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In 1998, NASA published a report on the Phase 1 Program, which included a section on "Lessons Learned for the International Space Station," excerpted below.
Reducing Risks Through Engineering Research
Space is a uniquely challenging environment. Accommodations must be made for solar and cosmic radiation, the presence of meteoroids, space debris, vacuum, temperature extremes, and the absence of gravity's effects. The exact modifications we make to our Earth-based technology and techniques in overcoming these challenges depend upon the length of time we plan to actually spend in space. Phase I was an opportunity to study and validate space station engineering considerations that differ from those encountered with the Space Shuttle. Through hands-on engineering research in a space station environment, we have been able to reduce the risks we will face during ISS assembly and long-duration operations. In particular, we had the opportunity to conduct a number of hardware and procedural demonstrations.
For example, preliminary results indicate that NASA's model for the trapped radiation environment around Earth underestimates the radiation exposure risk to astronauts during periods of high solar activity and overestimates the levels during periods of low solar activity. NASA has used the Phase I measurements, together with Shuttle data, to develop corrections to the existing radiation model, improving the average accuracy of radiation health risk predictions. NASA is working to develop improved planning and scheduling practices to minimize astronaut radiation exposure during extravehicular activities(EVAs), also known as "space walks." Space walks will be important during the assembly and operations of the ISS. The ISS module connections, solar array emplacement, and support truss deployment will require the active participation of astronauts. During research operations, some externally mounted experiments will need to be put in place and retrieved by astronauts on EVAs. Under the Phase I program, two science modules were modified and added to Mir (Spektr and Priroda). NASA was actively involved in funding and equipping research facilities for these modules.
The arrival of the redesigned modules necessitated the rearrangement of existing modules and systems on Mir, requiring a number of EVAs. Crews installed two new solar arrays on Mir under the Phase I program and retrieved a portion of one of the original solar arrays, transporting it via the Shuttle for ground analysis. Analyses indicate that the solar arrays suffered significantly more damage than anticipated from Mir waste elimination and Shuttle thruster residue. These findings have resulted in modifications to waste elimination procedures and protocols for ISS-Shuttle "proximity operations." NASA is factoring these results into the maintenance and replacement schedules for the ISS solar arrays.
U.S. astronauts have participated in several EVAs conducted solely from Mir (as opposed to those conducted from the Shuttle during docked operations). Dr. Jerry Linenger was the first to use the Russian Orlan EVA suit; his task was to deploy U.S. science equipment and to gain experience with Russian EVA hardware and procedures. Dr. Michael Foale participated in an important space walk to assess the damage to Spektr caused by the June 1997 collision between the station and a Russian Progress vehicle. Dr. David Wolf took part in a Mir space walk to further our experience with the Russian EVA suit and to conduct U.S. research. As a precursor to Dr. Foale's EVA, joint criteria and guidelines necessary to certify the safety of an unplanned EVA were developed. The knowledge we take away from these experiences is preparing us for the multinational endeavor of on-orbit ISS assembly.
Large space structures such as Mir and the ISS are considered "flexible" because they are composed of multiple modules and may oscillate when forces are applied at certain points. Large suspension bridges are good examples of flexible structures. Engineers must carefully calculate a bridge's design in order to avoid a final structure that could accidentally shake itself apart. Because it is impossible to build a full-scale model of the ISS on Earth (it would not be able to support itself in gravity), the structural behavior of the ISS can be predicted only through the use of precise mathematical and engineering calculations. This approach was used to "model" the behavior of the combined Shuttle-Mir docked complex when the Space Shuttle used its own thrusters to affect Mir's orientation. The equations accurately predicted the complex structure's behavior. The use of a "validated" model for predicting the response of the ISS to certain forces permits ISS design and construction to proceed with a higher degree of confidence. These tests also validated the ability of the Space Shuttle to deploy and maneuver elements of the ISS during assembly.
NASA has garnered practical experience on Mir in resolving a variety of space station problems. For example, Mir crews successfully dealt with the station's loss of electrical power, a fire resulting in temporary atmospheric contamination, and a cabin pressure leak. In all instances, Russia, with U.S. support, resolved these problems to permit the continuation of mission activities.
