It often feels like there just aren’t enough hours in the day to do what we aim to do, and for businesspeople, travelling all over the world from meeting to meeting, cutting down on travel time would seem like a tempting idea.
The world-famous Concorde was developed in the 70s as a very high-speed passenger plane to do just this, able to fly London to New York in under 4 hours. Let’s examine the technology and science behind Concorde which allowed it to perform such amazing feats, and then at the future of speedy travel.
Just looking at Concorde, you can immediately see differences from a standard plane. The extremely pointed nose and swept-back wings both help to streamline the plane, to reduce the air resistance (also called drag) and so reduce the fuel consumption of the Concorde.
The shape of the wing, called a “delta wing” also helped to stabilise the plane during flight, removing the need for stabilisers on the tail of the Concorde. This was helpful as added horizontal stabilisers would have further increased the drag on the plane.
The shape of the wing also helps create enough lift for the Concorde to fly.
Lift is the upward force created by wings as air flows over them, and is explained by Bernoulli’s principle.
Bernoulli’s principle is easiest to understand by considering a tiny parcel of air travelling along a straight streamline. If the parcel of air encounters a decrease in pressure, the back of the parcel will be subject to a higher pressure than the front. This means there will be a net force pushing from the back of the air parcel towards the front, and therefore causing the air to accelerate forwards.
This little example shows a very important result – when pressure decreases, speed increases and vice versa.
Now we consider our same parcel, this time travelling around a curved streamline. When travelling on a curved path, the direction of travel is constantly changing. Newton’s First Law tells us that there must be some force applied to the air to cause this change in direction (Newton’s Law says that a body will carry on travelling in a straight line at a steady speed unless some force is applied to it). So we can see there must be some force acting on the parcel of air.
Where is this force coming from? There is nothing actively poking this air parcel to force it to go in a different direction so we can conclude this force must be another pressure force, caused by a pressure gradient.
This second example tells us that when air travels on a curved path, there must be some pressure gradient present.
These examples have given us 2 really important results:
When pressure decreases, speed increases (and vice versa). This is Bernoulli’s principle.
When air travels on a curved path, there must be some pressure gradient present
Now we can think about a wing. When air meets a wing travelling through it, the air has to curve to get around it. This tells us that there must be some sort of pressure gradient across the wing.
If we imagine a wing with high-pressure air on the bottom and low-pressure air on top, we can imagine that this will cause a net force upwards to be felt by the wing – this is lift!
Returning to Concorde, the shape of the wings and the angle they meet the air at was chosen to maximise the amount of lift force created, while not making too much drag.
A key part of any vehicle is the engine. The location and type of engines on the Concorde’s was different from on other jets. Usually, engine struts are used to attach the engine to the body of the plane. In Concorde, the engines were attached directly to the underside of the wings. This was for two reasons. When flying at supersonic speeds, the high velocity of the air flowing past the plane can cause damage and stress to the outside of the plane, therefore the struts would be likely to break if they were used.
The second reason is to do with the flow of air around the plane. By not using struts and keeping the engines close into the body of the plane, the flow of air around Concorde is less disturbed, so the plane experiences lower drag force.
There was something else special about Concorde’s engines. They used afterburners to generate maximum thrust from the engines. The afterburners would take the exhaust gases from the initial engines and burn them for a second time along with added extra fuel. This meant the engines could produce huge amounts of thrust, allowing Concorde to reach its mind-blowing speeds.
Where there are engines there is, of course, fuel. Concorde had a number of fuel tanks but, unlike other planes, they were used for more than storage. The fuel tanks were actually used to help achieve aerodynamic stability.
We need to introduce the idea of the aerodynamic centre of an object. When a wing flies through the air, a number of different forces act on it, like pressure, lift and drag. These won’t all act at the same point – they might be spread over a large area, like pressure forces, or act away from the centre of the wing. When forces are applied to an object away from its centre, these forces create “moments” which cause the wing to tilt or tip.
