Gamera II human-powered helicopter team sets new unofficial 35-second flight duration benchmark

Jun 21, 2012
Gamera II in flight. Click for the hi-res version. Photo by Earl Zubkoff, Essential Eye Photographics.

(Phys.org) -- On June 20, students on the Gamera II human-powered helicopter team from the University of Maryland’s A. James Clark School of Engineering set a new, unofficial flight duration record of approximately 35 seconds. If verified by the National Aeronautic Association, this new time will supersede the team’s previous world record of 11.4 seconds set last July.

The Gamera II team is one of at least three competing in the American Helicopter Society Igor I. Sikorsky Human-Powered Helicopter Competition this summer. To win the $250,000 competition, an individual or team must build a helicopter powered only by human means that lifts off and hovers for 60 seconds, attains a height of three meters at some point during the 60-second flight and stays within a 10 square meter area during the flight.

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The June 20 flight was accomplished with pilot Colin Gore on board the new Gamera II vehicle – a sleeker, lighter version of last year’s rotorcraft that features improvements to its cockpit, transmission and rotor design. Gore is a graduate student in materials science and engineering at the Clark School.

Later in the day, a truss arm on Gamera II failed during a subsequent test flight. The team is repairing the vehicle overnight and plans to resume testing on Thursday. The team hopes to reach a flight duration of 60 seconds (one step towards completing the AHS Sikorsky Prize goals). Once flight tests resume, the Clark School will continue to provide a live stream of the flights on the Gamera homepage.

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rynox
4.5 / 5 (2) Jun 21, 2012
Probably not useful or practical, but extremely cool.
Telekinetic
2.8 / 5 (8) Jun 21, 2012
Probably not useful or practical, but extremely cool.


Good thing you weren't holding the purse strings for the Wright brothers.
Foundation
5 / 5 (1) Jun 21, 2012
But engines became lighter and more powerful. Aerodynamics and materials advanced a lot as well of course. Materials and aerodynamics can still advance, especially the materials. But unless we enhance human power in some way it probably won't be really useful.
Telekinetic
2.3 / 5 (6) Jun 21, 2012
"But unless we enhance human power in some way it probably won't be really useful."- Foundation

By exercising, one can build muscle mass that will enhance human power and overall health- and an effective exercise is pedaling a human-powered helicopter! I think the solution lies in improvements of prop and continually variable transmission design. Next year, they may very well take the prize.
krundoloss
3.5 / 5 (2) Jun 21, 2012
I wonder why they made it with 4 props? Why not just one really big one, and they could cut out all that infrastructure....
deatopmg
3.4 / 5 (5) Jun 21, 2012
@krundoloss - WHat happens to the body of the vehicle when one has only one rotor?
baudrunner
2.3 / 5 (3) Jun 21, 2012
I would first custom design a lightweight derailleur to transfer torque to the lifting rotor(s), then keep the entire package as small as possible. Then again, the conventional bike chain sprocket system probably is not suitable for this application. Better to use a continuously variable transmission with direct drive to a gear assembly and a single multi-bladed rotor. The chopper above looks too ungainly, and much too large to manage. It will take far too much effort to get that thing off the ground for any length of time.
antialias_physorg
3 / 5 (2) Jun 21, 2012
I wonder why they made it with 4 props? Why not just one really big one,

Because with one big prop the poor guy would be spinning in the opposite direction once he got off the ground (instead of the prop turning)

Also there is a tradeoff between strength and beam (propeller) length which isn't linear. If you make it too large it'll either be too heavy or break under its own weight.

The quad concept seems to be optimal in terms of weight, stability and the airflows of rotors not getting in each other's way.
Eikka
3 / 5 (2) Jun 22, 2012
By exercising, one can build muscle mass that will enhance human power


Yes, you can build muscle and get more power, you can easily generate 1-2 kW of power, but sustaining it is a different matter entirely. Lance Armstrong can sustain about 600 W for the duration of a race. An ordinary non-athlete can sustain only about 200 Watts.