Problems on Mir have led to a number of hardware, software, and procedural changes for the ISS. A February 1997 fire aboard Mir caused NASA to re-evaluate ISS fire control options. Mir operations demonstrated that a temporary shutdown of the station ventilation system can help prevent a fire from spreading. ISS software was subsequently modified to allow a temporary, single-command ventilation shutoff between modules. In addition, the incident made mission planners more cognizant of the location of critical hardware such as medical kits and fire extinguishers; ISS crew members must be able to reach emergency equipment quickly. The depressurization of the Spektr module after a collision with a Russian Progress vehicle in June 1997 validated the U.S. design (no cables running though open hatches) and demonstrated the importance of maintaining clear station passageways. Mir crew members had to rush to disconnect cables that connected the leaking Spektr module to the rest of the station before they could close the hatch. Spektr's depressurization also led to the redesign of some critical Russian ISS components; the intent is to make them more robust in the event of isolated depressurization on the ISS. The experience has also pointed out the need for astronauts to have portable life-support sensors to monitor total pressure, oxygen content, and similar parameters.
Researchers have also found that some corrosion on the inside of Mir resulted from otherwise benign contact between two dissimilar metals. When humidity levels on Mir are high, different metals can react corrosively at their points of contact. Protective coatings have been added to some ISS cooling lines to prevent similar problems on the international station.
Evaluations of the space station environment and hazards have led planners to alter the size and location of the ISS emergency crew return vehicle (CRV). Instead of having two smaller CRVs attached to the station, as originally intended, NASA and ESA are collaborating to build a craft capable of returning all seven ISS crew members to Earth in a single vehicle. To ensure that all crew members have access to a vehicle in the event of an emergency, one large CRV and one Soyuz vehicle will remain attached to opposite sides of the station at all times. NASA is currently assessing the need for a second large CRV.
Operating a Space Station
NASA fully expected that operating a space station would differ from operating a craft such as the Space Shuttle. These differences stem from the fact that Shuttle missions are short, well-defined missions of about 10 days, while station has ongoing operations that will see changes to the planned activities due to onboard circumstances. Our experiences aboard Mir have exceeded our expectations and allowed us to review and revise our ISS operations plan. The Phase I program has given us insights into long-term space operations that will help the ISS substantially reduce uncertainties while increasing station efficiency and operational safety.
Events on space stations often require last-minute changes to the manifest (inventory)of resupply flights. Frequent causes for these changes include hardware failures of vehicles or experiments. NASA underestimated this element for Phase I, but the Shuttle program has exhibited outstanding flexibility in responding to changing requirements on Mir and has paved the way to better support for the ISS.
Phase I lessons have emphasized that astronaut training objectives for long-duration crew members will differ from those NASA has traditionally employed for Shuttle crews. It is essential to address psychological factors early to maintain crew morale and efficiency throughout long-duration stays. Overall, mission training must be more general-skills-oriented than the intensive procedural practices that are emphasized in Shuttle training. Skills training will provide better flexibility and is more cost-effective for on-orbit station operations.
In conjunction with this emphasis on skills training, NASA will schedule on-orbit crew activities for the ISS very differently than the way it does for Space Shuttle missions. Shuttle missions are planned in great detail before flight to make optimum use of every available moment. Station crews will perform a wide range of duties, both planned and unplanned, and the Phase I experience has taught us that it is neither practical nor feasible to create extremely detailed day-to-day timelines for long-duration space station operations. The Russian program uses a more flexible approach to scheduling, in which crew members apply the fundamental skills they learned in training to the tasks required by the actual priorities of the day. For instance, solving a problem with an experiment's equipment may require sending a replacement part or repair tool to the station on an interim flight. Meanwhile, rearranging the research agenda would free time later to complete the problematic experiment once the repairs are complete.
This approach ensures that long-term goals for the entire mission are met. Phase I has verified ISS program planning and timelining tools; modifications and enhancements are being made to ISS flight planning strategies and concepts on the basis of this experience.
