Leaving the Planet: Science and Technology Results on the International Space Station
Carl E. Walz
Exploration Mission Systems Directorate
National Aeronautics and Space Administration
This paper will discuss the significance of the International Space Station (ISS) for science, but also its role in the evolution of our activities toward longer duration spaceflights. The “leaving the planet” title was selected in the belief that as a species we are destined to explore and to visit new worlds, and, perhaps, expand our civilization there. Starting with a brief overview of space stations in general, from an historical perspective, the paper will then focus on the ISS in terms of its assembly, operations, and overall research themes and results. The final portion of the paper will be a discussion about the future.
Chesley Bonestell’s picture of Werner Von Braun’s concept for a space station (Figure 4.1) appeared in Collier’s magazine in 1952. It’s fascinating to think that Von Braun had this vision back in 1946 when World
War II had just ended. So even back then, before the International Geophysical Year, people were thinking about what it would be like for humans to leave the planet and what the possibilities might be.
The toroidal design actually incorporated artificial gravity, so that people could walk around the inside at 1 G (the acceleration that Earth imparts to objects on or near its surface).
THE FIRST SPACE STATIONS
The United States did not build that kind of space station and neither did the Russians. However, the Russians, in a similar vein to us, had an idea that a space station capability should be developed, so they created a series of space stations called Salyut. Part of these stations were civilian-research oriented, and part of them were dedicated to military research.
Salyut first flew April 19, 1971. Two crews visited Salyut 1, but one visiting crew could not actually dock. The first crew experienced problems with the docking system, and so they ended up coming home early without actually staying on the station. The second crew successfully docked and stayed for approximately 23 days. However, due to a failure of the Soyuz capsule when they re-entered the atmosphere, all the crewmembers died. These experiences show that leaving Earth and going to space has tremendous risks. The Russians developed several more Salyut and Almaz space stations. The next three after Salyut-1 were failures. Either the Proton rocket they used blew up on the pad, or the station simply did not achieve orbit. So it was not until Salyut-4 that they were finally able to reestablish an orbiting station and carry out a succession of successful missions. Salyuts 4, 5, 6, and 7 were very successful, having a number of crewmembers visit and demonstrating a lot of space capabilities.
In the United States we had a military Manned Orbiting Laboratory (MOL) program that was planned but eventually did not get funded and did not fly. Although the United States decided not to carry out the MOL program, we did decide to do the civilian NASA Skylab program. Skylab was our first U.S. space station. It was a 75-ton laboratory built from a Saturn IVB stage, the upper stage of the Saturn V rocket. Skylab was launched into space on May 14, 1973, and was occupied by three crews, Skylab 2, 3, and 4. The crews stayed for periods of 28, 59, and then 84 days, respectively, during 1973 and 1974. From Figure 4.3 you can see that Skylab is asymmetric. During launch, aerodynamic forces caused one of the solar arrays to be ripped off. Fortunately this problem did not damage the pressurized module. The aerodynamic forces also ripped off some of the thermal protection system. So one of the first orders of business with Skylab was to actually do an in-flight repair and deploy a new sunshade during a spacewalk. That spacewalk was performed by the first crew and allowed the Skylab to function very well for the three missions.
The Skylab crews performed a number of microgravity physical science experiments and a number of physiological experiments, looking at how microgravity affected the human body, and also operated a solar observator (Figure 4.4).
Skylab stayed in space until 1979. After the Apollo
program ended in 1975, there was a plan that called for the space shuttle to fly to Skylab and re-boost it, giving it extra time on orbit. Unfortunately the first flight of the shuttle was delayed until 1981. Skylab’s orbit decayed, and it re-entered Earth’s atmosphere and mostly burned up. However, some charred hardware landed in Australia.
MIR AND SHUTTLE-MIR
In parallel with the U.S. Skylab activities the Russians were building and flying their Salyut stations. Then the Russians decided that they wanted to do something a little bit different and more advanced, and they launched a very successful modular space station, the Mir (Figure 4.5).
