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This project is from the same team that recently set the Guinness World Record by building a Human Powered Ornithopter (http://www.youtube.com/watch?v=0E77j1imd

This project is from the same team that recently set the Guinness World Record by building a Human Powered Ornithopter (http://www.youtube.com/watch?v=0E77j1imdhQ http://www.youtube.com/watch?v=0E77j1imdhQ)

Tichy 14y ago
That video seems weird: since apparently they launched the ornithopter with some machine, how is it even clear that it stayed afloat by using human power after launch? Where is the difference to a glider?
- pygy_ 14y ago
  > Where is the difference to a glider? It sustained altitude and speed for a while (short of 20 seconds). See this: http://www.youtube.com/watch?v=0E77j1imdhQ http://www.youtube.com/watch?v=0E77j1imdhQ
  - jrockway 14y ago
    Gliders can gain altitude and speed. There are plenty of spots on the surface of the earth where air is rising quickly enough to support a plane.
    - pygy_ 14y ago
      True. I guess we can dismiss the possibility of ascending currents in this case, since the test was performed on uniform land, at dawn.
      - marvin 14y ago
        Glider pilot here. That does make it less likely, but it is no guarantee that there were no rising air currents. Thermals are sustained by an atmospheric temperature differential, not "hot air rising". They are usually _triggered_ by the local temperature differences caused by the sun, but can also be triggered by a gust of wind.
        pygy_ 14y ago
        Thanks for teaching me something. I was referring to this[0] which is indeed hot air rising and only occurs at low altitude, you're talking about this[1]. Is there a possibility for the phenomena you describe to occur 10 meters above flat land at dawn? [0] http://en.wikipedia.org/wiki/Thermal http://en.wikipedia.org/wiki/Thermal [1] http://en.wikipedia.org/wiki/Thermal_wind http://en.wikipedia.org/wiki/Thermal_wind
        marvin 14y ago
        Hi, sorry for the late reply. I only briefly read the second link, but I don't think it's what I was talking about. I read the Wikipedia article on thermals a week ago, and it seems a bit brief. I was a bit quick with my first reply as well. This is a pretty big subject. Thermals can be triggered by any perturbation in the atmosphere - a gust of wind, a truck on the highway or a temperature differential caused by the sun. But they are _sustained_ by vertical temperature differences in the atmosphere: As an airmass rises, it expands due to the lower atmospheric pressure. This expansion causes the airmass to cool adiabatically, approximately one degree Celcius per 100 meters of gained altitude. However, meteorological conditions can cause the temperature distribution of the _surrounding_ air to be different. For instance, after a clear night with no clouds, perhaps the air from the ground up to 2000 meters altitude actually decreases in temperature 1.1 degrees Celcius per 100 meters of altitude gained. If an airmass on the ground starts moving upwards in these conditions, it will still cool adiabatically - but slower than the rest of the atmosphere cools due to the meteorological conditions. So a rising airmass will actually accellerate, because the airmass grows hotter relative to the surrounding air as it rises. This is a thermal. It will keep moving until the temperature of the atmosphere starts rising with altitude. Condensation (cloud formation, cumulus clouds are caused by thermals) can increase its vertical speed. But to answer your initial question: Yes, they can and do. But when the atmosphere is so _unstable_ (unstable atmosphere == temperature falls very quickly with altitude) that thermals are spontaneously triggered without help from the sun, it will usually mean bad weather or thunderstorms later in the day. So if the air seems calm at the surface, it will pretty much be guaranteed to be calm at 10 meters altitude. You can detect thermals at ground level by rapidly changing wind direction, often on nice summer days. In the air at low-ish altitudes (less than 2000 meters), thermal activity is indicated by turbulence.
rorrr 14y ago
That's not human powered, they accelerated it with a car. It's like saying hang-gliding is human-powered.
- sopooneo 14y ago
  By that reasoning, Yeager's X-1 was not rocket powered since it was launched from the bomb-bay of a flying B-29 prop plane. And a hang glider isn't powered at all. It has no thrust.
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  - recursive 14y ago
    Does partially human powered work better for you? Human powered implies that a human generated all the power needed for takeoff.
  - grannyg00se 14y ago
    It's kind of a tricky bit of language because a hang glider actually is human powered if you consider how its direction is changed and how it stays aloft. The human isn't just cargo sitting there doing nothing. Without the human "powering" the hang glider it wouldn't stay aloft if you simply pushed it off of a cliff. If you are specifically looking at thrust that is easier to talk about. In general, I wouldn't call a hang glider human powered either even though a certain amount of human power output is responsible for its sustained flight. This is in contrast to a craft with a non human power plant. Even in cases where the human is using some kind of power output to further assist the aircraft, the output of the power plant is several orders of magnitude larger than the human's output. Which in some cases may be simply moving a control mechanism. And then there are what could be referred to as human "assisted" craft where the human power output is actually equal to or close to the output of the non human power plant. I think the human assisted craft are more likely to be reasonably useful. We're just not suitable for the type of sustained power output that is required for fully human powered flight.
adamgravitis 14y ago
Both Todd and Cam are brilliant aero engineers. While not a fait accompli, this certainly isn't their first negotiation with nature...

