Solar Impulse [Archive] - PPRuNe Forums

Scuffers

23rd Apr 2016, 06:56

Personally, I think it's a total waste of time/money.

even if you could make solar panels 100% efficient, they are simply not going to generate enough power for anything significant to fly.

so, you're back to batteries/capacitors/etc. to store enough energy.

to put this in context, best current LiPo cells have a power density of ~0.5 MJ/kg (and that's without any casings/interconnects/management/etc.

compare this with A1 Jet at ~42.80 MJ/kg.

then factor in that the LiPo will still have the same mass as a flat battery as a fully charged one unlike burning off A1.

jolihokistix

23rd Apr 2016, 08:14

If the pilot needs to take exercise anyway, why can't they connect some pedals to a hand/foot generator for a little extra juice? Surely useful in an emergency, even possibly the difference between life and death.

Is the need to prove it can be done SOLELY on solar power so overriding?

sagan

23rd Apr 2016, 08:18

From an aviation perspective - interesting.

From all other perspectives an embarrassing failure that proves the green dream will cripple the real world.

How can that money have been approved.

$20 Million Bailout ?$170 Million Solar Impulse 2 Flight To Be Completed ? After More Than One Year! (http://notrickszone.com/2015/12/05/20-million-bailout-170-million-flight-solar-impulse-2-to-be-completed-after-more-than-one-year/#sthash.MmyrwZCb.dpbs)

Wickerbill

23rd Apr 2016, 08:24

Most people laughed at the Wright brothers 'wasting their time and money' . I refer you to Ian W post above!

Heathrow Harry

23rd Apr 2016, 10:58

If you don't try you can never move forward

Sure it hasn't been acording to plan but it's still pretty amazing - we're just at the start of portable electrical power - I supect it will be pretty important in 50 years

RealUlli

23rd Apr 2016, 11:22

From an aviation perspective - interesting.

From all other perspectives an embarrassing failure that proves the green dream will cripple the real world.

You sound like one of the balloon operators when told about the wright flyer. "Interesting. But with an endurance of just a few seconds, just useless."

We all know how that turned out.

For example, I can imagine a large orbital solar power station that beams down microwave energy along the Atlantic crossing corridors, the aircraft carrying just enough batteries to take off and land, in flight just using the beamed energy.

Another option might be extremely efficient flying wing planes with a solar panel surface (assuming 100% efficiency, a flying wing the size of an A380 could generate several megawatts of power, probably enough to stay aloft).

We're not quite there yet, but I don't see why we shouldn't get there at some point.

Herod

23rd Apr 2016, 12:06

Like the Wright Flyer and others, it's a "proof of concept" flight, and as such can be considered a success.

wiggy

23rd Apr 2016, 12:47

For example, I can imagine a large orbital solar power station that beams down microwave energy along the Atlantic crossing corridors, the aircraft carrying just enough batteries to take off and land, in flight just using the beamed energy.

So can I.

Now calculate the level of emissions that would be created in getting the "large orbital solar power station" into orbit in the first place (BTW assuming today's level of air traffic how many of those would be needed), and maintaining it once there......

Scuffers

23rd Apr 2016, 12:48

You sound like one of the balloon operators when told about the wright flyer. "Interesting. But with an endurance of just a few seconds, just useless."

We all know how that turned out.

For example, I can imagine a large orbital solar power station that beams down microwave energy along the Atlantic crossing corridors, the aircraft carrying just enough batteries to take off and land, in flight just using the beamed energy.

Another option might be extremely efficient flying wing planes with a solar panel surface (assuming 100% efficiency, a flying wing the size of an A380 could generate several megawatts of power, probably enough to stay aloft).

We're not quite there yet, but I don't see why we shouldn't get there at some point.

Look, all well and good, but unless you plan on changing the laws of physics, simply not going to happen.

big as the A380 wing topside is, it's never going to be big enough for anything like a megawatt of power from solar.

Now, at best, solar is ~1,000W/M2, so if you had a mythical 100% efficient solar cell array the size of the A380 wings (some 845 M2) then assuming your A380 is directly beneath the sun, on the equator, you only have some 0.85Mw to start with, and as soon as said plane (it may well be slightly better at 40,000 ft, but not by a massive factor).

