular aircraft?
posted by Chocolate Pickle at 11:22 AM on April 23, 2016 [1 favorite]
The other alternative is in-flight recharging from another aircraft, which could haul up the kWh from the ground for you. It would be expensive, inefficient and I'd hate to do the regulatory paperwork, but it could be done. Or you could lob batteries into the air for the aircraft to catch, letting it drop the exhausted batteries to passive-glide back for collection.
I doubt even Mr Musk would spend more than five minutes giggling at that one.
posted by Devonian at 11:28 AM on April 23, 2016
I doubt even Mr Musk would spend more than five minutes giggling at that one.
posted by Devonian at 11:28 AM on April 23, 2016
Solar Impulse has distinctive landing lights, and should be observable tonight while landing.
It does not show up on Flightaware.com realtime tracking.
posted by the Real Dan at 11:43 AM on April 23, 2016
It does not show up on Flightaware.com realtime tracking.
posted by the Real Dan at 11:43 AM on April 23, 2016
Is it showing up on any realtime tracking? Mr. Nat's actually just about to fly from PHX to SFO and I'm sure he'd love to see it..
posted by nat at 11:45 AM on April 23, 2016
posted by nat at 11:45 AM on April 23, 2016
(Would you ride in a blimp that was full of acetylene?)
Probably not. As I recollect acetylene is more dense than air, not really blimp material.
posted by speug at 11:52 AM on April 23, 2016
Probably not. As I recollect acetylene is more dense than air, not really blimp material.
posted by speug at 11:52 AM on April 23, 2016
As I recollect acetylene is more dense than air, not really blimp material.
Acetylene has a molecular weight of about 26. Nitrogen has a molecular weight of about 28. Acetylene does float, just not all that well.
But it sure burns really well.
posted by Chocolate Pickle at 11:56 AM on April 23, 2016
Acetylene has a molecular weight of about 26. Nitrogen has a molecular weight of about 28. Acetylene does float, just not all that well.
But it sure burns really well.
posted by Chocolate Pickle at 11:56 AM on April 23, 2016
Is it showing up on any realtime tracking?
It's on flightradar24, at least. They also have a live map on their website.
posted by effbot at 12:03 PM on April 23, 2016 [2 favorites]
It's on flightradar24, at least. They also have a live map on their website.
posted by effbot at 12:03 PM on April 23, 2016 [2 favorites]
Blimps would go a lot faster if you just poked a big hole in the back of them and let them go pthbbbbtt all over the place. Your destination may vary.
posted by sexyrobot at 1:05 PM on April 23, 2016 [5 favorites]
posted by sexyrobot at 1:05 PM on April 23, 2016 [5 favorites]
The other alternative is in-flight recharging from another aircraft, which could haul up the kWh from the ground for you.
Couldn't you recharge wirelessly from the ground? If you had, say, a network of solar installations at various points along the route.
posted by AdamCSnider at 3:52 PM on April 23, 2016
Couldn't you recharge wirelessly from the ground? If you had, say, a network of solar installations at various points along the route.
posted by AdamCSnider at 3:52 PM on April 23, 2016
Couldn't you recharge wirelessly from the ground? If you had, say, a network of solar installations at various points along the route.
Inverse square law says hi.
posted by Talez at 3:56 PM on April 23, 2016 [2 favorites]
Inverse square law says hi.
posted by Talez at 3:56 PM on April 23, 2016 [2 favorites]
If we're going to do wireless charging from the ground how about hot-air solar blimps with black envelope that stays aloft with a combination of solar heating above and heating from focusing stations (or lasers) below?
Or, what about huge gliders that ride thermal updrafts generated by regularly spaced massive nuclear power plants? They could be launched from electromagnetic catapults powered by electricity from the power plants (the electricity that isn't powering the massive blimp-heating lasers that is)
posted by Mr.Encyclopedia at 4:02 PM on April 23, 2016 [2 favorites]
Or, what about huge gliders that ride thermal updrafts generated by regularly spaced massive nuclear power plants? They could be launched from electromagnetic catapults powered by electricity from the power plants (the electricity that isn't powering the massive blimp-heating lasers that is)
posted by Mr.Encyclopedia at 4:02 PM on April 23, 2016 [2 favorites]
All hail the black envelopes of our impending nuclear-laser-zeppelins.
posted by bracems at 4:54 PM on April 23, 2016
posted by bracems at 4:54 PM on April 23, 2016
Couldn't you recharge wirelessly from the ground?
