U.S. space shuttle Atlantis. Photo Credit: Science.NationalGeographic.com
Space travel has fascinated so many of us since Kennedy promised we’d get a man on the moon. Scientists and engineers worked tirelessly to introduce humans to the rest of the universe and society has benefited greatly from their work. Space travel investment created many things from freeze dried ice cream and Tang to new, more accurate methods for heat transfer calculations. One of the huge improvements was the study of supersonic flow and the convergent-divergent nozzle. This nozzle has made space flight, supersonic jets and all kinds high speed transportation possible. It operates using some pretty interesting ideas.
Most of us are only familiar with nozzles as they apply to garden hoses or shower heads, but some of the same basic principles apply to these new supersonic devices. A converging nozzle increases the speed of the flow, like when you cover part of the head of the hose to spray the water farther. A diverging nozzle is a little less common but it reduces the speed of the flow, like when you adjust your shower head so it’s not blasting you. A convergent-divergent nozzle combines those two back to back and produces velocities greater than the speed of sound. If you’re thinking, “Wait, if a converging nozzle speeds up the flow and a diverging nozzle slows down the flow wouldn’t they just cancel each other out?” you’re pretty on top of your game. This is where compressibility effects come into play. Most of the nozzles we’re familiar with use water, an incompressible fluid, while these nozzles use gasses which are compressible. Imagine you’re coming back from a trip up in the mountains and you have a totally full water bottle and an empty one. The change in altitude will compress the air in the empty bottle, leaving it crumpled while the full water bottle will remain essentially the same.
Air can usually be assumed to act like an incompressible fluid for low speed, like figuring out how strong of winds will take down a billboard or how fast a fan can move air. When air speeds start to reach the speed of sound pretty neat things start happening but first we need to look a bit at what sound is. Sound waves are pressure waves that pass through air very fast, the important thing here is that they’re waves of high pressure. Now lets get back to the nozzle, our first section is a converging nozzle, this speeds up the flow. Lets say that the air is coming in really fast, like almost speed of sound fast, then as it passes through the nozzle it reaches the speed of sound. This means that any of those sound pressure waves trying to move back through the air will be caught in the throat of the nozzle. Kind of like when a person is walking towards the back of a subway train just as it’s leaving the station. They are moving back, but the train is moving forward, so a person standing in the station would see the person in the train as stationary. Also the air is moving so fast that not all of it can get through the throat as fast as it would like so it starts pushing and shoving like a bunch of college kids trying to get free food. This makes the throat of the nozzle a very high pressure region, so high pressure that the flow keeps accelerating through the diverging portion of the nozzle, where incompressible flows would start slowing down. The pressure of the air forces it out like gas out of a shaken soda bottle.
This simple design requires a deep understanding of the world we live in, and it provides the foundation for almost everything that moves at or faster than the speed of sound.
3D-Printed Make-up. Photo Credit: Time.com
Harvard Business School graduate, Grace Choi, has come up with an invention that allows users to print their own makeup within minutes. The user would simply find a hue they desire, use software to determine the exact color code, send the color code to the printer and the device prints this color onto blank materials that are used for powder, creams, or gel makeups. Printing one’s own makeup begin with a colorless makeup palette that is inserted into the 3D printer and ends with the desired color and amount of makeup one needs. The printer uses the ink solution to print only a top layer of color to the blank materials and voilà, instant makeup that is ready for application. There is the issue that the ink does not “seep” homogenously through the makeup but this is seen as a good thing by Choi saying that it would be added savings to the consumer. The printer does not print great quantities of makeup, only enough for the application. This printer is being called Mink and will be ready for retail next summer for about $300. This could be an enormous turn for the cosmetics industry as now this eliminates needs to go to high-end retail stores for brand name makeup for only a specific color. Cost will be significantly dropped as there is no need to buy unnecessary volumes of makeup one wears infrequently or for a single occasion. The costs added for brand recognition, labeling, and containers are also eliminated as it is made at home inside the printer. It is a very personalized way to present one’s self that is limited only to the creativity or imagination of the user, not by beauty standard setting corporations. Even as a man who does not wear makeup regularly, I am in full support of this innovating that gives creative control to individuals. Well done Choi. Watch the whole presentation here http://techcrunch.com/2014/05/05/mink-is-a-3d-printer-for-makeup/
Mouse Trap. Photo Credit: CottageLife.com
Even simple devices are feats of engineering evident in day to day life, from pencil sharpeners to staplers. They have become so ingrained in the way that we look at the world that the curiosity and wonder has worn off. These devices are so well made that it is almost impossible to ‘build a better mousetrap’; however this is worth considering.
