Human Powered Helicopter Aims To Break Records

An anonymous reader writes "A team of 50 from the University of Maryland has developed a human-powered helicopter, 'The Gamera,' which took two years to complete. The size of the helicopter is one third of a football field. The helicopter is made from light materials such as balsa, mylar, carbon fiber and foam and weighs about 210 pounds. The team aims to have it hover at least 3 meters off the ground."

Comments

Misleading summary

[Pheran]

The article summary is quite misleading given that the 210-pound figure includes the weight of the pilot.

Re:Misleading summary

[$RANDOMLUSER]

So that's the fueled weight.

Finally!

[Anonymous Coward]

Someone figured out an appropriate use for the football field.

Stored energy

[Iamthecheese]

I'm sure they wouldn't allow a helicopter that uses air earlier compressed by the human pilot so what about stored momentum in the blades and machinery? Also do air currents count as stored energy? Obviously this couldn't fly without the ground effect... Just some thoughts.

Re:Stored energy

[ceiling9]

Using energy stored as momentum would only allow for a temporary hop off the ground, until that momentum is used up - if the pilot can't sustain the power required for flight, the rotor would quickly slow down.. It sounds like the requirement that it fly for at least 60 seconds means that the human pilot has to be able to maintain the momentum of the rotor by pedaling with the power required for actually flying.

Re:Stored energy

[tlhIngan]

How do you make one that is not influenced by ground effect?

Easy, fly higher.

Ground effect only happens when you're close to the ground. A rule of thumb is that it's effect is negligble after you reach a height equal to half the wingspan.

So a rotor blade (or wing) of 3m length (6m rotor disc/wingspan), once above 3m in height, would have to be flying out of ground effect.

And yes, ground effect is a big deal - it lowers the amount of lift you actually need by quite a bit. Student pilots find this out on landing when all of a sudden the airplane floats down the runway. Experienced pilots find it when their plane seems to take off, but only bobs above the ground without really gaining altitude.

Re:Stored energy

[v1]

Using energy stored as momentum would only allow for a temporary hop off the ground,

Though one of the requirements of the challenge is at some point in the flight to get 3M off the ground. Using inertia in the blades would be an excellent way to do that. Get the blades up to speed, lowering their angle as you increase their speed and maintain a hover, (thus storing energy in the blades' inertia) then suddenly pitch the blades up at the 55 second mark or so when the pilot is exhausted, and the craft should "hop" as the blade inertia is momentarily traded for lift, hopefully getting the craft up to 3M.

Although the craft may then fall out of the sky like a rock. Hope the cockpit is over a padded surface.

Re:Stored energy

[ChrisMaple]

To answer your question literally, you design it so that at rest, the blades are high enough off the ground that the ground effect is insignificant.

To test that a given helicopter does not rely upon ground effect, insist that it take off from a surface consisting mostly of holes, such as a chain link fence suspended horizontally 100 feet in the air.

Re:Stored energy

[ChrisMaple]

To make this a little more obvious, consider that a hovering helicopter stays in one column of air, and that column of air is in downward motion caused by the helicopter pushing on it. The helicopter is trying to climb by grabbing air that is falling. As soon as the helicopter moves out of that falling column of air, it's grabbing on to stationary air, which is a lot easier.

When it's near the ground, there can't be any falling column of air because the ground is blocking the airflow.

Re:So it doesn't do anything yet.

[gregrah]

I agree. There's no way that this experience/technology could ever be applied to anything useful.

/sarcasm

Fuel

[RazzleFrog]

So is it fueled by Soylent Green?

Yet another premature article

[jklovanc]

The test flight is supposed to happen tomorrow. Why not wait till there are results before posting an article?

Units?

[PPH]

What kind of football?

How much excess power does vertical flight require

[Viol8]

...compared to just climbing up a ladder?

What I mean is the human body has easily enough power to raise itself up a vertical ladder or rock face so presumably a huge amount of this power must be lost just moving air around when that power is used inside a human powered helicopter. But how much power is wasted , or to put it another way , how much power put into the system is actually used to raise the mass of the helicopter?

Re:3 meters off the ground?

