Ever wonder if the Jetsons were the only ones with flying cars? Wouldn’t it be nice to escape the two dimensional world of traffic? The Jetsons had many many “highways” of cars going in every direction. Well, we might not be able to reach the potential yet, but there are developments striving to this goal.
Terrafugia is a company that was founded by MIT graduates has made great advancements in this area of research. They have created the Transition, an automobile that “transitions” into an aircraft. This aircraft is currently the epitome of this specific area of development.
The vehicle can move up to 65 mph on the road and 115 mph in the air. Traffic isn’t going to slow anyone down in this vehicle! The vehicle sports a 35mpg tank, matching many of the automobiles on the road today. When flying, however, it uses about 5 gallons an hour.
By folding the wings up vertically, the vehicle becomes able to fit on a normal road. It can hold 1 other passenger besides the pilot and sports a wingspan of almost 26 and a half feet.
This vehicle is rumored to be released in 2012, so we are bound to see these flying around in no time. However, this “carplane” sports a hefty price tag of $279,000.
Earlier in the semester, I wrote my first blog post on "A Robot that Flies like a Bird." The post was inspired by a video I saw last summer. Within the video, the head of the team Markus Fischer introduced the world to the first ever robot that flies like a bird; or so we thought.
Last week in class, the subject of my initial post came up in discussion. Mostly, we talked about rather interesting material which I had already covered. However, one subject that we touched on really stuck with me: this was not actually the first robot modeled after birds' flapping wings. The first successful robot was constructed several decades ago in the mid 20th Century. Unfortunately, this invention went mostly unnoticed. It was not until recently that anyone has truly received full and legitimate credit for copying flapping flight. The reason is that previous designs, successful or unsuccessful, have merely imitated the flapping motions of birds. Fresto's SmartBird actually copies those motions.
In order to generate lift and propulsion/thrust simultaneously, the SmartBird employs some incredibly sophisticated technology. The robot contains a small electric motor that spins two gears. These gears, located within the "body" cause the wings to move up and down. While in motion, the wings themselves twist, exactly the same way a real bird's wings do. The head is synched to the body via electronic motors and cables. This synchronization and flexibility enable the robot to maneuver impressively well through the air. The wings themselves also flex.
One of the reasons the bird can maintain such impressive flight patterns is that it directly communicates with its operator in real time. If something goes wrong and is not functioning properly, the operator will instantly know and can adjust accordingly to ensure the bird stays in the air.
Because of the technology used, and the team's ability to decipher and replicate birds' flapping motion, the SmartBird has 80% aerodynamic efficiency. In other words, it is essentially as efficient in the air as the herring gull that it was designed after. While it may not be the first airborne robot that is modeled after the flapping motion of a bird, it is by far the best. Nothing has come close in terms of accuracy and efficiency. Fresto has earned the right to claim they mastered and replicated birds' flight before anyone else.
Sugar Gliders are quickly becoming one of the most popular pets in the country. In all but four states you can take these furry little flyers home to perform tricks like these for you. But how do they achieve such controlled glides, as seen in the video’s best trick?
A sugar glider’s method of aerial locomotion is extremely similar to an animal we have already seen, the Flying Squirrel. They have a thin membrane that extends from both of their wrists to both of their ankles, called a patgium. When they jump in order to glide, they extend their limbs, stretching the patagium into a rectangular shape (shown below).
The patagium acts like a parachute, greatly increasing the sugar glider’s surface area, which leads to a much larger drag force opposing gravity. This allows a slow, controlled descent. Meanwhile, the glider’s initial jump provides all the horizontal motion it needs for the glide. In the wild, sugar gliders can cover a distance of almost 200 feet in a single glide!
Sugar glider
The sugar glider can also control its direction in few different ways. They can change the curvature or angle of the patagium in order to tilt the body in a desired direction and turn. It is also hypothesized that the sugar glider may use the rotation of its long tail to tilt its body (using conservation of angular momentum), much like the falling gecko.
One thing the sugar glider is not very good at doing in the air is braking. When it is about to land, the glider is able to slightly tilt its body and patagium upwards, which slows it by producing more horizontal drag. However, in order to come to a complete stop in the wild, sugar gliders actually collide into trees (like the gliding ants), and then use their claws to latch on to the trunk.