So where are you going to get "several megawatts of power" from?

this is not about a technology needing development so much as the physics simply don't stack up.

then consider that the Trent 900 is rated at some 80,000Lbf, which roughly equates to ~95Mw (40,000ft @ Mach 0.85) and the A380 has 4 of them.

Intruder

23rd Apr 2016, 13:59

That Trent 900 will be putting out 25% or less of its full rated thrust in cruise at 40,000'.

So, while the engineering of converting that electricity to usable thrust is a considerable challenge, it is not "impossible" to get a significant percentage of power used from solar. Also, solar could more feasibly serve the electrical load on an aircraft, reducing the drag on the engines from the generators.

Might it be cost effective? Not yet. It it possible in the foreseeable future? YES!

Wageslave

23rd Apr 2016, 14:44

That Trent 900 will be putting out 25% or less of its full rated thrust in cruise at 40,000'.
It it possible in the foreseeable future? YES!

95Mw is 95Mw. If the wing area can only provide .85Mw you are still less than 1% of the way there. That is nowhere near a "significant percentage" is it? It is probably less than the allowed shortfall between individual Trent 900s due to wear and tear.

And that 0.85% is with a 100% efficient solar cell and the entire wing area remaining at right angles to the sun.

So you need either a wing that is 120 times bigger or to turn the sun up a hundred and twenty fold. And never to fly at night, nor need to take off or go around (need 4 times that much power to do that). Factor in pv cell efficiency and make it perhaps 300 times bigger. Are you getting the picture?
Oh, and only ever fly wings level within the tropics at noon.

Why/how is it hard to see that maths and physics fundamentally prevent this happening?

Huge span ultra lightweight long endurance RPVs perhaps. Transport? No. Never from on board PV cells. Can't happen.

Teddy Robinson

23rd Apr 2016, 15:25

ExXB

23rd Apr 2016, 15:27

Coming up to sunrise on day 3. 83% of the journey done.

Every journey begins with a single step, and that money comes from private sources.

Scuffers

23rd Apr 2016, 17:38

Perhaps we are all missing the point, after all we tend to think of applicability in our own sphere of experience. Clearly this technology will not be outperforming turbofans anytime soon. But as a drone ?
Remember well that the predator/reaper met stiff resistance in traditional flying circles during the early days, until those on high realized that it had the ability to linger in an area of interest for 20+ hours. A developed version of this technology could be put to a similar use. Whilst it would be nice to think of benign applications, were I to place a small wager it would go on a military role.

well, yes and no,

the point of a drone is to be small, inconspicuous, remote etc, ie, the predators etc, they have bugger all wing area, thus to make them viable as solar powered, you would need wings the size of a Vulcan or the like, at which point, they would be far from inconspicuous and a pretty easy target!

then consider what happens when the sun goes down or cloud cover comes over?

Look, it's not about lack of belief in technology, it's simply a matter of physics, yes you can make a solar powered plane, but it will be usless for any practical purpose that we use planes for now.

Same goes for battery powered flight, yes it's obviously possible, but until battery (or capacitor) tech increased power density by a factor of 20+, it's simply not practical for anything other than toys and expensive demo's.

Next somebody will pop up and claim Hydrogen fuel cells are the answer - in which case I will point them at the issues around them at any major scale, and also where does Hydrogen come from (commercially).

FlightlessParrot

23rd Apr 2016, 22:07

Obviously this is a stunt. Stunts are important in the development of new technologies, because they're a way of pushing the limits of the possible in a quasi-sporting mode (i.e., to hell with the expense), and getting publicity.

Fossil fuels will be necessary for aviation for the foreseeable; therefore all the more need to replace fossil fuels wherever possible elsewhere, so that total greenhouse emissions can go down while still keeping air transport possible (I do know greenies who are opposed to aviation, and motor cars, and growth: but they're really puritans, and there are plenty of others who are actually just concerned about the environment). Solar Explorer may have some impact here, just as car racing has some impact on the vehicles we drive.

So yes, this has got bugger all to do with practical aviation directly; but it might have some indirect benefit.

flynerd

24th Apr 2016, 00:34

Looking at the live feed from post #1... Why is he flying West again? perhaps too early for film crews... Close to Golden Gate Bridge.

CargoFlyer11

24th Apr 2016, 00:51

https://www.youtube.com/watch?v=w5t8VdLpsOA

jolihokistix

24th Apr 2016, 01:45

We like the look of that! Go RR...

