The International Space Station
The ISS will be the largest and most advanced laboratory ever built for research in space. It is intended to return scientific, technological, political, and economic benefits to its international partners (United States, Russia, Canada, Japan, and certain members of the European Space Agency–Belgium, Denmark, France, Germany, Italy, Netherlands, Norway, Spain, and the United Kingdom). The partner governments have agreed to cooperate in the detailed design, development, operation, and utilization of this permanently manned civil space station consistent with an intergovernmental agreement signed in 1988 for Space Station Freedom and officially extended in 1994 to include Russia.
Originally envisioned as Space Station Freedom, the current U.S. portion of ISS resulted from U.S. government executive and legislative direction to NASA to significantly reduce cost, maintenance, and complexity while expanding the opportunities for cooperation with Russia. The current program's capability, cost, schedule, and risk containment have been significantly improved by Russia's inclusion (e.g., in the multiple paths to orbit provided by three different Russian launch systems, Russia's long-term orbital experience, and its self-docking spacecraft). A new management approach that incorporates a single prime contractor (Boeing) to the NASA program management team is intended to integrate and control the key aspects of the program, such as cost, schedule, and technical requirements. The ISS program is carried out by a program office and management and engineering teams at NASA's Johnson Space Center, with the Program Director and a relatively small staff at NASA Headquarters.
NOTE: FIGURE 9 TO BE INCLUDED SOON
Figure 9 Exploded view of the completely assembled International Space Station, shown as described at the March 1995 Incremental Design Review.
Source: McDonnell Douglas Aerospace
At completion, the ISS configuration will consist of 11 permanent, major pressurized modules along with the support systems to provide power, thermal control, life support, and all other necessary functions. The configuration of ISS when completely assembled is shown in an exploded view in Figure 9. Seven modules will be primarily dedicated to research: the U.S. Laboratory Module, the Centrifuge Module, the ESA's Columbus Orbital Facility (COF), the Japanese Experiment Module (JEM), and three Russian Research Modules. At this time, these modules have varying levels of design maturity (e.g., the JEM is essentially unchanged from the configuration planned for Space Station Freedom, while the COF has been redesigned to be smaller, and multiple designs and configurations are being considered for the Centrifuge Module). Three modules will serve primarily as crew habitats and provide life-support functions: the U.S. Habitation Module, the Russian Service Module, and the Russian Life Support Module. The Russian Functional Cargo Block (FGB) module will provide propulsion, navigation, and attitude control during the early assembly phases. In addition to the modules listed above, two Soyuz-TM vehicles (or further upgraded Soyuz vehicles) will be present at all times to facilitate crew rotation and provide the capability for rapid return to Earth of all crew members in case of emergency. The ISS will be resupplied mainly by the Russian Progress-M vehicle and a successor vehicle currently in development, the Progress-M2. The Progress-M and M2 will dock often at ISS, and there will likely be one or more of these spacecraft attached much of the time. The Space Shuttle will also dock at ISS to rotate crew members and to deliver payloads and supplies. In addition to the permanent modules and visiting spacecraft listed above, the ISS also features several nodes between the modules that provide additional pressurized volume. A summary of the assembly schedule is shown in Table 3.
TABLE 3 Milestones in the Assembly of the International Space Station Milestone Scheduled Date Launch Vehicle Comments Launch of FGB tug, November 1997 Proton FGB will be Russian-built, first element of ISS but U.S.-owned Launch of Node 1 December 1997 Space Shuttle First Space Shuttle launch and adapter to FGB in assembly process Launch of Russian April 1998 Proton Provides first crew habitat Service Module Launch of first May 1998 Soyuz Provides crew return Soyuz - TM vehicle, permanent crew of 3 possible Launch of U.S. November 1998 Space Shuttle Provides initial U.S. Laboratory Module research capability Launch of Japanese March 2000 Space Shuttle Provides additional Experiment Module research capability for Japan and U.S. Launch of European September 2001 Ariane 5 Previously planned for Module (Columbus launch on Space Shuttle Orbital Facility) Launch of U.S. February 2002 Space Shuttle Provides more living Habitation Module space and facilities for crew ISS Configuration June 2002 Space Shuttle Permanent crew of 6 Complete (launch possible of second crew transfer vehicle and last outfitting flight in assembly sequence)
NASA plans to assemble ISS in 44 launches, with approximately 28 launches using the U.S. Space Shuttle, 15 using Russian launch vehicles, and one using Europe's Ariane 5, in a phased assembly sequence over five years. Twenty-nine additional U.S. and Russian flights during the assembly sequence are projected as necessary to rotate crew members and for resupplying the space station with expendables such as food and propellant.
