Bats are interesting animals, in that they are the only mammals truly capable of sustained flight. Due to its poor eyesight bats have become such agile fliers that they have been able to adapt flying at night. Bats use echolocation to help them pinpoint their surroundings and allow for them to catch their prey. But what many people do not know is that bats use more than their astute sense of echolocation to help them become winged creatures of the night.
In a recent report in the Proceeding of the National Academy of Sciences, researches from the University of Maryland have found the tiny hair on the bat’s wings to be microscopic hair sensors. Scientists have been baffled as to what the tiny hairs are used for, and it hasn’t been until recently that they have discovered that these microscopic hairs act as airflow sensors for the bats. They suggest that the hair is part of a complex system of sensors that connects to the brain and allows for the bat to have a better flight response, especially since they are nocturnal creatures and flying at night could be hazardous for them as well.
Photo by Charles W. Melton, Near Famous Nature Photography
Ohio University biologist John Zook, hypothesized that these sparsely distributed microscopic hairs act as the bat’s touch receptors. The study’s co-author Susanne Sterbing-D’Angelo decided to test Zook’s hypothesis. Sterbing-D’Angelo and the research team at the University of Maryland created an artificial forest that mimics a bat’s flight at night. After they removed the hairs off the bat with diluted removal hair cream they ran them through the course. They filmed the experiment with a high speed infrared video camera and studied the results frame by frame. What they found was quite astounding. The bats without the hair flew faster, but had wider turns. They were still able to finish the obstacle course, but without the same precision and agility as those with the hair on their wings. The bats especially need to create sharp turns, not only to catch their prey, but also to avoid being a prey themselves.
A bat hunting a moth. Photo from Quest
The microscopic hair sensors on the bat’s wings allow for it to be able to tell the speed of the air as it moves past the wing. This is crucial in that it allows the bat to know at which speed they should be flying in relative to the wind. That is why the bats without the hair flew faster because they did not know how fast to go since they did not have the sensors. According to Sterbing-D’Angelo: “Those hairs, particularly at the edge of the wing, function as stall detectors . . . They let the bat know when the flight is getting iffy.”
The study is part of research grant by the United States Air Force. The study of how bats fly and can maneuver so swift and agile can be very beneficial if we apply it to our own aircrafts. The maneuver that bats are able to make can stall any of our highly advanced aircrafts. Christian Voigt, a bat researcher at Leibniz Institute for Zoo and Wildlife Research in Berlin says, “bats have this extra sensory modality that we don’t have.”
Bats are truly fascinating creatures in that we know so little about them. We disregard them as annoying pests of the night and even sometimes fear them. We all need to learn to appreciate the power of the flight behind this animal for in the end we learn most when we observe.
Geckos exhibit an unusual phenomenon that inspires exciting possibilities in human engineering. While frogs, lizards, and most other organisms that have self-orienting responses while falling use aerodynamics, geckos use principle of conservation of angular momentum.
Professor Robert Full’s lab at UC Berkeley has studied this behavior extensively. In the video from their study, notice how the gecko spins it tail clockwise in the vertical plane to induce counterclockwise horizontal yaw.
One of the chief issues with high altitude research rocket flights (from 30km altitude to 200km altitude) is recovery of the rocket and payload after the flight. Deployable parachutes often fail to deploy, or if they do cause the rocket to drift out of range of tracking equipment. They are also volume and mass inefficient, both of which must be minimized for high performance flights. The solution would presumptively be to innovative utilize hardware that is already on board the rocket for recovery.
The long, skinny anatomical arrangement (high length/diameter ratio) of many geckos and lizards parallels that of a sounding rocket. The only thing that needs to add is a tail for aerodynamic control- and we can provide that by extending a part of the rocket out the back.
The booster component of the rocket is made up of the airframe and the rocket motor inside the airframe. Once the fuel inside is used up, the spent motor is simply an empty aluminum casing. Luckily, the spent motor hardware should have about the right length/mass proportions when extended such that the forward closure of the casing is flush with the aft end of the rocket. We will henceforth consider the rocket airframe to be the “body” and the spent motor casing to be the “tail.”
