Tag Archives: Engineering

Wind Power at AstroCamp

Wind farms are a common sight these days, but humans have been using wind power for about 2,000 years. It wasn’t always for electricity, however, but to mill grain into flour, operate an organ, or pump water. How does a windmill do any of that though?

When you see a windmill, the part that sticks out most is also the most important: the blades. Blade designs and orientations have changed through the centuries, but they all serve the same purpose and have the same drawbacks. If a windmill has too few blades, the weight of the windmill is imbalanced and will have too much open area, catching very little wind and making it increasingly difficult to actually rotate to blades. Too many blades, and the windmill will be too heavy to easily move in the wind. In either case, power generated by the windmill suffers. Most wind turbines have three blades, and that’s the amount we see most commonly in our whirling windmills class here at AstroCamp.

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Number of blades is not everything though, as you can see above; the angle of the blades plays an important role as well. Our windmill has the usual three fins, but isn’t even moving because its blades are flat against the wind. When the wind hits the blades, it just pushes them back. Once you angle the blades, the wind begins to push the blades back as well as up or down, allowing the windmill to spin. The fins must be angled consistently, however, as if blades on opposite sides are both being pushed up, they will cancel one another out and the windmill will still not move.

Wind power

Adjusting the angle of the blades brought our windmill up to generating over 17 milliamps of current, though campers have gotten over 60 mA with theirs. That’s just the current generated from a tiny windmill in front of a fan, real wind turbines generate enough electricity to power thousands of homes and there are nearly 50 thousand wind turbines in the United States alone.

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The Greatest Telescope That Almost Wasn’t

Why put a gigantic telescope in space? It’s a common misconception that Hubble was placed in orbit to be closer to the stars. Really, the difference in distance between our planet’s surface and low Earth orbit is negligible compared to how far away Hubble’s research targets are. The great advantage of a space telescope is its location outside of our atmosphere.

Light from faraway objects is distorted as it passes through the air on the way to ground-based telescopes. The universe looks much clearer with no atmosphere in the way. When Hubble launched in 1990 it was expected to deliver incredibly crisp images, hubble_in_orbit1but the school-bus-sized satellite’s first pictures were blurry. Something had gone terribly wrong.

Painstaking analysis by engineers on the ground revealed the source of the blur: spherical aberration. Hubble’s massive primary mirror, supposedly the most precise optical device ever created, had been meticulously ground into slightly the wrong parabolic shape, the result of a faulty testing mechanism. The mirror was off by about 1/50th the width of a human hair– a tiny error with massive consequences.

With hefty research expectations, billions of dollars, and NASA’s reputation on the line, project scientists snapped into action. A backup version of the Wide Field Planetary Camera, the instrument that would go on to produce Hubble’s most iconic images, was retrofitted with corrective optics. An ingenious contraption of moving mirrors was devised to refocus light from the primary mirror as it entered four other detectors. All this was designed and assembled on the ground, 347 miles below the faulty hardware. The math had to be perfect.

Thornton4thEVAKathryn Thornton on the 4th EVA of STS-61. Credit: NASA

Seven astronauts undertook an audacious mission to repair the giant scope. The STS-61 crew completed a record-setting five back-to-back spacewalks for a total of over 35 hours of EVA time. Their work was a resounding success. Hubble had been redeemed, and NASA vindicated.

Hubble Servicing Mission 1 stands today as a masterpiece of engineering, determination, and teamwork. It corrected the vision of humanity’s most powerful eyes on the cosmos, clearing the way for decades of compelling imagery and game-changing research.

Screen Shot 2016-04-24 at 12.11.41 PMHubble’s unprecedented depth of field allows scientists to peer into the early history of the universe. Credit: NASA

Today, the space telescope addresses fundamental questions about the age and nature of the universe. Its stunning documentation of faraway phenomena brings the wonder of space down to Earth. STS-61 narrowly salvaged public confidence in America’s ability to effectively explore space by turning Hubble’s story from one of crushing defeat to one of redemption.
Diagram source http://hubblesite.org/the_telescope/hubble_essentials/index.php#work ; all other images cred NASA

Written By: Caela Barry

Meet Astrocamp’s Newest Class!

Ever cover the end of a garden hose with your thumb to turn it into a long-range water blaster? The same thing happens when wind is squeezed between mountain ranges. This is called the Venturi effect, and it’s how wind engineers make the most of their turbine placements. California’s desert valleys are home to America’s oldest wind farms because they function as natural wind tunnels.

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The San Gorgonio Pass wind farm, just down the mountain from Astrocamp, is one of the oldest in the United States. Its operational capacity is 615MW. For more on how a windmill actually produces electricity, click here! Photo credit: Gregg M. Erickson.

