Bio-aerial Locomotion 2011

The Pterosaur

October 15, 2011 at 6:55 pm

Pterosaurs were flying reptiles that existed from 220 to 65 million years ago. Pterosaurs are believed to be the earliest vertebrates to have achieved powered flight. What makes this truly amazing is that some species of pterosaurs were as large as giraffes, with a wingspan of about 12 meters. Pterosaurs achieved flight, not on bird-like wings, but rather on a large membrane of skin like we have seen on colugos and flying squirrels.

The membranes of skin that formed the wings of the pterosaur extended from an extremely long fourth finger on each arm down to the legs. These wings were made up of a very complex and dynamic structure which allowed active flight. First of all, the bones of pterosaurs were actually hollow and air-filled, much like a bird. Also, the outer parts of the wing possessed something called actinofibrils, which were very closely spaced fibers that possibly helped strengthen the outer edges of the wings. The wings also had a “thin layer of muscle, fibrous tissue, and a unique, complex circulatory system of looping blood vessels.”

There has been extensive debate over whether the giant pterosaurs were actually able to achieve and sustain flight because of their sheer size. The first problem with a creature so large achieving flight is getting it off the ground. Large birds generally use a running start to get themselves off the ground, but the larger pterosaurs are simply too big to do this on two limbs like a bird. Biomechanist Michael Habib published work that suggested that these creatures needed to use all four limbs in a “pole-vaulting maneuver” to achieve lift off. Habib discovered that if a pterosaur attempted to get off the ground just using their hind limbs, the bones would snap. Habib concluded that pterosaur species with a wingspan of 2 meters or greater had to use all for four limbs to achieve lift. Habib also added that this was, in fact, an easier way of getting off the ground saying “using all four legs, it takes less than a second to get off of flat ground, no wind, no cliffs.”

The other part of the debate over the flight of larger pterosaurs is whether they could actually sustain flight. A Japanese scientist by the name of Katsufumi Sato decided that it was impossible for a pterosaur to sustain flight based on calculations using modern birds. However, this work has been greatly disputed because the flight of a pterosaur cannot be compared to that of modern birds based on how different their wing structures are. Mark Witton of the University of Portsmouth along with Michael Habib of Johns Hopkins University argue that not only could pterosaurs sustain flight, they could fly up to 120 kilometers an hour and travel thousands of kilometers, covering continents.

Sources:

“Amazing Adaptations of the First Flying Animals | Pterosaur Evolution | Flying Reptiles & Birds | LiveScience.” Current News on Space, Animals, Technology, Health, Environment, Culture and History | LiveScience. 15 Oct. 2011. http://www.livescience.com/14922-amazing-adaptations-flying-pterosaurs.html.

“Ancient Giraffe-Sized Creature Pole-Vaulted into the Sky | LiveScience.” Current News on Space, Animals, Technology, Health, Environment, Culture and History | LiveScience. 15 Oct. 2011. http://www.livescience.com/8964-ancient-giraffe-sized-creature-pole-vaulted-sky.html.

“How Huge Flying Reptiles Got Airborne | LiveScience.” Current News on Space, Animals, Technology, Health, Environment, Culture and History | LiveScience. 15 Oct. 2011. http://www.livescience.com/3190-huge-flying-reptiles-airborne.html.

“Pterosaur.” Wikipedia, the Free Encyclopedia. 15 Oct. 2011. http://en.wikipedia.org/wiki/Pterosaur.

By Colby Mann | Posted in student post | Tagged pterosaurs | Comments (2)

Roboswift

October 15, 2011 at 5:43 pm

Inspired by the common swift, Roboswift was designed at the Delft University of Technology and Wageningen University in the Netherlands. The swift is one of the most efficient flyers in nature because of its ability to shift its wings by folding feathers over one another. This allows the swift to adapt to changes in flight conditions. The common swift can fly the distance to the moon and back almost five times in its lifetime.

The Roboswift measures 51 centimeters from wingtip to wingtip and weighs less than 80 grams. Unlike other bio-inspired aircrafts, the Roboswift has four “feathers” on each wing, which allow it to change the shape of the wings. To steer, it sweeps one wing back more than the other, creating a difference in the lift on the wings. The change in lift allows Roboswift to roll or make sharp turns in the air. The RoboSwift's propeller can also fold back to reduce air drag.

The Roboswift is being used for SPYING! Onboard lithium-polymer batteries power an electromotor that drives a propeller, allowing RoboSwift to follow a group of real birds for 20 minutes or perform ground surveillance for an hour. “RoboSwift carries three onboard micro cameras, with two mounted on the wing and one in the belly pointing downward. A display mounted to the robo-plane’s head will beam the images to the ground where pilots can get a bird’s-eye view.” A few military aircraft, such as the F-14 Tomcat and the English-German Tornado, are equipped with “swing wings”.

References:

http://www.dogonews.com/2008/3/5/it-s-a-bird-it-s-a-plane-it-s-a-roboswift

http://www.livescience.com/3742-secret-bird-flight-revealed.html

http://www.roboswift.nl/?page=design&lang=en

By Shahil Patel | Posted in student post | Tagged morphing wings, swift | Comments (2)

Morphing Wings

October 14, 2011 at 4:28 pm

One of the differences between man-made aircrafts and birds is the morphology of their respective wings. A Boeing-747 has stiff metal wings that barely change shape. Using the knowledge of wing surface area, other aircrafts were built with varying wing spans to accommodate ideal flying speeds and weights. However, birds can create their own ideal speeds by folding up their wings to fly faster or unfolding them to fly slower. The peregrine falcon is able to fly up to 325 km/h just by decreasing their wings' surface area. Recently, many scientists and engineers have been inspired to create aircrafts with morphing wings which imitates the wings of birds.