Tichy 14y ago

That video seems weird: since apparently they launched the ornithopter with some machine, how is it even clear that it stayed afloat by using human power after launch? Where is the difference to a glider?

pygy_ 14y ago
> Where is the difference to a glider? It sustained altitude and speed for a while (short of 20 seconds). See this: http://www.youtube.com/watch?v=0E77j1imdhQ http://www.youtube.com/watch?v=0E77j1imdhQ
- jrockway 14y ago
  Gliders can gain altitude and speed. There are plenty of spots on the surface of the earth where air is rising quickly enough to support a plane.
  - pygy_ 14y ago
    True. I guess we can dismiss the possibility of ascending currents in this case, since the test was performed on uniform land, at dawn.
    - marvin 14y ago
      Glider pilot here. That does make it less likely, but it is no guarantee that there were no rising air currents. Thermals are sustained by an atmospheric temperature differential, not "hot air rising". They are usually _triggered_ by the local temperature differences caused by the sun, but can also be triggered by a gust of wind.
      - pygy_ 14y ago
        Thanks for teaching me something. I was referring to this[0] which is indeed hot air rising and only occurs at low altitude, you're talking about this[1]. Is there a possibility for the phenomena you describe to occur 10 meters above flat land at dawn? [0] http://en.wikipedia.org/wiki/Thermal http://en.wikipedia.org/wiki/Thermal [1] http://en.wikipedia.org/wiki/Thermal_wind http://en.wikipedia.org/wiki/Thermal_wind
        marvin 14y ago
        Hi, sorry for the late reply. I only briefly read the second link, but I don't think it's what I was talking about. I read the Wikipedia article on thermals a week ago, and it seems a bit brief. I was a bit quick with my first reply as well. This is a pretty big subject. Thermals can be triggered by any perturbation in the atmosphere - a gust of wind, a truck on the highway or a temperature differential caused by the sun. But they are _sustained_ by vertical temperature differences in the atmosphere: As an airmass rises, it expands due to the lower atmospheric pressure. This expansion causes the airmass to cool adiabatically, approximately one degree Celcius per 100 meters of gained altitude. However, meteorological conditions can cause the temperature distribution of the _surrounding_ air to be different. For instance, after a clear night with no clouds, perhaps the air from the ground up to 2000 meters altitude actually decreases in temperature 1.1 degrees Celcius per 100 meters of altitude gained. If an airmass on the ground starts moving upwards in these conditions, it will still cool adiabatically - but slower than the rest of the atmosphere cools due to the meteorological conditions. So a rising airmass will actually accellerate, because the airmass grows hotter relative to the surrounding air as it rises. This is a thermal. It will keep moving until the temperature of the atmosphere starts rising with altitude. Condensation (cloud formation, cumulus clouds are caused by thermals) can increase its vertical speed. But to answer your initial question: Yes, they can and do. But when the atmosphere is so _unstable_ (unstable atmosphere == temperature falls very quickly with altitude) that thermals are spontaneously triggered without help from the sun, it will usually mean bad weather or thunderstorms later in the day. So if the air seems calm at the surface, it will pretty much be guaranteed to be calm at 10 meters altitude. You can detect thermals at ground level by rapidly changing wind direction, often on nice summer days. In the air at low-ish altitudes (less than 2000 meters), thermal activity is indicated by turbulence.

rorrr 14y ago

That's not human powered, they accelerated it with a car. It's like saying hang-gliding is human-powered.

sopooneo 14y ago
By that reasoning, Yeager's X-1 was not rocket powered since it was launched from the bomb-bay of a flying B-29 prop plane. And a hang glider isn't powered at all. It has no thrust.
- deleted 14y ago
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  [deleted]
- deleted 14y ago
  [deleted]
- recursive 14y ago
  Does partially human powered work better for you? Human powered implies that a human generated all the power needed for takeoff.
- grannyg00se 14y ago
  It's kind of a tricky bit of language because a hang glider actually is human powered if you consider how its direction is changed and how it stays aloft. The human isn't just cargo sitting there doing nothing. Without the human "powering" the hang glider it wouldn't stay aloft if you simply pushed it off of a cliff. If you are specifically looking at thrust that is easier to talk about. In general, I wouldn't call a hang glider human powered either even though a certain amount of human power output is responsible for its sustained flight. This is in contrast to a craft with a non human power plant. Even in cases where the human is using some kind of power output to further assist the aircraft, the output of the power plant is several orders of magnitude larger than the human's output. Which in some cases may be simply moving a control mechanism. And then there are what could be referred to as human "assisted" craft where the human power output is actually equal to or close to the output of the non human power plant. I think the human assisted craft are more likely to be reasonably useful. We're just not suitable for the type of sustained power output that is required for fully human powered flight.

adamgravitis 14y ago

Both Todd and Cam are brilliant aero engineers. While not a fait accompli, this certainly isn't their first negotiation with nature...