The mousetrap is an incredibly simple device. A block of wood with a spring, lever, and trigger mechanism. When tasked with the removal of these rodents it’s hard to imagine the jump from a block of wood and some wire to a mechanism of mouse management. The spring has to be strong enough to kill a mouse but not too difficult to set or too dangerous to leave lying around. The wood block has to be cheap enough to mass produce on a large scale but still strong enough to hold the spring when it is loaded and released. The trigger mechanism has to be sensitive enough to detect the nibblings of a small rodent but robust enough to allow the device to be moved without excessive misfire. All engineering problems contain important balances like this and the best designs will prioritize these properties and deftly balance them in an accessible package. The mousetrap has done this so well that the saying has stuck for decades.
If one were to attempt to build a better mousetrap one has to think of the drawbacks of the current models. The classic mouse trap is a one time use, clean up can get a bit messy, and when they snap on your fingers they sting pretty good. There are many designs out there working to solve these shortcomings, from poisons to frequency generators. If you’ve been reading this blog you know that we like to speculate on areas for advancement in a wide variety of disciplines. The vast majority of people are familiar with mousetraps and I would challenge you to comment any ideas that you might have for the future of the mousetrap. How would you build a better mousetrap?
Smart Duct. Photo Credit: Continuum-Dynamics.com
Submarines, UUV’s, and surface combatants all use the same or similar control surfaces like rudders, ailerons, flaps, and elevators to maneuver easily and safely underwater. (For more information on how control surfaces work here are some entertaining and educational videos). At high speeds and predictable flow areas, maneuverability using control surfaces is pretty effective, however, at low speeds this is not the case. There is a need for advanced low-speed maneuverability and the mitigation of cavitation-induced noise for all types of surface and underwater vehicles (check out WANDA). A solution to both that would avoid the use of high energy actuators would be ideal and the reduction or elimination of control surfaces in future designs would be even better. Theoretically.
Ducted propellers have been implemented in recent designs but changing the direction of flow out the trailing end through electro-mechanical actuators has been difficult to implement. Shape memory alloys (SMA) can make this deformable ‘Smart Duct’ a reality. A Smart Duct is a deformable shroud that changes the direction of flow of the propeller wash to provide a direct steering force to the vehicle. The duct itself is an electrically actuated structure that is covered by a flexible hydro-dynamically smooth sheathing whose primary movers are a set of high strength Nickel-Titanium SMA actuator cables. So basically…it’s a duct that can flex in different directions to get you moving where you want to go. A pretty basic idea but has tremendous value if it can be made and implemented correctly. SMA technology has made a series of successful demonstrations that allow for high force actuation that also greatly reduces the volume, weight, and number of moving parts as compared to competing designs. Typically made out of Nickle-Titanium, a 3% to 4% strain is possible with cyclic loads which is pretty dang impressive.
In January 2004, testing was done on the Smart Duct demonstrator at the Naval Surface Warfare Center, Carderock Division. The first tests were done with an empty duct in a water tunnel with a flow rate of 14.7 fps. The duct was able to flex and achieved a deflection of 0.7 in and resisted a peak force of 69 lb. A propeller + Smart Duct system was also tested as well and achieved similar results. Overall what these numbers mean is that effective flow turning angles of up to 15 degrees at thrust levels of operational submarines is possible with the Smart Duct. This is a pretty huge achievement. The future of this type of technology will possibly change the design of submarines and UUVs so be on the lookout for Smart Ducts. For more information please visit http://www.continuum-dynamics.com/lib-pro-duct.html.
The XStat, a syringe filled with dozens of tiny sponges, is a new tool to treat gunshot wounds in combat that its creators hope will work faster and more effectively than current methods. Photo Credit: NYDailyNews.com
Being on the front lines during a war is extremely scary. There are bullets flying around left and right and fear is inevitable. One of the greater fears while on the battlefield is getting shot. How quickly someone can treat the wound (correctly) could mean life or death. In the past, soldiers who faced a gunshot wound would be treated with gauze to clog the hole until they could be transported to a hospital. Soldiers face tremendous difficulties when using gauze for treatment. For example, if the wound is deep it is hard to get the gauze deep enough (especially when it is a bullet sized hole) to clog the bleed. If the gauze method doesn’t work the first time then the entire process has to be done again. Also, using gauze heightens the risk of infection because medics would force gauze into the wound with their hand so particulates in the air, dirt, grass, etc. could easily penetrate the wound.
An ingenious new invention will save precious seconds in treating life-threatening gunshot wounds on the battlefield. The XStat looks like a syringe filled with pills, but the capsules it contains are actually tiny sponges that plug wounds and stop bleeding minutes faster than packing them with gauze. Treating wounds with the XStat takes only a matter of seconds. The syringe is inserted directly into the wound and the medic presses down to release the sponges. In about 15 seconds, the sponges expand, creating a pressure that stops the bleeding. The minutes saved allow medics to move on to the next patient more quickly, and increase a wounded soldier’s chances of survival. The product, which received $5 million in funding from the U.S. Military, is currently in the final stages of approval by the U.S. Food and Drug Administration. Once approved, it will head into battle to increase the treatment process of wounded soldiers.