The rocket ascends traditionally, with center of gravity ahead of center of pressure to create stability (1). This is the same reason why arrows fly straight—because the heavy tip keeps the center of gravity (CG) forward of the center of aerodynamic force, i.e. the center of pressure (CP). CP can be imagined as where a cardboard cutout of the arrow’s shadow would balance, since there’s more surface area near the fins, the CP is closer to them than the nose.
At apogee, the motor casing is ejected out the back of the rocket and then locked in place by a circular bearing that can rotate in just one direction (2). This changes the CG/CP relationship such that they are close to the same distance from the nose tip. This means that the rocket will not favor a nose-first or tail-first re-entry, but rather a neutral horizontal profile.
As the rocket descends through the atmosphere, air pressure induces rotational movement on the motor casing “tail” via the unidirectional bearing to spin in a clockwise direction (3). Because of the conservation of angular momentum, the rocket airframe will flat spin counterclockwise as it descends (4). As the rocket descends, more air will push on the motor casing “tail,” causing it to spin faster, and causing the airframe to flat spin faster, increasing drag, distributing heat effectively, and slowing the descent rate as a function of altitude. The accidental recovery of the University of Cincinnati’s Pathfinder project via flat spin proves that the flat-spin recovery technique is sound. In this case, the rocket wasn't damaged from its impact in the ocean because enough energy was dissipated in the spin. It is the author's hope that the concept can be refined by the BU Rocket Team and other organizations in the near future.
Sources:
Active tails enhance aerobial aerobatics in geckos, A Jusufi, D I Goldman, S Revzen R J Full, Proc. Nat. Acad. Sciences, Vol. 1805, pp. 4215-4219 (2008)
Righting and turning in mid-air using appendage inertia: reptile tails, analytical models and bio-inspired robots, A Jusufi, D T Kawano, T Libby, R J Full, Bioinsp. Biomim., Vol. 5, 045001, 12pp. (2010)
Photo: Wiki Commons/CC License. From Mother Nature Network.
In 2001, marine biologist Silvia Macia along with her husband Michael Robinson saw an unusual incident. They had just witnessed a squid "flying" above the water (yes, above!). After discovering this magnificent discovery, they started research on squids; they asked whether any researchers have seen such a thing, a flying squid. This eventually leads to a study and along with other researchers, they find out that at least six different kind of squid species have been seen flying: squirting itself out of the water to fly above the water.
Group of flying squid off the coast of Brazil. Notice the jets of water propelling the squid through the air. Image: Bob and Deb Hulse, from Scientific American.
It was discovered that these squids fly similar to the flying fish that have been discovered already. With the exception that squids use their mantle fins as wings. Some squids have also been seen pushing water out of their funnels to create propulsion when they are in the air. The key for the squid to get out of the water is jet propulsion. The squid fills up with water then expands its mantle (the cloak of soft tissue that surrounds the body) and shoots it out of its funnel (the flexible tube located below its head). And using the squid's funnel, positioning it, to change the direction of where the squid is heading. The squids are able to jet up 2 meters above the water and can go forward for as long as 10 meters.
Scientists have said that the squids are seen flying because they are running away from a predator. The discovery by Macia is probably because of the boat noise that caused the squid to react and flee. Squids use this advantage to escape danger.
There hasn't been any physics discovered on how the squids do fly yet, but it is indeed true. This discovery is one of many coming. Evolution has caused the squid to survive, learning to use their mantle and funnel to "fly".
The German company, Festo specializes in Pneumatic and Electrical automation technology. This means that their research is directed toward the mastery and optimization of efficient airflow. At this company they have ongoing research in the automation field with their Bionic Learning Network. Here they take engineers and scientists from their company along with people from other companies and universities, to do research and develop new automation and energy efficient bio mechatronic technologies. Biomechatronic technology uses light weight mechanisms in combination with electric propulsion and smart control and regulation systems powered by intelligent software to create new technologies. In this network they try to use nature as a model to adapt technologies to industrial applications, in other words they use nature as an inspiration for engineering.
