Monthly Archives: November 2015

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.


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.


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.

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.

Happy Thanksgiving

Everyone knows that on Thanksgiving you eat lots of turkey and it makes you sleepy somehow…except that it probably doesn’t. There is a lot of information out there about this subject, and much of it seems to disagree with itself. Let’s examine the whole idea from the beginning.

Thanksgiving celebration and dinner

Thanksgiving celebration and dinner

Courtesy of Rutgers University

It all starts with proteins, which are large molecules that facilitate a tremendous number of different functions within living organisms like humans. Proteins are kind of like words, except instead of being made up of letters, they are built from amino acids. There are twenty different amino acids, and they make up the protein alphabet. By putting these in different sequences, proteins can be varied just like words with different combinations of letters. However, unlike words that might be ten letters long, the average protein in humans is just under 500 amino acids in length*!

One of these amino acids is called tryptophan, and it can be found in turkey! This particular amino acid is involved in a biochemical pathway that produces serotonin, which in turn produces  is often associated with positive emotions, where melatonin helps the body keep up with the day-night cycle by anticipating darkness and contributing to feelings of sleepiness. So far so good! Turkey has tryptophan and tryptophan turns into something that makes you sleepy!



The problem is that turkey doesn’t have very much tryptophan. Most amino acids come from food, and many foods have much more tryptophan than the delicious main course for Thanksgiving. Some have suggested that the unique combination of tryptophan-filled turkey and carbohydrates on Thanksgiving could help enable the tryptophan-to-melatonin pathway. While there may be some truth to this, cheddar cheese contains more tryptophan than turkey and a grilled cheese sandwich would meet the same requirement, yet somehow nobody seems to have heard of the Great Grilled Cheese Nap-ternoon Effect [not a real thing].

Tryptophan Chart

Common foods tryptophan contents compared to turkey. Source: (see above)

Still, many people can anecdotally recall just how tired they are on Thanksgiving, and this whole myth had to come from somewhere. There are likely a few contributing factors which are admittedly a little less fun and definitely sound less cool and scientific. First of all, people often feel fatigued after lunch as their bodies turn their attention to digestion, a phenomenon not unique to the holiday feast. In addition, everyone hears about how tired Thanksgiving should make them, which leads to something called the placebo effect, essentially making people tired because they think they should be.  On top of that, Thanksgiving often has the wonderful effect of bringing families together…which results in lots of travel, cleaning, discussion, cooking, and football without a lot of time for sleep. Sounds like a great recipe for a tired afternoon.

Happy TG JPL

AstroCamp Staff visiting JPL earlier this year!

*How Big is the Average Protein,


The Speed of Fire

How fast is fire? We sent a burst of flame through a fluorescent light tube to explore the propagation of an alcohol-burning reaction along an enclosed path. In our experiment, the frontier of flame sped along at over six feet per second. Fire behaves very differently in other environments. In space, combustion becomes almost unrecognizable.


Gif: SpaceFire1

Flames speed along the tube, rebounding at each end.

Fire heats the air around it, causing molecules to speed up and spread out. On Earth, warm air rises as the cooler, thicker surrounding atmosphere sinks towards the base of the flames. This current delivers fresh oxygen to the base of the fire, and it continues burning for as long as the fuel supply lasts. In space, there’s not enough gravity to pull the cold air down, so flames burn spherically. Without the pull of a convection current, oxygen isn’t carried to the source of the reaction; instead, it diffuses into the fire. Random motion of air molecules isn’t a very efficient way to bring oxygen and fuel together, so flames in microgravity burn out much more quickly than we’re used to seeing here on Earth.


In microgravity, flames are shaped like spheres instead of teardrops. This color image is from the FLEX (Flame Extinguishment) experiment on the ISS. Image credit: NASA/GRC

Fire is a serious hazard on a spacecraft because there’s nowhere to escape to. Reliable fire-extinguishing technology is a vital part of safe, sustainable space travel. Strategies that work well on Earth, however, don’t always do the trick hundreds or thousands of miles above its surface– new tactics are required. In the last several years, combustion experiments on the ISS have begun to reveal the mysterious and fascinating behavior of fire in microgravity.

A few years ago, scientists studying space combustion noticed something phenomenal going on after their experimental flames died out: the fuel kept burning. No visible light was emitted, and the reaction was much cooler — around 700 degrees Fahrenheit instead of the usual 2500 or so — but the fuel burned away nonetheless. This behavior isn’t usually observed on Earth, but if we can find a way to replicate it consistently, it could be used for applications such as low-emission auto engines.


A droplet of heptane fuel burns in microgravity in this false-color time-lapse image. The droplet appears yellow and becomes smaller as it burns. Green areas are initial soot structures. Image credit: NASA

Microgravity research is already yielding exciting knowledge about the nature of fire outside of Earth’s influence, and there’s much more to come. Dr. Forman Williams, UC San Diego, is one of the investigators working on the FLEX-2 experiment to demystify space combustion. In 2013, he summed up the state of the field: “when it comes to fire, we’re just getting started.”

