Tag Archives: public programs

How Kites Fly

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Recently the National Air and Space Museum hosted Kites of Asia Family Day.  It featured lots of kite activities, cultural crafts, indoor kite flyers, and Japanese kite masters.  All of the incredible kites and amazing activities made me wonder how many people actually understand how kites fly.

To understand how a kites flies, you need to define what a kite is.  A kite is a heavier-than-air object that flies… just like an airplane.  Most kites have three main components: the kite body (which comes in many different shapes and sizes), the bridle (or harness), and the control line (or tether).  The kite body is made up of a framework and outer covering.  The framework is usually made from a lightweight material like wood or plastic.  Paper, fabric, or plastic is then stretched over the framework, turning it into a sort of wing.  The bridle and the control line help the kite flyer control the kite.  In flight, the kite is connected to the kite flyer by the control line, which is connected to the kite by the bridle.  The kite pivots and dives about the point where the bridle connects to the control line.

kite diagram

Kite diagram

The four forces of flight (i.e. Lift, Weight, Drag, and Thrust) affect kites in the same way they affect airplanes, and anything else that flies.  Lift is the upward force that pushes a kite into the air.  Lift is generated by differences in air pressure, which are created by air in motion over the body of the kite.  Kites are shaped and angled so that the air moving over the top moves faster than the air moving over the bottom. Daniel Bernoulli, an 18th century Swiss mathematician, discovered that the pressure of a fluid (like air) decreases as the fluid speeds up.  Since the speed of the air above the kite is greater than the speed of air below, the pressure above is less than the pressure below and the kite is pushed into the air and — Tada — lift!  Weight is the downward force generated by the gravitational attraction of the Earth on the kite.  The force of weight pulls the kite toward the center of the Earth.  Thrust is the forward force that propels a kite in the direction of motion.  An airplane generates thrust with its engines, but a kite must rely on tension from the string and moving air created by the wind or the forward motion of the kite flyer to generate thrust.  Drag is the backward force that acts opposite to the direction of motion.  Drag is caused by the difference in air pressure between the front and back of the kite and the friction of the air moving over the surface of the kite.  To launch a kite into the air the force of lift must be greater than the force of weight.  To keep a kite flying steady the four forces must be in balance.  Lift must be equal to weight and thrust must be equal to drag.

Wind is obviously a big part of kite flying.  But what do you do if you don’t have any wind or you’re trying to fly your kite inside?  Check out the video of this national champion indoor kite flyer from the family day.  There obviously wasn’t any wind inside, so how was he able to fly kites in the middle of the Space Race gallery?  The kite flyers create lift, drag, and thrust with various walking patterns, arm movements, and spinning to make the indoor kite flying experience like a dance.  Whether inside or out it doesn’t matter whether the wind moves over the surface of the kite or the kite is pulled through the air — lift must overcome weight and thrust must overcome drag to keep the kite soaring.

To learn more about the four forces of flight visit the How Things Fly website.  And to learn more about the aerodynamics of kites and experiment with different kites, visit the NASA website.

Michael Hulslander is manager of onsite learning at the National Air and Space Museum in Washington, DC.

Learning to Capture the Sun

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The Public Observatory Project is just over a year old now, and in that time we’ve been  experimenting with the telescope to discover what is visible in the daytime sky and devise ways that our visitors can have the best experience possible.  One of our goals is to use our equipment to take images of the Sun, so that we can share our star’s day-to-day activities with the visiting public as well as those who can’t make it to the Mall to look through our telescopes.  We wanted to capture true-to-life images of the Sun as it appears through our telescope and make interesting features clearer and more apparent.

It would be dangerous to use a normal telescope to look at the Sun because the Sun’s concentrated and unfiltered light would damage your eyes.  One of the tools we use to look at the Sun safely is our Lunt Solar Systems hydrogen-alpha telescope that filters out all but one wavelength of red light. This makes it safe for viewing a part of the Sun’s atmosphere, called the chromosphere.  To take images of the Sun, I started out with this telescope, as well as a Lumenera SKYnyx 2-0 Color camera that fits where the eyepiece usually goes. We also have a laptop with software to control the camera, called Lucam Recorder.  With these in hand, I set off to take some of my first images of the Sun.

sun

This image of two prominences was taken on June 8, 2010.

