Tag: ISS

Free Contact Lines
How a simple drop of water sits on a surface is a strangely complicated question. The answer depends on the droplet’s size, its chemistry, the roughness of the surface, and what kind of material it’s sitting on. Vetting the mathematical models that describe these behaviors is especially difficult since droplets often get stuck, or “pinned,” along their contact line where water, air, and surface meet.
To get around this issue, researchers sent their experiment to the International Space Station, asking astronauts to run the tests for them. Without gravity‘s influence squishing drops, the astronauts could use much larger droplets than they could on Earth. Larger drops are less likely to get pinned by a stray surface defect, so on the space station, astronauts could place droplets on a vibrating platform and observe their contact line freely moving as the drop changed shape. Under these conditions, the experiment tested many surfaces with different wetting characteristics, thereby gathering data to test models we cannot easily confirm on Earth. (Image and research credit: J. McCraney et al.; via APS Physics)
October 25, 2022
“The World Below”
Since the first cosmonauts and astronauts entered orbit around our planet, they’ve held a unique perspective. Thanks to the timelapse photography of recent astronauts aboard the ISS and the editing skills of photographer Bruce W. Berry, Jr, the rest of us can enjoy a taste of that viewpoint. Turn up the volume, fire up the big screen, and enjoy.
I particularly like how several of the sequences show off the depth of the atmosphere. Earth’s atmosphere is incredibly thin compared to the size of our planet – less than one percent of Earth’s radius – but thanks to the shadows that clouds cast on one another, you can really appreciate their height in sequences like the one at 2:26. (Video credit: B. Berry, Jr. using NASA footage)
February 27, 2019
Drinking in Space
Earlier this year, the Capillary Beverage experiment launched to the International Space Station with new open-topped “Space Cups” for astronauts to test. Now those of us back on Earth are getting a glimpse of the cups in microgravity action. The geometry of the cups is wide on the back-end with a tightening v-shape near the mouth. This shape guides the liquid by using capillary action to wick it toward the spout.
One of the key goals of the experiment was to observe how the liquid drained–what shape it assumed in the cup and where and how much liquid was left behind. The researchers want to compare the real-life performance of the cups with their numerical models and simulations, which will help design future microgravity liquid transport systems for fuel, waste management, and other applications.
Although the experiments have a wider purpose, the space cups also do a great job allowing astronauts to drink from more than just pouches. Check out the gallery demo above to see how they hold up against astronaut silliness! (Video and image credits: NASA/IRPI LLC, GIF source)
November 30, 2015
Get Your Own Space Coffee Cup
A few weeks ago, we reported on the espresso machine NASA and the ESA sent to astronauts aboard ISS. The Capillary Beverage Experiment, known colloquially as the “Space Coffee Cup”, is an accompanying project that aims to use our understanding of fluid behavior in microgravity to design an open cup that simulates earthbound drinking experiences. As you can see above, astronauts are already enjoying drinks with it. The cup’s special shape is optimized so that surface tension can replace the role gravity plays in drinking on Earth. Where we pour drinks on Earth, the cup wicks liquid to the spout using surface-tension-driven capillary action. Right now there are only a handful of 3D printed cups on-orbit and here on Earth, but the company that designed them wants to manufacture glass versions for use here on the ground. So if you’d like your own space coffee cup, be sure to check out their Kickstarter campaign! (Video credit: IRPI LLC; image credit: NASA/IRPI LLC; Kickstarter project link)
ETA: To those who have been asking, that’s European astronaut Samantha Cristoforetti, who is (clearly) a Star Trek fan. I believe she’s doing a tribute to Captain Janeway’s coffee. (Black.)