Wind energy has seen massive expansion since it first gained traction in the 1980s, and it continues to grow. In 2014, U.S. wind farms generated over 180 million kilowatt-hours of electricity. That’s enough to power about 15% of domestic households. A recent Harvard study indicates that establishing a widespread turbine network across the central plains of the U.S. would power the nation many times over. Taking hydropower and other forms of electrical generation into account, Europe and China produce comparable levels of renewable energy, and many other regions are in hot pursuit.

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Global renewable electricity production by region, historical and projected. Source: International Energy Agency.

Many of the engineers who will propel the world into a more sustainable future are training in today’s elementary classrooms. The skills they’ll need as future problem-solvers can and should be learned now. AstroCamp’s newest curriculum offering encourages young people to practice the engineering cycle in an environment that balances collaboration, friendly competition, and real-world relevance.

WW KeyCroppedTheir goal: Create, through several iterations of design and testing, a turbine to maximize power production from a model wind source, then team up with classmates to power a LEGO skyscraper!

 

Tabletop Rockets Science

Temperature is a measure of energy. Adding energy to a substance makes it hotter; removing energy makes it colder. Warm, energetic molecules move faster and farther, spreading out over a larger volume of space.

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This balloon has been cooled to hundreds of degrees below zero (Fahrenheit), condensing the gas molecules inside. At room temperature, the condensed gas spreads out and expands, stretching the balloon back out to its original size!

We can make a gas less dense by heating it up. Less dense substances float in denser substances. This is how hot air balloons work! The warm gas inside is thinner and lighter than the air outside, so the balloon rises up through the thicker, heavier air around it. In this experiment, we’ll harness the temperature-dependence of density to turn ordinary tea bags into miniature rockets.

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Step 1: Cut the staple, string, & folded paper away from the top of the tea bag. Step 2: Empty & unfold the bag to form a cylinder. Step 3: Ignite the rocket from the top.

Tea bags work well for this demonstration because they’re light, flammable, and conveniently shaped.  Emptying and unfolding the bag yields an open-ended cylinder. As the delicate paper burns, the air inside the cylinder heats up and becomes less dense. At the same time, some of the tea bag is converted to smoke, leaving a super-light skeleton of ash behind. Takeoff occurs when the structure becomes so light– and the air inside so thin– that the rocket is, overall, less dense than the air around it.

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WARNING: flaming tea bags follow unpredictable flight patterns. If you try this experiment at home, be sure to choose a non-flammable setting, and keep a fire extinguisher handy.

Kids And Their Robots

Rough terrain. Unsurpassable obstacles. Navigating the rocky unknown with little help from home. These are the challenges space robots face as they explore distant worlds and the engineering problems tackled by the teams that design the rovers. Grade school might be a little early for NASA recruiting, but it’s a great time to start playing with the endless possibilities of robotics! At AstroCamp, kids create LEGO rovers to surmount all kinds of space-like challenges. The rovers must handle uneven ground, avoid unclimbable walls and murderous drop-offs, and collect samples to bring back to home base. It’s not just a building challenge, either! Students program their robots to get the job done with minimal human interference.

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In advanced classes, pairs of young engineers invent & build robots from scratch. Each step of the process requires teamwork, creativity, and plenty of persistence. Campers quickly discover that programming is rarely a one-shot deal. They learn that the best line-following robots take their time, and that adding a sensor or claw often means tweaking programs to account for the extra weight. Like grown-up rocket scientists, they must revise and re-test their design to develop it into a working system.

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In space, the tactical difficulties of pushing the final frontier ever outward have led to some truly awesome machines. Curiosity was lowered to the Martian surface from a hovering sky-crane– and that’s after riding the thin local atmosphere to a screaming halt with the help of a giant supersonic parachute. Curiosity’s predecessor, Spirit, crashed into the red planet amidst a cluster of airbags, coming safely to rest after a series of bounces up to 5 stories tall. Philae, the lander Rosetta dropped onto a comet last year, wields harpoons inside its washing-machine-sized body, designed to help anchor the lander in a spot where its solar panels could charge. Unfortunately, the harpoons didn’t deploy on impact, but what an idea! Space inspires incredible robotic inventions.

At the middle and high school level, robotics lays the foundation for a lifetime of problem-solving on Earth and beyond. Students learn that failure provides valuable insights. They experience trial and error as necessary steps in the innovation process. They also gain practical knowledge as they’re exposed to the basics of design and programming, making them less likely to be intimidated by future engineering opportunities.