Through some experimentation, I found out that different exposure settings revealed very different details on the Sun. First I cranked up the exposure to capture the faint prominences coming off the edge of the Sun and took a series of images. Next, I turned down the exposure to what I thought was an appropriate level to capture details on the Sun’s surface before taking a second series of images. I used a processing program called the GIMP to merge the two images by selecting the disk detail and moving it on top of the prominence image.  But, something wasn’t quite right. This didn’t look much like what I was seeing with my own eyes. So, I turned to a local amateur solar imaging expert and friend of the National Air and Space Museum: Greg Piepol.

Greg’s solar imaging work, which you can check out on his website sungazer.net, has been praised for its beauty and attention to detail. My colleague at the Observatory and fellow Sun imager, Katie Moore, and I were thrilled that he agreed to come into the Museum and show us how he captures such stunning images.

Greg taught us several things that improved our imaging. The first and most important was that we had been drastically overexposing the disk of the Sun, which washed out the details we were trying to capture. Greg also taught us how to better use an image stacking program called Registax, which takes individual frames from a movie file and stacks them together, thereby removing a lot of noise caused by Earth’s turbulent atmosphere. Astronomers call this “seeing,” which is what makes the stars twinkle. He also showed us other image processing techniques in the GIMP, such as levels adjustment and color correcting that brought out details on the Sun.

sun

This image was taken on July 28, 2010, the day after Greg Piepol came to visit. The small dark Sunspot near the top of the disk is about the same size as the Earth!

This was most certainly closer to what we had seen in the telescope. But of course, as they say, practice makes perfect. Over the next few months I took pictures as often as I could. I learned the extreme importance of making fine adjustments to the filters inside the telescope to get exactly the right details. I learned the advantages of using a double-stacked filter on top of our telescope to help make the darker wispy absorptive lines in the solar atmosphere, called filaments, truly pop out.  I also learned the importance of careful processing to coax the most detail possible out of the raw data.  It is interesting to compare the final product to one of the raw, unprocessed images to see what a difference it makes.

This is a single frame from the raw video before the image is processed

This is a single frame from the raw video before the image is processed

sun

This final processed image of a Sunspot was taken on July 30, 2010

A large prominence on the Sun, taken on September 15, 2010

A large prominence on the Sun, taken on September 15, 2010

This mosaic of 2 images highlights a large Sunspot group, as well as a dark filament in the Sun’s chromosphere.

This mosaic of 2 images highlights a large Sunspot group, as well as a dark filament in the Sun’s chromosphere.

And so, the journey continues! The Sun is always changing, and there are always more techniques to be learned and perfected. If you get the chance, come see the Sun for yourself at the Public Observatory, which is open Thursday through Sunday, 11 am to 3pm for the month of October, weather permitting.  We are ordering an upgraded camera and some new software to better process these images, so be on the lookout for new images online!

Erin Braswell is an Astronomy Educator at the National Air and Space Museum.

Spacesuit in need of repair

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I have a really cool job.  When I’m out and someone asks: “What do you do?” I reply: “I work at the National Air and Space Museum.”  The response is usually: “Wow, that’s cool” and then I say: “Yes it is very cool.”  One of the things that makes being an educator here great is our teaching collection. I’m lucky, I work with a curatorial and collections staff that considers our needs as educators and provides the public with deaccessioned items they can touch and examine up close.   Our teaching collection currently contains real space food, shuttle tiles, bits of airplanes, meteorites, uniforms and other assorted items.  However, not all the items are real; our most popular replica is the shuttle era space suit.  The suit has been part of the Discovery Station Program for over ten years.  It was purchased with a grant from the Smithsonian Women’s Committee and is part of the Living and Working in Space Discovery Station, our most popular station, largely because of the suit.  The station gets an average of 40,000 visitors yearly, but that’s only a portion of the crowds the suit sees.  It has also become a key object used for family days, story times and school tours.

Mock Space Shuttle Suit

Mock Space Shuttle Suit

Beth Wilson demostrates dressing for spaceBeth Wilson demostrates dressing for space.