For all of the soldiers out there I would like to thank each and every one of you for your dedication and service!
Artist’s depiction of the Star Tours motion simulation theme park attraction. Photo Credit: a.dilcdn.com
Prompt: Entertainment engineering brings to light some of the more light-hearted aspects of engineering. Entertainment in itself is one of America’s most popular pass times and encompasses subjects such as film, television, music, games, reading, comedy, theater, circuses, magic, street performance, parades, fireworks, animal shows, and the list just goes on and on. Entertainment holds a very special place in the world and always has; whether in the form of the plays of Ancient Greece, the jesters of the medieval times, the shooting exhibitions from the days of the wild west, the black & white films that the soldiers of early wars watched to forget about their harsh reality, or the 3D special effects that seem to captivate us all on the building-sized screens of today, entertainment has always been there to help relieve the stress of those who indulge in it. Today this is especially important for the citizens of this great country as we work longer hours, spend more time stressed, and find the well-appreciated release provided through entertainment to be more and more refreshing. For all these reasons and many more, the entertainment industry is here to stay and will constantly require great engineers to keep it afloat and help it to progress. Pick 3 forms of entertainment and describe how a mechanical engineer could contribute to them, or 1 form and 3 considerations.
Recently I went to the Halloween Horror Nights at Universal Studios and I was pretty surprised at some of their choices to enhance the entertainment experience on some of their latest attractions. We are all familiar with roller coasters and their exhilarating speed, drops, and turns, but modern attractions at theme parks are going beyond simply high speeds and elevation to immerse guests into their worlds. As an engineer hired to further study and implement some subjects of my curriculum into new attractions, I would take kinematics/relative motion, machine design, and optics into consideration.
- Kinematics/Relative Motion
At many theme parks there is an influx of attractions that heavily rely on the principles of kinematics and relative motion to simulate movement in a small enclosed area. This is opposed to large physical roller coasters that take up tremendous amounts of space, cost incredible amounts of money to build, and raise many safety concerns and standards that have to be met especially for faster moving attractions. Disneyland in California has Star Tours in which the passengers are taken from planet to planet by only rotating from their seats. Universal Studios in Hollywood has the Transformers Ride 3D which does both real translating of the passengers cart as well as simulated motion. I much prefer the Transformers ride because if you are only simulating motion, you eventually realize that you are not actually moving but a combination of both confuses the mind and makes it wonder whether you are actually moving or not.
- Machine Design
Still I believe the E-Ticket attractions are still the bigger roller coasters where you zip though loops upside down and through the air at face melting speeds. Machine design takes into account all the loads on all the components of the ride and ensuring with a factor of safety that those loads will not cause a failure. A corrosion study can also be done to mitigate the effects of corrosion to not only prevent certain kinds of corrosion that are likely to happen, but also avoid an unexpected failure due to fatigue or stress. Taking a statistical approach to the possible loads that the ride will introduce on components will make the design the safest and most enjoyable that it could be.
As a mechanical engineer there is not a course in my curriculum that approaches this study directly but it would be an area I would like to further study. 3-Dimensional movies and attractions make the audience believe that the action is really happening inches from their faces. Further developing this technology to make it more realistic would definitely improve the experience of the audience. Optics could also improve the experience by making images seem unrealistic like in the Clowns 3D maze at Horror Nights. The 3D glasses made certain images appear closer than they were but there were sections of the maze that blurred the line between real actors and projected imagery. I was stunned when I thought a menacing clown was only a screen projection but then came out of the screen was smiling right in front of my face. I was impressed but more scared by this effect.
SBI water resistant material. Photo Credit: SBIFinishing.com
Water is definitely not a friend for materials such as metals, electronics, wood, etc. For example, when metal is submerged underwater it increases the rate of corrosion of the metal (i.e steel). So we must consider how we can fight against these negative effects the water produces against devices that are made for the water like boats. There are metals out there that are able to neglect the negative attributes of water; however some of us may not have the money to spend on corrosion resistant steel. So what has been done is to create a coating that could be placed over the metal to act as a layer to protect these metals.
There are many coatings out there today however each of these coatings may serve a different purpose. When developing vehicles or devices for underwater purposes it is important to choose a coating that provides cathodic protection. Cathodic protection is used to prevent the metal from being corroded and is usually cheaper than straight out buying corrosion resistant steel. These coatings do come in different colors so you could alter the color of the metal to your choosing. If you are worried about meeting certain specifications no need to worry. There are coatings that go through testing to ensure performance. For example, a coating called Alocit made by A&E Group was tested by the navy and it is 1 of the 3 that meets the specification for the US Army Corps of Engineers! This coating provides great resistance and adhesion. The best part about this and other coatings is that the installation is simple!