If you imagine pushing a cube along on a table, if you pushed in the centre you’d expect it to move in a straight line without turning or tipping. However, if you applied your force at one side, you’d expect the cube to turn as well as move. This is because you would’ve applied a moment (defined by the equation Moment=Force x Distance from Centre of Mass) as well as a force. The aerodynamic centre of an object is the location where the moments created by the forces acting on that object are constant, so even if you change the angle of the wing, the moments won’t change. Due to the differences between subsonic (below the speed of sound) and supersonic (above the speed of sound) flight, the aerodynamic centre of Concorde can shift backwards as it speeds up from subsonic to supersonic.
This shift unbalances the aircraft and could cause the nose to tip downwards. To counteract this, fuel is pumped from tanks at the front of the plane to tanks at the back, to rebalance the craft. The opposite can be done when the plane slows down, so the fuel can actually be used for stabilising, as well as powering the jet engines.
If you picture Concorde in your head, you imagine a gleaming white aircraft punching through the air. It turns out that the choice of white paint for the outer surface of Concorde was no coincidence. The white paint was, in fact, a very high reflectivity material, chosen to keep Concorde cool. As the plane moved through the air at high speed, the friction with air particles caused a heating effect – even the inner walls of the plane became warm to the touch.
The white paint was chosen to help Concorde reflect this heat away from itself. It’s well known that black objects emit and absorb radiation best, while white is the best colour for reflection – this was used to the plane’s advantage in this situation.
There were significant problems with Concorde and its flight, one of which was the “sonic boom” it made.
When a plane flies, it pushes on the air in front of its nose and compresses it. This makes waves of compressed air which travel forward at the speed of sound. However, if the plane is travelling at supersonic speeds, the waves of air are travelling slower than the plane, so new waves get in the way of old ones and they are forced together into a single shock wave.
This fast-moving air can cause damage to buildings, break glass and be loud and startling. This lead to Concorde only being allowed to fly at supersonic speeds over oceans, meaning it only had a small number of routes open to it.
Concorde had its last flight in 2003 and since then supersonic flight has been at a standstill. But China had recently revealed plans for a hypersonic aircraft (hypersonic flight is defined as flight at 5 times the speed of sound).
China’s craft, the I plane, earned its name from its shape – when viewed from the front it looks like a capital letter I, due to its 2 pairs of wings, one on top of the other.
Using two pairs of wings means the plane can create more lift, meaning it has enough upward force to carry more passengers than a single-winged plane would. The second pair of wings can also disrupt the sonic boom waves by redirecting them.
So is hypersonic flight the wave of the future? Nothing can stop the sonic boom shockwaves from being created when you fly above the speed of sound, so these will always remain a problem. However, in an ever-faster-moving and more hurried world, it seems likely that sonic boom will soon just be an unfortunate consequence of our need for speed.admin Categories: Articles Tags: engineering, physics, science 10013 Robotics Revolution – Soft Robots and the Promise They Hold
When we hear the word “robot”, we probably think of “the Terminator” from the 1980s movie, or maybe a huge moving arm in a car factory. But a new and expanding field is introducing a new type of robot, with huge potential into our world. We could be seeing these robots being used for a huge assortment of tasks, such as helping surgeons perform operations or testing water quality in the sea.
Soft robotics is a self-explanatory term – it is a subfield of engineering and robotics dealing with robots made from compliant materials, making the robots more animal-like than most robots we see in films and on TV. This area has recently hit the headlines after having huge success making “muscles” which can lift up to 1000 times their own weight. So, is this a one-off success story, or an expanding area to watch?
In December last year, researchers from Harvard and MIT published research on robotic muscles they had made which can twist, grab and hold heavy weights. These incredible mechanisms are based on origami and, depending on how they are folded, will deform differently when triggered.