[vlm]

So... a carnie wearing stilts will look down at you and laugh?

Not is your "ground" is actually a deep body of water...

Re:How much excess power does vertical flight requ

[vlm]

...compared to just climbing up a ladder?

What I mean is the human body has easily enough power to raise itself up a vertical ladder or rock face so presumably a huge amount of this power must be lost just moving air around when that power is used inside a human powered helicopter. But how much power is wasted , or to put it another way , how much power put into the system is actually used to raise the mass of the helicopter?

You're mixing mass, power, and impulse all together. impulse = F * delta t = m * delta v

So the force is pushing down with the combined weight of the vehicle for a certain time in order to hover in place, which is equivalent to accelerating a mass (lets say, the vehicle) to a certain velocity. So hovering for 10 minutes takes the same impulse as accelerating (lets say, horizontally) to some absolutely ridiculous velocity. I forget the crossover but, hovering a copter for X minutes is equivalent to pushing a car 0 to 60.

The power level is in the low single digit horsepower for a good athlete for a minute or two. Good luck dissipating even one horsepower for a "long time".

Also note that people climb extremely slowly. Over a long term, best expressed as seconds per foot rather than ft/sec. Classic high school physics problem is having the strongest track athlete try to climb a flight of stairs as quickly as possible, with the horsepower result usually being pretty depressing.

idea!

[roman_mir]

I have an idea! How about they take a small 2 stroke engine and add it to the thing. Also a closed cockpit would be nice. Make the vehicle a bit more compact, maybe 1/4 of the size and then we can start having a conversation about something that's useful.

Re:How much excess power does vertical flight requ

[smellsofbikes]

...compared to just climbing up a ladder?

What I mean is the human body has easily enough power to raise itself up a vertical ladder or rock face so presumably a huge amount of this power must be lost just moving air around when that power is used inside a human powered helicopter. But how much power is wasted , or to put it another way , how much power put into the system is actually used to raise the mass of the helicopter?

I'm not exactly sure what you're asking here, but think about it this way. Gravity is accelerating you downwards. When you stand on a ladder, the ladder's structure is resisting your weight, which is why you stay up. With a helicopter or airplane, you don't have a structure to hold you up, so instead you accelerate air downwards using wings. You push the wings through the air, they accelerate air downwards, you get supported.

So the easiest answer to your question is *all* the power put into the system actually raises the mass of the helicopter. A slightly more nuanced answer would be that the mass of the whole system (pilot + helicopter) minus the pilot's weight, is how much energy it takes to raise the mass of the helicopter, but that's sort of silly.

A side-note: there's something called ground effect that changes how helicopters (and airplanes and anything else relying on accelerating air downwards to maintain flight) work. When a wing is within about one wingspan of the ground, the air it forces downwards is somewhat constrained between the ground and the wing, giving the wing more lift than it would in free air. As a result, if you're within a wingspan of the ground it requires significantly less power to stay in the air. (If you watch airplanes land you'll see this effect as a change in their angle of approach just before they land.) The Sikorsky Challenge requires the helicopter to hover at a height that is within ground effect for most practical designs, so the idea of making a practical human-powered helicopter is even harder than making something that fulfills the Sikorsky Challenge.

Re:7 Deadly Sins...

[digsbo]

Then you go ahead and do what you see as beneficial to humanity, and let them do what they see as worthwhile. But before you criticize people attempting something amazing that you don't see as worthy of your blessing as being beneficial to humanity, ask yourself if you always apply the same judgment to your own actions. I'm sure the ecological footprint of the energy you've used to post on ./ is well worth it for disseminating your grand wisdom to the rest of us. Sorry to be a dick, but boy you come across as an arrogant ass in your post, holed away in some ivory basement somewhere.

This completely avoid the conversation about how they are making incremental advances in design and testing technology, of course.

Re:How much excess power does vertical flight requ

[Nick Ives]

Also note that people climb extremely slowly. Over a long term, best expressed as seconds per foot rather than ft/sec.

I think you mean best expressed as inches per second or even better, cm/s. If you were moving seconds per foot then you'd be in some kind of Braid style dreamworld where motion in a given direction affected the flow of time.