ExXB

24th Apr 2016, 06:21

Apparently winds are delaying the landing.

Great picture of it over the bridge. http://www.bbc.co.uk/news/science-environment-36122618

Edited to add: She's landed now.

deptrai

24th Apr 2016, 22:21

3 days of single pilot operations, with 20 minute controlled naps. Testing the limits of human performance as much as tech aspects.

RealUlli

25th Apr 2016, 06:03

Look, all well and good, but unless you plan on changing the laws of physics, simply not going to happen.

big as the A380 wing topside is, it's never going to be big enough for anything like a megawatt of power from solar.

Now, at best, solar is ~1,000W/M2, so if you had a mythical 100% efficient solar cell array the size of the A380 wings (some 845 M2) then assuming your A380 is directly beneath the sun, on the equator, you only have some 0.85Mw to start with, and as soon as said plane (it may well be slightly better at 40,000 ft, but not by a massive factor).

So where are you going to get "several megawatts of power" from?

this is not about a technology needing development so much as the physics simply don't stack up.

then consider that the Trent 900 is rated at some 80,000Lbf, which roughly equates to ~95Mw (40,000ft @ Mach 0.85) and the A380 has 4 of them.

Ok, thanks for the numbers. (I'm sorry I didn't look them up myself)

I wasn't thinking about getting an A380 to fly on solar. That's obviously impossible. What I'm imagining is more like a giant flying wing that carries much less, has the same wing span as the A380 but a much deeper wing, e.g. 80m wide, 40m long, carrying maybe 20 metric tons of stuff (maybe less - I'm just guessing things). That gives 3200 m2, yielding 3.2 MW.

This kind of plane would be much slower than a conventional plane, with extremely low wing loading.

What I don't know is, will passengers accept travel times in excess of 24 hours? In conventional planes, space for seats is expensive. In that hypothetical plane, space will not be a problem, weight will be. (And of course, flying through the night... ;-))

Crew block time will be a problem, I'm not quite sure how to overcome that. Fully automatic will be out, since I imagine the plane will need minders, unless you want it to look like a subway car in a poor city after a while. The cost structure will change for sure.

However, the main question remains - can a plane like that be made to fly? I really don't know if that is feasible. Probably not alone.

wrighar

26th Apr 2016, 14:28

As an example for area, RAF Coltishall has just been converted to a solar farm, just under 50MW at peak generation (i.e half an engine).

http://www.edp24.co.uk/polopoly_fs/1.4510766.1461675459!/image/image.jpg_gen/derivatives/landscape_630/image.jpg

Derfred

28th Apr 2016, 02:46

then consider that the Trent 900 is rated at some 80,000Lbf, which roughly equates to ~95Mw (40,000ft @ Mach 0.85)

Can we back up a minute? How did you get from thrust to power here?

DaveReidUK

28th Apr 2016, 06:25

How did you get from thrust to power here?The OP appears to have multiplied take-off thrust by cruise speed. :O

Scuffers

28th Apr 2016, 12:17

Not quite.

read this:

Aerospaceweb.org | Ask Us - Convert Thrust to Horsepower (http://www.aerospaceweb.org/question/propulsion/q0195.shtml)

and I picked 80,000Lbs as it's broadly the mid-spec for the Trent 900

As an aside the Rolls-Royce MT30 genset is rated at 40Mw and is based on the Trent 800 core, if you then take into account different duty cycle ratings and inefficiencies of the Aero engine vs. genset, it actually stacks up about right.

DaveReidUK

28th Apr 2016, 15:30

Not quite.

read this:

Aerospaceweb.org | Ask Us - Convert Thrust to Horsepower (http://www.aerospaceweb.org/question/propulsion/q0195.shtml)

and I picked 80,000Lbs as it's broadly the mid-spec for the Trent 900

I think you need to read that example more carefully.

It calculates, based on NASA data, that a 747-200 in the cruise generates around 16 MW per engine.

The Trent 900 develops roughly one-and-a-half times as much thrust as the JT9D, so around 24 MW per engine.

Scuffers

28th Apr 2016, 15:43

who said anything about at cruise power?

Yes, at cruise, the Trent is probably at ~24Mw, however, what would it be if you push the throttles forward all the way?

(Or are you suggesting that the engines never have to be run at anything above cruise power?)

DaveReidUK

28th Apr 2016, 15:59

who said anything about at cruise power?

