Human-powered Helicopter Fails to Lift Off

Peter writes "The Human-powered helicopter didn't even get off the ground. A team of University of British Columbia engineering students tried to win the $20,000 US prize offered by the American Helicopter Society. Three metres off the ground and hover for a minute was the challenge. But before the rotors were able to produce enough buoyant force they hit each other. More details: Vancouver Sun."

No, it's a follow-up

[Anonymous Coward]

To this story [slashdot.org].

Does strike me as feasible

[AKAImBatman]

A normal helicopter needs several Kilowatts of engine power to produce enough lift to even get itself off the ground, much less loaded down with a human. The human body constantly generates an approximate 200 watts. In case anyone's wondering, that's about 0.26 horsepower [slashdot.org], and that's assuming that you can apply the full 200 watts of your energy.

It's fun to see them try, but the physics say that the energy just isn't there. Perhaps if the copter weighed almost nothing, and it was constructed of super-strong materials. Of course, then we'd have unobtainium. :-)

Re:Does strike me as feasible

[Kynde]

The human body constantly generates an approximate 200 watts. In case anyone's wondering, that's about 0.26 horsepower, and that's assuming that you can apply the full 200 watts of your energy. It's fun to see them try, but the physics say that the energy just isn't there.

That's not entirely accurate. I think the 200 watts is an approximation of the heat we emit in room temperatures. That's not the only source of power we have. We can also, for example, pedal.

Considering that we can run uphill fairly fast, the physics indeed says the power to overcome gravity most certainly is there, atleast for short periods of time. It's another question entirely wether we have the power to lift ourselves and the helicopter machinery using that technique. It will mostly depend on the efficiency vs the weight of the machinery.

Re:Will someone hep me?

[D.Throttle]

The team used a counter-rotating design. The outer wing rotates clockwise and the inner wing counter-clockwise. The outer wing which is situated above the inner wing naturally flex and hangs down. It was hanging down to the point at which each wing made contact and shattered into countless pieces rendering thousands of man hours and about $30,000 worth of materials useless.

Re:What a shame

[dykofone]

Counter-rotating rotors, a lower set goes one way (let's say clockwise) and the set above it goes the other way (let's say anti-clockwise).

The torsion created by each set of rotors balance out, preventing the need for a tail rotor to prevent spinngin. It was one of the upper rotors that hit the lower rotors in this case, which is thought to be due in part to heat and humidity (probably since the top rotors were longer, the heat and humidity caused them to bow, and they didn't generate enough lift to pull themselves out of the way of the smaller lower rotors as they lifted up).

Some more info here [copters.com]

Re:Just a question...

[dykofone]

Simplicity and weight, I would guess. Each gear in bycicle tranny weights about .6 pounds(about .3 kg, for those of you counting along anywhere else in the world).

100 of those and you've got yourself another 60 pounds you have to lift, plus the extra mounting brackets, cables, shifters, chance for breakage, etc.

Besides, having guys run in circles to get the thing up to speed brings back images of the good old days of push-start props on airplanes.

energy storage is forbidden

[bani]

its one of the rules for the competition. a big rubber band would violate the rule and disqualify them.

Re:Nitpick

[kidgenius]

Techincally, buoyancy force is the total volume of the fluid displaced multiplied by the density. That is how "lighter than air" craft are able to stay aloft. Aircraft, use lift.

can't be all that bad...

[bani]

...russians are rather fond of using the dual counterrotating design.

http://www.airliners.net/open.file?id=056899
ht tp://www.airliners.net/open.file?id=123084
http:/ /www.aeronautics.ru/kamov/ka5201.jpg
http://www.a eronautics.ru/archive/vvs/ka27-01.htm
http://www. zap16.com/mil%20fact/kamov%20Ka-50.htm

Re:Does strike me as feasible

[AKAImBatman]

500 watts is a lot for a human. But it's also something most humans can only do for short bursts. i.e. Your body stores up glucose for when it's needed. As long as you're stored glucose is being burned, you can reach potentially huge increases in physical power. But once the glucose fuel is exhausted, your power ratings become dependent on your body's ability to produce more glucose. This ability goes down as the lactic acid builds up in the muscles, making high levels of production that much more difficult.

Even if we assume a constant 500 watts, we're still terminally short of what would be needed for rotationally powered flight. In addition, a person capable of 500 watts would have a much higher weight, thus offsetting some of his gains. In comparison, the smallest 1 person helicopter weighs in at 254 pounds, but produces 55 horsepower! A human can't (normally) even produce 1 horsepower, and if he can it's for a VERY short period.