The basic design for the completed ISS can be viewed as a reconfigured Space Station Freedom joined to a previously planned next-generation Mir Space Station. The ISS design uses approximately 65-75 percent of Space Station Freedom's hardware and systems and also uses proven robust hardware from Russia such as the Service Module, the self-contained FGB tug, the hardware for automated rendezvous and docking, the Soyuz-TM and Progress-M, and the Soyuz launch vehicle.
ISS is to be developed as it is constructed using a three-phased timed approach. Phase 1, as described in Chapter 4, commences before ISS assembly in space begins and consists of a series of flights combining astronaut and cosmonaut crew activities on the Space Shuttle, Soyuz, and the Mir Space Station. The object of this phase is to gain in-orbit experience that will reduce the technical risk associated with assembly and operation of ISS in a manner analogous to the Gemini program that preceded the Apollo program. Phase 1 operations are controlled by Moscow mission control, while the Johnson Space Center develops the capability of monitoring Mir.
Phase 2 begins the assembly of ISS with the launch of the FGB tug in December 1997 on a Proton booster, closely followed by a Space Shuttle launch to attach a pressurized node that will serve as the interface to the U.S. side of the ISS and another Proton launch to deliver the Russian Service Module. The Service Module is very much like the current core module of the Mir Space Station. A Soyuz-TM crew-return vehicle arrives on the fourth flight and will permit the space station to have a permanent crew by providing a means for emergency return to Earth. A series of 10 more flights through mid-1999, five U.S. and four Russian, will complete Phase 2. (Phase 2 is complete when the U.S. Laboratory Module is completely outfitted with research equipment.) At this stage, one of the four large U.S.-provided PV arrays will be in place, and power will also be provided by arrays on the FGB and Service Module.
The third and final phase will complete the assembly with delivery of additional U.S. and Russian modules as well as additional PV arrays and other supporting hardware and systems. During Phase 3, the delivery of modules and components contributed by Japan (the JEM–a large pressurized laboratory and outside work platform), Russia (research modules), Canada (mobile servicing system with a robotic arm) and Europe (the COF, a laboratory module) will also take place. On completion of Phase 3, scheduled for 2002, a permanent human presence is planned for ISS with a six-person crew and an operational life of 10 years.
The ISS will provide accommodations for pressurized and unpressurized payloads as a means of satisfying users in both the scientific research and technology development areas. Three basic categories of U.S. payloads and prospective users exist: (1) pressurized microgravity and life sciences, (2) commercial and technology research, and (3) unpressurized external attachment payloads. The International Standard Payload Rack (ISPR) will be the primary location for pressurized payloads within the U.S., Japanese, and European modules on ISS. ISPRs have standard power, data, thermal control, nitrogen, waste gas, fire detection, and mechanical interfaces, and can accommodate about 1.5 m3 and 700 kg of equipment.
Research using the facilities provided by the international partners is likely to contribute significantly to the scientific and technical use of ISS. The Japanese contribution to ISS, the JEM, differs from the other ISS modules because, in addition to being able to house pressurized payloads, the JEM will have its own airlock that opens to an "exposed facility" where payloads that require placement outside the pressurized environment (such as for scientific observations, communications research, and materials exposure research) can be located. The JEM will also have a manipulator located outside the module that will enable the crew to both move payloads from the airlock onto the exposed facility and retrieve them without extravehicular activity. The NASDA payloads inside the JEM will focus on microgravity sciences (e.g., furnaces, electrophoresis, and protein crystallization facilities) and space life sciences research (e.g., cell culture equipment). The ESA plans to build and attach its COF to ISS and is currently planning facilities to conduct research in areas including human physiology (e.g., to study blood constituents and cardiopulmonary parameters), cell and tissue cultures (with the capability to fix and freeze samples and perform some analyses on-orbit), and microgravity sciences (e.g., to study materials at temperatures and to study fluid phenomena). ESA is also considering opportunities to conduct space science, Earth observations, and technology development research with payloads located outside the pressurized volume of ISS. Information on Russian payloads planned for ISS was not available, but Russia has indicated that the research areas prominent aboard Mir will be continued on ISS. Although providing world-class facilities for cooperative scientific research in space is a primary goal of ISS, major gains may come from the practical knowledge gained through other, more basic aspects of the program such as the assembly of the structure in orbit.