The Circle of Electromagnetism

Electricity is one element of physics that we encounter on a daily basis. It powers our televisions and our computers, and keeps the lights on at home. Magnets are something we think of as less common, only using them when we need to navigate using a compass or stick something to our fridge. But electricity and magnetism are really just two sides of the same idea!

We can see some examples of this relationship using the induction coil. There are two parts, so let’s tackle them one at a time. First, whenever electricity runs through a wire, it creates a magnetic field. If the wire is in a circle, the magnetic field will be the strongest through the middle. By stacking up several loops of wire to make a coil, we can create an electromagnet.


Electromagnetism at AstroCamp. Pressing the button sends electricity through the wire solenoid which is coiled around a nail to create a magnetic field.

Not only can electricity be used to create a magnet, but magnetism can be used to create electricity. When a conductor, like a metal wire, experiences a changing magnetic field, an electric current is created. We can even use this electricity to power a lightbulb! This process is called induction, and it is the basic principle by which electricity is generated in almost all power plants.


Strong neodymium magnets are rotated inside a coil of copper wire, producing a current. The needle moves back and forth, indicating the the current produced in this way is alternating, or AC current.


This wind farm in Palm Springs employs this exact technology to generate electricity from the wind! Photo from best of the best tours!

If you want to learn more about these concepts or just see them in action, there is more about them here and hereCombining both of these ideas, we can see why the small metal ring hovers. Turning on electricity through the coil of wire creates a magnetic field that is felt by the metal ring. Then, through the process of induction, electricity is created in the ring, as you can see with the light bulb example below.



The ring is now an electromagnet with electricity running through it! The magnetic field from the ring and from the coil are pointed in opposite directions, so they repel, causing the ring to hover in midair. By submerging the ring in liquid nitrogen, we can lower its resistance and increase the electric current. A stronger current creates a stronger electromagnet and the ring shoots up to the ceiling!

DIY Moon Science

Earth’s gravitational force pulls on all objects equally, speeding them up with an acceleration of 32 feet per second per second. This means after one second of falling, an object will speed up to 32 feet per second, or about 22 miles per hour. After two seconds, that will double to 64 feet per second (or about 44 mph). Any object dropped near Earth WILL feel this acceleration.  However, this is only part of the story.

As an object moves through the atmosphere, it runs into trillions upon trillions of tiny obstacles– air molecules. More collisions equate to more air resistance. Something that’s light and has a large surface area in its direction of movement, like a parachute, loses a lot of speed as it plows through the atmosphere. Heavier or more streamlined objects aren’t so easily slowed down as they travel through the air.

Orion Parachute

 The Orion Spacecraft descends safely to a gentle splashdown landing last December under the care of three large parachutes. Photo from NASA.

A good ratio of mass to forward-moving surface area is one way to be aerodynamic. Another way to move quickly through the atmosphere is to follow close behind something that’s clearing air molecules out of the way, like one cyclist drafting another in a race.

gif 2 [Paper]

Paper has low mass and high air resistance. Here, the book clears air molecules out of the way, so the paper falls straight to the ground at the same speed as a book! You should try this simple DIY experiment!

To see this idea in action, grab a book and a sheet of paper of about the same size. Drop them side by side and notice the difference. Both have similar air resistance, but the book’s greater mass means that it doesn’t decelerate as easily as the single sheet. Now try placing the paper on top of the book and dropping both at once. With the book clearing the way, the sheet of paper doesn’t have anything to run into, and it falls at the same rate as its heavier companion!

Apollo 15 Commander David Scott performed a similar experiment before coming home to Earth. Thanks to the moon’s extremely thin atmosphere, a hammer and a feather dropped side by side hit the ground at the same time.

Check out the full video below:

The Invisible Fire Extinguisher

You’ve heard of fighting fire with water, but did you know that gases also have the power to douse flames? A gas can smother a blaze by creating a barrier between burning fuel and nearby air.

Extinguisher1Removing any of the three requirements for fire stops the combustion reaction. Image credit: Ohio Northern University

Fire needs three things to burn: fuel, energy (heat), and oxygen. Take away any of these, and the combustion reaction can’t go on. Carbon dioxide gas is denser than air, so it sits nicely in a container and falls down like water when poured out. It’s also non-flammable, so it smothers burning fuel.

In this experiment, we scoop carbon dioxide gas into a pitcher, then pour it down a tube towards a row of candles. It’s invisible, but its interaction with the flames reveals its presence. As CO2 engulfs each candle, it isolates the wick from the surrounding oxygen. Without oxygen, the burning reaction stops!


Many household and industrial fire extinguishers take advantage of this science. Under high pressure, a lot of CO2 can be stored in a small space. Red canister extinguishers often contain reserves of carbon dioxide gas, ready to separate oxygen from burning fuel in an emergency.