Beth Wilson demonstrates dressing for space

During the summer of 2006, I was rolling the suit back into its case and the glove fell off.  I took a good look at the suit and was distressed to see how it was aging.  Hundreds of thousands of hands touching it over the years had taken their toll. But I allowed it to be used with the public while I pondered where I could find $45,000 to replace it.  With no funding forthcoming, the suit just wouldn’t survive another busy season. I decided that it should remain on view in its case and brought out only for special programs.

As the Museum’s Development office looked for funding sources, someone mentioned our aging suit to ILC Dover’s Bill Ayrey.  ILC Dover is the company that designs and manufactures NASA’s space suits, beginning with the Apollo Missions.  Bill generously offered to repair the suit.   So, last fall Bill drove down, picked up our suit and took it to ILC Dover.  The very talented seamstresses sewed on new arms, Bill cleaned the pants, re-stuffed the suit, acquired recent mission patches and updated the gloves.  The crew at ILC Dover could not have been more helpful or generous with their time and talent. I am grateful for all the effort that went into the refurbishment.  I can honestly say it looks brand new.  In fact, Bill and his crew did such a good job that an ILC employee mistook it for a real shuttle suit!

ILC Seamstresses pose with the newly repaired suit

The suit made it back to the museum last month. I was on the phone with a colleague at another museum when the call came in that Bill had arrived.  I told her: “I’m sorry.  I’ll have to call you later, my space suit is back from ILC!”  To which she replied: “You have the coolest job ever.”   “Yes,” I said. “Yes, I do.”

Beth Wilson is the Discovery Station Program Coordinator at the National Air and Space Museum.

Catching Rays

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As spring quickly approaches and being outside is becoming more and more inviting, we Public Observatory staff continue to enjoy spending time outside with our portable telescopes.  Every sunny day between 12:30 p.m. and 2 p.m., except for Mondays, we invite visitors near the Independence Avenue entrance to take a look at the sun through our specially equipped telescopes.

Observing

The Sun is approaching the active portion of its 11-year cycle, so visitors these days are now more likely to catch a glimpse of an interesting feature on the surface of the Sun.  Many visitors have been able to observe dark sunspot groups in our white light telescope, or spy an interesting prominence in the sun’s atmosphere through the telescope equipped with a hydrogen alpha filter.  However, the sunspots eventually move out of view and the prominences stop being quite so, well, prominent.

Luckily, there is a way to preserve these fleeting features so that all visitors will get a chance to see them regardless of how the sun chooses to behave that day. We have started taking pictures of the Sun’s interesting features through our different telescopes.  Here are those images for your viewing pleasure!

Sun

Here is an image of the Sun that was taken right here at the Museum on February 18th. In order to capture this image, we used a camera attached to our hydrogen alpha telescope. This telescope reveals the Sun’s chromosphere, filtering out all light except the red light given off by excited hydrogen atoms.  This image shows the two large prominences that appeared on the Sun that day. You can also see some surface texture on the Sun, which is called granulation. If you were to look through our hydrogen alpha telescope, this is pretty much exactly what you’d be able to see!

Progresssion

We took pictures later on in the day to see how the prominence changed, and could take pictures the next day as well. Over time, this loop prominence became twisted before disappearing from our view.

Sun

We took this picture of the Sun’s chromosphere with our Calcium-K telescope on March 4th. The Calcium K telescope filters out all but the purple light coming from excited Calcium atoms in the Sun’s atmosphere. You might notice a few brighter spots on the Sun’s surface, especially near the top right. These are hotter areas on the Sun called plages (pronounced like you’re saying “blah” except with a p).

Super Prom

We took this image of a super-prominence in the chromosphere of the Sun using our hydrogen-alpha telescope on March 17th.  This prominence is truly gigantic; it’s about 5 earths tall 22 earths long!

While these pictures are pretty great, nothing quite compares to seeing the sun live through a telescope. It’s always exciting to see what the Sun is up to on any given day. We’re outside the Museum every sunny day except for Monday between 12:30 p.m. and 2 p.m., so stop by and catch a few rays!

Erin Braswell is an Astronomy Educator at the National Air and Space Museum