Small Seeds Inspire Big Ideas

October 10, 2011 at 4:53 pm

Many of us can remember as a child being fascinated by maple seeds, with their single wing, spinning gracefully to the ground. As it turns out, scientists also have been amazed by this process. So much so that since the 1950s, engineers have been trying to replicate the flight of these seeds.

http://www.msnbc.msn.com/id/33451937/ns/technology_and_science-science/t/robotic-craft-mimics-falling-maple-seeds/#.TpMfic12mPU

http://www.msnbc.msn.com/id/33451937/ns/technology_and_science-science/t/robotic-craft-mimics-falling-maple-seeds/#.TpMfic12mPU

Maple seeds, a type of samara, use autorotation to create passive stability. Autorotation is a deceivingly complex process. Essentially as a seed falls, it begins to rotate on it own around its center of mass, the seed. This causes horizontal airflow due to the wing’s rotation and vertical airflow due to the seed falling. The resulting forces are an upward lift, opposing gravity, and a horizontal drag. Because the tip of the wing is moving the fastest, it has more lift than any other part of the seed, therefore the wing tilts upward. The angle of tilt, referred to as the coning angle, reaches a constant when the outward centrifugal force equals lift. Once all the forces are balanced the result is a seed rotating in a stable helical pattern and falling at a terminal velocity.

Here the helical pattern of fall can be seenhttp://blogs.discovermagazine.com/80beats/2009/06/12/how-a-maple-seed-twirls-and-whirls-and-stays-aloft/

Here the helical pattern of fall can be seen http://blogs.discovermagazine.com/ 80beats/2009/06/12/how-a-maple-seed-twirls-and-whirls-and-stays-aloft/

In the past, engineers have failed to create a design that has the stability of the falling maple leaf. Researchers at the University of Maryland Clark School of Engineering finally developed successful design, called RoboSeed NAV, in which the wing and the propeller are separate components allowing the wing to tilt without moving the whole aircraft. The aircraft has a propeller to create torque which creates an upward thrust. Therefore not only does the robot glide to the ground, but it also had the ability to fly with great control. Another key element of the design was the fact that they created the wing to closely resemble the wing the maple seed.

There are a couple of advantages of having an aircraft with the same aerodynamic properties of a maple leaf. First, minimal power is needed to maintain or create passive stability, which is beneficial to micro-scaled aircrafts that have minimal battery life. Second, if the aircraft runs out of power, it can slowly fall to the ground at a low terminal velocity resulting in minimal damage, thus making the aircraft very reusable.

It is anticipated the design could be seen in toy stores in months from now. Eventually these flyers could be used as low atmosphere satellites that are completely autonomous (require no motor function), thus using no energy. They could also be used for mapping of caves and rooms.

References:

  • Alexander, David. “Nature’s Flyers: Birds, Insects, and the Biomechanics of Flight”. page 51 (link to Google books); September 22, 2011
  • Bryner, Jeanna. “Robotic Craft Mimics Falling Maple Seed“. msnbc.com. October 10, 2011
  • Gerardi, Steven. Pines, Darryll. Ulrich, Evan. “Autonomous Flight of a Samara MAV” Web. October 10, 2011. [pdf]

By Sam Nichols | Posted in student post | Tagged , , | Comments (3)

Internal Adaptation for the Tree Lizard

October 10, 2011 at 1:09 pm

So far in this class we have talked about many external adaptations in animals for flight. However the Neon Blue-Tailed Tree Lizard shows that animals can adapt internally as well to help them take to the skies.

The Holaspis guentheri, or the Neon Blue-Tailed Tree Lizard, hails from a large area in Africa, where its natural habitat is in the forests. They can grow to be up to 12 centimeters in length, but the average is 9 to 11cm. As their name suggests they have line of very bright blue running down their tail. In addition there are also lighter yellow stripes down the body of the lizard.

A study done in 2009 using the Neon Blue-Tailed Tree Lizard and two similar lizards showed that although the tree lizard shows no external adaptations for flight it still indeed was gliding. The team calculated how far the lizard would fall if it just jumped off a 2 meter high object and fell like a rock. The tree lizard was on average going about one half meter for every two meters of height. After their calculation they found that this is .2 meters farther than their calculation predicted.  The only problem was they did not know was why these lizards were still able to glide.

