After ISS, a mix of human outposts
More than 70 nations use the International Space Station (ISS) for research today, and a growing realization of its value is driving a sense of urgency to continue the unique facility after the scheduled 2020 shutdown, and replace it once it is gone.
China is leading the way on replacement by default, since U.S. concern about China's military-space program has blocked its full participation in the ISS (although Chinese experiments are beginning to find their way into the station racks).
Instead, Chinese space experts have taken the occasion of the International Astronautical Congress (IAC) here to reveal unprecedented detail about the country's planned Mir-class orbiting laboratory, and invite international partners to join its taikonauts there once it is operational after 2020.
Russia, too, has voiced tentative plans to orbit its own small space station, and the U.S. station managers expect—or at least hope—that commercial interests will orbit their own stations eventually.
“The work that we're doing withand Orbital [Sciences Corp.] as our cargo providers is a really important step in that direction, as are the companies that are competing for commercial crew delivery to low Earth orbit, because those are the stepping stones to help those providers be ready to service and maintain a space station,” says Julie Robinson, ISS program scientist. “So I can very much imagine in, say, 2030, that one of those commercial providers will be ready to operate small space stations that would continue to meet research needs, and those research needs would be in demand because of all the results we've had from the space station.”
and its potential international partners on deep-space exploration are scrambling to use the ISS as a technology proving ground for an eventual trip to Mars. There is a use-it-or-lose-it sense of urgency because of the station's long-term funding uncertainty at the hands of hard-pressing politicians worldwide.
China apparently does not have a space-funding problem and is moving ahead steadily on plans sketched at the IAC in Naples, Italy, last year to launch a second small Tiangong-class space station in the next five years, along with an unmanned cargo carrier, and use them with the planned Shenzhou 11 to begin human-tended science. After that, they will start work on their Mir-class station in a 43-deg. orbit.
China also is eager to collaborate with Russia or Europe to use its Shenzhou spacecraft and perhaps the cargo carrier to support the ISS. And it is ready to open its nascent space facilities to foreign partners.
“All countries are entitled to the equal right to share the resources in outer space,” says Chinese Vice President Li Yuanchao, who addressed the opening session of the IAC. “. . . China is willing to share with all countries, including the developing countries, the experiences of developing space technology to promote the economic progress, in the spirit of development through cooperation and sharing of outer space, enhance international aerospace exchanges and cooperation, and make sure that the outcomes of space technology benefit all mankind.”
In technical presentations at the international congress, Chinese space officials said they are open to joint activities ranging from foreign-astronaut visits to the new station to docking foreign modules there (see illustration).
“There are different levels of collaboration,” says Ming Li of the China Academy of Space, who gave a fairly detailed account of China's station-assembly plans. “For manned missions, we are very open. The first manner is system-level collaboration. That means our partners can build the space modules [on] their own and [launch them with] their own launch vehicles, like the ISS. In the ISS, there are different modules from Japan, from Europe and also from Russia.”
Plans call for three main modules in the Chinese station: a central core similar in function and size to the Russian Zvezda service module on the ISS and two experiment modules mounted in a cruciform configuration around a central node. That would leave room for two non-Chinese modules at the other end of the core, also mounted at 90-deg. angles, Ming says.
Lofting the core to orbit must await completion of China's new spaceport at Hainan Island, and the big Long March 5B launcher, he notes. Also in development are the new human-tended space lab, which will allow more work on the techniques that will be needed to build the larger station, and the cargo vehicle to carry supplies up to orbit and trash down. Initially, the cargo vehicle would burn up on reentry, but Ming says a recoverable upgrade is also possible.
The new station will accommodate crews of three, rotating back to Earth every six months, he says. Its assembly will be aided by a relocatable robotic arm attached to the core module, which is another potential area for international collaboration.
“We tried to have some collaboration in Europe and Canada, but not yet,” Ming says. “The preliminary design is designed by my colleagues. We would like to have some collaboration with, especially, Canada. We know the Canadarm is very famous, and also very reliable.”