They work by exploiting pressure differences – they are made from an inner folded ‘skeleton’, with a fluid (like air or water) surrounding it, all sealed inside a ‘skin’. To make the robot move, a vacuum is created inside the sealed casing, which causes the skin to collapse onto the skeleton, creating tension and moving the muscle. To help you imagine it, it’s just like putting a spring inside a vacuum packing bag and sucking all the air out – you’d expect the spring to compress as the outside bag presses in on it. This action causes the skeleton to shrink down to just 10% of it’s original size, which means it has a really large range of movement. Another great thing about these robotic ‘muscles’ is the materials they’re made of. They can be made out of relatively thin layers of plastic, meaning they can even be made transparent – speakers which can produce all frequencies of sound which we can hear and are completely transparent have been made using this technology!
A wide variety of robots have been made; some can pick objects up, as well as twisting and moving them. Some can even be attached to people’s skin, controlling their movement. NUI Galway’s Dr Ellen Roche, a biomedical engineer took this idea one step further. Before Dr Roche’s incredible work, people with acute heart failure, whose hearts could no longer pump their blood could be fitted with an LVAD (left ventricular assist device), which literally takes the blood from the very bottom of the heart, sends it through a pump and injects it right into the major artery coming out of the top of the heart.
At first glance, this sounds like a completely reasonable solution. However, as usual, problems lurk just beneath the surface. When blood comes into contact with a foreign surface, the platelets in the blood automatically think they must be outside of the body. Their natural response in this situation, is of course to make the blood clot. This can be absolutely disastrous – if a blood clot travels around in your blood stream, it could block a blood vessel and lead to a stroke or heart attack. To stop this happening, patients with an LVAD need to take blood thinners, which can cause dizziness, weakness and can stop you healing properly from even a small cut. Dr Roche’s idea was to use soft robotics to make a sleeve for the heart, which could pump with it, most importantly never coming in contact with the blood. Dr Roche used the technology I mentioned before to make a silicon sleeve, with fibres capable of contracting and relaxing, to fit around the sleeve.
This process took considerable development – the heart’s motion isn’t a simple squeeze. The heart actually squeezes and twists together at the same time, with different layers of muscle causing these different movements. Dr Roche’s sleeve also has 2 layers, one of which squeezes and one which twists. The sleeve also plugs into the heart’s own electrical network – the tiny electrical signals which tell the heart when to pump, produced by the pacemaker cells, can be tapped into by Dr Roche’s device so the sleeve pumps in time with the heart. Although more testing is needed, this amazing device could change millions of lives and revolutionise the way we look at treating failing organs and other conditions. For example, the same technology is now being used by scientists at Harvard to create exoskeletons to help stroke patients walk again.
In other parts of the world, researchers and engineers are taking inspiration from nature to build their soft robots. At the BioRobotics Institute in Pontedera, Italy, scientists have created robots with movement based on that of octopuses. Octopuses have no bones or hard parts in their bodies, so are an ideal model for a soft robot.
Researchers have created segments which can twist and turn like an octopus’s tentacles. By attaching a camera to this flexible rod, they formed a tool for surgery which allows surgeons to get a close-up view of exactly what they’re doing, from whatever angle they want. If more were needed to convince you that soft robots have buckets of potential for changing the world, they are also seriously cheap to make – with costs for making a robotic arm coming in at under $1, soft robots seem to secure themselves a place in the future of robotics.
If you compared the running of a car factory 50 years ago to today, the impact of traditional “hard” robots (the kind made of metal and nuts and bolts) would be as clear as day. In my opinion, soft robots are on their way to making similar changes to the face of healthcare, manufacture and more in the near future.
Sources:admin Categories: Articles Tags: engineering, student advice, technology 10006 Look – No Hands! The Rise of Driverless Cars
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We take for granted the flood of information our senses supply to our brains every second, helping us to understand what’s happening around us. Without this, how would we be able to cook dinner, do our jobs, or drive a car? But the car we drive is blind to the world we see – so how could it drive itself? With driverless cars currently being tested by engineers in cities all over the world, let’s take a look at some of the tech they use to get from A to B.
