Human powered flight (lazy Jethro :) )

[Jethro_uk]

Catching up on iPlayer suggestions, and I happened to watch the fascinating "Invented in the north" programme

it briefly touched on the idea of human powered flight, which jogged my memory about a few news stories from years ago. However, the subject has gone quiet of late.

I was idly wondering what the possibilities are of knocking up something, given the advances in materials sciences ? Pedal power seems the most obvious (we already have bikes). Would it be possible to press an existing (lightweight !) bike into service ?

The main areas of attack are wings, and propulsion (assuming a fixed-wing design is the only viable option ... flapping wings seem a tad juvenile).

So we need a wing that can generate enough lift at (say) 20 mph for the rider and machine (say 120 Kg ????)

And a propulsion system that can push that weight along in the air the moment the wheels leave the ground. Maybe an assembly of propellers driven by the pedals ?

If we set modest targets (no need to climb above 2 metres :) ) and basic control (no need to loop the loop), how doable is it *really* ?

I probably could dig out the necessary equations etc, but I'm hoping folks here have those at their fingers :)

Just to add some spice, if the whole endeavour is fundamentally impractical, how much extra energy would be needed to assist ?

[Matthias Czech]

Am 03.07.2017 um 12:37 schrieb Jethro_uk:

A pedal-powered plane already flew over quite a distance.

[Andy Burns]

I believe an Austrian company has sponsoring research for a number of years ...

There was also the Sikorsky prize winner

[Jethro_uk]

So 31kg, but a dedicated design ... interesting the notes about control.

[newshound]

Plenty of good stuff already out there, but to quote or probably misquote Scotty, you can't get round the laws of nature.

People have looked into flight on other planets as you vary gravity and atmospheric density. We're not at the optimum point on earth; however much you improve the technology then a pretty fit person isn't going to be able to do much, and only then on a calm day.

And we already know what is possible, just look at the pelagic birds.

[alan_m]

Channel 4 had a program Speed with Guy Martin Series 1 Episode 3: Human Powered Aircraft (45 minutes)

I believe it is still available on their watch it again service.

[Jethro_uk]

Tx. I'm sure I can find it somewhere :)

[The Natural Philosopher]

you can easily calcilate how much power you need for level and climbing flight by looking at rate of descent (or airspeed and gliding angle, if youy like).

Taht times the amount of weighhjt you need to carrty, is te rate of peotentual energy loss you have to overcome to srat aloft. As for climbing, well imagine running up a set of stairs 1000 feet high, carrying an airfarme on your back.

Ther are no magic solutions. The problem remains what it always has been since leonrado da vincii, the dreaded 'watts per pound' that you need to get up and stay up.

HUmn beings are not built for even brief high value watts per pound and even birds only maage it for small wingspans.

It is just about poossible to pedal a huge flimsy structure into the air on a dead calm day. But that's it..

[Jethro_uk]

Pretty much what I intuitively guessed (if it's not common by now, it never will be.)

Which leads onto the supplementary Q about how much additional power is required, (in the event we ever get a nuclear battery).

On a related note, another programme in the series, about Midlands innovation did touch on the problem with electric vehicles (being the battery) and - as you would expect - had f*ck all answers. Although I dod like the concept of the cars body being able to hold charge.

In the same programme, there was a flywheel-maintained train which runs about 10 miles from where I live.

It seems slightly nonsensical in this day and age that I have to watch a national TV programme to find out something you'd think would be headline local news.

Midlands appear to be very good at keeping things under their hat :)

(It runs from Stourbridge Town centre to Stourbridge mainline, apparently).

Of course if we can get frictionless bearings perfected, flywheels are the way forward (literally, if gyroscopic forces are accounted for :) )

[The Natural Philosopher]

In general 50 Watts per lb will get you a sort of light aircaft/airliner sort of pereformace and it gets better uop ro aroun 150W/lb which is sort of warbird performance - hawker tempest etc.

You can calculate the thing in that 9.8 watts will raise one kilogram one meter in one second.

For those who think in pounds, do your own bloody sums.

anyway with decemnt electric motors and props I used to fly lightweight modesl level on 12W/lb. 50W/lb gave a brisk rate of climb, 100W/lb is serious aerobatic and 150W/lb is capable of sustained verictical climbs.

battery electric planes are available commercially for full size use and perform well, for a short time.

Beacuse the watts per lb gives simalar performance in aa model as the full size, that is the metric to use.

[Jethro_uk]

Really useful stats, thanks.

No idea what an *average* human adult (male) can pump out for relatively long periods ... I do know the brain draws some stupid figure on full throttle - 100W ?

All of which highlights how incredibly efficient natures solution to energy storage and distribution is. If we could make a battery with the energy density of glucose, we'd be away !

[Jethro_uk]

In answer to my own question:

suggests 400W - about 1/2 horsepower.

[Jethro_uk]

Ah, but efficiency ?

[The Natural Philosopher]

Yep. about that.

I can get 100W out of a 5 oz lipo battery and a motor weighing 2 ounces (though only for ten mins) Energy density of diesel or gasoline way above glucose.

[The Natural Philosopher]

should fly a pilot weighing 4lb nicely...

Oh....

[Chris Hogg]

Just about double in fact: carbohydrates approx 4 kcal/g, fats & oils approx 8 kcal/g

[Chris J Dixon]

I suppose it isn't news now because it has been running for quite some time. It is an interesting solution, but isn't really scalable in a way that can be applied more generally.

Chris

[Brian Gaff]

Well its been done, but most of the pilots have been very fit people to say the least. You seem to need lightweight materials obviously and some kind of skin material like clingfilm. apparently the big issue is stability and not flying backward in a headwind! Most of the ones I've heardabout usually fall to bits on landing as they are not very strong. Brian

[Brian Gaff]

I suppose if you really want to be different you cold climb up the stairs to a high roof. Sit down for a rest and a drink, then get in a glider and hope to catch a thermal. On the other hand why worry about that. Use solar and even nuclear. Google are reputedly interesting in a nuclear powered drone for using like a communications hub in disaster areas. I'd be a bit wary myself of a large lump of nuclear material in the air over me if something went wrong with the technology. Brian

[The Natural Philosopher]

around 85%.

plus a 75% prop efficiency.

glocuse? probably around 5%