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  #1  
Old 22-04-2010, 06:10 PM
bloodhound31
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Hypothetical: Gravity and birds.

I had a strange dream the other night, the earth lost it's gravity.

Stranger still, a friend told me they had the same dream and the sky was full of dead birds.

Spooky.

However, apart from the cataclysmic events that would probably follow, a question came to mind.


What would the dynamics of a bird in flight be like if there was air, but no gravity? How would the aerodynamics of lift, drag and propulsion change for a feathered bird?

Baz.
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  #2  
Old 22-04-2010, 06:17 PM
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Not sure about the birds but there sure would be a lot less s**t in my backyard.
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  #3  
Old 22-04-2010, 06:23 PM
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No gravity= No atmosphere= No aerodynamics (and lots of dead birds).

Regards

Steven
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Old 22-04-2010, 06:27 PM
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I'm not sure if they've taken birds into space yet.
But have a read of this.
http://news.google.com/newspapers?ni...g=6704,2579611
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Old 22-04-2010, 06:35 PM
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Originally Posted by jjjnettie View Post
I'm not sure if they've taken birds into space yet.
But have a read of this.
http://news.google.com/newspapers?ni...g=6704,2579611
Remember that simpson episode when homer breaks a container full of ants in zero gravity in the space shuttle cabin?
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  #6  
Old 22-04-2010, 07:29 PM
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Originally Posted by sjastro View Post
No gravity= No atmosphere= No aerodynamics (and lots of dead birds).

Regards

Steven
Yes, Obviously. But let's just say there was atmosphere and no gravity.

E.G. There is atmosphere and micro (nearly none) gravity in the International Space Station.

Could a bird actually still maneuverer in this environment? What would change?
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  #7  
Old 22-04-2010, 07:31 PM
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Originally Posted by jjjnettie View Post
I'm not sure if they've taken birds into space yet.
But have a read of this.
http://news.google.com/newspapers?ni...g=6704,2579611
Thanks Nettie, thats an interesting read. Shame it doesn't go into it a bit more.
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  #8  
Old 22-04-2010, 08:44 PM
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Quote:
Originally Posted by bloodhound31 View Post
Yes, Obviously. But let's just say there was atmosphere and no gravity.

E.G. There is atmosphere and micro (nearly none) gravity in the International Space Station.

Could a bird actually still maneuverer in this environment? What would change?
There can be no controlled flight without having a centre of gravity.

Regards

Steven

Last edited by sjastro; 22-04-2010 at 08:58 PM.
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  #9  
Old 22-04-2010, 09:55 PM
Nesti (Mark)
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Originally Posted by bloodhound31 View Post
Yes, Obviously. But let's just say there was atmosphere and no gravity.

E.G. There is atmosphere and micro (nearly none) gravity in the International Space Station.

Could a bird actually still maneuverer in this environment? What would change?


I don't believe that I would have any trouble flying an aerobatic RC plane (a 3D/4D model) in zero G, that's because it uses a symmetrical aerofoil, and a center of gravity (CG) along the longitudinal axis. All I would be doing is using a small amount of thrust. It would behave very similar to a low powered vertical dive with the CG on the neutral point...no sweat!

If I used a glider I would have the nose trimmed so far forward (down) that thrust angles might cause forward tumbles. Also, the weight in the wings would cause huge moment forces in relation to the amount of air-speed I would have available (rotational mass versus air loads)...so to roll-into and out-of a turn would be insanely difficult...but not impossible.

Birds would still be able to fly however, I believe that they would literally crash into everything, in that they would retain propulsion but would have limited control if any AND their aerofoil camber would work against them, causing them to constantly climb.

Birds don't have the ability to understand what's going on and thus compensate by altering the way in which they fly; they would continually try to fly as per normal, constantly assuming gravity is there to work against.

The biggest issue would be vertigo and disorientation.

The bird with the greatest chance of success, in my opinion, would be small, highly agile, very light-weight, light wings, and accustom to aerobatic flight (tight turns)...swallows are the Kings of the sky.

A bird possibly capable of compensating and altering it's flight might be a Peregrine Falcon; they dive, are accustom to inverted flight and often experience weightless conditions when recovering from tumbles when taking down prey.
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Old 22-04-2010, 11:00 PM
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Mark, thank you for this insight and thorough answer. Perhaps that's why the birds in this blokes dream are all dead because they crash into stuff..

I am no expert, but I agree, that a bird would be used to countering gravity and therefore would lose some control in none.

I thought similar about the more aerobatic species too, as a moth, with a relatively slow wingbeat, might have less directional and momentun/inertia control than something with a much faster wingbeat say, like a bee.

I bet an eagle would have great difficulty in zero g, but a hummingbird would have no problem.
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  #11  
Old 22-04-2010, 11:28 PM
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Originally Posted by bloodhound31 View Post
Mark, thank you for this insight and thorough answer. Perhaps that's why the birds in this blokes dream are all dead because they crash into stuff..

I am no expert, but I agree, that a bird would be used to countering gravity and therefore would lose some control in none.

I thought similar about the more aerobatic species too, as a moth, with a relatively slow wingbeat, might have less directional and momentun/inertia control than something with a much faster wingbeat say, like a bee.

I bet an eagle would have great difficulty in zero g, but a hummingbird would have no problem.


I did consider a Humming bird, as that seems like an intuitively good choice, but realized that it is essentially a helicopter (thrust versus gravity) for most of its flying life. This means that it would be the most affected bird perhaps of all in that its major consideration - gravity - is removed.