Canadarm served NASA's space shuttle fleet, and Canadarm2 helped assemble the ISS. Ming says the Chinese-designed mechanism used on the Shenzhou and other vehicles for pressurized docking will be adapted to work with other spaceflight systems, if warranted.
“Once we have collaboration with Russia and Europe, I think we will use international standards, combined with Chinese design,” he says, noting that the “Shenzhou manned spaceship and the cargo spacecraft can also provide transport service for space facilities such as ISS.”
Like the ISS, the Chinese station will use control-moment gyros for attitude control, with a bipropellant propulsion system to reboost and maneuver, built for a 10-year service life. To conserve consumables, a regenerative life support system is being contemplated, Ming says.
Chinese scientists want to use their nation's space station for the same types of microgravity research already underway on the ISS, including combustion studies, materials science, life science and other work that takes advantage of orbital free fall. Weijia Ren of the Technology and Engineering Center for Space Utilization at the Chinese Academy of Sciences outlined plans for experiment racks in the large Chinese station.
In form and function, they duplicate many of the facilities on the ISS. Three racks will be set aside for life sciences, including a glove box and sample refrigeration; two will handle fluid experiments; two will be dedicated to materials science, including a high-temperature furnace; and two will be used for fundamental physics. Also in the plans are three multipurpose racks, including facilities for extremely low-acceleration microgravity experiments, and a centrifuge for 1g experiment controls and “partial gravity” for other applications, Weijia says.
One general-purpose rack will include operating controls for the Chinese station's robotic arm, which in the illustration appear to reside on a laptop, just as on the ISS. Weijia notes the racks will be built to ISS standards for power and other utilities.
China already is working to establish human spaceflight cooperation with the French and German space agencies for microgravity research and space medicine, which could extend to Shenzhou flights, according to Ming.
“We can collaborate in training and selection of astronauts, who would fly together with Chinese taikonauts,” he says. “There is no difference for developing countries, and also for developed countries.”
Russia has tentative plans to orbit its own small space station, as well, after getting as much utility as possible from its investment in the ISS, according to Alexey Krasnov, the human-spaceflight chief at Russian space agency.
“And then, potentially, we will end up with a smaller structure on low Earth orbit,” Krasnov says. “At least in the Roscosmos understanding we will not endeavor building a national space station similar to the ISS scale, because we believe we will utilize low-Earth-orbit infrastructure largely for innovation, technology tests, as a laboratory and manufacturing capability for new materials, for experiments.”
Russia operates the oldest module on the ISS and has assured itself in a two-year test series that the old hardware can double its 15-year design life, according to Sergey K. Shaevich of the Khrunichev State Research & Production Space Center, which built it.
After subjecting the ground-engineering version of the flight pressure vessel to pressure cycling and simulated bending loads around the docking ports at each end, engineers found microcracks in the aluminum hull. The cracks did not grow under additional testing, and the hull was cleared for 15 more years of service. However, Shaevich says Khrunichev has some ideas about how to repair the cracks, should it become necessary, based on inflight refurbishment done on Soviet-era Salyut stations.
Also noted was degradation of the adhesive used in the orbital-debris shield, he says. But the hardware was cleared after ballistic testing on the ground, and a reanalysis of the debris environment at Zarya's position. Launched on a Proton rocket in November 1998, Zarya formed the basis for the ISS when assembly began with the arrival of the first U.S. node on the space shuttle Endeavour the following month.
The U.S. has conducted similar work on that node, and in general, agrees with the Russian assessment that the station structure will last until 2028. At one point, NASA considered recycling station modules after that by moving them into the cislunar space that is likely to be the next area of human spaceflight activity (AW&ST Oct. 10, 2011, p. 46). However, William Gerstenmaier, NASA's associate administrator for human exploration and operations, said at the IAC here that that will probably prove impractical, given the difficulty of moving heavy hardware out of low Earth orbit. But the old modules still might prove useful as free-flying assets at some point in the future, he says.