The word “Mir” means “World” or “Peace.” The first element of the space complex was launched on February 19, 1986. Mir incorporated an autonomous rendezvous and docking system, the Kurs system, which allowed these large modules to be able to find each other and to autonomously dock. This was highly sophisticated technology for its time. When crews were on board the Mir they had a backup capability where the crew could dock additional modules as well. They also had a very short but very capable robotic arm that could move the modules around from the docking configuration to their final configuration. Mir consisted of a number of modules. It started out with a base block that really had its heritage from the Salyut series and provided vital crew life support and habitability functions. In addition, other modules included Kristall, Priroda, and Spektr. These modules reflected some of the science that would be done in space.
Seven U.S. astronauts flew on Mir during the Shuttle–Mir cooperative program, the first being Norman Thagard. From the Shuttle–Mir experience, the U.S. learned a great deal about what was involved in flying long-duration missions. Our NASA long-duration spaceflight experience up until that time, excluding the Skylab missions, involved Spacelab-Shuttle flights of about 2 weeks duration. Jumping to durations of several months was a completely different story. The chance for the United States to participate in the Shuttle-Mir gave us opportunities for a close look at what kinds of challenges existed for the flight crews, design and sustaining engineers, and flight controllers in mission control for long-duration flights. Figure 4.6 shows Shannon Lucid with Sasha Kaleri. Lucid was the second American to make a long stay on Mir. She was aboard Mir for 186 days.
We learned quite a bit from the Shuttle-Mir program, including having a chance to look at some of the Russian technology. Typically the Russians could bring things up to their space stations, but they could not bring them back down. So they would use them up, and then they would just throw them away. The shuttle, however, provided a capability to bring back large items of equipment, thus giving the United States an opportunity to see what worked, what did not work, and help advance technology.
THE INTERNATIONAL SPACE STATION
Now let’s move on from the Mir program to a historical perspective of the ISS. The ISS involves a consortium of nations—the United States, Russia, Canada, the European Space Agency, and Japan—working together on its development and operation. The first launch of ISS was a Russian element, the Functional Cargo Block, or FGB, on November 20, 1998. It was launched on a Proton rocket from Baikonur, thus initiating a new era of human spaceflight.
Shortly thereafter, on December 4, 1998, we launched our first U.S. element, Node-1, during the STS-88 mission. Node-1 and the FGB were attached using the shuttle’s robotic arm.
Once those missions had taken place there was a fairly large time gap before construction continued. The next module to go up was the Russian Service Module, launched on July 12, 2000, which is basically the living compartment for the ISS, providing the early life support system for the station. It was behind schedule, so there was a hiatus of about a year and a half in assembly flights, which enabled us to do a lot of testing of our ISS elements on the ground to verify their proper functionality. The launch of the service module broke a logjam and initiated the launch of a
number of shuttle flights which added, among other things, the Z1 Truss, which provided the control moment gyros and the first U.S. solar arrays that provide power for the station. The first crew launched to the ISS on October 31, 2001, from Baikonur, and then in February 2001, we brought up the Destiny Laboratory, which is the U.S. laboratory. At this point we were ready to begin scientific research onboard the space station, although construction of the ISS still was not complete. We continued on with a number of assembly flights—adding an airlock, a robotic arm (provided by Canada), and starting to build out the truss elements, but the assembly was halted due to the Columbia accident, which occurred on February 1, 2003. It took us until July 2005 to get the shuttle flying again. The STS-114 mission was the first post-accident shuttle flight, and it was mostly a resupply mission. Another year passed before we actually started bringing up more the elements, starting with a build-out of the solar trusses. The October 2007 configuration of the space station is pictured in Figure 4.9.
The completed ISS consists of hardware components developed by the five program partners. The following components are included:
Zarya (Functional Cargo Block)
Unity Node 1
Zvezda Service Module
P6 Truss with a Solar Array
External Stowage Platform
Canadarm2 Robotic Arm
Quest Joint Airlock
Pirs Docking Compartment & Airlock
Mobile Base System for Canadarm
P3/P4 Truss with Solar Array
S3/S4 Truss with Solar Array
External Stowage Platform 3
Harmony Node 2
The next flight is on the launch pad right now ( January 2008). We are hoping to launch in the early February time frame.1 That flight will bring up Europe’s Columbus laboratory module. Future components to bring the ISS to its assembly complete configuration include:
Japanese Logistics Module
Special Purpose Dexterous Manipulator
Japanese Pressurized Module
JEM Robotic Arm
S6 Truss with Solar Array
Japanese Exposed Facility
Docking Cargo Module
Node 3 and Cupola
EXPRESS Logistics Carriers 5, 1
The year 2008 should also see the first flight of ESA’s Autonomous Transfer Vehicle (ATV) which will dock to the Russian Service Module and be used for station re-supply and orbit re-boost. The Japanese also plan to contribute the HII Transfer Vehicle (HTV) for station re-supply. If all goes well we will increase the crew size from three to six in 2009.
