Monthly Archives: April 2011

ISS Research in the Decade Ahead

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International Space Station astronaut Suni Williams recently addressed a symposium at the AAAS (American Association for the Advancement of Science) annual meeting regarding research in extreme environments. In this entry for A Lab Aloft, she shares her perspective on extreme research on the International Space Station.

The upcoming decade of utilization is an exciting time for the International Space Station. As an astronaut, I had the opportunity to help build the station, to live and work on it, and I hope to go back someday. I think many people are unaware of the different aspects of this incredible laboratory: the various control centers; the communications that are involved just to prepare, make, and operate the station; as well as the different countries involved. Just providing operations for the station requires a tremendous amount of communication and control. And for the last 10 years, the station has also been furthering science.

There are fascinating opportunities for scientists with the space station going forward. An awareness of this can spur on ideas of ways to do investigations in space. Just looking at the science that has already been done during the last decade of assembly is inspirational. Think about it; when building projects are being erected, they do not usually operate at the same time. Take a hospital, for instance—it does not take patients while under construction. When you sit back and look at how much research was done while the station was under construction, it is pretty amazing.


Astronaut Sunita L. Williams, Expedition 15 flight engineer, performs one of
multiple tests of the Capillary Flow Experiment (CFE) investigation in the
Destiny laboratory of the International Space Station. CFE observes the flow
of fluid, in particular capillary phenomena, in microgravity.
(NASA Image ISS015E05039)

Compared to other laboratories, being in such a harsh environment adds some unique challenges. It also requires a lot to take care of it. When a toilet brakes, when the oxygen generation system does not work, when a solar array does not supply power, the crew are the only six people who can and have to go out and fix things. Control systems have to be maintained and this reduces the amount of science we can get done, compared to six people in a friendly environment here on Earth.

One of the main differences between the space station and other laboratories is that most labs work on only one experiment discipline, perhaps with variables. On the station, however, you really have to multitask; there are so many different investigations that people have wanted to do for a long time: biology and biotechnology, Earth and space sciences, education, human research, physical sciences, and technology. In a given day you could be doing experiments in all of these fields, which is different from other labs.

When interfacing with primary investigators on the ground, they are the scientists and I am somewhat of a tech operator while on the station. Astronauts are the hands-on connection, and there are good and bad parts to that. Sometimes we may need coaching from the investigator, but in exchange we bring an untainted perspective. We know what to look for from training, but we may notice some phenomenon that raises questions. This interaction is known as the human in the loop and it is really necessary. For instance, I was able to make unexpected observations for the Capillary Flow Experiment during my time on the space station. It was exciting to help scientists make new discoveries! There are some experiments we can automate 24/7, but others we don’t really know if we will find something without a critical eye observation.


Astronaut Sunita L. Williams, Expedition 15 flight
engineer, works at a portable glovebox facility in the
Destiny laboratory of the International Space Station.
(NASA Image ISS015E08308)

Now that I have returned from my work on the station, I am amazed to see the results coming out. For instance, there has been some exciting progress in vaccine development and even an approach to delivering a chemotherapy drug, due to space station investigations. This research is targeted to benefit people all over the world.

We all have to be a little bit patient, however, in waiting for such findings. For instance, I flew in 2006 and it is now 2011 and we are just now starting to see these positive results. What is encouraging now is that since science experiments have been going on, they are building upon themselves and yielding results. Follow-up experiments will continue to further investigate the problems and seek answers. I think getting concrete results is the most rewarding part of working on the space station and now is the time that we should start seeing it more frequently as science experiments get done.

We have a decade to use this lab, and it is time to start investing in the work. We are going to have humans in space for the next 10 years living and working on the station. The research and technology testing will provide us enough data and information for us to smartly build the next spacecraft to take us a little bit further. We need to find out things about the human body, the atmosphere, the spacecraft and how it is surviving. We are investigating things that happen in low earth orbit, and this gives us the confidence for humans to go one step farther. So I hope this is the stepping stone and inspiration for the next generation of explorers. We have to go someplace else.

Suni Williams is a NASA astronaut with and flight engineer for the International Space Station. She launched to the station on STS-116 (December 22, 2006) as part of Expedition 14 and Expedition 15, returning to Earth with STS-117 (June 22, 2007). During her increment in space, Williams set a new record for females of 195 days in space. In today’s blog, Williams shares her thoughts and perspective as a crewmember aboard the International Space Station with the readers of A Lab Aloft.



Boiling it down to the bubbles: It is about heat transfer

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This week, comments from guest blogger and International Space Station Associate Program Scientist Tara Ruttley, Ph.D., as she reflects on the physical science of boiling in space.

If you don’t think of yourself as the type of person who could ever be interested in physics, let’s boil this down.

