The first half of the first decade of the 21st century saw a good amount of activity in space, though most of it was directed at evolutionary developments of existing hardware and the implementation of technologies and plans that had been in existence for a longer time.
NASA had been working on inflatable habitats since the early 1990s and by 2000 the first three units had been delivered to the Moon, where they expanded the living and working space of Copernicus Base almost ten times, creating space for larger laboratories, storage facilities and the first larger hydroponics experiment outside of Earth.
An inflatable habitat protected against radiation and micrometeorites by a lava tube was one thing. To use such an habitat in orbit, where it had to protect its inhabitants against the same issues, however was a different matter. The first habitat, along with some new improvements, was sent to SOC Hephaestos in 2000, both to test it in space as to experiment with it, by coupling and decoupling the module several times. In the end the inflatable experiment, albeit with a few minor adjustments, was permanently added to Hephaestos.
By 2004 NASA felt they had gathered enough information on the matter. Data showed an increased protection against radiation due to several new polymers used in its construction. The many layers of kevlar also increased the protection against micrometeorites.
Earlier the CIA had been able to recover basic information about the Soviet Gel Pack Protection and handed it to NASA. NASA, who investigated how to increase the protection and to close a leak when a micrometeorite punched through dozens of layers of an inflatable habitat, further developed the system into a self sealing layer. This layer consisted of a polymer gel in a high density polyethylene bladder. If punctured, the gel locally hardened from exposure to vacuum, sealing the puncture. Additionally the gel increased radiation protection and provided an extra measure of defense against laser weapons.
This new method of protection for habitation modules was published by NASA, allowing the Soviet Union to profit from this development of their own idea. At least for habitation modules it made the earlier developed whipple shield gel combination obsolete before it had even been implemented.
By 2005, NASA decided to retire the two deck version of the Manned Command Mission Module, replacing it with a combination of the single deck MCMM with an Inflatable Habitat Module, which provided more than four times its internal volume.
The Soviet Union saw the same potential in inflatable habitats. Their DOS and MOK modules always had been larger than NASA’s modules, to be able to provide more space. Their sheer size however caused an extra risk during launch. Inflatable habitats could be folded into small packages and would still end up larger than the already used modules.
With the modules used to build up the Zvesda Moon Base on the other hand, the Soviets had some prior knowledge about size changing modules and made use of it.
Where NASA made use of a fixed central spoke, surrounded by the packaged up module, the Soviet Union was able to construct a module where the central spoke telescoped outside, allowing to wrap up the modules into even smaller forms, while the material needed for the internal space was confined to a conventional part of a module.
But NASA and the Soviets were not the only ones interested in the technology of inflatable habitats. The other spacefaring nations had an interest as well, as it allowed tightly packed up station modules that could be inflated to a much larger space and provided superior defense against radiation and micrometeorites.
ESA had begun developing the technology in the mid 1990s and a first test had been done on Columbus in 2002. By 2005, ESA decided to return to the Moon and to make use of the inflatable habitats. The last ESA lunar landing had been in the Marius Hills region, where ESA previously had discovered a 65m ‘skylight’ in a lava tube, making the area a perfect location for establishing the first ESA lunar base.
ESA prepared carefully, by first establishing a space station, named Da Gama. But other than NASA, they placed the station in the L1 point directly between Earth and the Moon, where not only the Moon could easily be reached, but also interplanetary space.
For the moment ESA used Da Gama as a staging point for landing near the skylight their last lunar exploration had discovered. Three remote controlled landers touched down nearby, before a crew of three landed in June 2005, preparing to construct multiple elevators and flights of stairs down into the skylight, finishing them by February 2006.
A small waystation was kept topside, near the skylight, where a large array of solar panels provided the power for the station within the lava tube, with a backup of superconducting batteries for the times when the lunar surface was dark. Two habitat modules were the core of the new Galilei Station, and had a monopropellant powered lift station in case the elevators failed and stairs somehow collapsed.
Already there were plans to build up an inflatable elevator system so that astronauts could transfer from topside down into the lava tube in a shirtsleeve environment.
Already in the planning stages of Da Gama and Galilei during the mid to late 1990s, ESA decided that they needed a more efficient engine to save fuel. A solid core nuclear engine, comparable to the American NERVA and the Soviet RD-0411 engine was designed and named Viking. But rather than using liquid hydrogen like NASA and the Soviets, ESA went for a cheaper alternative, using ammonia. It had the advantage of easy storage and high density, while it provided roughly sixty percent of the specific impulse of hydrogen. To make up for it, the use of cermet materials allowed to run the engine hotter than others.