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Aerodynamics, Fire, & the Coanda Effect

Imagine a torpedo in a wind tunnel. Incoming air slips around the torpedo’s nose, slides along its surface, and flies off its blunt back end. The air stream can’t navigate sharp corners, but as long as a smooth contour is available, it clings to that curve. This is called flow attachment, or the Coanda effect.

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The Coanda effect on an airplane wing.


Image source: http://cdn.theatlantic.com/static/mt/assets/jamesfallows/angleOfAttack.jpg

A fluid is anything that can flow freely– think water or air. Thanks to the Coanda effect, we can get a stream of fluid to go anywhere we want by giving it a smooth surface to follow. Helicopters and other VTOL aircraft use this principle to enhance lift! If a blade contour is smooth everywhere except a single edge, then that edge is where passing air slides off (just like in the image above). If the edge is angled towards the ground, then the air moves downward as it leaves the blade surface. Every action has an equal and opposite reaction; in this case, the downward momentum of the air translates to upward momentum of the aircraft. This isn’t the main way that airplanes gain altitude (that’s the Bernoulli effect), but it’s a useful way to improve performance. The Coanda effect can triple the Bernoulli lift on a blade or wing!

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In this experiment, we put a cylindrical container in the path of a breath of air and attempt to blow out a candle on the other side. The air stream splits in two and follows the curved surface. There’s no sharp edge for the two halves to slide off of, so they hug the contour of the obstacle until they run into each other on the far side. The collision redirects the flow, causing a burst of air to continue on past the cylinder– almost as if it wasn’t there.

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Try it for yourself with a round container and a candle! Please use adult supervision testing experiments using fire.

Hydrophobic Nanotech: Magic Sand

You’ve probably seen how oil and water get along (or don’t), but did you know that this behavior could help control oil spills and alleviate desert water shortages? Oil isn’t the only substance that doesn’t want to associate with water. One innovation that has harnessed the power of water resistance is hydrophobic (“water-fearing”) sand. Sand1

Marketed as Magic Sand in the toy industry and Nano Sand for more practical purposes, hydrophobic sand begins as normal beach dust. A trimethylsilanol vapor treatment coats the grains in non-polar molecules –– the same kind of molecules oil is composed of — making them unlikely to interact with water. You can actually see a silvery coat of air form around the sand when it’s submerged!

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So, why does this work? Let’s think for a moment about what polar and non-polar mean. Water is a great example of a polar molecule! Here’s a picture of the basic structure of H2O:

h2o

Image courtesy of http://butane.chem.uiuc.edu/pshapley/Enlist/Labs/Clouds/Clouds.html.

As you can see, it’s not symmetric. The two hydrogen atoms (white) lean off to one side of the oxygen atom (red). In water, oxygen has a partial positive charge and hydrogen a partial negative charge. The offset position of these atoms gives the water molecule one positive side, where the oxygen sticks out, and one negative side, where the two hydrogens sit next to each other. In other words, the molecule has two poles. It’s polar! You’ve heard the phrase opposites attract. Water molecules are perfectly constructed to bind with other molecules that have positive and negative poles. Molecules without poles, however, are immune to this electromagnetic attraction. We call these kinds of molecules — you guessed it — non-polar. Non-polar molecules don’t have a positive or negative end. Try as you might to get them to bind with polar molecules, the two won’t mix. You’ll always end up with large clumps of polar molecules, large clumps of non-polar molecules, and not much interaction between the two.

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This assortative behavior has fantastic real-life applications. Mix non-polar hydrophobic sand with non-polar petroleum from an oil spill, and they’ll bind seamlessly until the mixture grows heavy enough to sink. This fix is currently too expensive for widespread use, but the science is solid.

Several years ago, hopes were high for water-repellent sand to act as an artificial water table below the topsoil in desert areas where agriculture is prevalent. The hydrophobic layer would increase time between waterings and protect plant roots from salts in the deeper soil. Promising as it sounds, there hasn’t been much recent news about this application. Magic Sand seems to be relegated to the toy industry for now… at least until the next time an engineering team gets hooked by its world-changing potential.

WELCOME TO OUR ASTROCAMP BLOG

We would like to thank you for visiting our blog. AstroCamp is a hands-on physical science program with an emphasis on astronomy and space exploration. Our classes and activities are designed to inspire students toward future success in their academic and personal pursuits. This blog is intended to provide you with up-to-date news and information about our camp programs, as well as current science and astronomical happenings. This blog has been created by our staff who have at least a Bachelors Degree in Physics or Astronomy, however it is not uncommon for them to have a Masters Degree or PhD. We encourage you to also follow us on Facebook, Instagram, Google+, Twitter, and Vine to see even more of our interesting science, space and astronomy information. Feel free to leave comments, questions, or share our blog with others. Please visit www.astrocampschool.org for additional information. Happy Reading!

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