May 25, 2015
Espresso in Space
The International Space Station resupply mission launched yesterday included a long-awaited fluid dynamics experiment that offers astronauts a taste of home: the ISSpresso espresso machine. Built by two Italian companies, the specially-designed espresso maker contains a non-convectional heating system and high-pressure piping to safely enable proper brewing using real coffee while in microgravity. The machine is also ruggedized to withstand launch forces; prototypes were even dropped in drop towers to simulate microgravity brewing conditions. The machine dispenses the brewed espresso into plastic packets, but another experiment aboard the ISS, Capillary Effects of Drinking in Microgravity, includes 3D-printed cups designed to allow orbiting astronauts to sip their beverages from open containers without spilling. They’re an improvement on a design created by astronaut Don Pettit in 2008 while in orbit. The cup’s sharp interior angle causes surface tension and capillary action to wick liquid upward to the spout. (Image credits: Lavazza; NASA/Portland State University/A. Wollman)
April 15, 2015
Flames in Space
The jellyfish-like light show in the animations above shows the life and death of a flame in microgravity. The work is part of the Flame Extinguishment Experiment 2 (FLEX-2) currently flying aboard the International Space Station. When ignited, the fuel droplet creates a blue spherical shell of flame about 15 mm in diameter. The spherical shape is typical of flames in microgravity; on Earth, flames are shaped like teardrops due to the effects of buoyancy, which exists only in a gravitational field. The bright yellow spots and streaks that appear after ignition are soot, which consists mainly of hot-burning carbon. The uneven distribution of soot is what causes the pulsating bursts seen in the middle animation. When soot products drift back onto the fuel droplet, it causes uneven burning and flame pulses. The final burst of flame in the last animation is the soot igniting and extinguishing the flame. Fires are a major hazard in microgravity, where oxygen supplies are limited and evacuating is not always an option. Scientists hope that experiments like FLEX-2 will shed light on how fires spread and can be fought aboard spacecraft. For more, check out NASA’s ScienceCast on microgravity flames. (Image credits: NASA, source video; submitted by jshoer)
September 12, 2014
Spitting Droplets
Any phenomenon in fluid dynamics typically involves the interaction and competition of many different forces. Sometimes these forces are of very different magnitudes, and it can be difficult to determine their effects. This video focuses on capillary force, which is responsible for a liquid’s ability to climb up the walls of its container, creating a meniscus and allowing plants and trees to passively draw water up from their roots. Being intermolecular in nature, capillary forces can be quite slight in comparison to gravitational forces, and thus it’s beneficial to study them in the absence of gravity.
In the 1950s, drop tower experiments simulating microgravity studied the capillary-driven motion of fluids up a glass tube that was partially submerged in a pool of fluid. Without gravity acting against it, capillary action would draw the fluid up to the top of the glass tube, but no droplets would be ejected. In the current research, a nozzle has been added to the tubes, which accelerates the capillary flow. In this case, both in terrestrial labs and aboard the International Space Station, the momentum of the flow is sufficient to invert the meniscus from concave to convex, allowing a jet of fluid out of the tube. At this point, surface tension instabilities take over, breaking the fluid into droplets. (Video credit: A. Wollman et al.)
January 31, 2013
Science off the Sphere: Thin Films
Stuck here on Earth, it’s hard to know sometimes how greatly gravity affects the behavior of fluids. Fortunately, astronaut Don Pettit enjoys spending his free time on the International Space Station playing with physics. In his latest video, he shows some awesome examples of what is possible with a thin film of water–not a soap film like we make here on Earth–in microgravity. He demonstrates vibrational modes, droplet collision and coalescence, and some fascinating examples of Marangoni convection.
March 12, 2012
Cloud Streets from Space
Cloud streets flowing south across Bristol Bay hit the Shishaldin and Pavlof volcanoes, which part the air flow into distinctive swirls called von Karman vortex streets. As air flows around the volcano, a vortex is shed first on one side, then the other. Although the usual example for this type of flow is the wake of a cylinder, vortex streets can extend behind any non-aerodynamic body immersed in a flow. The same phenomenon is responsible for the singing of power lines in the wind. As astronaut Dan Burbank observes, “It’s classic aerodynamics, but on a thousands of miles scale.” (Photo credit: Dan Burbank, NASA)
January 12, 2012
Testing Flames in Space
In microgravity, flames behave very differently than on earth due to a lack of buoyant forces. On earth, a flame can continue burning because, as the warm air around it rises, cooler air gets entrained, drawing fresh oxygen to the flame. In microgravity, both the heat from the flame and the oxygen it needs to burn move only by molecular diffusion, the random motion of molecules, or the background environmental flow (air circulation on the ISS, for example). This video shows a test of the Flame Extinguishment Experiment (FLEX) currently flying onboard the ISS. A fuel droplet is ignited, burns in a symmetric sphere and then eventually extinguishes either due to a lack of fuel or a lack of oxygen. Check out this NASA press release for more, including great quotes like this:
“As a Princeton undergrad, I saw in a graduate course the conservation equations of combustion and realized that those equations were complex enough to occupy me for the rest of my life; they contained so much interesting physics.” – Forman Williams
December 13, 2011