The ESA nuclear transfer stage, named Verne, was able to transport up to 80 tonnes of material to Da Gama and return to rendezvous with Columbus to refuel. Two of the Verne stages were built and launched, regularly transporting material to Da Gama.
For China the development of inflatable modules was heaven sent. As these modules were generally lighter than comparable conventional space station modules, it allowed them to launch larger modules with their smaller launch vehicles.
The first Chinese inflatable habitat module was launched in 2006 and docked with the Tiangong 3 Complex, where it nearly doubled the available space. A second module followed in 2007. The massive improvement in usable space made China consider to add an inflatable section to their Shenlong and Shuguang spacecraft to increase the comfort of the crew on longer duration missions.
Another problem for humans in space was the general lack of gravity and its effects on the human body.
The space agencies tried to minimize the amount of time spent in microgravity to six months for their astronauts, cosmonauts or taikonauts. Stays on the Moon and Mars were longer, as there was at least some gravity, but especially the astronauts and cosmonauts that journeyed to Mars had more difficulties with their health.
A stay of nearly two years on Mars, followed by six months of microgravity left everyone much weaker and in desperate need of medical attention and physical therapy once they had returned to the surface of the blue planet.
Physical training in space only had a limited effect on the degradation of bone density and muscle mass, although it at least made sure the heart didn’t suffer once the astronaut or cosmonaut returned to Earth.
While the effects were valuable for the medical field as finding ways to counter the effects meant that osteoporosis for elderly people could be treated as well, a more permanent solution still had to be found. The most obvious one was to use rotation to simulate gravity with the help of the centripetal force.
There were many things to consider however. Distances from the center of the rotation to a habitat where simulated gravity was needed could only be made so far, considering existing technologies and abilities. To have a stronger effect, the rotation had to be faster for a centrifuge with a smaller diameter. On the other hand humans had problems once a centrifuge rotated too fast. Tests had shown that rotations of more than twelve rotations per second lead to nauseated and dazed test subjects.
Long term experiences on the Moon had showed that the gravity there was sufficient to prevent the worst effects of osteoporosis and reduction of muscle mass. With this knowledge, the space agencies tackled the problem on their own.
NASA decided to combine the inflatable habitat technology with the rotational habitat. In its launch stage not larger than a dual deck MCMM, the centrifuge, once inflated and stabilized by Hoberman flexible structures, had a diameter of fifteen meters. Rotating five times per minute, it was able to provide a simulated gravity of 2 m/s² or 0.2 Earth gravities. It also provided a living space of 200 square meters and volume 85 m³, allowing comfortable living conditions for a crew of four.
To counter precision effects of moving a space station or a spacecraft around, NASA either intended to use two counter rotating centrifuges or use a smaller counter rotating flywheel. Computer controls in combination with gyroscopes were needed to prevent the centrifuge from tumbling as the crew moved about, changing the center of mass for the centrifuge. These computers continuously controlled the center of mass and held it as close to the normal center as possible with storage tanks and pipes filled with water, pumping it around.
By 2008 NASA had two test articles built and attached to SOC Hephaestos, where the modules became a rapid success. By 2010, the Rotational Habitat Module was finalized and prepared to be integrated into the future plans of NASA, not replacing the Inflatable Habitat Module, but complementing it.
The Soviet Union’s choice of providing a rotational habitat also made use of inflatables technology, however their setup could be called more conventional. Two solidly constructed telescoping spokes from a central bearing held a pair of inflatable habitats in place, together with a couple of tension cables for added security. It had a diameter of sixty meters and with just three rotations per minute could provide a simulated gravity of 3 m/s² or 0.3 Earth gravities.
The torque of the habitat section was canceled out with the help of four counter rotating steel flywheels. Additionally generators were hooked up to the flywheels and the rotating section, providing additional power generation if needed.
The first Soviet rotating habitat was launched in 2009 and attached to MOK, before a second was sent towards Venus on VEK 1.
Much like NASA, ESA decided to use a fully inflatable structure with Hoberman structures, but also followed the more classical design with two separate habitats on two long spokes. The spokes were made up by a truss structure with additional tension cables strengthening it, while an inflatable tube was running along the inside of the truss structure and a ladder allowing transit from the rotation hub down into a habitat module. Both habitat modules were largely conventional inflatable habitats that were connected to the spokes and set into rotation, with five flywheels to cancel out torque.