All in all, the ISS is going to be quite a vehicle when fully assembled, and we have made tremendous strides since we’ve recovered from the Columbia accident. All the ISS partners are looking forward to the completion of the construction in the next couple of years.
ISS Operational Results
The ISS, as you can imagine, is a very complex platform as regards engineering integration and scientific research. One fact worthy of note is that we did not put all the hardware together on the ground before launching it into orbit. We put almost all the U.S. elements together on the ground, but Russian elements were in Russia and the U.S. elements were in the United States. They had similar data buses, but they were not identical. Therefore we had to do testing using surrogate systems and hope those surrogate systems really did reflect how the actual space systems work. What we found when we put the two surrogate systems together for the first time, Russian and U.S., was they did not play together. There was a slight difference in the timing between the two data busses. We discovered this shortly before we were set to launch the Russian Service Module where, in orbit, U.S. and Russian data buses would have to communicate together. Fortunately, our engineers were able to scramble and resolve that timing issue, and their speedy work allowed us to launch the service module and then unleash the ISS construction flood gates.
And that was only one issue. There are numerous other issues that had to do with various systems, such as propellants and the control of the solar arrays, when different spacecraft come to dock. We are continuously learning how to operate this very large, complex vehicle. We are also gaining experience in crew operations, systems operations, and crew-system interface options.
As regards crew operations and training; this is the first large-scale human spaceflight effort to have a highly integrated international crew. Again, with a consortium of nations that are working together, we have to figure out ways to build teamwork in crews with varied backgrounds so that they can work together effectively. This applies both to the flight and ground crews. The ISS partners have worked very hard to do that.
The ISS will also serve as a test-bed to develop skills that will be needed for going to the Moon, and, at some time in the future, for going to Mars. Imagine if you were going to Mars, for example. Most probably, your training would not be complete when you left Earth. It would be completed on the 6- to 9-month trip out to Mars. On the ISS we are trying to develop protocols and procedures to use in-flight training capabilities; for example, ways to do refresher training. We will also be studying how we can train more for broad skills rather than doing very specific task training, When you get to Mars, or even on the station, you cannot anticipate everything that your crew might have to do. You make sure that your crews have the basic toolbox of skills and that they can adapt, do some rehearsals in space, and
then execute successful operations, such as spacewalks, for example. There will also be a need for advanced habitation and life support systems. When we go to the Moon, and even more so when we go to Mars, we have to cut the supply cord. It’s going to be very difficult, if not impossible, to re-supply missions to Mars. Therefore closed-loop life support systems are very important, as well as evolved medical care and counter measures. These kinds of capabilities may be needed for the Moon, but will definitely be needed for Mars.
With the ISS, we can refine some of these capabilities. We have launched our oxygen generation system already, and we hope by the end of the year to launch the rest of our environmental life support system suite to more completely close the environmental loop on the station, so we can take urine, for example, and reprocess, purify, and drink it or make oxygen from it. The oxygen generation system, for example, uses water, so we could use reprocessed urine to make oxygen to breathe! Also, we’re looking at some of the needs for healthcare and how we can develop better health maintenance systems and exercise protocols for our crew members.
Another area covers automation, robotics and human–machine interface. We will have two robotic arms onboard the ISS. How can we best use these arms and the crew interfaces necessary to operate them, not only by the crew but by the ground? These are capabilities that are going to be needed for the Moon. We are already involved in work sponsored by the Advanced Capabilities Division at NASA Headquarters looking at robotic agents to help crew members on the lunar surface. For going to Mars, we’re going to need a big spacecraft. We will probably need automated assembly capabilities to put such a spacecraft together, as it will be launched in pieces on heavy-lift launch vehicles. Also, as we go farther away from Earth, we will need better autonomous systems. So our ISS experience can help us to validate our robotic designs, concepts, tools, and some of our operational scenarios and test what works and what does not for in-space assembly.
