Dienstag, 1. September 2015 - 10:31 Uhr
At some time in 2016, China will launch the Tiangong 2 space laboratory. The launch will break a fairly long period of inactivity for China's human spaceflight program, which underwent an uncommon surge of activity after Tiangong 1 was launched. 2014 and 2015 have been years without any Chinese astronaut launches, so we are keen to see some more action.
Nothing is happening in space, but not much has happened recently in China's official state media, either. That's not surprising. In some ways, it's probably business as usual, as preparations for the Tiangong 2 program advance steadily behind closed doors. The silence also reflects the new conservatism in reporting on Chinese spaceflight, which was gradually opening up before it was abruptly reset by some new government policies.
Let's recap what we know. Tiangong 2 will use the same basic module as the Tiangong 1 space laboratory, a small cabin with sleeping quarters for two astronauts. There will probably be few visible differences on the inside or the outside of the laboratory, but there will be changes. The most important one will be a new regenerative life support system.
Other changes seem likely when the lessons of Tiangong 1 are incorporated, but overall, Tiangong 2 will probably represent a fairly incremental evolution in design. The floor of the module could be changed, and there could be some visible differences there. Astronauts on the first expedition experienced problems, and the second expedition took up some new panels to correct them. China may also choose to modify the docking system, but it will probably look the same as it did on Tiangong 1.
As with Tiangong 1, Tiangong 2 will be launched by a Long March 2F/G rocket, a modified version of the rocket used to launch Chinese astronauts.
Only one crew expedition will fly to Tiangong 2, unlike the two expeditions that occupied Tiangong 1. The astronauts will launch on the Shenzhou 11 spacecraft, and there will probably be three of them. The mission commander will probably be a veteran astronaut, and at least one of the other astronauts will be a rookie. Most probably, there will be two rookies on the crew.
Beyond this, we really don't know who will fly. The Shenzhou 11 crew will probably live aboard Tiangong 2 for longer than any previous Chinese crewed mission. They could easily stay on board for a month or even longer. That makes sense when logistics don't need to be conserved for other missions, and the life support system itself is improved.
Now to the real breakthroughs. Tiangong 2 will receive a visit from China's first cargo spacecraft, dubbed Tianzhou. This is a pressurized module with a lot of design heritage from the Tiangong laboratory design, but it's larger. Tianzhou will launch aboard a Long March 7 rocket, which has yet to make its debut. The module is too heavy for the Long March 2F/G to loft.
Tianzhou is expected to dock with Tiangong 2 after the Shenzhou 11 crew has departed. It is unclear exactly what it will do while it is docked to Tiangong. Simply getting the cargo spacecraft to fly and dock with another spacecraft could be enough of an achievement for its debut mission. But China has given vague hints of other experiments, such as a possible propellant transfer. Right now, it isn't really clear if this will happen.
In some ways, the Tiangong 2 program seems less ambitious than the Tiangong 1 program that preceded it. That's a fair observation, but it needs to be taken in context. The entire Tiangong program is designed to test technology for the future Chinese Space Station, which is expected around 2022. Trying out a new life support system, other new technologies, a longer crew endurance and a brand new cargo spacecraft is probably enough for the next phase. These are tasks that were not performed by Tiangong 1, and they must be trialed before the space station is launched.
But some mysteries remain. What is the fate of the originally proposed Tiangong 3 laboratory, which was expected to use a larger module? Will China drop Tiangong 3 from its plans and proceed directly to launching the large Chinese Space Station? Right now, it isn't clear to us. The Chinese themselves may not know for certain, either.
A decision may be pending until the full results of Tiangong 2 are taken into account. If certain critical elements did not work, they may need to be tested again. That may prompt the launch of Tiangong 3 as a remedial program for the tasks unaccomplished by Tiangong 2. If Tiangong 2 works perfectly, there may be no need to continue the Tiangong program at all.
So Tiangong 3 may now be an optional project instead of another progressive step towards the space station. If this is the case, we can't necessarily expect Tiangong 3 to be exactly the same as the original plan, which was reported to be a much larger module than Tiangongs 1 and 2. Tiangong 3 may well use another small Tiangong module instead of this larger module, which was originally expected to be a prototype for the core module of the space station.
For the moment, we can only wait and hope that more news filters through from official sources.