There's no point in building a human powered helicopter that requires a professional athlete to ride it, and even so, 600 Watts isn't much.

Good thing you weren't holding the purse strings for the Wright brothers.


It's one thing to invest in something that is merely thought unfeasible, and in something that is demostratably unfeasible. For instance, fighting 9.81 m/s^2 of gravity for 100kg of mass, you need to constantly accelerate an equal mass of air in the opposite direction. A simple back of the envelope calculation shows that this should require about 4.8 kW of power, excluding any ground effects that would ease the load.
Eikka
1 / 5 (1) Jun 22, 2012
Of course, since F=ma we can double the mass of air, halve the required acceleration and only need 1/4 the power. Double the airmass yet again, and you get to an amount of power that an ordinary human could manage with a bit of training (~300W)

The problem is that 400 kg of air is 342 cubic meters at STP, or the interior volume of an entire house. This amount of air has to pass through the propellers every second to generate the necessary lift, and you only have 300 Watts to do it, which means the propellers have to be absolutely huge - and you still have a 100 kg weight limit for the entire thing.
antialias_physorg
3 / 5 (2) Jun 22, 2012
There's no point in building a human powered helicopter that requires a professional athlete to ride it, and even so, 600 Watts isn't much.

You mean just like there is no point in having professional athelets that can do stuff others can't?
Maybe that will be a sports device (or even for races)?
Maybe other materials will allow for a lighter build that can be moved by a normally trained person?
Maybe there will be additional aids (like small helium bags) that will reduce the energy needed for liftoff?

Point being: this isn't a finished product but a feasibility study for a small part of one. Imagine how much fun it would be if you could, on your day off, take a 'bike ride' above the city instaed of through it.
Eikka
1 / 5 (1) Jun 22, 2012
You mean just like there is no point in having professional athelets that can do stuff others can't? Maybe that will be a sports device (or even for races)?


That'd be a pretty boring sport; see who can hover in place for more than a few seconds. There are already competitions like that, like weightlifting, and they do tend to be a bit... pointless.

Maybe other materials will allow for a lighter build that can be moved by a normally trained person?


From the 100 kg I mentioned, the person will be about 75 kg. There's not that much room to improve.

Maybe there will be additional aids (like small helium bags) that will reduce the energy needed for liftoff?

You need relatively large bags, and why not make a personal dirigible? Why waste energy in being a helicopter?

Point being: this isn't a finished product but a feasibility study for a small part of one.


This isn't a feasibility study, this is an engineering competition, kinda like Ruby Goldberg machine
Maat
2 / 5 (4) Jun 22, 2012
Even if materials and technologies improve markedly this will never be practical so long as we have more efficient, and dare-I-say convenient, ways to produce power than human effort. If you can get the technology to the point of being able to fly this thing with the same effort as riding a bicycle I would still just slap an electric motor on it and save myself the fatigue if I was going to use it for practical purposes... using it solely for exercise or as a toy is a completely different story, but I don't consider that to be a practical application of a helicopter.
Eikka
1 / 5 (1) Jun 22, 2012
Actually, the required power calculation was a bit off. I forgot to multiply the required power by the increase in airmass, which makes doubling the airmass require half the power, not 1/4.

So you need to move 16 times the mass of air than what you want to lift if you want to do it with 300 Watts of human power. You only have to accelerate it a little, but the necessary volume of air per unit of time is so great that the sweep area of the rotors has to be as big as a football field, and I don't think that is an exaggeration.

With an airplane, it's much easier because the "rotors" are the fixed wings, moving in a straight line instead of turning back on themselves. Still, the wings are pretty big: http://en.wikiped...Daedalus

There's also interesting problems in operating a very low powered, very light aircraft. Like, the heat of the sun preventing you from landing or steering properly because of small updrafts.
antialias_physorg
5 / 5 (1) Jun 22, 2012
This isn't a feasibility study, this is an engineering competition, kinda like Ruby Goldberg machine

Like soccer playing robots or autonomous cars. The former still have a ways to go. The latter went from such a "it'll never work/what's the point?"-stage to something that'll be something we'll consider normal in a decade or two.