An aircraft imitating the flight of an eagle:

These types of aircrafts are ideal because they can make flight much more efficient. Morphing wings can reduce drag, reduce power, conserve fuel, control flutter, and reduce turbulence. Engineers at Penn State are developing these wings with a "cellular truss structure" which represents a wing skeleton. Memory alloys, metals that retain the same shape, can provide the flexibility to morph wings.

Memory alloys

NASA is trying to approaching these aircrafts by using nanotechnology. Carbon nanotubes or carbon fibers can not only bend when a current runs through it, but also can reduce the weight of an aircraft. Another idea is that a computer could use nanosensors along the wing to measure air pressures and morph the wings to increase flight efficiency.

Pretty soon, one aircraft will not only be more flight efficient but also be used for many other purposes. If it shortens its wings it could fly like a fighter jet, if it extends its wings it could fly like a commercial plane. A morphing wing passenger jet could decrease travel time using folded wings and land without a long runway using fully expanded wings. Man-made aircrafts will reach a level of flight paralleling that of nature.

References:

Airplane Wings That Change Shape Like A Bird's Have Scales Like A Fish. Science Daily. Apr. 22, 2004.

From Research to Reality: Morphing Aircraft Wings. Composites Manufacturing. October 12, 2011.

Nanotechnology in Defense. UnderstandingNano.com.

Shape-memory alloy. Wikipedia.

By Kevin Ma | Posted in student post | Tagged morphing wings | Comments (2)

The Walkalong Glider

October 13, 2011 at 12:11 pm

In 1971 Paul MacCready founded AeroVironment, Inc.. Considered the father of human powered flight, MacCready went on to invent flying devices with his company ranging in everything from solar powered flight to the Gossamer Condor, which flew over the 23-mile long English Channel off of only the power of an onboard cyclist.

And as the saying goes: like father, like son.

When Paul MacCready’s son, Tyler MacCready, was only about 13 years old, he already had developed a livelong passion for flight. When he wasn't helping his father work on the Gossamer Condor he and his older brother were competing to see who could make a better paper glider. Through their competition they realized that by moving their hands underneath the glider they could drastically affect its flight.

From there Tyler and his brother went on to experiment with their toy invention and attempt to find which models would work the best. Their father, of course, played a major role in helping them understand the mechanics of flight and how they could increase the performance of the glider.

Tyler MacCready demonstrating his invention.

So how does it work?

Despite the amazing simplicity of its design, the Walkalong Glider is actually quite complex.

As quoted from his appearance on his fathers TEDTALK: “The idea is that it soars on the lift over your body like a seagull soaring on a cliff. As the wind comes up, it has to go over the cliff. As you walk through the air, it [the air] goes around your body, but some has to come over you, so you just keep the glider positioned in that up current. You can turn it left or right by putting the lift under one wing or another.”

To elaborate, MacCready is controlling both the pitch and the roll axes of the glider by the placement of his hands underneath the wings. In the case of a roll turn, that is achieved by varying which wing is experiencing more updraft from your hands. In this scenario, to turn left, one would have their hands slightly more on the right wing. The glider would then perform a banked turn. This is pictured below:
Control About Roll Axis
In the case where we are looking to change the pitch of the glider, that involves the movement of our hands forward and backwards. Moving forward will put more lift on the front of the glider thus increasing the angle of attack. This process is pictured below:

But be careful!

If you increase the angle of attack too much, then the glider will experience stall and come crashing down.

Since its discovery there have been many variations of the Walkalong Glider. The most simple and functional one that I was able to find is called the tumblewing. For information and instructions on how to make your own tumblewing glider please click here.

Sources:

1. Walkalong Glider History

2. Paul MacCready Biography

3. Walkalong Glider with Tyler MacCready

4. How to Fly a Walkalong Glider

5. Introduction to the Tumblewing

By David Villari | Posted in student post | Tagged gliding, soaring, toys | Comments (5)

The Unmanned Ornithopter

October 13, 2011 at 12:01 pm

Leonardo da Vinci was one of the first people to truely dive into the depths of trying to create and design the ornithopter, a machine shaped like an aircraft that is held aloft and propelled by wing movements. He focused much of time and effort trying to sketch a design where the aircraft would be powered by human movement. As engineering advanced and technology became more innovative, many aviation enthusiasts began trying to build ornithopters that were not powered by humans at all.

One of the first people to successfully build an unmanned ornithopter was a 19th century French engineer named Gustave Trouvé. He created his model of the unmanned ornithopter by implementing twelve gunpowder charges attached to the belly of the aircraft that would fire in succession allowing the wings to flap. The aircraft flew for only 70 meters, but Trouvé's desgin proved to the scientific community that an unmanned ornithopter could be built.

Unmanned Ornithopter built by Gustave Trouvé

Fast foward about 140 years from the time of Trouvé's first launch of his ornithopter, and we now find that technology has allowed engineers to build ornithopters that actually look like the birds that original ornithopters were trying to mimic since the idea first came to life back in the days of the Renaissance and Leonardo da Vinci. A leading company in the field of automation called Festo, has developed a robotbird, that can take-off, fly, and land without any human interaction whatsoever. The robobird, which was insipired by the herring gull, or what we know as a sea gull, has tremendous agility and aerodynamics that allow it to move in the manner that a real bird would The design of the Smartbird is a huge step in the field of biomimicry because the bird is powered solely on a microchip processor that can scan its surrounding and environments to let the bird know where to fly. This type of automation is could one day possibly be used for military purposes or in search and rescue missions. The possibilities are endless.