Now if we were to talk about powering ultralight airplanes, then I'd be a bit more optimistic.

Re:Just a question...

[TigerNut]

The aerodynamic drag induced by trying to spin rotors at high speed would keep you from just continually accelerating the blades, just like you can't automatically go faster on a bike by putting on extra gears or steeper ones.

Re:No pretesting?

[Phurd Phlegm]

These were engineering students, and yet no one thought to do the basic physics calculations (like: what is the power required and can a human generate it) before building a prototype. I thought that was what engineering is all about.

I know it's kind of expected that no one on Slashdot reads the references before pontificating, but this (click on "choosing the final Thunderbird design") [mech.ubc.ca] seems to indicate they did do the calculations and they did expect a human could produce enough power.

It appears they were in error, or that there were other things (e.g., stability) that interfered. That's no reason to expect they won't improve the design and get it working, though. I think it's a pretty cool challenge and certainly beats the usual student project of "design another <known thing>".

Re:Does strike me as feasible

[Anonymous Coward]

The helicopter is designed to lift off with ~425 Watts of human power. See the bottom of this page:

http://batman.mech.ubc.ca/~hph/index2.html [mech.ubc.ca]

Dan.

Re:Does strike me as feasible

[pclminion]

So, does that mean that no energy is expended holding yourself at the top of a chinup?

There is work being done on a microscopic scale in your muscles. You might need a background in muscle biology to completely understand this, but this [accessexcellence.org] is the modern theory of how actin and myosin (the two proteins which make your muscles work) actually cause muscle contraction.

Basically, your muscle fibers are made up of billions of tiny ratchets which cog against another fiber, kind of like a rack-and-pinion steering system. When your muscle is applying force to an object, say, when doing a chinup, the ratchet teeth "slip" and the fibers slide past each other. To counteract this, the ratchets must flex again to pull the fiber back. All this ratcheting work eventually winds up as heat in your muscles.

If your arms were made of steel, it would take no energy to hold a chinup. This is because steel arms have no moving parts. It is important to know that your muscles are indeed still "moving" while holding a chinup, but at a microscopic scale you are not aware of. That's why it requires an exertion of energy to maintain a flexed position.

That is how they did...

[Gordonjcp]

... the first human-powered cross-Channel flight. I know one of the guys who was on the support boat for it, and who was heavily involved with the project. They figured it was easier to get a cyclist and teach them to fly an aircraft, than to get a pilot and train them up as a champion cyclist.

Re:No pretesting?

[Dave_B93]

I was at the attempted liftoff.

This was the first time that they had the whole thing assembled, and in some ways you could tell. I think some simple resistance based testing would've shown that chain structure was too fragile to propel the wings properly ( either that or the chain was somehow damaged in the first crash where the blades ran into each other.)

It was also kind of obvious they had never practiced how they were going to start the thing. they had 4 volunteers, (one on the end of each rotor) running around helping the rotors get started. One of the guys on the lower blades was pulling too far down causing the other guy to let go. That is why the blades collided the first time, forget all this not enough lift on the top blade, it was human error.

The second attempt (after repairing the damage caused by the first attempt). looked more promising, the blades actually seemed to be moving quite well, and in fact the upper blade had started producing enough lift that it looked like there was no danger of hitting the bottom one ( even with human error) , but then they ran into the problems with the chain. Imagine the sound that your bike makes when you're in the wrong gear going up a hill. The skipping noises etc... it sounded just like that.

I left after the third attempt when the chain just came off. it didnt' look like they were going to get anywhere, and I'd already been there for about 2 hours.

As for why they'd never practiced with the thing beforehand, I speculate that it is because they didn't know if the thing would survive. If somehow it had gotten off the ground, only to crash after 30 seconds, they would've beaten the record, but wouldn't be able to recreate it. This way they would atleast have witnesses...

Re:That's just silly

[Anonymous Coward]

http://en.wikipedia.org/wiki/Avro_Arrow [wikipedia.org]

Re:Huge Glaring Problem.

[aculeus]

Actally, every helicopter pilot is taught how to land if their engine fails. As long as the helicopter is 100 feet off the ground or going faster than 30 mph, even with catastrophic engine failure, it can still land. It is called autorotation [helis.com]