What are the problems on human powered aircraft?

In summary, the main problems on making a human powered aircraft are the low power to weight ratio and the limited lifting power of humans.
  • #1
vishnu2315
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i have planned to make a human powered aircraft.For that i want to know about the problems on making that.
 
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  • #2
You want to read up on the Gossamer Condor.

Flight of the Gossamer Condor
 
  • #3
vishnu2315 said:
i have planned to make a human powered aircraft.For that i want to know about the problems on making that.
For one thing, assuming you can build a craft capable of flight, it's exhausting work keeping the thing aloft. ?:)

I'm sure if the airlines could find a way to do so, they would make their passengers do all the work of keeping the plane in the air and flying it from point A to point B, rather than purchase all that expensive fuel and all those even more expensive engines. :biggrin:

It's much more comfortable to relax with a nice drink in First Class, than huffing and puffing trying to stay in the sky. :wink:
 
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  • #4
vishnu2315 said:
i have planned to make a human powered aircraft.For that i want to know about the problems on making that.
The main problem is low power to weight ratio.
 
  • #5
russ_watters said:
The main problem is low power to weight ratio.
That's easy to overcome. Simply use lighter than air.

Unfortunately the best candidates spend too much time in Washington. The rest of us can't seem to generate the needed hot air.
 
  • #6
Humans are weak. Imagine lifting 550 pounds a foot every second, that is 1 horsepower. A person could sustain lifting ~30 pounds a foot every second for a sustained period. That is ~1/20 of a horsepower.

You can't do much with 1/20 of a horsepower.
 
  • #7
vishnu2315 said:
What are the problems on human powered aircraft?
The air is not thick enough.
The human needs to be an athlete.
The craft must be stable and fly itself as the rider will be exhausted most of the time.
The lifting surfaces must be efficient which requires long wings to reduce drag.
Long wings do not help directionally stability which is essential to maintain lift.
The craft must be low weight but also strong enough to survive atmospheric disturbances and hail stones.
There is no economic imperative.

Birds have hollow bones as structure with feathers as an addaptive aerofoil surface.
The heaviest bird flying reliably today is the Kori Bustard, males weigh about 18kg.
 
  • #8
2milehi said:
Humans are weak. Imagine lifting 550 pounds a foot every second, that is 1 horsepower. A person could sustain lifting ~30 pounds a foot every second for a sustained period. That is ~1/20 of a horsepower.

You can't do much with 1/20 of a horsepower.

That's a fairly pessimistic estimate of human power output - most reasonably in-shape people can maintain 150 watts for a period of an hour or more (which is about 1/5 of a horsepower), and professional athletes might be able to do more like 350-400 watts (1/2 horsepower or so). Of course, even with half a horsepower available, the power to weight ratio is still a hugely limiting factor for a human powered aircraft.
 
  • #9
cjl said:
That's a fairly pessimistic estimate of human power output - most reasonably in-shape people can maintain 150 watts for a period of an hour or more (which is about 1/5 of a horsepower), and professional athletes might be able to do more like 350-400 watts (1/2 horsepower or so). Of course, even with half a horsepower available, the power to weight ratio is still a hugely limiting factor for a human powered aircraft.

Your numbers are optimistically unrealistic and you can't back it up with data. You are stating that an "in shape" person can maintain a consistent exertion of lifting 110 pounds per foot per second for hours on end (no rest, consistent energy output like a motor can do). Say a 110 pound person ascended stairs at the rate of 1 foot per second (1/5 of a horsepower or 110 pound⋅ft per second). In one hour that person would have climbed 3600 feet. Simply stated - in eight hours that person could be at the top of Everest.

I challenge you to produce 1/10th of a horsepower for 15 minutes (consistent power output, no breaks). Think of it in imperial units.
 
  • #10
2milehi said:
Your numbers are optimistically unrealistic and you can't back it up with data. You are stating that an "in shape" person can maintain a consistent exertion of lifting 110 pounds per foot per second for hours on end (no rest, consistent energy output like a motor can do). Say a 110 pound person ascended stairs at the rate of 1 foot per second (1/5 of a horsepower or 110 pound⋅ft per second). In one hour that person would have climbed 3600 feet. Simply stated - in eight hours that person could be at the top of Everest.