I think the dynamics of a zero-G environment call for a small, agile, lightweight flier, something which avoid fast or erratic movements. Also, a wing which produces thrust along the longitudinal axis (unlike a hummingbird) and turns would require a full 90deg bank (like what Swallows do).

Unusual that "lightweight" is a consideration in a zero-G environment, until we start looking at rotational mass, then we must consider that it takes the same amount of force to arrest a roll as what it takes to enter the roll, otherwise the roll will continue.

It's a big call...not sure if any bird could do it.
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  #12  
Old 23-04-2010, 02:52 AM
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In a gravity environment birds and insects perform work to get airborne. When landing work is mainly done by gravity.

In a zero G environment, an object is in free fall which means there is a fictitious force of equal but opposite magnitude to the weight of the object.

While a bird and insect in free fall can take off at any given angle, there is a vertical component of the force acting in the same direction as the fictitious force. Under these conditions gravity doesn't overcome the inertia of the vertical force.

In order to land a bird or insect will have to perform the work instead of gravity.

So how can the biomechanics of a bird or insect be utilized to perform the work for landing instead of gravity?

Regards

Steven
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Old 23-04-2010, 08:15 AM
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Quote:
Originally Posted by sjastro View Post

So how can the biomechanics of a bird or insect be utilized to perform the work for landing instead of gravity?

Regards

Steven
Quite right.

But, to put it in plain English and lets use a simple analogy:
Anyone of you tried to drive in Europe or US?
Or, anyone of you tried to switch from manual to automatic transmission cars (easy) or vice versa (VERY scary experience for some people.. not me, I am manual person :-) )

Now, all those skills mentioned above are learned, acquired... and our intelligence is involved in the process (Nesti's comments about flying)
Now imagine those skills are programmed in your genes and/or hard-wired in your brains... Poor insects and birds.

Last edited by bojan; 23-04-2010 at 08:53 AM.
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  #14  
Old 23-04-2010, 09:49 AM
Nesti (Mark)
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Quote:
Originally Posted by sjastro View Post
In a gravity environment birds and insects perform work to get airborne. When landing work is mainly done by gravity.

In a zero G environment, an object is in free fall which means there is a fictitious force of equal but opposite magnitude to the weight of the object.

While a bird and insect in free fall can take off at any given angle, there is a vertical component of the force acting in the same direction as the fictitious force. Under these conditions gravity doesn't overcome the inertia of the vertical force.

In order to land a bird or insect will have to perform the work instead of gravity.

So how can the biomechanics of a bird or insect be utilized to perform the work for landing instead of gravity?

Regards

Steven

Who are you directing your question to Steven?

Myself, I've not mentioned anything about taking-off or landing, only normal [straight and level] flight, ie "a wing which produces thrust along the longitudinal axis", or turns. In my opinion, in a zero G environment, there is no such thing as a take-off or landing (true?), as the moment you touch something or bang into something, like the floor, a body will bounce and become airborne again, so it makes no sense...you might as well call it another wall instead.
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Old 23-04-2010, 12:32 PM
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Quote:
Originally Posted by sjastro View Post
No gravity= No atmosphere= No aerodynamics (and lots of dead birds).

Regards

Steven
A lot of dead everything else as well
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  #16  
Old 23-04-2010, 12:35 PM
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A lot of dead everything else as well
Look on the bright side. You'd be able to take fantastic pictures in incredible seeing as long as your O2 tank doesn't run out
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Old 23-04-2010, 12:40 PM
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There's only one way to find out if they could fly or not....test it out on the ISS

Only one problem....you'd have this little bird flying around getting into everything and if any of the astronauts are wearing glasses, you can bet on it that the bird will end up sitting on the rim of their glasses Take that from experience of someone who's raised quite a few baby birds
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Old 23-04-2010, 12:42 PM
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Look on the bright side. You'd be able to take fantastic pictures in incredible seeing as long as your O2 tank doesn't run out
Go around to BOC Gases and hook yourself up to a 50000 litre O2 tank
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  #19  
Old 23-04-2010, 02:56 PM
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Originally Posted by Nesti View Post
Who are you directing your question to Steven?

Myself, I've not mentioned anything about taking-off or landing, only normal [straight and level] flight, ie "a wing which produces thrust along the longitudinal axis", or turns. In my opinion, in a zero G environment, there is no such thing as a take-off or landing (true?), as the moment you touch something or bang into something, like the floor, a body will bounce and become airborne again, so it makes no sense...you might as well call it another wall instead.
The flight paths of birds and insects are not horizontal straight lines. In an idealized situation the simplest pathway is an inverted flattened parabola. The take-off is the elevation or the where the gradient of the parabola is positive, the landing is where the gradient becomes negative.

A zero g environment is either an accelerated frame of reference where the gravity and reaction forces cancel out, or an inertial or stationary field in a gravity free field.

The question is whether birds and insects can fly in parabolic pathways in a zero g environment. My gut feeling is no. The descent requires the bird or insect to perform work instead of gravity to land.
If this is not possible the simplified pathway is an angled straight line, a one way trip to oblivion or a really bad headache.

Regards

Steven
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  #20  
Old 23-04-2010, 03:00 PM
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There's only one way to find out if they could fly or not....test it out on the ISS
Japanese scientists threw boomerangs while at the ISS.
Is this good enough?

Regards

Steven
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