This week, comments from guest blogger and International Space Station Principal Investigator Dr. Mark Weislogel, as he reflects on the importance, advantages and joys of long-duration investigations on the space station.

Scientists who have not used the International Space Station before don’t always have a feel for how space experiments can be as successful, if not more so than those using other low-g environments. Researchers used to the shuttle experience think in terms of a very small window of time to make changes and adapt. Short duration investigations are intense and competitive. In hindsight, it seems they are high risk. If you have a three-hour slot to run your experiment and some setback occurs that cannot be resolved, you lose a portion of your data.

On the space station this can also happen, but when you engage in long-duration investigations, you quickly realize that you have time to think things over. Because of this, when unexpected events occur, you can respond in a creative and curious way. The success factor of long-duration experiments is high—barring any failures in equipment, a risk in any lab. In fact, you are very likely to discover things you would not anticipate; things completely peripheral to the goal, which you will observe for the first time, due to man’s limited experience in microgravity.

When a setback occurs on the station, you get partial results and then the investigation goes into storage or offline for a time. When you come back, you’ve had time to think about things. In my experience with the Capillary Flow Experiment or CFE, the participating astronaut also had suggestions, an advantage to working with humans in space. Procedures were changed around from the previous run and we ended up with more data than ever planned and saw new things en route. [Ground operations for the CFE investigation took place at the National Center for Microgravity Research and Glenn Research Center, Cleveland, Ohio.]

NASA astronaut Scott Kelly, Expedition 26 commander, works on the hardware setup for a Capillary Flow Experiment (CFE) Vane Gap-1 experiment. The CFE is positioned on the Maintenance Work Area in the Destiny laboratory of the International Space Station. CFE observes the flow of fluid, in particular capillary phenomena, in microgravity.
(NASA Image ISS026E017024)

Transitions in fluid locations due to slight changes in container geometry. As a central vane is rotated in this elliptic cylinder container critical wetting geometries are established leading to wicking along the vane-wall gap, and/or a bulk shift of fluid from right to left.
(Image Credit: Suni Williams)

Time and resources factor into any discovery, of course, and significant astronaut involvement makes a big difference, too; certainly more so than in automated or robotic investigations. But even with the Capillary Channel Flow or CCF investigation that I am working on right now, it is amazing! If you have a pump and some valves, you can configure them in many ways you did not anticipate and widen your data set. You want to get what you planned on, but it is a delight to get all this extra information that you never expected!

My previous experience dealt with handheld, small experiments, so to me CCF is a complicated investigation. CCF is focused on two-phase flow—a liquid system with gas bubbles. In space, the gas does not rise and we have not had many opportunities to study systems like this in microgravity. The investigation has pumps and valves and plungers and separation chambers. While there are other studies devoted only to two-phase flow, CCF has two-phase flow all throughout it just to generate the flow that we are interested in watching. CCF operates continuously, controlled from the ground through the Microgravity Science Glovebox or MSG interface and does not require crew interaction.

We have gotten to the point with CCF where we can get around 20 data points per day and we are on our way to where we can get hundreds and hundreds of data points in a 24/7 operation. The system is working, though there are setbacks—often times with loss of signal during our commanding or due to our own thing—in trying to take inventories of where the fluids and gases are in the system. We are regularly downloading high resolution, high speed images and plotting them right alongside of our analysis on the ground and seeing new things there, too. The 24/7 collection is exhausting, but we know we can do it!

In the image above, single and multi-bubble migration and phase separation are driven passively by specific control of container shape. A taper in a polygonal sectioned conduit leads to capillary pumping of liquid from right to left driving bubble left to right. Such mechanisms may be invoked by fluid systems aboard spacecraft to separate and store fluids by phase without moving parts.
(Image Credit: Scott Kelly and Cady Colemen)

On the ground, the joint German-US team started with 24/7 operations to learn the experiment in the first 2 to 3 weeks. Then the team travelled to Germany and slowed the pace, learned the system, then ramped up again to 24/7 operations. [Development and ground operations for CCF take place at the German Aerospace Center, headquartered in Cologne, Germany.] Our operations are much more controlled than before, because we were working 16-hour days to support that. The team then continued running for a few weeks until we finished our first set of objectives.

Unexpected developments are part of the joy in microgravity investigations. When you make a discovery, you think, “Oh my, of course this should happen!” But no one has seen it before, because no one has had this nice low-g environment for such a long duration. This is fun because it kindles the same kind of excitement that you have in your lab when you are definitely discovering something. It’s very exciting!

The thing is that the chances for discovery are much higher with long-duration investigations on the space station. This is because we do not live in that environment. You may be trying to verify a theory—and that is great—but en route you are very likely to see things to compliment or supplement your investigation and even take you in different directions. You won’t have thought of these discoveries until you actually see them. That’s what it is like with fluids in microgravity, as well as with combustion, materials science, and other fields.

One thing I feel very good about is that most of my investigation results can apply in the real world right away. Our work has already led to design concepts to improve the performance and reliability of advanced systems, such as condensing heat exchangers and waste-water treatment devices. It can also help with liquid fuel tank and fuel transfer designs. The results give new insight, confirm theories, and are useful for space and ground research. So there is not always a long lead time between the science products and their use. This generates a good feeling, seeing that there is contribution in an observable timescale. This is not common in science and usually takes decades to realize. Instead, these results can improve design and space system design right now.

Dr. Mark Weislogel is a professor in the Thermal and Fluid Sciences Group in the Maseeh College of Engineering and Computer Science at Portland State University. He has research experience from government and private institutions. While employed by NASA, he proposed and conducted experiments relating to microgravity fluid mechanics. This unique subtopic area within fluid mechanics provides significant challenges for designers of fluids management systems for aerospace applications. Weislogel continues to make extensive use of NASA ground-based low-gravity facilities and has completed experiments via space shuttle, the Russian Mir Space Station, and the International Space Station. While in the private sector, Weislogel served as principal investigator for applied research projects concerning high-performance heat transport systems, micrometeorite-safe space-based radiators, microscale cooling systems, emergency oxygen supply systems, and astronaut sleep stations. His current research includes passive non-capillary cooling cycles for satellite thermal control and capillary fluidics at both micro- and macro length scales. Weislogel has written over 50 publications; see http://web.cecs.pdx.edu/~mmw/ for further details.