Yes, at cruise, the Trent is probably at ~24Mw, however, what would it be if you push the throttles forward all the way?

If you really believe that you can get 80,000 lbf out of a Trent in the cruise at 40,000 ft, I would get on the phone to Derby and Toulouse straight away and let them in on the secret.

Scuffers

28th Apr 2016, 16:22

really?

Trent is more efficient at 40,000ft than at ground level, they are very much optimised for running at cruise altitude.

So, A380 at 40,000ft loses an engine, does it fall out the sky or do the other three make up the loss in thrust? (How about if it loses 2 engines?)

What do you think it's max thrust would be at 40,000ft?

DaveReidUK

28th Apr 2016, 18:27

Trent is more efficient at 40,000ft than at ground level, they are very much optimised for running at cruise altitude.

Well that depends how you define "efficiency" - if you use SFC as a measure, it's roughly twice as good on the ground at takeoff thrust compared to the value in the cruise. In fact you could argue that the engine is optimised for getting the aircraft off the ground in the first place. :O

So, A380 at 40,000ft loses an engine, does it fall out the sky or do the other three make up the loss in thrust? (How about if it loses 2 engines?)No, of course it doesn't fall out of the sky.

A loss of two engines on an A380 or 747 (roughly analogous to losing one engine on a twin) would necessitate the remaining engines producing double their normal cruise thrust if the same airspeed and altitude were to be maintained.

But, as you will have seen from the article you quoted, normal cruise thrust is about a quarter of T/O thrust, so even doubling that will only equate to around 50% of the latter.

What do you think it's max thrust would be at 40,000ft?In lbf? I don't know. MCT is normally expressed in terms of N1 or EPR, rather than lbf.

But think about it - if an engine was capable of producing SL take-off thrust at 40,000 feet then it would mean that a 747/A380 could maintain height and speed on one engine, which it clearly can't..

procede

29th Apr 2016, 06:02

L/D of about 20. Weight is 500 000 kg, thus 5 000 000 N.
Trust requied is 5MN/20=250kN. Cruise speed of 250 m/s results in 62.5 MW.

DaveReidUK

29th Apr 2016, 07:18

Neat approach. :ok:

Dividing that per-aircraft value by 4 gives a per-engine figure of around 16 MW in the cruise.

Interestingly, that's almost identical to NASA's value for the 747/JT9D - maybe they did their sums with a Shuttle on top. :O

procede

29th Apr 2016, 07:34

L/D of 20 is a bit optimistic at Mach 0.8. About 16 is probably more realistic, so it would be 20MW per engine.

ExXB

2nd May 2016, 13:56

Two hours into next sector

Solar Impulse - 10th Leg from San Francisco to Phoenix (http://www.solarimpulse.com/rtw)

Goodbye Silicon Valley!
André Borschberg took off on May 2nd 12:03UTC from San Francisco to Phoenix, Arizona. Si2 spent a week in California after Bertrand Piccard's 3-day flight that marked the completion of the Pacific Crossing. It was a great opportunity to meet with the public and Silicon Valley's tech companies, to spread the #futureisclean message. The flight is expected to take 16 hours and 23 minutes, crossing 720 miles over the Mojave Desert and will arrive in Phoenix Goodyear Airport at around 4:23AM UTC.

Dubaian

4th May 2016, 06:59

Re funding - an earlier poster says it's private? Don't think so. Most (if not all...?) of it is from Masdar / Mubadala - which are Abu Dhabi Govt organisations.

FlyANA

4th May 2016, 11:38

What about getting this solar power on a blimp? Like a hybrid car, the buoyancy of the gas cancels out weight for passengers/cargo/equipment and the solar cells power props for momentum?

procede

4th May 2016, 12:27

Slight problem is that the props also need to counteract drag, which is huge for a blimp at any significant speed.

ExXB

4th May 2016, 12:30

Re funding - an earlier poster says it's private? Don't think so. Most (if not all...?) of it is from Masdar / Mubadala - which are Abu Dhabi Govt organisations.

Here's a list of their partners Solar Impulse RTW (http://www.solarimpulse.com/partners). Not all are large financial contributors - for example ICAO gave no money, but technical assistance. IATA gave a small bit of cash, etc. The Swiss government, gave them access to a disused hangar at Payerne.

