Please turn on javascript in your browser to play chess.
Science Forum

Science Forum

  1. Subscriber Crowley
    Not Aleister
    14 Apr '10 08:18
    Wow.

    http://www.solarimpulse.com/sitv/index.php?lang=en
  2. Standard member avalanchethecat
    Not actually a cat
    15 Apr '10 12:47
    Wonder if it goes fast enough to stay ahead of the terminator? Or does it have to land in the evening?
  3. 16 Apr '10 02:54
    Originally posted by avalanchethecat
    Wonder if it goes fast enough to stay ahead of the terminator? Or does it have to land in the evening?
    http://en.wikipedia.org/wiki/Solar_Impulse#Proposed_circumnavigation

    Proposed circumnavigation

    The team hope that a round-the-world flight will be possible in 2012. The flight would circle the world near the equator, but essentially in the northern hemisphere. Five stops are planned to change pilots. Each leg will last three to four days, limited by the physiology of the human pilot. [11]

    Once improved battery efficiency makes it possible to reduce the weight, a two-seater is envisaged to make a non-stop circumnavigation.[11]
  4. 16 Apr '10 02:55
    http://en.wikipedia.org/wiki/Circumnavigation#Aviation

    Aviation

    Since the development of commercial aviation many thousands of people have flown around the world. Some regular routes, such as the old Pan American Flight One, circled the globe, and today planning such a trip through various connections is quite simple.

    The first flying man-made airship to circumnavigate the world was the LZ 127 Graf Zeppelin, which did so in 1929.

    Aviation records take account of the wind circulation patterns of the world; in particular the jet streams, which circulate in the northern and southern hemispheres without crossing the equator. There is therefore no requirement to cross the equator, or to pass through two antipodal points, in the course of setting a round-the-world aviation record. Thus, for example, Steve Fossett's global circumnavigation by balloon was entirely contained within the southern hemisphere.

    For powered aviation, the course of a round-the-world record must start and finish at the same point and cross all meridians; the course must be at least 36,787.559 kilometres (22,858.729 mi) long (which is the length of the Tropic of Cancer). The course must include set control points at latitudes outside the Arctic and Antarctic circles.[3]

    In ballooning, which is totally at the mercy of the winds, the requirements are even more relaxed. The course must cross all meridians, and must include a set of checkpoints which are all outside of two circles, chosen by the pilot, having radii of 3,335.85 kilometres (2,072.80 mi) and enclosing the poles (though not necessarily centred on them).[4]
  5. 16 Apr '10 03:00
    22,858.729 miles / 24 hours = 952.447041667 mph

    952 mph / 761.2 mph = Mach 1.25.

    i'm guessing a solar-powered aircraft is not going to make Mach 1.25 anytime soon:

    http://en.wikipedia.org/wiki/File:FA-18_Hornet_breaking_sound_barrier_(7_July_1999).jpg

    http://upload.wikimedia.org/wikipedia/commons/thumb/c/cc/Flea_Hop_HB-SIA_-_Solar_Impulse.jpg/450px-Flea_Hop_HB-SIA_-_Solar_Impulse.jpg
  6. Standard member sonhouse
    Fast and Curious
    16 Apr '10 19:31
    Originally posted by zeeblebot
    22,858.729 miles / 24 hours = 952.447041667 mph

    952 mph / 761.2 mph = Mach 1.25.

    i'm guessing a solar-powered aircraft is not going to make Mach 1.25 anytime soon:

    http://en.wikipedia.org/wiki/File:FA-18_Hornet_breaking_sound_barrier_(7_July_1999).jpg