Everyone who wants to spend their entire flight in a high-power beam of microwaves, raise their hand. (And how do you fly across an ocean?)
Of course, we could carpet the planet in Tesla coils...
posted by Chocolate Pickle at 5:56 PM on April 23, 2016
Everyone who wants to spend their entire flight in a high-power beam of microwaves, raise their hand. (And how do you fly across an ocean?)
Of course, we could carpet the planet in Tesla coils...
posted by Chocolate Pickle at 5:56 PM on April 23, 2016
Of course, we could carpet the planet in Tesla coils...
Sadly it would kill mobile data along with cell phone calls.
posted by Talez at 6:02 PM on April 23, 2016
Sadly it would kill mobile data along with cell phone calls.
posted by Talez at 6:02 PM on April 23, 2016
Sadly it would kill mobile data along with cell phone calls.
You make it sound like that's a bad thing.
posted by Chocolate Pickle at 6:06 PM on April 23, 2016 [1 favorite]
You make it sound like that's a bad thing.
posted by Chocolate Pickle at 6:06 PM on April 23, 2016 [1 favorite]
Currently circling not far from the Golden Gate, waiting for clearance to proceed. Also, this flightradar24 link seems to be a bit more reliable (the previous one occasionally decides that they have landed).
posted by effbot at 6:30 PM on April 23, 2016
posted by effbot at 6:30 PM on April 23, 2016
As a guy who wants a ~30Kwh hybrid EV RV to cruise around in, this is somewhat relevant to my interests.
This is more like the future I thought I'd be living in back in the 90s.
posted by Heywood Mogroot III at 7:48 PM on April 23, 2016
This is more like the future I thought I'd be living in back in the 90s.
posted by Heywood Mogroot III at 7:48 PM on April 23, 2016
This CNN article has nice video of the landing. Graceful looking thing. I was wondering how hard it would be to land, a super-glider like that really doesn't want to stop flying. (Wikipedia has the takeoff speed at 20kt.) This Wired article from 2013 has more info on takeoffs and landings, including a nifty landing gear setup to handle crosswinds.
posted by Nelson at 7:50 AM on April 24, 2016 [1 favorite]
posted by Nelson at 7:50 AM on April 24, 2016 [1 favorite]
anyone know if on prior stops people have been allowed to go see it? i don't see anything on their website. since they built a portable hangar for it at moffett, just peering over the fence you're not going to see much unless they explicitly opened it up to the public.
edit: ah, according to google public open houses have happened before. here's hoping for one at moffett!
posted by joeblough at 1:01 PM on April 24, 2016
edit: ah, according to google public open houses have happened before. here's hoping for one at moffett!
posted by joeblough at 1:01 PM on April 24, 2016
> lob batteries into the air for the aircraft to catch, letting it drop the exhausted batteries to passive-glide back for collection.
Yes! Linear induction motor flinging the payload down a set of rails with a ramp at the end. Fly it up & over the intercept path & glide in to gently meet the recipient.
If an Arduino (or Lego Mindstorms) can fly autonomously, a mid-air battery flung/lobbed from below & gliding back should be do-able.
posted by morganw at 9:15 PM on April 24, 2016
Yes! Linear induction motor flinging the payload down a set of rails with a ramp at the end. Fly it up & over the intercept path & glide in to gently meet the recipient.
If an Arduino (or Lego Mindstorms) can fly autonomously, a mid-air battery flung/lobbed from below & gliding back should be do-able.
posted by morganw at 9:15 PM on April 24, 2016
well, poop. they explicitly mentioned today that they could not afford to put on a public viewing at moffett due to security restrictions among other things.
posted by joeblough at 3:58 PM on May 1, 2016
posted by joeblough at 3:58 PM on May 1, 2016
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posted by the Real Dan at 9:25 AM on April 23, 2016 [2 favorites]