At first they thought that the Tree Lizard might be altering its body mid-air, much like the flying snake does. After careful examination of the video they took though, they found that this was not the case. So what was causing the Tree Lizard to outperform its relatives?

The team brought the two other lizards and the Tree Lizard in to get x-rays. They found that the other two lizards had very typical bone structure, however the Tree Lizard was unique. The Tree Lizard had a slender build, and the bones had not ossified as much as they had in the other two lizards. These less dense bones are not as massive as its relatives are, and thus the Tree Lizard has become the superior glider of the three.

This finding is important not just because it has identified another animal as having some sort of aerial capabilities, but rather that we must look beyond just the external adaptations that animals have.  Perhaps there are more species out there that have unique adaptations that we cannot just simply see.

A Pair of Tree Lizards
Neon Blue-Tailed Tree Lizard

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  1. Journal of Experimental Biology. "Neon Blue-tailed Tree Lizard Glides Like A Feather, Thanks To Light Bubbly Bones." ScienceDaily, 22 Jul. 2009. Web. 10 Oct. 2011.
  2. Bieke Vanhooydonck, Greet Meulepas, Anthony Herrel, Renaud Boistel, Paul Tafforeau, Vincent Fernandez and Peter Aerts. Journal of Experimental Biology. Ecomorphological analysis of aerial performance in a non-specialized lacertid lizard, Holaspis guentheri, 19 May 2009.  10 Oct. 2011.

By Nathan Thompson | Posted in student post | Tagged , , | Comments (1)

The fastest animal on Earth “The Peregrine Falcon”

October 7, 2011 at 1:40 am

Though the peregrine falcon is described as the fastest animal on Earth, it is not the fastest when in its level flight which is only in the range 40 to 55 mph but in fact, when in its hunting dive. Experiments done have demonstrated that the diving speed of the peregrine falcon exceeds 200 mph. According to an experiment done in 2005 by Ken Franklin, the speed of the falcon reaches a value of 242 mph which is the fastest speed ever observed till now.

The peregrine falcon can measures from 14 to 19 inches (36 to 49 cm) with a wingspan ranging from 3.3 to 3.6 feet (100 to 110 cm). Also, it weighs from 530 to 1600 grams.

Consequently, people might wonder how such a small animal can fly at this subsonic speed? The answer lies in its ability to morph its wing.

The peregrine falcon can fly at an altitude of over 3500 feet . Initially, before diving, the falcon brings its wings close to its body. During its descent, as its speed increases, one wing tends to be pushed forwards with its head tucked in to that side while the other wing is pulled back. As for the tail, it is folded and the feet is tucked in. Consequently, that manoeuvre streamlines the bird by decreasing its cross-section presented to the air. The body of the falcon becomes more aerodynamic and air resistance is minimized.

Peregrine falcon in a dive

Another interesting question that people might point out is how is the body of the peregrine falcon adapted to perform a stoop at this speed? The falcon has special adaptations in its nostrils which allow it to breathe at such tremendous speed. Each nostril contains a rod and two fins behind it. As air rushes past the nostrils, the flow is broken up and slowed by the rods and fins which enable the falcon to breathe normally without being overwhelmed by the force at which air enters its nostrils. Moreover, the eyes of the peregrine falcon are designed so that the falcon has a clear view of its prey throughout the dive. Each eye is equipped with an nictitating membrane which protects it from dust and other debris in the air and an additional secretory gland to prevent drying up of the cornea. The dark markings around its eyes also reduce glare, improving visual contrast.

Here is a video of a peregrine falcon attacking a red-tailed hawk which is too near to its nest. Note that the red-tailed hawk is larger that the peregrine falcon with a body length of 18 to 26 inches , wingspan of 3.2 to 3,6 feet and weighs 690 to 1460 grams but this fact does not prevent the peregrine falcon to attack.

Quite an amazing video isn't it?

Observe the extraordinary speed at which the falcon strikes the hawk. Slow motion videos show that the falcon spreads its toes open to grab the prey at the moment of contact but because of the high speed at which this occurs, it instead rakes the prey, usually with its hind talons. Since this happen so fast,  it seems like the falcon is performing a closed-foot strike.