ISS Research Themes and Results
ISS research themes can be grouped into five areas as:
Assuring the survival of humans traveling far from Earth,
Expanding our understanding of the laws of nature and enriching our lives on Earth,
Creating technology to enable future explorers to venture beyond low Earth orbit,
Observing Earth, and
Educating and inspiring the next generation to take the journey.
The website http://www.nasa.gov/mission_pages/station/science/experiments is a really useful resource because you can see all the various investigations that we have done or will be doing onboard the ISS. Results, when appropriate, are listed there as well, making it a great resource.
Now for a few science statistics. Through Expedition 15, we have initiated 125 investigations, 94 of which have been completed. On Expedition 15, we conducted 38 investigations. Interestingly, the initial prognosis for Expedition 16 was that we would be lucky if we got any science done at all because the crew would be so busy with robotics and space walks. Well, it turns out that although they are busy with those things, we have 60 investigations underway on the ISS right now, and the crew, Dan Tani, Peggy Whitson, and Yuri Malenchenko are doing a great job of completing these experiments. So given the limitations of small crews and ongoing assembly, we are doing really well in accomplishing science on the ISS. In fact, not the next shuttle, but the shuttle after that has some additional space available and we were able to get six shuttle middeck lockers assigned to bring up additional science investigations to conduct on the station.
Currently we have nine dedicated U.S. science racks on orbit. By the end of the year we’ll have two more—the Combustion Integrated Rack (CIR) and another express rack that is scheduled to launch by the end of the year. Shortly after that, we will have a number of other research racks available, including the Fluids Integrated Rack, the Material Science Research Rack, the Window Observation Research Facility, and the Muscle Atrophy Research and Exercise System. Furthermore, because we are in a partnership with the international community, we also have opportunities to utilize facilities in their laboratories; the ESA Columbus Module and JAXA’s Kibo pressurized laboratory module.
Let’s now address the issue of assuring the survival of humans traveling far from Earth. By way of example let’s consider three ongoing or recently completed investigations.
One of the issues that we have during long-duration space travel is that our bones de-mineralize. The freed-up calcium then has to go someplace. It goes through the bloodstream to the kidneys and it can, under certain conditions, form renal stones. While we have not had people in the U.S. program get renal stones, it has happened on the Russian side. We therefore carried out an experiment utilizing potassium citrate to help reduce the risk of renal stones. Researchers found that the potassium citrate was very effective, and it will now transition from an experimental stage to medical practice. This represents a big success from ISS research.
Exercise during long-duration spaceflight is very important. If we were leaving the planet and never coming back to Earth, exercise would not be a big deal, because if we were just going to stay in microgravity our bodies could change and would adapt to space, and we would be fine. But the fact that we have to return to a gravity field means that we have to stay in shape while we are in microgravity. So on the ISS we have the treadmill, which you see in Figure 4.11.
We also have two exercise bikes, one Russian, one U.S., and also a resistive exercise device. We typically have 2½ hours a day where we are allowed to exercise. In the FOOT experiment, we actually had sensors located on the pants that Expedition 6 commander Ken Bowersox is wearing in Figure 4.11. These pants measure bending angles of the knee during exercise. There was also a sensor in his running shoe to record the force of his heel and toe strikes when he was running on the treadmill. In the picture you can see the bungees attached to Ken. These bungees hold us to the treadmill and provide a force that we thought was equal to about what our weight was on Earth when we would exercise. It turned out from data collected during the FOOT experiment that the force, the reaction force that we were getting while running, was less than what we had expected. That was distressing because we thought we were getting a good stimulus to our bones; but we were only getting about 80 percent. The FOOT experiment was the first to measure that. As it turns out, we have subsequently set up this FOOT experiment on the ground and in bed-rest studies, and we’ve seen that same effect. One of the things that we found was that because the treadmill has a vibration isolation system, designed to preserve the microgravity environment on the station, when we step on to that treadmill, the treadmill actually moves away from us and so it reduces the amount of force that we get. This was an interesting result and it will change the way we do future mountings for the next
treadmill, the T2 as it’s called, that will be located in the Node-3.