Flying squirrel
It is remarkable how similar sugar gliders and flying squirrels are, despite being only distantly related. Sugar gliders are marsupials, like kangaroos, while flying squirrels are placental mammals, like humans. Yet natural selection has independently given these creatures analogous structures like the patagium (jumping from trees) and large, cute eyes (because they are nocturnal).
Incidentally, for people looking for exotic pets, flying squirrels can now be found at certain pet stores, alongside those adorable sugar gliders.
Elegant yet notoriously aggressive, a swan is not only one of the largest birds to fly, but it is also very unique. Being mostly aquatic, it makes sense that this bird would have webbed feet. However, this has been shown to not only be for better control and movement in the water, but also an extensive adaptation to their flight.
Weighing in at anywhere from 22 to 33 lbs, this bird is just a few pounds less than the heaviest bird that is still capable of flight: the Kori Bustard. The Kori Bustard, a horribly clumsy flier, struggles greatly to get up into the air and doesn’t tend to stay up for very long, so how is it that the swan can achieve flight from the water without a moving start?
Here is where their adaptations come into play. We all know very well that wet wings wont fly. This is shown by the post “A Kettle of Bald Eagles”, where the bald eagle picks up a fish that is too large for it to fly away and falls in the water. When this happens it is forced to “swim” its way to shore to dry its wings.
The Swan, on the other hand, has a gland, the ‘preen gland’, at the base of its tail that secrets water-resistant oil. Using its long neck, it reaches back and uses it’s bill to spread the oil across its feathers. This allows it to spend as much time as it wants in the water without needing to dry off.
A Swan’s wingspan ranges from a massive 79-138 inches, allowing for long and powerful downstrokes to counteract its weight and give it forward motion.
Even with waterproofed feathers and large wings, it is still a considerable feat for this animal to achieve flight. This is where its webbed feet become a unique flying adaptation. As shown in the video below, the swan uses its feet as paddles to help it move across the water faster while taking off.
In this situation, the paddling is increasing the forward velocity of the bird, thus it feels a greater value of lift allowing it to achieve flight because lift is directly correlated to velocity as shown in the equation below:
L= ½(CL PSV^2)
where CL is the coefficient of lift dependent on many factors such as the shape of the object, P is air density, V is velocity, and S is the wing area.
These paddles for feet also come in handy when landing. Normally, when a bird lands it will use a very high angle of attack on its wings to induce a stall, however since the Swan is so massive, it still tends to come in very fast for a landing. As shown in the video below, it will use its feet to surf across the water to slow down even more.
In class we covered how vortices are generated at the tips of wings. We learned that this is due to high pressure air from under the wing spilling over the wing tip and moving into the area of low pressure above the wing. This causes a large "tornado" of air to form off of the wing tip. This vortex is very dangerous as it can cause other planes to lose control, but less obviously it is a major source of drag for the plane creating it.
Relatively recently, aerospace engineers have begun to focus more and more on diminishing these vortices to a minimum both to increase safety, and also profit. If planes give off a smaller wing tip vortex then they can fly and land much closer together, minimizing costs. Possibly the most major benefit of a reduced wing tip vortex is the reduced drag which accompanies it; pilots can then use less fuel to go the same speed, increasing profit.
Blended winglet
The most broadly implemented solution to the wing tip vortex problem is to add a winglet to the end of the wing. A winglet is an extra length of wing turned upwards, or grafted perpendicularly onto the end of the wing. This prevents the high pressure air under the wing from spilling over into the low pressure zone on top, greatly reducing the vortex generated. The blended winglet is the most common form, it is simply a smooth curving up of the end of the wing. It has been found to increase the fuel efficiency of a Boeing 707 6.5%. No wonder many modern planes integrate them into their design!
Commercial jet with winglets
If the implementation of a blended winglet or other vortex mitigating device is so beneficial to the design of an airliner, one might wonder why birds or other flying animals seem to lack them. In reality, they don't! Birds simply compensate for wingtip vortices in a slightly different manner. They have wingtip feathers with a small amount space in between them, and this acts the same as a winglet. The small spaces between the feathers allows a bird to minimize their wingtip vortex by aiding in the smooth escape of trapped air. Mother nature beat us to the punch, we just didn't know where to look!