The following sections summarize NASA's current plans for ISS. Unlike the section in Chapter 4 that describes research that has been conducted over the last nine years on Mir, the following sections describe plans, intentions, and projected research that is scheduled to take place on new facilities on a new space station beginning in about 1999.
The drive to understand gravitational influences on biological systems is emphasized by the predominance of life science experiments in the current plans for ISS. The life and biomedical science facilities are scheduled to begin to join the ISS in 1999 with the addition of the Gravitational Biology Facility and the Human Research Facility to the U.S. Laboratory Module. The primary role of each facility is to increase the understanding of gravity's influence on basic biological processes. Research using the Gravitational Biology Facility will focus on cell, plant, and developmental biology, whereas research using the Human Research Facility will focus on physiological adaptation mechanisms to microgravity.
The Gravitational Biology Facility consists of two ISPRs and modular specimen habitats. The combined mass of 700 kg includes generic research equipment, support systems, and analytical equipment needed to conduct research in cell, tissue, plant, and developmental biology. Human research will be conducted using the Human Research Facility which will focus on cardiovascular, neuropsychological, musculoskeletal, hematological, metabolic, and immunological areas of interest. It will consist of a suite of equipment contained in up to four racks which will be delivered to the space station over a six-year period. The intended primary use of this latter facility is to enable work towards the development of effective countermeasures to mitigate deleterious effects of space flight.
The Centrifuge Facility is scheduled to join ISS in 2001 with a four-arm centrifuge, and later in 2004 with an eight-arm centrifuge. The ability to enable research using whole animals and plants at gravity levels between zero g and 2 g on up to 8 habitats, will provide new capabilities and promote basic research on the influence of gravity on biological systems. NASA projects that the Centrifuge Facility and the Gravitational Biology Facility will eventually be able to house a variety of species for research. Several different modular habitats are planned to be able to maintain rodents; terrestrial plants in all phases of growth; fish, amphibians and aquatic plants; animal, plant, and microbial cell cultures and tissue cultures; bird and reptile eggs; and insects. Refrigerators and freezers will be on board to preserve samples prior to their return to Earth. The Life Sciences Glovebox will provide for animal and sample handling and help enable rapid turn-around experimentation. It will be accommodated in an ISPR, provide access for two crew members simultaneously, and will accommodate two of the modular habitats. Video display and the control panels are included internal and external to the facility.
Since the early Apollo missions, microgravity experimentation has been performed on materials and fluids systems. In fact, much of the design experience that has gone into space station microgravity facilities has evolved over decades of Apollo, Skylab, Spacelab, and Shuttle flights. Early experiments in which astronauts rotated water drops before flight cameras evolved into drop dynamics, single-crystal and dendritic growth experiments, and surface-tension-driven convection experiments on Spacelab. On ISS this type of research will be pursued as part of the research program to be conducted in the Advanced Fluids Module of the Fluid Physics Dynamics Facility/Modular Combustion Facility (abbreviated as the Fluids/Combustion Facility). The planned Advanced Fluids Module experiment rack will consist of several experiment-specific test chambers, each carrying ancillary equipment such as cameras, laser optics, heaters, etc., to accommodate experiments in the areas of interface configuration, thermocapillary flow, particle dispersion, and gravity-jitter (the spectral range of oscillatory accelerations arising from crew motions, machinery, rocket firings, and so on occurring in orbiting spacecraft).
The Combustion Module will share a facility with the Advanced Fluids Module. It also has a history of evolution throughout the earlier days of U.S. space flight, being generated from sounding rocket, Space Shuttle mid-deck, get-away special, and Spacelab experiments. The Combustion Module will be contained in an experiment rack with several viewing ports to allow for various diagnostics as required by anticipated experiments in comparative soot-flow diagnostics, forced-flow flame spread, fiber-supported droplet combustion, and radiative ignition and transition to spread.