Carbon dioxide is also stored under high pressure in the lab. When released into a container at room temperature, it condenses into a very cold solid– touch it for more than a split second, and you’ll experience the burn-like symptoms of contact frostbite.

You may know solid CO2 better as dry ice! Dry ice gets its name from a peculiar behavior: when it melts, it doesn’t make a puddle. This transition, straight from solid to gas without passing through a liquid state, is called sublimation.


Water can sublimate, too! Mt. Everest, with its high altitude, low pressure, dry air, and strong sunlight, is one place where ice turns directly into vapor. Image credit: Benjamin D. Oppenheimer (

Modeling Outer Space

You’re carrying an awful lot of weight right now. It’s hard to tell, but every square inch of you is supporting fifteen pounds of atmospheric pressure! Multiply that by the number of square inches on the surface of a human body, and you’ll find you’re bearing a hefty load.


Atmospheric pressure results from the weight of the air above you. Credit: Peter Mulroy,

Our senses don’t usually register atmospheric pressure because it’s part of our natural habitat. It’s easier to observe the significance of the air around us by removing it and seeing what happens. You don’t know what you’ve got until it’s gone! The vacuum chamber is the perfect tool for exploring atmosphere-free science.

One of the most telling differences between solid, liquid, and gaseous states is the way each one occupies space. A solid object keeps both its size and its shape, no matter where you set it down. A liquid changes shape to match the container that holds it, but still takes up a fixed volume of space.  Gases follow no such rules. The molecules in a gas will spread out indefinitely, filling any space available. We can observe this by trapping some gas in a stretchy container and exposing it to vacuum conditions.


At the microscopic level, a marshmallow is a sugar-and-gelatin sponge full of tiny air pockets. In other words, it’s a stretchy (and delicious) container with gas trapped inside! When we remove the air around the marshmallow, the gas within expands to fill the surrounding vacuum. The bubbles stretch bigger and bigger until they pop and the air escapes. When the air returns, there is nothing inside the tiny bubbles of the marshmallows, so they shrink back down below their original size.

Water is another interesting low-pressure test subject. By removing the air nearby, we effectively lift fifteen pounds of weight from each square inch of the water’s surface. This does not mean that the water is getting hotter. Instead, the drop in pressure brings the boiling point of the liquid down below room temperature.


Water in a vacuum evaporates rapidly at room temperature. Newly formed water vapor condenses on the inside of the chamber, running down in droplets.

Happy Anniversary, Humans in Space!

November 2, 2000. It was a dark night on our planet. More than 200 miles above Earth’s surface, a Soyuz rocket began a slow dance in the bigger darkness of space. The docking sequence took three hours and forty minutes. At its end, the International Space Station welcomed the first of hundreds of human residents. The outpost has been inhabited ever since.


Expedition One crew members pose after water survival training. From left: Flight Engineer and Russian Cosmonaut Sergei Krikalev; International Space Station Commander and U.S. Astronaut Bill Shepherd; Soyuz Commander and Russian Cosmonaut Yuri Gidzenko. Credit: NASA

Bill Shepherd, Yuri Gidzenko, and Sergei Krikalev passed 4 busy months on the ISS. First, they moved in. Critical life support systems waited to be set up. Supplies needed unpacking. After waking up the station and settling themselves, the astronauts hosted visiting crews, received unmanned spacecraft, made improvements to the station, and conducted research. Their work set the precedent for the next decade and a half of sustained experimentation in low Earth orbit.


Shepherd rehearses an extravehicular activity (EVA) mission in Russia’s Hydrolab training facility. Scuba divers stand by to assist. Aquatic neutral buoyancy practice is a key component of astronaut training around the world. Credit: NASA

Since Expedition One, over two hundred astronauts and scientists have spent time on the ISS. Cool-burning flames have been studied and extinguished in microgravity. Lettuce has flourished in space. Students have peered through digital windows from their classrooms into our planet’s most distant human-operated research lab.

The station has built a foundation of knowledge about space travel’s effects on the human body. That knowledge is expanding even further thanks to identical twin astronauts Scott and Mark Kelly. Scott recently broke the record for most time spent in space, just over halfway through his year of orbital residence. Mark holds down the fort on the ground. The Twins Study includes ten independent investigations of everything from physiology to behavioral health to space-induced genetic changes.


Veggie, the plant growth system used on the ISS, basks in energy-efficient LED light. Credit: NASA/Orbital Technologies

These are just a few of the many imaginative, futuristic ISS experiments bringing home big benefits. Technology driven by space-based farming research keeps produce fresh in supermarkets worldwide and aids food preservation in developing countries. Climate scientists use the unique perspective of low Earth orbit to better predict and respond to natural disasters. The Twins Study deepens our understanding of ourselves as a species. Space poses unique problems that stretch the margins of human creativity and cleverness. Rising to these challenges not only brings us closer to interplanetary travel, it also motivates life-changing science right here on Earth.


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