In the past Festo has come up with technologies like the AirJelly or the Airray, which have been able to fly and move through the air with the use of helium and biomechatronic systems. But their latest invention is called the SmartBird. This SmartBird uses biomechatronic systems to achieve flapping flight and take of and landings under its own power.
To make this SmartBird the engineers were inspired by the Herring Gull and its wings but they had to test different wing contours, angles of inclination, and shapes to try to maximize lift and propulsion. The one they ended up using, has never existed in nature. Many people did not think it had the potential to create the lift and propulsion needed to get the bird off the ground, but then again people never thought flapping flight would be achieved either.
Engineers took inspiration from the Herring Gull.
The SmartBird is made up of about 130 components including lightweight wings made of carbon fiber parts, sensors, and motors. It weighs only 485 grams and has a wingspan of about 2 meters. The controller of the bird can modify the wing position due to changes in wind or airflow. This is called active wing torsion and this makes the flapping flight possible. This means that the wings can adjust their rotation in their upward and downward strokes due to environmental changes. It has a primary wing, the hand wing, which is for propulsion, and a secondary wing, or arm wing for lift. An electrical motor with a two-stage gear creates the flapping motion. The flapping and bending forces are made by a reflexible link and a crank mechanism. This crank mechanism does not have a dead center so it runs evenly and creates a smooth flight. The wingtips move separately from the wing due to a motor with sensors, so the controller knows the wing position at all times. The head and torso move in opposite directions with the help of two motors and cables that bend aerodynamically and simultaneously to counter and correct the weight displacement. This makes the SmartBird more maneuverable and agile. The tail can also move up and down and can curve to create lift and act as a rudder to steer the bird where is needs to go (Festo).
The flapping motion of the SmartBird.
According to its creator Marcus Fisher, this is one of the most aerodynamically efficient creations ever built in the automation field. It is about seventy to eighty percent aerodynamically effective because of the design. Another component that makes it so efficient is the smart technologies that adjust the active torsion to the changes in the wind or airflow. This optimizes the efficiency because of it adjusts in time with the changes in the environment.
Some of the carbon fiber parts in the SmartBird.
Fasto achieves flapping flight by mimicking the flight of seagulls. With a biomechatronic system, the engineers were able to create a highly efficient machine that can fly without a fixed wing. The two part wings create lift and propulsion and sensors monitor air conditions so the sensors can adjust the motors to the environment just like real Herring Gulls do. People for a very long time did not think flapping flight was possible, but with this new technology, who knows what engineers can do next, a plane that flies like the birds?
In a previous post from the last quarter, Grace Ingalls talked about the physics of how hummingbirds fly. The hummingbird was described to fly more like an insect rather than a bird since it was able to hover in every direction as opposed to conventional birds who flew only in a forward direction. Impressed by this maneuverability, researchers in Japan have cleverly built a robot based off of the humming bird model.
Japanese researcher Hiroshi Liu, from Chiba University, developed a robotic hummingbird using the properties of a real hummingbird. It is 10 centimeters long and weighs 2.6 grams which is very similar to the size and weight of a real hummingbird. (TechCrunch).
It flies freely in mid air by flapping its four small wings up to an astonishing 30 times per second. Hiroshi Liu claims that this design is more stable than a helicopter as it can quickly and efficiently fly in all directions. (TechCrunch).
Even though it is very versatile, Hiroshi Liu said that, "The next step is to make it hover to stay at one point in mid air." Liu plans to equip his robot with a camera by March 2011 which means that being able to hover at one point would be crucial for any meaningful video feed (AFP).
But AeroVironment, funded by DARPA, went a step ahead and actually installed a camera on their hummingbird robot.
These hummingbird robots pose great benefits to our society whether it be by providing video feed to rescue teams or the military; the hummingbird robots equipped with cameras will enable us to see live video of places where humans, land robots, or large unmanned aerial vehicles (UAVs) cannot reach.
Its amazing how much we can benefit from the nature of how a little bird flies.
Japanese researcher Hiroshi Liu, from Chiba University, developed a robotic hummingbird using the properties of a real hummingbird. It is 10 centimeters long and weighs 2.6 grams which is very similar to the size and weight of a real hummingbird. (TechCrunch).