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Solar Impulse plane doing epic global flight

weltweit

weltweit

Well-Known Member
http://www.bbc.co.uk/news/science-environment-31772140

So, Monday they are due to take off on the first leg of an attempted 35,000 mile circumnavigation of the globe, power coming from 17,000 solar cells on the wings to drive the four propeller engines. The aircraft has a greater wingspan than a 747 but seats only one pilot at a time. Perhaps the greatest challenge might be when they have to cross the pacific which may take 5 days and nights during which the pilot will get only small pieces of sleep.

Quite an exciting adventure and a technological step forward which may lead to all sorts of things in the future.
 
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The idea that still hasn't taken off is

HALE (high altitude, long endurance) over 30,000 ft (9,100 m) and indefinite range

http://en.wikipedia.org/wiki/Unmanned_aerial_vehicle

A HALE drone would replace some satellite functionality. In the past the expectation has been that a drone could be cheaper and more flexible than satellite. Looking at the cost of some military drones, instead of being cheap and expendable they've been expensive and plagued with problems........

U-2 has a much higher mission-success rate in the Pacific theater than Global Hawk does — 96% versus 55% — and is selected for missions much more frequently. When an aircraft operates at 50,000-55,000 feet as Global Hawk does, it can’t fly above some of the storms encountered in the Pacific the way U-2 can. Global Hawk’s weather limitations are compounded by the absence of a de-icing system, which means it cannot fly through clouds for prolonged periods and thus is confined to operating in fair weather — unlike all the manned aircraft in the Air Force fleet.

De-icing isn’t the only feature left out of the Global Hawk design to save money or weight. The drone also lacks an on-board “sense and avoid” system that would enable it to steer clear of other aircraft, whether they be commercial jetliners or enemy fighters. That means ground operators piloting the drone need a radar picture of the areas where it is flying to assure safety. If tracks from nearby ground radars are not available, then Global Hawk will require support from radar planes or other aircraft — an expense that typically isn’t included in comparisons of what it costs to fly the two planes.

Another key difference between U-2 and Global Hawk is that the drone is much more dependent on its satellite uplink to sustain flight than the manned plane. Without a continuous connection to pilots thousands of miles away, Global Hawk’s ability to do anything, including simply staying aloft, is hobbled. That might not be much of a problem in peacetime, but in wartime enemies like China will be using electronic jamming, cyber attacks and anti-satellite warfare to disrupt such links, and that could severely compromise drone operations.
Click to expand...

http://www.forbes.com/sites/lorenth...ones-arent-the-answer-to-every-military-need/


Costs

The U-2’s cost per flying hour has “remained fairly stable” at about $32,000
Click to expand...

Global Hawk across all variants dropping to about $24,000 per flying hour
Click to expand...
(in 2010 it was $40,600)

http://archive.airforcetimes.com/ar...Air-Force-wants-keep-Global-Hawks-retire-U-2s

-----------------------------------------------------------------------------------------------------------------------------------------------

Solar impulse is a step towards HALE drones. But it still needs.......

A "sense and avoid" method.

Low operating costs

and

Probably needs a de-icing system :cool:
 
First leg was completed today from Abu Dhabi (Al Bateen Executive Airport, AZI/OMAD) in the United Arab Emirates, landing in Muscat (Muscat International Airport, MCT/OOMS) in the Sultanate of Oman.

They had an issue with one of three DC/DC converters which might have stopped some cockpit electrical kit from functioning, but this was traced to a faulty monitoring circuit and the aircraft was deemed good to go.

At the end of the flight they had to fly a holding pattern above Muscat, because winds on the ground were above the aircraft's design limits.
 
weltweit said:
First leg was completed today from Abu Dhabi (Al Bateen Executive Airport, AZI/OMAD) in the United Arab Emirates, landing in Muscat (Muscat International Airport, MCT/OOMS) in the Sultanate of Oman.

They had an issue with one of three DC/DC converters which might have stopped some cockpit electrical kit from functioning, but this was traced to a faulty monitoring circuit and the aircraft was deemed good to go.

At the end of the flight they had to fly a holding pattern above Muscat, because winds on the ground were above the aircraft's design limits.
Click to expand...

Excluding an auto pilot sounds like a bad idea. Later in the trip they could be stuck in the air for some time waiting for winds drop to safe levels.

Perhaps their assumption is that once the sun sets, wind speeds will drop to an acceptable level?
 
HAL9000 said:
Excluding an auto pilot sounds like a bad idea. Later in the trip they could be stuck in the air for some time waiting for winds drop to safe levels.

Perhaps their assumption is that once the sun sets, wind speeds will drop to an acceptable level?
Click to expand...
Are you certain they have no autopilot? because they have spoken about the pilot being able to get 20 minute naps while flying the 5 day stretch over the pacific.
 
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weltweit said:
Are you certain they have no autopilot? because they have spoken about the pilot being able to get 20 minute naps while flying the 5 day stretch over the pacific.
Click to expand...