There are already competitions like that, like weightlifting, and they do tend to be a bit... pointless.

Not to the weightlifters.
Anything is pointless to someone. Art, sports, religion, science (sometimes all to the same person - just ask a nihilist). That doesn't mean someone won't have fun doing this stuff. Sikorsky set out a prize and people are having fun competing for it. Sikorsky (being a helicopter manufacturer) can learn a thing or two about low power/lightweight design/construction in the process.

People are whining about state sponsored science being expensive. Here you have corporate sponsored science and still you are whining.
antialias_physorg
not rated yet Jun 22, 2012
You need relatively large bags, and why not make a personal dirigible?

Dirigibles are harder to steer the bigger they get. there may be an optimal mix gehere between lift provided by (muscle) power and that provided by a gas.

From the 100 kg I mentioned, the person will be about 75 kg. There's not that much room to improve.

You can do a lot with 25kg if you move to metal foams, aerogels, or graphene sheets. who knows how big the rotors could become?

so long as we have more efficient, and dare-I-say convenient, ways to produce power than human effort.

People go on treadmills or ride bikes. Sure there are more convenient ways to get a treadmill moving (or than riding a bike accross town). But that's not the point of doing these things, is it?
Eikka
1 / 5 (1) Jun 22, 2012
Like soccer playing robots or autonomous cars.

Both of those have real applications and answer real problems. First they play soccer, then they run down criminals.

A human powered helicopter on the other hand is just a "can you do it?" - all the groundbreaking work in materials and construction are done somewhere else, and this is simply an application with no real use.

The Sikorsky prize is more of a marketing stunt, because their name will be connected to it if anyone succeeds - and a relatively cheap one at that.

who knows how big the rotors could become?


The craft is already down to 32 kg, so you're running into diminishing returns. It's not a question of how big can you make it - I'm sure you can - the rotor will just be too large to be practical in any sense.

there may be an optimal mix here between lift provided by (muscle) power and that provided by a gas.

You need roughly 1 m^3 of helium to lift 1 kg. The balloon will be infeasibly large anyhow.
Eikka
1 / 5 (1) Jun 22, 2012
That doesn't mean someone won't have fun doing this stuff. Sikorsky set out a prize and people are having fun competing for it.


The point isn't that people aren't allowed to have fun. There's no better learning opportunity than trying to build the impossible. Sometimes you may even succeed.

The point is that the less you know, the simpler, more feasible things seem, as evidenced by people who compare this thing to the Wrights' Flyer (and by Dunning & Kruger). People in general lack a sense of proportionality, but that's not really the problem; the real issue is that nobody bothers to check their facts to see if their intuition is anywhere near reality.
Telekinetic
1 / 5 (2) Jun 22, 2012
"People in general lack a sense of proportionality, but that's not really the problem; the real issue is that nobody bothers to check their facts to see if their intuition is anywhere near reality."- Eikka
Your problem is that you're so constipated no amount of power assistance would get you off the ground. Ever hear of the Daedalus human-powered airplane? Of course a winged craft is easier to keep aloft, but they DID it, in spite of the centuries of skepticism. With new materials and improved prop design, the chopper will eventually fly.
Eikka
1 / 5 (1) Jun 24, 2012
Ever hear of the Daedalus human-powered airplane?


Yes. I even linked the wikipedia page, which you might have noticed if you had bothered to actually read anything I wrote.

Even the Daedalus is impractically large, even though the craft itself is incredibly light at 31 kg. The problem is that the person you are transporting weighs so much more that any advantage in materials or construction can't make the craft any smaller, and it is already infeasibly large to be of any practical use.

Unless your point is making an airplane for midgets.

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