I challenge you to produce 1/10th of a horsepower for 15 minutes (consistent power output, no breaks). Think of it in imperial units.

I produce more than that all the time riding my bike. I don't have a power meter on my road bike, but based both on comparisons to stationary bikes with power meters and based on calculations estimating rolling resistance and aerodynamic drag, combined with my knowledge of my cycling speed (I have GPS logs for my rides), I definitely output 150+ watts regularly. As for data, will this do? It isn't for me, but I think it shows my point...

http://www.cyclingpowerlab.com/CyclingPowerOutput.aspx
http://users.frii.com/katana/biketext.html
http://toonecycling.com/2012/03/26/tour-de-tuscaloosa-power-data/ (this guy is in significantly better shape than I am - note that he has a 1 minute power output of almost 600W, a 25 minute power output of 307W, and a 2.5 hour output of 272W)
http://www.cyclingmusings.com/2011/02/golden-cheetah-quick-start-guide.html [Broken]

(I'd really love to have a power meter on my bike, since I'd be very curious to see the data, but it's $1k+, and sadly I can't justify that right now)
 
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  • #11
2milehi said:
Your numbers are optimistically unrealistic and you can't back it up with data. You are stating that an "in shape" person can maintain a consistent exertion of lifting 110 pounds per foot per second for hours on end (no rest, consistent energy output like a motor can do). Say a 110 pound person ascended stairs at the rate of 1 foot per second (1/5 of a horsepower or 110 pound⋅ft per second).
I agree with CJl's numbers and this is easily googlable, but you should also try looking at it another way (comparing it to real exertion) to make it lot easier to see.

For biking, max efficiency is at somewhere around 100 rpm. Assuming each foot pushes down a foot, that's only 33 lb of force per pedal stroke. Not much for a strong leg.
In one hour that person would have climbed 3600 feet.
When I wrestled in high school at 120 lb, we would run stairs or stadium steps for 45 min at a time. At a 120 step/min pace, that's about 240 ft-lb/sec on the up-steps.
Simply stated - in eight hours that person could be at the top of Everest.
There's a big, big difference between "an hour or more" and 8 hours. Not to mention the cold, snow and gear. Not a realistic comparison.

People do race up skyscrapers though: http://www.startribune.com/with-skyscraper-stair-climbs-fitness-races-to-new-heights/198494531/

And maybe someone will pop-in and provide stairmaster results.
I challenge you to produce 1/10th of a horsepower for 15 minutes (consistent power output, no breaks). Think of it in imperial units.
You're really really far off base here. 1/10th horsepower is a pretty light bike ride -- I'd barely even consider it exercise. If you want a photo of my exercise bike's screen I can provide one for you.

Also, the first in the "Gossamer" series planes (like the video in post #2) required about 300W to stay airborne:
https://en.wikipedia.org/wiki/Gossamer_Albatross
 
  • #12
Let's ignore the uncalibrated bike screens and look at the physics of it.

Say a pro bike rider weighs 137.5 pounds. That rider would have to lift an additional 137.5 pounds (that is three plates of 45 pounds and a 2 1/2 if you ever lifted weights) one foot vertically every second and sustain that to create 1/2 horsepower. I don't see a bike rider being able to do that, they are too scrawny. So the other extreme would be for the bike rider to lift himself 2 feet vertically every second. That is 7200 feet in an hour and I don't see that happening either.

Anyway we are arguing over a fraction of a horsepower. I submit to cjl - go to Home Depot and move 10 eighty-pound bags of concrete about 50 feet, then move 'em back to where you found them. I am sure that is no more than 1/10th of a horsepower.
 