As mentioned above, the Advanced Fluids Module and the Combustion Module share the Fluids/Combustion Facility, the core of which will be delivered to the ISS in 1999. The Combustion Module will join the core at that time, but the Advanced Fluids Module will not be available until 2001. Along with the capability to conduct research on gases and liquids in the Fluids/Combustion Facility, the capability will also be available for research on solidifying systems such as ceramics, electronic materials and metals and alloys. The Furnace Facility will first become available for such experiments on ISS in 1999 and be completed by 2002. Similar to the Fluid/Combustion Facility, the Furnace Facility consists of a core rack that houses diagnostic controls, which will be delivered initially with an instrument rack. When completed with a second rack, it will contain a high-gradient furnace, thermophysical properties measurement furnace, magnetic damping furnace, and a general purpose Bridgman furnace.
The Biotechnology Facility will continue the studies to understand complex protein structures by having protein crystal growth as one of its two major program components. Cell tissue studies on mammalian tissue cultures and their response to microgravity will be supported by the second component of the program. The one-rack facility will contain support utilities for a variety of investigation-specific experiments and will become part of ISS in 1998.
The Microgravity Sciences Glovebox will provide the capability to manipulate samples within an enclosed environment and the flexibility for short-duration, rapid turn-around experiments. This glovebox will feature a command and monitoring panel and a video unit and will be accommodated in a modified ISPR. Although planned for development by ESA, baseline planning has it originally interfacing with the U.S. Laboratory Module with future accommodation being feasible in the JEM and COF.
In keeping with the goals of the NASA program to understand the evolution and makeup of planetary systems, two space science experiments are planned that will utilize the opportunity of the long-duration collection times provided by the Mir platform to both capture cosmic dust particles and examine the efficacy of capture media. These fall within the external attachment payload category for the Phase 1 (Mir) portion of the program and are designated the Mir Sample Return Experiment and the Particle Impact Experiment. To date, one space science experiment has been selected to fly on the ISS in 2001 as an attached payload. A joint project of NASA and the U.S. Department of Energy, the Alpha Magnetic Spectrometer (AMS) experiment will study the properties and origin of cosmic particles and nuclei originating from outside our galaxy and look for antimatter and dark matter. Current plans call for flying the experiment on a Space Shuttle mission in 1998 as a precursor to the work on ISS and for operating the detector for three years on ISS before it is returned to Earth. The AMS experiment is an international collaboration of 37 universities and laboratories. Beyond these experiments, the NASA Office of Space Science, which is responsible for research in astrophysics, space physics, and planetary science, currently does not have plans to use ISS for its research.
The ISS provides a platform for conducting ongoing Earth science programs for the NASA Mission to Planet Earth program. As noted earlier, ISS's inclination orbit (51.6o) permits frequent revisits to selected sites at the highly populated low and mid-latitudes. In addition, test sites can be imaged throughout the diurnal cycle, thereby permitting the investigation of short-lived phenomena such as the daily buildup of cloud cover or the response of vegetation undergoing drought stress. The Stratospheric Aerosol and Gas Experiment (SAGE) III is planned as an attached payload. Using the self-calibrating solar occultation technique, SAGE III will measure profiles of atmospheric aerosols, ozone, nitrogen dioxide, temperature, pressure, and water vapor. Lunar occultation observations will measure key nighttime species, nitrogen trioxide, and chlorine dioxide.
In order to increase commitment by U.S. industry and impact national competitiveness, commercialization and engineering will be allocated 40 percent of the resources for research by the time Phase 3 is reached in ISS development. This is reflected in a combination of research and development programs anticipated over the 1999-2002 time period incorporating a total of 33 space station racks, 13 in the U.S. Laboratory Module, 10 in the JEM and 10 in the ESA Attached Pressurized Module. Fourteen external sites with power and data will provide additional capability. An example of such an external payload is the Hydrogen Maser Clock.
Materials processing, biotechnology, materials and environmental effects and technology demonstrations will all be represented. A Commercial Protein Crystal Growth and a Generic Bioprocessing Apparatus will culminate many years of microgravity research experimentation by providing commercial products. Other planned commercial development programs include a demonstration of a solar-dynamic power module, processes for liquid-phase sintering, and superconductor materials in devices.