No doubt the UAE contributed a lot of money. That's what they had to do for the 'prestige' of being the origin/destination.

Chu Chu

6th May 2016, 01:05

Solar cells on an A-380 -- or better a 787 -- could take some of the generator load off the engines and save fuel. At least if they weren't too heavy . . .

But except for maybe communications or surveillance platforms, solar aviation seems like something to think about after we've shut down all the fossil fueled power plants and are all driving electric cars. The Impulse is a great demonstration of solar in general, but I'm not convinced about solar aviation.

300hrWannaB

6th May 2016, 17:42

I was about to contribute something along the lines of contributory power systems, as opposed to primary power systems. Chu Chu makes an interesting point.
Consider the situation with cruise ships. Several designs have now been created that have big automated sails as well as fossil fuel power sources. These significantly reduce the fuel requirements for the journey, and aren't just for pose value. Cost/value remains marginal, or they would all use them.

Consider the aviation world again. Personally, I rather like the idea that the A320 or 777 with 2 engine failure and a loss of electrical power might be able to rely on alternate PV power for the instruments/radios/computers/actuators enabling a controlled glide descent to an airfield. I don't imagine that you'd need too many m2 of pv to power the electronics.

Romeo Tango

6th May 2016, 17:56

Quite an expense for something that would be very rarely needed and then would only work half the time

wiggy

7th May 2016, 12:07

300hrWannaB...

Personally, I rather like the idea that the A320 or 777 with 2 engine failure and a loss of electrical power might be able to rely on alternate PV power for the instruments/radios/computers/actuators enabling a controlled glide descent to an airfield. I don't imagine that you'd need too many m2 of pv to power the electronics.

Ummm, well regardless of the expense perhaps one way around the possible lack of daylight would be to use wind power instead of solar.....:E

Edit to add: Sorry, on second thoughts even for me that comment's a bit cruel. 300hr, Most commercial twins have "Ram Air Turbines" or "RATs" to help cater with, amongst other things, a double engine out.

https://en.wikipedia.org/wiki/Ram_air_turbine

Tourist

8th May 2016, 07:06

The place where this tech makes a lot more sense is on this beast....

http://www.pprune.org/military-aviation/463101-new-gen-airships-hybrid-air-vehicles-uk.html

Plenty of area, minimal thrust required most of the time.

Scuffers

9th May 2016, 17:09

Solar panels are not weight free, and neither is the supporting wiring/inverters/etc.

Tourist

9th May 2016, 18:11

Watch some of the videos about solar impulse. The are extraordinarily light. More than worth the trade-off on something like a blimp, and getting lighter and more efficient by the day.

Scuffers

10th May 2016, 06:15

yes, 1,600Kg's light.... and carries one person.

Tourist

10th May 2016, 06:49

That's 1600Kg for the aircraft Scuffers, not the solar panels.

I don't disagree with you re the viability of solar powered passenger flights in heavier than air vehicles, but the applicability of the tech to blimps is obvious.

Zephyr has better than 1KW per Kg. Not bad, and getting better all the time.

Scuffers

10th May 2016, 08:22

The big problem here is that it's a tenuous bit of tech without a real application.

What's the 'must-have' application for blimps?

short answer is - NONE. if there was, they would be out there now being used.

People will then go on about using them for internet connectivity etc, but being blunt, this is a non starter too, (if anything, Elon's SpaceX will be the big step forward for global networking).

Look, I am not anti solar, just that this is NOT the right application.

Tourist

10th May 2016, 10:16

By "this" do you mean passenger travel or Blimps?
Or ultra long endurance UAVs?

The last is very much a starter and in production now.

Tourist

10th May 2016, 10:18

There was absolutely no "must-have" application for anything like Predator/Reaper.......

....and then some clever chaps built one despite zero interest from anybody.

ATC Watcher

10th May 2016, 10:55

Personally, I rather like the idea that the A320 or 777 with 2 engine failure and a loss of electrical power might be able to rely on alternate PV power for the instruments/radios/computers/actuators enabling a controlled glide descent to an airfield. I don't imagine that you'd need too many m2 of pv to power the electronics.

Solar panels only work with daylight, so need to store energy for rest of time , means batteries, additional weight and problems ( not only 787 but also Solar impluse /Hawai )
However great potential for GA / daylight ops. Many Gilders today already use this to keep battery power at max.