In the area of nutrition, one of the things we’re trying to understand is, what is space normal? How do peoples’ bodies change while they’re up there in space? So we have established the Nutrition experiment involving the taking of blood and urine samples regularly, processing them in a centrifuge, and storing them in a minus 80 degree freezer to await return to Earth for analysis. We are trying to do a very comprehensive study to track nutritional markers such as vitamins and minerals using these in-flight blood and urine samples to understand the trends for long-duration astronauts.
Going hand-in-hand with nutrition is another experiment called Stability. It is possible that the food we bring up to the ISS actually degrades in space and that could affect astronaut nutrition. So we are trying to understand what happens to the food that is up there for up to a year before it is used. Furthermore, it has been reported that some of our pharmaceuticals, when we have brought them back from space, are shown to be ineffective. So, what happens to those pharmaceuticals in space? We think it might be radiation, but we’re going to try to find out definitively.
So these are just some of the examples of things that we are doing on the ISS to try to assure the survival of humans traveling away from Earth.
We are also trying to expand our understanding of the laws of nature. The opportunity to conduct experiments in microgravity is unique. On Earth when we do experiments, the gravity (G) factor is always present. We take it for granted. But we hope to try to understand some forces that do not have the kind of impact that gravity does, but, nonetheless, affect how things occur in the physical world. Going into space allows us to better understand these fundamental phenomena. By way of example let’s look at three experiments. The first one is called the BCAT, the Binary Colloidal Alloy Test, which is trying to get fundamental information on the rate of phase separation especially near the critical point for certain alloys. Colloids2 occur everywhere in nature and in industrial processes. So getting a better fundamental understanding of how colloids behave is very important to these industrial processes. In fact, J. Hunter Waite, Jr., Space Research Laboratory, University of Michigan, who is the principal investigator of colloids, has been approached by a detergent manufacturer to try to understand better some of the forces involved there. So the word is getting out that what we develop or understand from space can have implications on Earth.
Another exciting thing we are doing is trying to understand capillary flow. In a gravity field the capillary flow can be overcome by the forces of gravity. However, in space it is very easy to observe and investigate capillary flow, in this particular case using a sample in a jar-like container. In conducting the experiment, we measure and photograph how the liquid behaves and
how it wets the container along the edges. We then compare it to computer simulations of what the behavior is expected be theoretically. In one experiment one example behaved per the theory to within one percent, while another one under different conditions behaved completely differently, compared to what was expected theoretically. This is an example of where you get one question answered and another question pops up. This experiment has been very useful in helping us to understand capillary flow and will be very important in helping us to control fluids in space. In space, fluids are important for everything from propellant systems to life support systems. So the better we understand how fluids behave and how we can influence them, the more successful we will be in building new spacecraft.
The last experiment we will discuss here is a material science experiment, called C-SLAM, the coarsening in solid liquid mixtures. Basically we are looking at the kinetics of metallic particle growth not affected by buoyancy or other gravitational forces. You have small particles in the mixture, and they tend to get smaller, while the big particles tend to get bigger. We’re trying to understand the mechanics and rates of this coarsening process. This has a wide variety of applications, from the manufacture of turbine blades to how dental fillings behave when they’re installed in your mouth.
All three experiments are still active onboard the station. In the case of two of them (BCAT and Capillary Flow), you can shake them up and re-do the tests. They actually have a lot of capability. The CSLAM employs equipment set up in a microgravity science glove box, because it is a tin-lead mixture. There is a chance that the lead could get out into the station environment, so we actually have a glove box there where we can do these experiments and protect that onboard environment.
Now let’s consider some examples of the technologies that we’re developing to enable our crews to go beyond low Earth orbit. We have developed a “lab on a chip” portable test system to do microbial monitoring. One of the things we have to do during a long mission is make sure that we do not have microbes growing onboard the space vehicle, which could be bad for peoples’ health. They can also be bad for the machinery, especially some of the liquid systems. Microbes, basically slime colonies, can grow and cause problems in pumps and in tubing. So we try to keep track of that. During flights, our standard way of doing microbial monitoring was to use gels and a Petri dish, making observations over several days. The LOCAD portable test system shown in Figure 4.12, that Suni Williams is demonstrating, allows us to get a near-immediate microbial assay, thus saving a lot of time and giving us more accurate results. So if we do have a problem with microbes we can take action more quickly.