We found that more time should be planned for crew changeover, orientation, and experiment setup at the beginning of long-duration missions. Stowage and inventory control are also crucial areas for which adequate on-orbit time must be allotted. Feedback from early Phase I astronauts led mission planners to expand the crew on-orbit support system, which consists primarily of a laptop computer that serves the multiple functions of training, entertainment, language teacher, and information resource. Phase I astronauts since Dr. Shannon Lucid have used the portable computer to brush up on the particulars of experiments immediately before experiment start-up or to review EVA hardware and procedures before a space walk. This capability complements the skills-based approach to training discussed earlier.
Phase I work has led to the development of a process for mission social and psychological support (often referred to as "psycho-social" support). A team was placed in the Moscow Mission Control Center to provide a day-to-day direct interface for the American astronauts on Mir. The astronauts knew the members of this team on a personal level, especially the mission manager and crew physician, and came to rely on this team for general support and answers to questions.
This Moscow-based NASA operations team was in turn supported by teams in Houston, Texas and Huntsville, Alabama. Critical psycho-social support was provided to Phase I astronauts through a variety of means. In addition to close personal relationships with their ground teams, Phase I crews required frequent contact with family and friends. This contact provided the long-duration crew member with a sense of continued involvement in family life. Communications included teleconferences with family, regardless of the family's location on Earth.
Electronic mail and other methods of getting news from home were also employed. The crew on-orbit support system was tailor-made for each astronaut with items of interest to him or her, including a family picture album and video messages from friends. This type of activity turned out to be much more important than initially expected and will be emphasized for the ISS. Maintenance and repair operations are primary drivers of training and scheduling requirements on space stations.
Unlike the Space Shuttle, on which most maintenance is performed after it returns to Earth, ISS crews will be required to make almost all repairs on orbit. Maintenance will be anticipated and accommodated in station scheduling. Phase 1 has given us valuable, first-hand experience in balancing station maintenance and research operations.
The Mir experience has shown that noncritical station systems can be operated until they fail, and only then exchanged or overhauled as part of routine maintenance and repairs. This approach will be implemented on the ISS since it reduces the overall demand for spare parts and minimizes costs.
Regarding back-ups for critical equipment, the Phase I experience has shown that the crew and station can recover from many potentially hazardous situations through the use of robust backup systems, which sometimes use totally different technology than the primary system that failed. It is also clear from Phase I experience that spare parts for critical systems must be available onboard for immediate use. We have learned in our work with the Russians that all station activities must be planned such that there is always a path to the crew return vehicle, and that the vehicle should always be ready if needed to return the crew safely to Earth.
Phase I gave the American and Russian space programs the opportunity to become familiar with each other's experiences and infrastructure. As a result, we can better combine our capabilities to maximize mission resources. The same type of teamwork will enable the partner nations to make the most of their space elements to supply the ISS safely and efficiently.
One example of this teamwork was the use of by-product water from the Space Shuttles' electrical power generation. The Shuttle fuel cells combine oxygen and hydrogen to form water and power. Instead of following the standard practice of dumping this water overboard, the Shuttles used this by-product to supply Mir with potable water. On Mir, the water was either used for human consumption or converted back to oxygen and hydrogen by using solar power. The Shuttle also used its systems, on occasion, to revitalize Mir's atmosphere during docked operations. By utilizing existing resources, space was freed on supply missions to Mir for other items, such as scientific equipment.
Making the best use of all ISS partners' spacecraft will ensure that the ISS is supplied as efficiently and safely as possible. During Phase I, NASA had the opportunity to become familiar with the capabilities and reliability of the Russian Soyuz vehicle and Progress supply craft. The cargo carrying capacity of the Space Shuttle was used to significantly advance the state of Mir research, allowing researchers to return both scientific samples and engineering prototypes to Earth for analysis. NASA's role in sample and equipment return was excellent practice for Shuttle operations that will be used to build and supply the ISS. Each type of vehicle has strengths and weaknesses, and Phase I has provided the opportunity to optimize operational plans.
It is important for ISS crew members to be familiar with all ISS equipment provided by every partner nation. The United States and Russia used Phase I to get a head start on achieving this operational flexibility. For instance, NASA astronauts were trained to use the Soyuz return vehicle if the need arose. Similarly, cosmonauts and astronauts could use either American or Russian launch and entry space suits (suits that provide an individual life support system and are worn inside the spacecraft) and other support equipment while traveling between the ISS and Earth. Over the course of Phase I, crew members designated to participate in EVAs were also trained to use both types of EVA space suits. Additionally, both the Shuttle and Mir airlocks were used for space walk access. This ability to work in concert with different national facilities and equipment will enable future ISS crews to achieve higher standards of efficiency and safety.