Last bit on RAT and Airbii : visit at Air Transat A330 /Azores and Air Asia A320 /Java final reports to see the limits of RAT power.

Derfred

11th May 2016, 17:29

My personal imagination tells me that the potention real-world application of this is that solar powered UAVs with sufficient battery capacity to get them through the night could be launched for long missions of weeks, months or years.

With further advances thes vehicles could possibly maintain altitudes above weather and commercial traffic.

The commercial and/or military applications are huge. These vehicles could essentially perform roles currently only available to satellites at a fraction of the cost. A bit scary too... Big brother gets closer and closer.

Google would probably deploy a few thousand of them to provide low cost broadband to the world (in lieu of it's fanciful blimp idea). By my calculations they would need around 4000 of them to cover the entire globe at 200NM spacing. Obviously the poles would be a problem in winter.

The point of an around the world "stunt" in a manned vehicle isn't to demonstrate that we could all someday be flying in solar powered A380's. The point is to generate media attention, the attention of scientific bodies and governments, the attention of venture capitalists looking for the next big thing, and to get you and I talking.

It's not beyond my imagination that we could develop the technology to the point where we could launch a low cost UAV to FL500 and leave it on a set course (or a holding pattern) for a year or so carrying a useful communications payload.

ExXB

15th May 2016, 14:51

Now in Tulsa Solar Impulse - 11th Leg from Phoenix to Tulsa (http://www.solarimpulse.com/rtw)

The calm after the tornado
It took 48 hours to adapt to unpredictable weather across the U.S., devise multiple new strategies to cross the country, scout out and find a host airport, empty an entire hangar to house the 72 meters of our solar wings, organize the arrival of our team and reunite everyone in an organizational whirlwind. All this was successfully accomplished to welcome a silent, serene, zero-fuel airplane, confident in its unlimited autonomy, to the runways of Tulsa, the “black gold” capital of Oklahoma. The world can indeed live at a different pace!

Scuffers

15th May 2016, 17:33

It's not beyond my imagination that we could develop the technology to the point where we could launch a low cost UAV to FL500 and leave it on a set course (or a holding pattern) for a year or so carrying a useful communications payload.

the problem with that is LEO satellites are getting much cheaper every month as are the launch costs, to the point SpaceX are already looking to launch their own LEO constellation for net connectivity (the way they are heading is looking like they could put up enough in 2 launches to cover the planet).

in reality, the number of planes/blimps/whatever to do this job would simply be far to expensive and have too high a running costs for anything practical.

ExXB

25th May 2016, 11:28

Lucky 13 ... enroute to Pennsylvania

Solar Impulse - 13th Leg from Dayton to Lehigh Valley (http://www.solarimpulse.com/rtw)

ExXB

11th Jun 2016, 08:42

En route to JFK:

Historic flight over the Statue of Liberty
This flight will bring Solar Impulse over the Statue of Liberty to New York City, with a final landing at JFK.

Mozella

16th Jun 2016, 20:17

"Most people laughed at the Wright brothers 'wasting their time and money'"
Not the same thing. Sunlight converted to electricity doesn't have enough energy density to make this "fuel" viable......... EVER.

Your analogy to the Wright brothers is like saying, "Improved satellite cameras and the proliferation of camera equipped drones along with millions of cell phone cameras means we're on the verge of proving that unicorns and Yeti exist.

Chu Chu

16th Jun 2016, 23:07

Of course, I don't remember hearing much about commercial applications for the Gossamer Condor or the Rutan Voyager. Sometimes a feat of aviation is just that.

ion_berkley

16th Jun 2016, 23:35

Not the same thing. Sunlight converted to electricity doesn't have enough energy density to make this "fuel" viable......... EVER.

You might want to let Airbus know then that they are wasting their time.
Zephyr ? unmanned aircraft system UAS (http://www.militaryaircraft-airbusds.com/Aircraft/UAV/Zephyr.aspx)

the problem with that is LEO satellites are getting much cheaper every month as are the launch costs, to the point SpaceX are already looking to launch their own LEO constellation for net connectivity (the way they are heading is looking like they could put up enough in 2 launches to cover the planet).

in reality, the number of planes/blimps/whatever to do this job would simply be far to expensive and have too high a running costs for anything practical.