The next-generation Solar Impulse, known as HB-SIB, will have a wingspan of more than 236 feet. It will not have a true autopilot. The airplane lacks sufficient power to maintain any type of predetermined flight altitude in the event of a strong downdraft, according to Borschberg, and it is so delicate that an autopilot could cause problems in unusual circumstances. Instead, Borschberg says, the airplane will have an electronic co-pilot of sorts capable of maintaining a directional heading and alerting the pilot to any problems with the performance of the airplane
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There's a vibration system to alert the pilot if something goes round wrong

http://www.wired.com/2012/02/after-60-hours-solar-impulse-pilot-feeling-better-than-expected/

The autopilot cannot maintain height, sleepy pilot at the end of a long flight waiting for suitable landing winds. There might be problems?
 
SI2 took off at 02:35UTC on the second leg from Muscat to India, a distance of 1465km. SI2 had a successful landing a short time ago at Ahmedabad, India.
 
Solar Impulse Si2 has been prepared for flight, batteries have been connected and solar cells checked, piloted on this leg by Andre Borschberg who has also been preparing for the flight, it will takeoff in the next hour from Ahmedabad (India) flying to Varanasi (India) on the third leg of its round the world journey.


Project website at:
http://www.solarimpulse.com/rtw
 
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So, they did eventually takeoff and are due to land in Varanasi in the next few minutes, watch the landing at :

 
how long be for they knock up a solar powered drone. If you make them small, solar and acting as essentially proximity mines. Manufacture them in the 1000's, give em some basic autonomy- model on bird flock behaviour for instance. You've esentially killed civilian airflight with an arial minefield.
 
DotCommunist said:
how long be for they knock up a solar powered drone. If you make them small, solar and acting as essentially proximity mines. Manufacture them in the 1000's, give em some basic autonomy- model on bird flock behaviour for instance. You've esentially killed civilian airflight with an arial minefield.
Click to expand...
lne_rafm_fa05654_large.jpg
 
While I am interested in this solar powered round the world flight, enough to follow it, I am not sure apart from adventure what it will being in terms of technological progress. Solar cells are getting more and more effective, will it persuade us to install more, or governments to subsidise more? I wonder ..
 
I notice that, like with many aircraft, visibility out of the cockpit is pretty limited, I guess they are flying on instruments most of the time, still if I were the pilot I would like bigger windows.
 
@solarimpulse #MCC in Monaco HB-SIB Best Ground speed up to now: 117 Kt = 216 Km/h

216 km/h is moving some for a solar powered plane .. I think they have jet stream assistance :)
 
weltweit said:
I notice that, like with many aircraft, visibility out of the cockpit is pretty limited, I guess they are flying on instruments most of the time, still if I were the pilot I would like bigger windows.
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It might be due to the large temperature range they might have wanted to keep the windows small (either minimize heat leakage/solar heating)

"In the absence of any heating, the cockpit and the pilot will be facing extreme temperatures: from +40°C to -40°C!"

http://info.solarimpulse.com/en/our-adventure/human-challenges/#.VQspIOEntp0

or

perhaps weight issues?
 
I have been asking myself what happens to the two side wheels which appear when Si2 is on the ground, at take off or landing when Si2 is airborne. I think I can see in a photo on the website that these wheels fold back and upwards to rest along the back of the cockpit piece. One question solved then.
 
Si2 remains at Mandalay (Myanmar) awaiting better weather over china.

Interestingly they state that the 17,000 solar cells on Si2 have an efficiency ratio of 22.7% which is apparently better than those fitted for domestic applications which only have 16% efficiency. Seems to me if the maximum is 100% then even 22.7% isn't very good.
 
Apparently the limit with a single cell is 33% (according to Wikipedia, 29 % is more realistic, "The most popular solar cell material, silicon, has a less favourable band gap of 1.1 eV, resulting in a maximum efficiency of 29%")

Where Does The 67% Of Energy Loss Go?
  • 47% of the solar energy gets converted to heat.
  • 18% of the photons pass through the solar cell.
  • 02% of energy is lost from local recombination of newly created holes and electrons.
  • 33% of the sun's energy is theoretically converted to electricity.
  • 100% total sun's energy.
If the theoretical limit for silicon cells is about 30%, what happens to the other 6% that is lost from the best production cell efficiency of 24%? Some sunlight is always reflected off the surface of the cell even though the surface is usually texturized and coated with an anti-reflective coating. In addition there are some losses at the junction of the silicon cell with the electrical contacts that carry the current to the load. Finally, there are some losses due to manufacturing impurities in the silicon
Click to expand...

http://solarcellcentral.com/limits_page.html

There's still room to raise this 33% number.

  • Have multiple layers to capture photons of different energy.
  • use lenses to concentrate the light.
  • Add layer to capture heat, thermophotovoltaic to capture infrared radiation.

triple junction to improve efficiency (multiple layers method to get more power)

http://spectrum.ieee.org/green-tech/solar/powerful-pvs-approach-50-percent-efficiency

lens to get more power

http://spectrum.ieee.org/green-tech/solar/tapping-the-power-of-100-suns
 
Hi HAL9000 great stuff, thanks for that. Perhaps some of those, despite them just being in research atm, might also have added weight to the Si2 aircraft, lenses probably would ..
 
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