Wow competition is heating up as there is already a well established group called Upturn going after the prize. They also have a Kickstarter campaign and are much further along with a working model that is now getting tuned. http://www.kickstarter.com/projects/1594333219/make-aviation...
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?
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.
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?
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.
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.
Wow. I spent most of my undergrad extracurricular effort working on my university's HPH team. Incredibly difficult challenges in aerodynamics and structures. The goal is to go for a whole minute and reach 3 m altitude. In the few decades the prize has been offered, the record has been seconds and centimeters high.
Is storing energy against the rules? for example pedaling for an hour or two to store up say mechanical energy in a flywheel, spring tension, hydraulic pressure or other means then just put the rotors in gear to lift off?
I have to assume so. Leverage is presumably allowable though.
Once you're in the business of storing mechanical energy, you haven't solved the problem of sustained human-powered flight and you're really just a technology epoch away from using a motor and a capacitor.
They are right on the edge of flight/no flight. The driver is pedalling flat out and it's not flying. Then it hovers for a few seconds, then it goes back to on the ground.
This guy seems closer to the win. He's been iterating on this thing for years and is the current record holder. He also founded and sold Zero Motorcycles.
Cameron and Todd backed the Upturn project on Kickstarter, they didn't create it. NTS Works (the organization behind Upturn) is in competition with AeroVelo (the organization behind Atlas).
It depends where you live. I regularly make a 35 mile drive to a place that's only twenty miles away. A vehicle that used 75% more fuel per mile than my car could let me make the same trip in almost half the time for the same amount of fuel.
Market is where land commute takes time. Eg., in Bay area, there are lot of people who commute from South Bay to San Francisco. Slow traffic is common during peak hours and it is frustrating. I see this area as one of the best places to try local air-commute.
It would add the third dimension to the commute space. Like the fast-lanes in freeways, lanes could be formed by altitude.
It seems a bit pointless when it would be relatively easy with a dirigible (i.e. add a bag of hydrogen or helium). On a windless day, your pedalling should propel you quite a distance anywhere you want to go. Problem solved, with technology that is at least hundred years old.
Thanks for the link. It appears that you are allowed to drop the ground level from below the helicopter :-)
One thing that is slightly more in the spirit of the contest is to have rotors tht do not provide lift at all and hence have low drag, build up lots of potential energy, and then adjust the angle of attack to get lift. Storing potential energy to get a 30 second launch and subsequent 30 second drop will be 'challenging', though.
I guess that both will be covered by "3.2 For any and all questions regarding acceptance of entries, eligibility of an entrant, pilot, crew or aircraft under the regulations, or any other matter relating to the AHS prize, the decision of the AHS is final."
OK, thanks. So how about I use strong carbon fibre shell with air pumped out. There is no lighter than air gas involved and the whole machine can be (just slightly) heavier-than-air. I bet they would outlaw that too, under the 'catch all' rule mentioned below. Nothing but extremely hard work will do ;)
It'd have to be a very strong shell to actually give you buoyancy above simply not having anything. Carbon fibre is strong in tension, while a material which can support a vacuum must be strong in compression. The weight of any shell is going to be much greater than the buoyancy you'd gain.
It looks like the state of the art right now gives us absolutely huge devices that barely even make it off the ground. Does anybody have any confidence that a human powered helicopter could ever be practical for real transport? Unless we humans somehow manage to multiply our sustained power output by several times, I don't see this happening.