Whilst you are correct that launch costs are still declining rapidly. Its no where close to being cheaper, especially when you take the ground segment into account. Fundamentally its far harder to address most of the intended applications from 300+KM altitude than from 10-25KM in the stratosphere

Ian W

17th Jun 2016, 12:06

@ion berkley

While long endurance solar cell powered flights in the stratosphere by Helios NASA - Helios (http://www.nasa.gov/centers/dryden/news/ResearchUpdate/Helios/) and Zephyr Zephyr ? unmanned aircraft system UAS (http://www.militaryaircraft-airbusds.com/Aircraft/UAV/Zephyr.aspx) type aircraft are demonstrably feasible - although not validated by extended flight. There are also any number of UAS that are battery powered both commercial and toys. The implications from the media releases that in a few years South West and Easyjet can be expected to be flying pax on all electric aircraft is completely false. Solar impulse like Gossamer Albatross only shows that there may be niche uses. The amount of energy for powered flight has not altered so the energy density has to be sufficient. Currently there is no battery or electrical generation system that provides anything close to hydrocarbon fuel energy densities which exceed battery capabilities by several orders of magnitude.

ExXB

20th Jun 2016, 15:36

Heading for Seville. Solar Impulse - 15th Leg from New York to Seville (http://www.solarimpulse.com/rtw)

The Atlantic Crossing
Another multiple-day flight is on its way over the Atlantic Ocean. Bertrand Piccard will be making this first transatlantic solar and electric crossing with zero fuel and zero emissions.
The flight will last between approximately 90 hours and 110 hours, representing the longest distance we have had to fly this year. He took off at 6:30AM UTC, 8:30AM CET and 2:30AM EDT on June 20th from JFK in New York and will be landing in Seville Airport over three days later.

Heathrow Harry

21st Jun 2016, 09:21

braver man than me for sure...................

Espada III

22nd Jun 2016, 21:36

Doing well. Close to the Iberian peninsula now.

ExXB

23rd Jun 2016, 06:29

Flight Time 2d 23h 56m 4s
Distance 6272 km (100 %)
Altitude 278 ft (85 m)

They had hoped for Le Bourget, but as any football fan knows, France covered by storms.

mickjoebill

23rd Jun 2016, 06:49

https://www.periscope.tv/w/ajor2DFETEtCWHBWTm5FSmJ8MVJER2x3TExZWnFLTPNXBJ-okSjC02J5PJHUTCpZudO7y134sYfeko3j3SFq

Replay of the landing as broadcast live on periscope, from the ground crew on the tarmac.

Mickjoebill

Dubaian

24th Jul 2016, 06:12

Now en route CAI - AUH

Expected to take about 48 hours. Great achievement -if it makes it - but slightly clouded in my view by the cooked batteries which had to be replaced.
Still round-the-world on solar power alone is quite something.

mutt

24th Jul 2016, 06:55

https://www.solarimpulse.com/leg-17-from-Cairo-to-Abu_Dhabi

It's an impressive achievement. Good luck to them with the Arabian heat.

ExXB

24th Jul 2016, 13:27

My goodness >30kts at 30,000 feet.

mutt

24th Jul 2016, 21:31

They were doing 25 kts in the climb to that altitude. Impressive wing design.

Their flight planning was quite intriguing, takeoff at dawn to avoid temperature and winds. Hold off the coast of Saudi for a number of hours during the hottest part of the day, therefore avoiding extremely unpleasant temperatures and thermals.

Looking forward to seeing them complete the journey tomorrow.

CONSO

26th Jul 2016, 04:26

approx 4 am local time

Dubaian

26th Jul 2016, 05:13

Safely down at Al Bateen Executive Airport, downtown Abu Dhabi. (Not at AUH).
Great achievement. Hadn't appreciated it's unpressurised so 30,000 ft is even more impressive.

ExXB

26th Jul 2016, 08:33

Wonder what Picard's next project will be ...

Heathrow Harry

26th Jul 2016, 08:42

yes - well done - some impressive engineering and flight planning !!!

8/8ths Blue

26th Jul 2016, 10:02

er...maybe a couple of you missed the point. Experimental and Pioneering it was... bringing together and building a team capable of utilizing renewable energy to accomplish something that has NEVER been done before. Flying Round the WORLD using absolutely NO (Fossil) FUEL !! Now how much did that cab cost the other day back to the airport?? Tesla would be pleased... and so am I. Well done to ALL who played their part in the team.