Hypothetical: Gravity and birds.

[bloodhound31]

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.

[multiweb]

Not sure about the birds but there sure would be a lot less s**t in my backyard. :thumbsup:

[sjastro]

No gravity= No atmosphere= No aerodynamics (and lots of dead birds).

Regards

Steven

[jjjnettie]

I'm not sure if they've taken birds into space yet.
But have a read of this.
http://news.google.com/newspapers?nid=1665&dat=19820325&id=gG8dAAAAIBAJ&sjid=2CQEAAAAIBAJ&pg=6704,2579611

[multiweb]

:lol: Remember that simpson episode when homer breaks a container full of ants in zero gravity in the space shuttle cabin?

[bloodhound31]

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?

[bloodhound31]

Thanks Nettie, thats an interesting read. Shame it doesn't go into it a bit more.

[sjastro]

There can be no controlled flight without having a centre of gravity.

Regards

Steven

[Nesti]

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.

[bloodhound31]

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.

[Nesti]

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.

[sjastro]

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

[bojan]

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.

[Nesti]

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.

[renormalised]

A lot of dead everything else as well:)

[multiweb]

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 :)

[renormalised]

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:)

[renormalised]

Go around to BOC Gases and hook yourself up to a 50000 litre O2 tank:)

[sjastro]

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

[sjastro]

Japanese scientists threw boomerangs while at the ISS.
Is this good enough?

Regards

Steven

[renormalised]

That's way too dangerous!!!. I'd rather get hit in the head by a "ball of feathers" than a lump of wood or hard plastic!!!. A bird won't do the same sort of damage a boomerang can:)

[multiweb]

That would explain the sudden radio blackout they had last week...did it come back? :)

[Nesti]

No Steven, the question was actually this, "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?"

What I've been trying to describe, is what type of flight dynamics would be needed for flight in a zero G environment, then asking what type of bird might have the best chance of doing it. I have not entered into whether a bird is taking-off or landing as yet because I feel we must determine if normal flight is even possible first (the basics); before tackling more complex issues.

I agree with you that it would more than likely be impossible for birds to do so however, if there was a species that could do it, what species would it be. But first of all we must know what type of dynamics is required for basic straight and level first, then turns, and then we can bring our attention to ascent and descent (two meaningless words in zero G BTW).

You wrote, "The flight paths of birds and insects are not horizontal straight lines". I agree, lift must balance the field of acceleration, that's why stated that a symmetrical aerofoil would be needed as a cambered wing would generate lift unnecessarily as gravitation is not a factor. A symmetrical aerofoil would only come into play when a turn is initiated (angle of attack to generate lift).

The subject of landing and take-off is a different issue to sustained flight and wasn't the original question however, I responded by saying that landing on the ground - the floor - would be no different than landing into a wall, in that there is no up or down. That would also apply to landing on the ceiling.

For an aircraft, straight and level flight is indeed possible in zero G and best achieved by using a symmetrical aerofoil (no lift generated), good control surface area, minimal wing tip/tail mass, the ability to apply aileron force against engine torque (prop). Every control throw would require an equal and opposite throw to counteract the input. If you want an example, look no further than an aircraft in a parabolic free-fall which simulates a zero G environment..it's simply pitching the nose over at the same rate as the field of acceleration. Can a bird fly a parabolic free-fall trajectory with it's wings open, you bet, Hawks do it all the time.

Now is it possible for a bird to make directional changes while in a parabolic free-fall? Of course.

Can a bird take-off in zero G. Yes. If it's holding onto something, beats it's wings and lets go, that's a take-off...and it can do this in any direction as all directions are the same.

Can a bird land in zero G. No, it can only collide, whether it be the floor, wall or ceiling.

The single biggest issue would be that a bird would not be able to understand what is going on, so it would assume that the mysterious force of gravity was ever-present and make mistakes...but can it learn to compensate?!

[bojan]

Fish, dolphins... ;)

[JD2439975]

:rofl: Classic, love it.