References

By Jean-Marc Tsang | Posted in student post | Tagged , , | Comments (9)

Top Gun

October 6, 2011 at 2:50 pm

A problem with aircraft, primarily jet fighters, is that when executing a fast turn, the wings are put under extreme forces. This force, known as G's is the aircraft's acceleration compared to its free-fall. To elaborate 1 G is a person sitting down at sea lavel. An F-16 fighter can pull about 9 G's at around Mach 2+. In the early days of flight, as people pursued higher and higher speeds, it was quickly apparent that aircraft would need different wing sizes and shapes depending on their speeds. Geoffrey T Hill looked to seagulls and their moving wing tips when in 1924 when he designed the Westland-Hill Pterodactyl 1, the first aircraft with variable wings. Only the tips could change position, but this innovation allowed the Pterodactyl to overcome stalling and rolls.

The idea of variable wings was toyed with repeatedly in the following decades, but it wasn't until the waning years of WWII that the idea was seriously revisited. Some birds are known to change the whole shape of their wing, in order to achieve greater high speed mobility, and to achieve faster speeds. The jet fighter Messerschmitt P1101,

P1101

which was never mass produced, had fully variable wings that could only be changed before takeoff. The US after the war expanded on the idea with the Bell X-5,

X5</a>

another experimental plane and its in flight fully adjustable wings, which allowed it to make faster turns than normal fixed wing aircraft. The first production variable-wing aircraft was the F-111,

F111

which was succeeded by the F-14.

F14

These aircraft had superior high speed mobility compared to their fixed wing competitors, and the variable wings made them multi-capable fighters. The idea of variable wing aircraft soon spread to other countries, and even to this day, many countries' primary fighters are variable wing aircraft such as the Panavia Tornado, Sukhoi Su-24, and the MiG-23.

Sources:

Wikipedia articles:
Westland-Hill Pterodactyl
Variable-sweep wing
F-111 Aardvark
Grumman F-14 Tomcat

By Matthew Farmer | Posted in student post | Comments (3)

Bees Can Fly?

October 5, 2011 at 7:52 pm

This question might seem one of the most absurd, but it is one that has baffled scientists for over 70 years. In 1934, a French entomologist, one who studies insects, August Magnan and his assistant calculated that a bee was physically incapable of flying.

Aerodynamically that is. But bees fly everyday! So, this question has been baffling scientists around the world for quite some time. It has been observed that bee's wings flap almost randomly in a non-oriented pattern. Therefore, it should not be able to be keeping them afloat in the air.

After 72 years, the question has finally been answered.

Thanks to greater technology and a better understanding of aerodynamics, Michael H. Dickinson, the Esther M. and Abe M. Zarem Professor of Bioengineering, and his postdoctoral student Douglas L. Altshuler and their colleagues at Caltech and the University of Nevada at Las Vegas, have finally understood how honeybees fly!

Bee Flight

Three Angles of Bee Flight

They used a large robotic replica of the honeybee wing and many high-speed cameras which were obviously previously unavailable to the scientists of the past. By using the high-speed camera, they were able to capture the wing movement of the honeybee and the most peculiar part about it was that the honeybee did not flap its wings like other insects!

"The secret of honeybee flight, is the unconventional combination of short, choppy wing strokes, a rapid rotation of the wing as it flops over and reverses direction, and a very fast wing-beat frequency."

According to Dr. Magnan 70 years ago, bees would be expected to beat wings at the same rate of other insects and at a larger arc of almost 180 degrees. After careful observation, it has finally been found that they beat their wings extremely fast, 15% faster than other insects at a rate of 230 beats per second.

Bees are often called peculiar because their method of flight is extremely inefficient, choppy and different from other insects.

When bees are performing other tasks such as transporting nectar or pollen, they increase the arc of their wing strokes, but continue flapping at the same rate. Dickinson notes that, "it would be much more aerodynamically efficient if they regulated not how far they flap their wings but how fast."

Bees are kind of stupid if you think about it.

Sources:

1. "Flight Of The Bumble Bee Is Based More On Brute Force Than Aerodynamic Efficiency." Science Daily: News & Articles in Science, Health, Environment & Technology. Web. 05 Oct. 2011. <http://www.sciencedaily.com/releases/2009/05/090507194511.htm>.
2. "Scientists Finally Figure Out How Bees Fly | LiveScience." Current News on Space, Animals, Technology, Health, Environment, Culture and History | LiveScience. Web. 05 Oct. 2011. <http://www.livescience.com/528-scientists-finally-figure-bees-fly.html>.

By Chris Hui | Posted in student post | Tagged , | Comments (1)