You’re hungry. It’s pasta time. Your pot of water is on the stove, you’ve turned on the maximum heat, and the wait for boiling begins. You are staring impatiently at the pot when the water looks like it’s starting to swirl. You’re anxious to see the bubbles that signify that you can put your pasta into that water. But what do those bubbles tell you and what makes them the key indicator of perfect pasta water temperature?

 

 

On Earth, water boils via natural convection.
(Image courtesy of Markus Schweiss via Wikipedia)

 

To simplify a bit, boiling is actually a very efficient heat transfer process and, in this case, boiling transfers the heat from the fire on your stove to the water that will cook your pasta. It seems straight-forward enough here on Earth: you turn on the burner, wait a few minutes, and when all those small bubbles appear, you’re ready to get cooking.

As you wait for your pot of water to boil, there is a complex process going on in there. First, the liquid on the bottom of the pot closest to the heat source starts to get hot; as it does, it rises. The rising hot water is replaced by the cooler, more dense water molecules. The water molecules in your pot continually exchange in this way, thanks to gravity, eventually warming the entire pot of liquid. This is known as natural convection—the movement of molecules through fluid—which is a primary method of heat (and mass) transfer.

  

Without buoyancy or convection, boiling fluids
behave quite differently in space.
(Video courtesy of NASA)

 

But natural convection is not enough, as it does not yet provide those bubbles you need for your pasta. To get those bubbles, you have to wait long enough for the bottom of the pot to get hotter than the boiling point of the water. When the boiling point is breached, you finally begin to see the tiny bubbles of water vapor you’ve been waiting for! The bubbles rise, due to buoyancy, and then collapse as they reach the denser, relatively cooler water at the surface of the pot. This motion not only helps to move the water around more quickly (think stirring), but the bubbles themselves transfer heat energy as well. This bubble formation is called nucleate boiling; a far more effective way to transfer heat than natural convection on its own. In fact, so effective that ultimately it leads to more complex boiling called transition boiling—the highly turbulent bubble flow that indicates the water is now hot enough to cook your pasta.

In space, however, bubbles behave differently. Without gravity, the effects of buoyancy and convection are absent. The warmer water cannot rise; instead it remains near the heat source, getting hotter and hotter. Meanwhile, the remaining water further away from the heat source stays relatively cool. As the heated fluid reaches its boiling point, the bubbles do not rise to the surface. Instead, the bubbles that do form coalesce into one large bubble that sits on the heated surface. Within the bubble lies precious heat energy, trapped! The result is a seemingly inefficient or at least very different, way to transfer heat.

 

 

Image of liquid boiling on a heater array during the low gravity
 produced by NASA’s KC-135 aircraft. Blue regions indicate
regions of low heat transfer.
(Courtesy of University of Maryland)

As it turns out, there are plenty of scientists out there who are fascinated with the fact that if you boil water in space, you get one large bubble that tends to “swallow” smaller bubbles. Why the fascination? Well, beyond the gains in fundamental thermodynamics “textbook” knowledge, because boiling is such an effective heat transfer process, understanding more about this complex process can help to build more efficient cooling systems for Earth and space. For example, automotive engineers are interested in designing compact, energy-efficient systems to cool off hot car engines, based on the heat transfer mechanics of boiling.

In fact, your own refrigerator uses a coolant with a low boiling point and some associated pressure changes in order to keep your food cold inside. By transferring heat from the fridge air to the coolant to the point of boiling, heat ultimately dissipates from the bubbles and radiates out into the air in your home. In essence, although the air inside of your fridge may seem cold to you, it is actually warm enough to boil its coolant, which is the very heat transfer process responsible for keeping your food cold.

The Boiling Experiment Facility or BXF, which launched on STS-133 in February 2010, will enable scientists to perform in-depth studies of the complexities involved in bubble formation as a result of heat transfer. For instance, what roles do surface tension and evaporation play during nucleate boiling when buoyancy and convection are not in the equation? What about the variations in the properties of the heating surface? By controlling for gravity while on the International Space Station, scientists can investigate the various elements of boiling, thus potentially driving improved cooling system designs. Improved efficiency in cooling technology can lead to positive impacts on the global economy and environment; two hot topics that have much to gain from boiling in space.

Dr. Tara Ruttley is an Associate Program Scientist for the International Space Station (ISS) for the National Aeronautics and Space Administration (NASA) at Johnson Space Center (JSC) in Houston. Her role in the Program Science Office consists of representing and communicating all research on the space station, and supporting recommendations to the ISS Program Manager and to NASA Headquarters, regarding research on the ISS. Prior to her role in the ISS Program Science Office, Dr. Ruttley served as the lead flight hardware engineer for the ISS Health Maintenance System, and later for the ISS Human Research Facility. She has a Bachelor of Science degree in Biology and a Master of Science degree in Mechanical Engineering from Colorado State University, and a Doctor of Philosophy degree in Neuroscience from the University of Texas Medical Branch. Dr. Ruttley has authored publications ranging from hardware design to neurological science, and also holds a U.S. utility patent.