    http://upload.wikimedia.org/wikipedia/commons/thumb/c/cc/Flea_Hop_HB-SIA_-_Solar_Impulse.jpg/450px-Flea_Hop_HB-SIA_-_Solar_Impulse.jpg
    Did you hear the radio transmission about the takeoff speed? 27 knots. The plane is loaded with Li-ion batteries to fly at night, at least the full version will. This flight got to about 45 meters, a bit better than the one meter of my post. They are taking it one step at a time. One thing clear, the body of that plane would not take much sheer stress, it could be torn apart by bad downdrafts. Wonder why they didn't coat the whole body and rear tail structure with PV?
  7. 17 Apr '10 06:24
    by "anytime soon" i meant the next century. although upon further reflection, i guess with exponential tech growth we could see something in the next 50-500 years.
  8. 19 Apr '10 06:25
    Originally posted by zeeblebot
    by "anytime soon" i meant the next century. although upon further reflection, i guess with exponential tech growth we could see something in the next 50-500 years.
    And I'm guessing never. There probably simply isn't enough energy in sunlight to achieve supersonic speeds. If it was necessary to charge up over a number of days before going supersonic (and going round the earth) then the whole point (keeping up with the sun in order to provide power) would become unnecessary.
  9. Standard member sonhouse
    Fast and Curious
    19 Apr '10 06:28 / 1 edit
    Originally posted by zeeblebot
    by "anytime soon" i meant the next century. although upon further reflection, i guess with exponential tech growth we could see something in the next 50-500 years.
    Talking about mach 1 or better solar powered flight. That would seem impossible considering the amount of energy available only from the surface area of the wings. I suppose battery or some other form of energy storage could allow a slow flight that lasted days or weeks and excess energy stored enough to make a quick dash to supersonic flight for a few minutes but then you would run out of energy and be back to regular flight of a couple hundred klicks or less.
    There would be severe constraints to this effort, larger wing area to allow more PV collection space would exponentially raise the amount of energy required to get to mach 1 or better. Like you say, any time soon would be a few hundred years down the line if then. To say nothing of the increased buffeting on the plane's body as you approach mach 1. This test flight plane is so light if some supersonic jet just flew by at mach 1 it would be torn apart.

    I don't see solar flight as anything more than a stunt at least at this stage of the game.
  10. 19 Apr '10 09:11
    you're both right . i was thinking more of the materials tradeoff, like sonhouse.
  11. Standard member sonhouse
    Fast and Curious
    22 Apr '10 13:37 / 6 edits
    Originally posted by zeeblebot
    you're both right . i was thinking more of the materials tradeoff, like sonhouse.
    The problem with solar flight is using solar energy just to stay in the air. A better system would be just using a helium dirigible paved with light PV panels and using that for propulsion only, not lift. It seems obvious to me a much more efficient use of solar energy, to say nothing of by design having a hundred times the surface area for energy collection. More lift power to have much more battery storage onboard to get through nightimes and storms, maybe even a tethered version to just collect energy to use on the ground. I can even see a system that uses H2 as a lift gas, for one thing it is more efficient then helium, much more readily available and if used as a tethered PV collection site, some of that energy can be used for electrolysis of water to regenerate H2 to make up for losses through the skin, something you cannot do with helium. If it is unmanned, who cares if the dam thing blows up other than the annoyance of replacement, no lives would be lost.

    Another thought: How about a hybrid He/H2 system of lift, start out mostly with helium, then use hydrolysis or some catalyst system to generate H2 which would mix with the existing helium and slowly replace the helium with H2 which would greatly extend the useful life of the original helium without actually making new helium, the mixture would just go from 100% helium to 100% H2 over a period of years in unmanned flight. You could even have lightweight pumps on board to take out a portion of the gas, compress it in tanks to make the thing sink to the ground for maintenance.

    I see I am not the only one to think of this, but I think I am the originator of the He/H2 hybrid idea:
    http://turtleairships.blogspot.com/

    The He/H2 idea would be much safer than pure H2 for manned flight because the mixture of He/H2 would never burn in the first place, making that technology a viable alternative to pure helium ships. Not sure what the minimum He needed to keep H2 from being explosive but whatever that limit is, you could then land for the purpose of refilling with He, which seems obvious to be a greatly reduced usage of precious helium for lifting bodies and as the mixture goes towards pure H2, the lifting power goes up so the cargo carrying capacity would go up also somewhat anyway.