  • #13
2milehi said:
Let's ignore the uncalibrated bike screens and look at the physics of it.
How far off do you really think being uncalibrated means? 10%? 20%?
Say a pro bike rider weighs 137.5 pounds. That rider would have to lift an additional 137.5 pounds (that is three plates of 45 pounds and a 2 1/2 if you ever lifted weights) one foot vertically every second and sustain that to create 1/2 horsepower.
You've upped the horsepower from what we were discussing before. Since you aren't a pro it makes it harder for you to use your intuition to see it.
In any case, as said before you can easily verify this stuff via a quick google:
http://www.bicycling.com/training/2015-tour-de-france/you-versus-tour-de-france-pro
I don't see a bike rider being able to do that, they are too scrawny.
Not sure what else can be said here other than now that you've seen others provide sources, it is your turn to start doing some of your own research. Your intuition/imagination is not providing you the right answer.
I submit to cjl - go to Home Depot and move 10 eighty-pound bags of concrete about 50 feet, then move 'em back to where you found them. I am sure that is no more than 1/10th of a horsepower.
That is a useless test because moving an object horizontally doesn't require applying any power to it.
 
  • #14
russ_watters said:
How far off do you really think being uncalibrated means? 10%? 20%?

You've upped the horsepower from what we were discussing before. Since you aren't a pro it makes it harder for you to use your intuition to see it.
In any case, as said before you can easily verify this stuff via a quick google:
http://www.bicycling.com/training/2015-tour-de-france/you-versus-tour-de-france-pro

Not sure what else can be said here other than now that you've seen others provide sources, it is your turn to start doing some of your own research. Your intuition/imagination is not providing you the right answer.

That is a useless test because moving an object horizontally doesn't require applying any power to it.
I would add that there's a huge difference between lifting with arms and efficient use of leg muscles.

I don't know what the problem is here. The answer is what the answer is. The data is there. It's been collected. It's not a matter of opinion. Personally I thought a human body could produce about 5W continuously. But I'm willing to admit I was wrong. The data is clear.
 
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  • #15
Jeff Rosenbury said:
I would add that there's a huge difference between lifting with arms and efficient use of leg muscles.
Yes. Lifting an object up, carrying it, then putting it back down is a zero output, zero efficiency process. There is basically nothing calculate about it. And even if it is useful to know the input energy, it's impossible to calculate with any accuracy.

For biking or rowing or any other human-powered output process, measuring the output is pretty easy and accurate because a quality exercise machine actually regulates the load by generating electricity. This can be accurately indexed or measured. The input energy (calories burned) is the inaccurate one.
 
  • #16
russ_watters said:
That is a useless test because moving an object horizontally doesn't require applying any power to it.
But aircraft still consume fuel when flying horizontally.
 
  • #17
2milehi said:
Let's ignore the uncalibrated bike screens and look at the physics of it.

Say a pro bike rider weighs 137.5 pounds. That rider would have to lift an additional 137.5 pounds (that is three plates of 45 pounds and a 2 1/2 if you ever lifted weights) one foot vertically every second and sustain that to create 1/2 horsepower. I don't see a bike rider being able to do that, they are too scrawny. So the other extreme would be for the bike rider to lift himself 2 feet vertically every second. That is 7200 feet in an hour and I don't see that happening either.

Anyway we are arguing over a fraction of a horsepower. I submit to cjl - go to Home Depot and move 10 eighty-pound bags of concrete about 50 feet, then move 'em back to where you found them. I am sure that is no more than 1/10th of a horsepower.

Let's ignore the "uncalibrated" bike screens, sure. Yesterday, after work, I went on a bike ride. With my bike, my backpack, and myself, I weigh about 215 pounds (~190lb for me, 5lb for my backpack, 20lb for the bike). On a hill during the ride, I climbed 550 vertical feet in about 23 minutes (measured by GPS). This means the power used for climbing alone was about 115 watts. Based on some rough estimates online, I'd guess that the drag and rolling resistance adds another 50 watts or so, so my total power output was around 165 watts. This is around 1/5 horsepower, and I'm definitely not an athlete of any kind.

As for pros, let's look at a famous Tour de France climb. The Alpe d'Huez climbs 1071 meters in 13.2 km. The record fastest climb was by Marco Pantani, in 1997, who ascended it in 37 minutes 35 seconds. He weighed 57kg, and Tour de France bikes weigh 6.8kg, for a total weight of 63.8kg. To lift 63.8kg 1071 meters in 37:35, the average climbing power was just under 300 watts (about 0.4 horsepower). In addition, to travel 13.2 km in 37:35, he had to average about 13mph (21kph). This requires another 50-80 watts to overcome aerodynamic drag and rolling resistance, for a total average power output of 350-380 watts (0.47-0.51 horsepower). Interestingly, this is a climb of over 3000 feet in a bit more than half an hour, which isn't far from your "7200 feet in an hour" calculation.