 

 

Dr. Tara Ruttley
(NASA Image)

Research to Watch on the STS-133 Shuttle Launch to the International Space Station

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The STS-133 shuttle flight, which launched to the International Space Station on February 24, 2011, includes 5 investigations for crewmembers to perform, delivery of 24 studies with hardware or samples, and 22 investigations with samples or data coming home on the return trip. Allow me to share with you a few of the highlights from this extensive list.

A major milestone from this flight is the final outfitting of the interior of the space station laboratory. NASA launched the last of the Express Racks on STS-133. These workhorses are bench-like structures used to support experiment equipment with power, data, and thermal sensors. The final addition of Express Rack 8 completes the furnishing of the laboratory, making way for full use of the station for research. Future National Lab users will employ about 50 percent of the space available in these racks, doing research that will benefit discovery and economic development of the nation through 2020 and beyond.

Cytokines on a Mission

This flight also includes a unique experiment that will study the very puzzling effects of spaceflight on the immune system. The Effect of Space Flight on Innate Immunity to Respiratory Viral Infections investigation looks at the impact of microgravity on the immune system by challenging it with respiratory syncytial virus (RSV). These studies will help determine the biological significance of space flight-induced changes in immune responses, which astronauts experience in microgravity. NASA and the National Institutes of Health (NIH) are both interested in using the space station to understand the immune system for astronauts and for the health of people here on Earth.

Boiling without Buoyancy

The first premier boiling facility, the Boiling eXperiment Facility (BXF) also launched on STS-133. This equipment enables the study of boiling in space, paving the way for two new investigations to take place on station: Microheater Array Boiling Experiment (BXF-MABE) and Nucleate Pool Boiling Experiment (BXF-NPBX). The boiling process is really different in space, since the vapor phase of a boiling liquid does not rise via buoyancy. Spacecraft and Earth-based systems use boiling to efficiently remove large amounts of heat by generating vapor from liquid. For example, many power plants use this process to generate electricity. An upper limit, called the critical heat flux, exists where the heater is covered with so much vapor that liquid supply to the heater begins to decrease. The goal of BXF-MABE is to determine the critical heat flux during boiling in microgravity. This will facilitate the optimal design of cooling systems on Earth, as well as in space exploration vehicles.

 

Without buoyancy or convection, boiling fluids behave quite differently in space.
(Video courtesy of NASA)

 

The second experiment, BXF-NPBX, studies nucleate boiling, which is bubble growth from a heated surface and the subsequent detachment of the bubble to a cooler surrounding liquid. Bubbles in microgravity grow to different sizes than on Earth and can transfer energy through fluid flow. The BXF-NPBX investigation provides an understanding of the heat transfer and vapor removal processes that take place during nucleate boiling in microgravity. This knowledge is necessary for optimum design and safe operation of heat exchange equipment that uses nucleate boiling as a way to transfer heat in extreme environments, like the deep ocean for submarines and microgravity for spacecraft.

All Fired Up

Also on this flight are some great new combustion experiments. Burning and Suppression of Solids (BASS) tests the hypothesis that materials in microgravity burn as well, if not better than, the same material in normal gravity, all other conditions being identical. Structure and Liftoff In Combustion Experiment (SLICE) investigates the characteristics of flame structure, such as length and lift, using different fuels with varied levels of dilution. SLICE uses a small flow duct with an igniter and nozzle to collect data as a flame detaches from the nozzle and stabilizes at a downstream position. Combustion is dramatically different in space, as seen in the photo below. These studies aim to make spacecraft safer from fires and combustion processes more efficient in microgravity.

 

A flame in Earth’s gravity (left) vs. microgravity (right).
On Earth, warm air rises and cools, leading to the shape of
the orange flame. In space, there is no buoyancy, so the
flame is blue-hot and spherical.
(Image courtesy of NASA)

 

Not So Lost In Space

One of the more publicized technology demonstrations on STS-133 is a humanoid robot that seems like something right out of a sci-fi movie. Robonaut serves as a springboard to help evolve new robotic capabilities in space. Over the next few years, tests of this technology on the space station will demonstrate that a dexterous robot can launch and operate in a space vehicle, manipulate mechanisms in a microgravity environment, function for extended duration within the space environment, assist with tasks, and eventually interact with the crewmembers.

 

The current Robonaut iteration: Robonaut 2.
(Image courtesy of NASA)

 

I am eager to see the results from the various studies beginning, ongoing, and returning from the space station via STS-133. This is an exciting time of full utilization of our laboratory in low Earth orbit!

For a full list of experiments available on this flight, see the STS-133 Press kit or visit https://www.nasa.gov. 

 

Julie A. Robinson, Ph.D.
International Space Station Program Scientist