The next experiment is called smoke and aerosols
in microgravity (SAME). SAME is operated in the glove box because it generates smoke. What we’re looking at is the how smoke forms, what form the smoke particles takes, and how it affects some prototype fire detectors. One of the bad things that could happen on a space station is a fire like the one on Mir in 1997. We are trying to make sure that our fire detectors are (1) responsive when there is a fire and (2) do not give us any false alarms. So this experiment will allow us to better understand the characteristics of smoke from materials on space stations, and then allow us to develop better smoke detectors.
Another technology shown here is an electronic nose (E-nose) Air Event Monitor (Figure 4.13). Again, it gives us a quicker understanding of the kinds of events that might happen in the environment where we would have to take action either by turning on atmospheric scrubbers or putting on gas masks.
Viewing Earth from Space
From the ISS we also have the opportunity to observe Earth from space. One of the cool things about the ISS is that we get a chance to fly over some areas quite frequently, and we can get great views of some physical processes on the planet as they are occurring. Figure 4.14 is a excellent image taken from the ISS of an erupting volcano.
One of the things the ISS gives us a chance to do is to look at Earth over extended time periods. For example, on the ISS mission in December 2001 one of the first things that was done was to photograph this big, circular object, the Manicougan impact crater
We are very fortunate that we now have a record
of Earth observations dating back to the first human spaceflights. So we can compare observations over some 40 plus years of spaceflight and see how certain areas have changed over time. It is a very powerful tool. This imagery is available on the “Gateway to Astronaut Photography of the Earth” Web site.3
We are also working to help encourage the next generation to take the journey; to try to inspire students to study science, technology, engineering, and math.
One example of such activities is EarthKAM, where students remotely control a camera mounted on the ISS to photograph sites of scientific interest on Earth. A worldwide educational community can command this camera. The EarthKAM is attached to the Earth-facing window of the service module and is attached to a computer. The coordinates and times for the pictures are sent up from the ground to the computer. The computer tells the camera to take the pictures, the pictures are automatically downloaded to the computer, and then further downloaded to Earth. In this way the students can get feedback on the pictures that they wanted to take.
Challenges for the Future
In closing let’s address the future of the ISS. Now, challenges certainly remain. Just completing the station is a great undertaking. You are sure to have seen the news concerning the problems that we had with the shuttle that led to a delay in the December flight, rescheduled for February 2008. This followed the launching of a number of very successful on-time flights. However, every once in a while we end up with a problem, and it just takes a while for us to work through it. So completing the station is a massive undertaking.
Post-shuttle, transportation and station re-supply is going to be a very important element. We will have up-mass requirements pretty well covered with Russian
Available at http://eol.jsc.nasa.gov/.
Progresses, the ATV from ESA, and the HTV from JAXA. However, the down-mass, which was a problem for the early Russians stations, could be an issue for us. So we are working through that issue right now to try to develop down-mass capability. One potential approach is the Commercial Orbital Transportation System (COTS) program run by NASA’s Commercial Crew and Cargo Program Office. Within the COTS program there is one company, SpaceX, which is developing a system that will both bring cargo up and down on a commercial basis. They, of course, have to demonstrate their capabilities. NASA is “incentivizing” these
private companies by partially funding their activities.4 Other avenues are also being explored.
So those are a couple of the future challenges that we have. What we have seen is that the ISS is coming together, and we believe it will increase its scientific production in the future, with additional crew members, additional partner laboratories to provide new opportunities for science and for our investigators, and the Autonomous Transfer Vehicle, a maturation of international partner re-supply capabilities.
So the vision of ISS, a laboratory in space supporting multidisciplinary research, is being achieved. It represents a continuation of humanity’s desire to explore and become “extraterrestrial,” if you will. We are getting important scientific, technical, operational, and inspirational results from the station and will continue to do so, and the trend for future research opportunities on ISS looks very positive.