Just because you don't find this level of power output credible doesn't mean it doesn't exist.
 
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  • #18
I recall a quote by one of the teams that built an HPA. It went something like... It's easier to teach a racing cyclist to fly than teach a pilot to produce the required power.
 
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  • #19
technically a blimp is aircraft.

Here's your human powered aircraft


notice its speed even in a hangar with no wind.
 
  • #20
The basic problem with humans' sustaining flight- is physics. Gravity of the earth, density of the atmosphere, hence buoyancy; strength and endurance of our muscles... sustained human flight isn't happening.
 
  • #21
Some interesting links:

https://en.wikipedia.org/wiki/MIT_Daedalus
http://web.mit.edu/drela/Public/web/hpa/Daedalus_feasibility_study_I.pdf
http://web.mit.edu/drela/Public/web/hpa/Daedalus_feasibility_study_II.pdf
http://web.mit.edu/drela/Public/web/hpa/hpa_structure.pdf
http://web.mit.edu/drela/Public/web/hpa/SG_HPAG_daedalus.pdf

Daedalus still holds the record for longest and farthest human powered flight. Figure 6 in the first reports shows compiled data of human power output versus time. It seems you can deliver 200W for 5 hours. Daedalus was powered by an Olympic cyclist and the longest flight lasted almost 4 hours.
 
  • #22
Some interesting links:

https://en.wikipedia.org/wiki/MIT_Daedalus
http://web.mit.edu/drela/Public/web/hpa/Daedalus_feasibility_study_I.pdf
http://web.mit.edu/drela/Public/web/hpa/Daedalus_feasibility_study_II.pdf
http://web.mit.edu/drela/Public/web/hpa/hpa_structure.pdf
http://web.mit.edu/drela/Public/web/hpa/SG_HPAG_daedalus.pdf

Daedalus still holds the record for longest and farthest human powered flight. Figure 6 in the first reports shows compiled data of human power output versus time. It seems you can deliver 200W for 5 hours. Daedalus was powered by an Olympic cyclist and the longest flight lasted almost 4 hours.
 
  • #23
 
  • #24
Olympic rowers hold 600 W for nearly 6 minutes. The world's best (New Zealand athlete) last year averaged 395.6 W for an hour. The guy has eight consecutive Olympic and world championship gold medals; I'm guessing he win again in Rio.
 

What are the problems on human powered aircraft?

1. What are the challenges of designing a human powered aircraft?

Designing a human powered aircraft poses several challenges, including ensuring the aircraft is lightweight, aerodynamic, and strong enough to support the weight of the pilot and sustain flight. Additionally, the aircraft must be designed to minimize drag and maximize lift to achieve efficient flight.

2. How do human powered aircraft overcome the limitations of human strength?

Human powered aircraft typically use a combination of lightweight materials, such as carbon fiber, and efficient aerodynamic design to overcome the limitations of human strength. Some aircraft also incorporate mechanisms, such as gears or pulleys, to increase the power generated by the pilot.

3. What are the safety concerns with human powered aircraft?

One of the main safety concerns with human powered aircraft is the risk of crashes and accidents due to the lack of onboard power and propulsion. Additionally, the lightweight and delicate nature of these aircraft can make them more susceptible to damage and turbulence during flight.

4. How do environmental factors affect human powered aircraft?

Environmental factors such as wind, temperature, and air density can significantly impact the performance of human powered aircraft. Pilots must carefully consider these factors and adjust their flight strategies accordingly to achieve optimal flight conditions.

5. What are the current advancements in human powered aircraft technology?

Recent advancements in human powered aircraft technology include the use of advanced materials, such as graphene, to make the aircraft even lighter and more efficient. There is also ongoing research into new aerodynamic designs and propulsion systems to improve the speed and range of human powered flight.

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