Space stations are composed of very fragile and sensitive components such as optics and solar arrays; space vehicles working near or docking with stations must maneuver very carefully with minimum thruster firing. For example, firing a thruster too close to a solar panel could damage the energy-gathering solar cells or cause the array to oscillate, potentially bending or breaking it. Significant damage to an ISS solar array could decrease the transmission of power to the station, affecting its ability to support research, or even affecting its safety. Excessive speed during docking could also damage the docking module or adversely affect station orientation. A series of successful rendezvous operations with Mir allowed NASA to fine-tune its approach and docking protocols for the ISS. NASA has chosen to adapt a Russian docking mechanism for the ISS, saving time and development costs for the ISS program. Phase I operations have flight-proven this type of docking mechanism, along with a number of sensors that will enhance rendezvous capability with the ISS. We also learned that a series of externally mounted tracking lights on the station could greatly increase visibility during docking operations. Plans for the ISS have been modified to add this feature.
NASA also used the Phase I experience to modify activities that occur after flight. NASA did not fully appreciate the attention that should be given these activities. For example, we have been able to modify the astronauts' rehabilitation programs upon their return to the gravity environment.
Working With Our Russian Colleagues
With the exception of the Apollo-Soyuz Test Project in 1975, U.S.-Soviet space cooperation was largely limited to the exchange of scientific data. Two decades ago, the American and Soviet space programs took the first step in working together in human space flight. Today, the Phase I program has given the United States and its partners the opportunity to integrate and validate engineering, management, and operational approaches before the much more complex tasks of assembling, operating, and conducting research on the ISS.
Coordinating and integrating two robust space programs and their supporting infrastructures that have operated independently for decades has been a formidable task. Phase I experience strengthened the professional ties between American and Russian engineers, scientists, technicians, and managers.
By working closely throughout the Phase I program, we advanced the working relationships and intercultural understandings that will allow ISS assembly, operations, and research to proceed smoothly. All the planning, training, and logistics for Phase I was coordinated with Russian specialists and instructors well before the first Phase I mission. American training teams lived and worked in Star City, Russia to help coordinate and conduct the U.S. science training for both the astronauts and the cosmonauts. NASA concluded Phase I with a very thorough understanding of how the Russians plan and train for a flight after 4 years of working shoulder to shoulder with our Russian colleagues.
Creating integrated control center operations for Phase I was challenging. We had to learn to interpret each other's "standard documentation" and decide how to allocate and track responsibilities between the two different space organizations. We overcame time differences and language barriers and successfully integrated our national systems for global communications coverage with the station. Crew members communicated with ground personnel in both the United States and Russia. This coordination added a margin of safety for the execution of sensitive station operations, during which unbroken communications with ground personnel were essential. Many Americans who will operate and use the ISS participated in this integration and will take this knowledge with them through the next phases.
Phase I research operations provided the international scientific community with a critical rehearsal for the ISS. The Phase I research program involved investigators from universities and research institutes across the Nation and throughout the world. Phase I investigators included leading scientists from Canada, France, Hungary, Japan, Russia, the United Kingdom, and the United States. Throughout Phase I, American, Russian, and other international investigators used each others' laboratory equipment, shared data and specimens, and will continue to plan new and exciting projects. ISS research will be performed by scientists from all over the world, whose experiments will have been peer-reviewed and selected by international committees of experts to ensure that the very best scientific work is done on the ISS. The ISS will include laboratory modules supplied by the European Space Agency, Japan, Russia, and the United States. Canada will provide a Remote Manipulator System (a "robotic arm" similar to the one used on the Space Shuttle); Brazil, France, Germany, Italy, Spain, and Ukraine will also provide hardware for the ISS. By working together in the first phase of ISS development, the United States, Russia, and other ISS partners have actively prepared for multinational ISS operations.
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Responsible NASA Official: John Ira Petty