Driverless cars typically have over 10 different types of sensor – from laser range finders to near view cameras and radar to GPS. These sensors help build up a picture of what the world looks like, so the car can navigate itself safely. But how do they all work together to create a driver as good as (or better than) you or me?
Arguably the most important sensor on a self-driving car is its laser range finder, or LIDAR, which uses pulses of laser light to build up a 3D picture of the surroundings. Google’s self-driving car has no fewer than 64 laser beams with an impressive 200m range. Over a million laser beams are sent out per second and reflect from objects around the car. The reflections are picked up by sensors in the car and the time for the pulse to travel out and back is calculated (as laser beams travel at the speed of light). This means the distance to the nearest object can be worked out and therefore the car can build up an image of the 200m surrounding it.
On the smaller scale, radars on each wheel use the same method to keep an eye on the cars in front and behind it, making sure there is a 2-4 second gap between each car. A near vision camera mounted on the front of the car looks out for unexpected obstacles like pedestrians and cyclists, and can even recognise hand signals and road signs. But the most impressive part of a driverless car is how it takes these signals and somehow understands what to do with them.
The computer sitting inside an autonomous car contains huge amounts of data. Maps covering huge swathes of the world, hundreds of road signs and signals, shape and motion descriptors and plenty more are all stored in the car. These are used in conjunction with the data received from the sensors to help the machine make decisions.
Neural networks are programs which recognise patterns in data, loosely based on the human brain. Cars use these networks to understand the data from their sensors. Inputs are fed into the first layer of the network and weighted according to how important the algorithm thinks they will be. Some function is performed on the data and the outputs are then fed into the next layer and so on. This process allows the computer to classify and cluster data to look for patterns, which can then be compared to the huge bank of data sitting in the computer.
But these dream machines are far from infallible. Some things cause a real problem for driverless vehicles. Roadworks regularly block roads but always look different, use different signs and signals, and don’t have any database or schedule for cars to refer to. Roadworks are an ongoing problem for designers and a range of solutions have come forward from different quarters. Some have resorted to a call centre approach, suggesting that humans could help to guide confused vehicles around tricky situations. But can you really call a car which operates like this “autonomous”?
Another idea is based on communication between the car and the construction area itself. If the two could communicate with one another, the construction site could act as a broadcasting beacon, telling the cars to reroute or adjust their course. However a lot of information would need to be given to the car – how many lanes are left open, exactly where is the construction happening (to a very fine degree of accuracy) etc.
A further problem with this is authentication – how can the car tell the difference between a real-life construction site and a hacker rerouting your journey for their own dubious reasons. Yet another idea for solving this problem is simply to stay well away from any problem zones. If a database of roadworks can be created, cars can simply create new routes which bypass these areas completely. Although this seems like a credible solution, it shows us that at the moment, cars are nowhere near achieving the important, yet elusive, ‘common sense’.
It has been shown that 90% of car accidents are caused by human error – surely robots will then be much safer than a lift from mum or dad. But with autonomous vehicles come a new risk – hacking.
With such a focus on cybersecurity nowadays, it is surprising how easily autonomous cars can be hacked. In a study led by researchers at the University of Washington, it was found that by simply putting stickers on road signs, they could cause a misclassification of the sign with a 100% success rate. Through this, malicious hackers (or just bored graffiti artists) could cause huge problems and many accidents through changes in speed limits or changes in the meaning of important signs. 3M, the company which gave us Post-its, have come up with a resolution – creating bar codes which are invisible to the naked human eye, but can be read by autonomous vehicles and provide information like GPS location or where the next set of traffic lights will be.
Can Driverless Cars Save Lives?
Driverless cars will play a huge role in our future and hopefully, have the capacity to save many lives which would otherwise be unnecessarily lost. Humans as drivers have many flaws and shortcomings. However, the way we adapt to unexpected circumstances and make split-second decisions is unparalleled – it remains to be seen if any robot can live up to old-fashioned common sense.
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Sources:admin Categories: Articles Tags: engineering, Student opinion, technology