The ESA design, 30 meters in diameter, rotated five times per second and produced a simulated gravity of about 4 m/s² or 0.4 Earth gravities in the lower deck and 3.4 m/s² or 0.34 Earth gravities on the upper deck. But rather than testing it on Columbus, ESA sent the first experimental module to Galilei in 2010, where it was docked to a more conventional Cook module that had been launched earlier.
As it was on Earth and in cislunar space, NASA and the Soviet Union looked for ways to make life and research easier on Mars. There had long since been thoughts about utilizing the already existing infrastructure of the Martian city itself to provide living space for the astronauts and cosmonauts on the Red Planet, but no one was sure if the building materials used by the Ziggies were up to the task. The risk of first repairing a building and then have it collapse around the crew while they moved in, was too big.
Eventually however both NASA and the Soviet Union discovered several buildings in their areas of Honore City where the building substance was good and which only had limited damages done to them during the event that lead to the destruction of the city.
Advances in adhesives and the development of inflatable air locks made both powers seriously consider to turn several existing buildings into more permanent bases on Mars.
NASA managed to find a building the size of a normal apartment building in Manhattan, which only had limited damage opening the ground floor to the Martian atmosphere. Over four months in 2004 of work, the building was cleared out by the astronauts, who discovered a number of useful looking artifacts, and prepared to be closed up and made inhabitable.
Until the arrival of the inflatable airlock, the building was closed up and the astronauts tried their best to get rid of the Martian dust inside the building, but complained about the lack of a vacuum that worked on Mars.
Once the airlock arrived, it was first connected to one opening of the building by screw anchors, before being sealed by adhesives. A second opening was used to install life support systems, which made use of the martian resources of water and atmosphere to slowly replace the martian atmosphere inside the building with a breathable one.
On March 22, 2005 after a large number of tests to make sure that the building was airtight and in no danger of collapsing, the Lowell Mars Research Center was deemed to be habitable by NASA and the astronauts began to move in. On May 4, the move was completed and the old landing site was converted into a landing field for future expeditions.
On the Soviet side of Honore City, the Soviets discovered a building of comparable size. After preparation, sealing and testing, they began to move in on March 27, 2005, finishing their move by May 1.
Future expansions of both new bases were already planned, especially making use of the transparent top stories of the buildings, which were considered to be perfect to add hydroponic or aquaponic cultures to improve the food situation on Mars.
Parallel to the move into more permanent quarters on Mars, NASA and the Soviet Union developed reusable Mars Landers for crew and material. Without the need to land additional large scale modules on the Martian surface, the actual requirements for landing on Mars were reduced.
Fuel for the return vehicles was already produced locally in the form of methane and oxygen, so a reusable landing and ascent vehicle made sense. A restartable engine running on these fuels was just a minor issue for NASA and the NPO Energia, a reusable heat shield provided more of a challenge.
NASA had already considered the development of a reusable, actively cooled heat shield during the 1960s and the 1970s, but never concentrated on it on the grounds that a conventional ablative heat shield was cheaper. Now however the research was actively considered again and by 2006 NASA tested an active cooled heat shield that had liquid oxygen pumped through it to act as heatsink before being injected directly into the plasma shock layer produced by reentry.
After ten reentry tests, NASA deemed the technology to be useable for Mars. Based on this technology, Douglas developed the Phoenix Mars SSTO and tested the first prototype in 2009. Weighing about 32 tonnes, the Phoenix was capable of launching a payload of 2 tonnes into orbit, including four astronauts, with a return capability of 4 tonnes.
NASA purchased three Phoenix SSTOs for the use on Mars. Phoenix 1 and 2 reached Mars with the 2011 mission.
The Soviet Union on the other hand made use of their KGB agents, acquiring an already existing active cooling technology from the Indian space program, where it was used for the MOV reusable space capsule. Additionally, rather than developing a completely new SSTO launch vehicle for Mars, like NASA, NPO Energia refitted their already existing and working Mars landers with the heat shield system, reducing the costs needed for the development and any need to reacquaint their cosmonauts with a new system.
The Soviet Mars SSTO, named Bizan, had similar characteristics to the NASA Phoenix, but was already used by the Soviet Mars Base in 2009.
The use of SSTOs on Mars reignited the race between the United States and the Soviet Union. Who could get the most and best artifacts back to Earth in the shortest amount of time and profit from them.