Time Enough for Tiangong

by Morris Jones
Sydney, Australia (SPX)
Jul 12, 2011

It's taken long enough, but it seems that we are finally getting close to the launch of Tiangong 1, China's first space laboratory. This small, cylindrical spacecraft will almost certainly take off before the end of September 2011, and will probably lift off a lot sooner than that. Chinese media reports now seem focused on this, although an exact launch date has yet to be specified.

It's time enough for the launch. Tiangong was originally expected to launch in 2010, and was also once slated for launch in the first half of this year. Why the long wait?

Admittedly, launches in China's human spaceflight program are stretched thinly at the best of times. The last launch in this program was Shenzhou 7, which took off in late 2008. This historic mission produced China's first spacewalk, and rounded off the first sequence of "solo" Shenzhou missions.

Part of the reason why we have waited so long is almost certainly a lack of any haste on the part of the Chinese. Tiangong does not need to meet any rare "launch windows" to fly to a distant planet, nor is it due to meet up with anything that's already in orbit. Launch officials can wait until they are ready, and not worry about other constraints.

But it seems likely that there have been some technical factors at work. Tiangong is a brand new spacecraft, although it almost certainly draws on much of the engineering experience (and probably some of the same systems) from previous spacecraft. Some gremlins would have almost certainly crept into the system, as they do with mature spacecraft designs.

Tiangong is also expected to host a crew on the first laboratory launched in this program, which places additional pressure on engineers to make sure it's spaceworthy.

There's also a positive reason for the delay. It's possible that engineers have re-designed some of the spacecraft's systems as it was being assembled. China's Shenzhou astronaut launch spacecraft has undergone several changes in its design as successive Shenzhou missions were flown. Some of these were simply about making prototype test spacecraft ready to carry astronauts, but other changes were deeper. In one case, the wiring topology on Shenzhou was re-designed, which reportedly produced a large saving in weight.

Tiangong could have already experienced several engineering makeovers before the first vehicle was even launched. Thus, the first vehicle is probably not really the first design for Tiangong. China has not only avoided launching an early prototype: They have avoided building a totally new spacecraft to include these upgrades. Viewed from this perspective, China is arguably accelerating the Tiangong program by quickly moving past these earlier revisions.

CG animation and a model of Tiangong exhibited recently at a UN office in Vienna yielded little further clues to the spacecraft or its mission. Yes, there are a few more antennas clustered around the laboratory's docking port than we knew about before. Some of these could be used for rendezvous and docking purposes. We have also been shown rough CG footage of astronauts entering the laboratory, which seems to be outfitted like a typical space station module. A central corridor for the crew is surrounded by equipment and storage racks. Apart from that, we don't have any good photos or diagrams of exactly what lies inside.

Tiangong 1 will presumably orbit in a solo mode for at least two weeks. This will give controllers time to "check out" the spacecraft in orbit, and make sure it is ready for its next tasks. The next stage in this program will be the launch of the unmanned Shenzhou 8 spacecraft, which will dock with Tiangong 1. On the ground, engineers and technicians will also need time to get this second spacecraft ready for launch from the same site at Jiuquan.

A report from a German group supplying an experiment package to be carried on Shenzhou 8 provides some insight into this. This report, published some months ago, states that Shenzhou 8 is "foreseen to be launched in September 2011."

If this is the case, then it seems more than likely that Tiangong 1 will be launched in August, to ensure that there's enough time to get Shenzhou 8 ready for flight.

Tiangong 1 is destined to remain in orbit for at least two years. Shenzhou 8 will return to a controlled landing a lot sooner. In February this year, I reported on a communication from DLR, Gemany's space agency, on the mission. DLR told me that the flight, carrying the German experiments back to Earth, would last between 20 and 22 days. This suggests an October landing for Shenzhou 8 is probable.

After waiting years for more activity in China's human spaceflight program, we now have two launches coming up within the space of roughly two months. It's pleasing to finally see some progress, but we will still have to wait longer for the next launch of a crew of Chinese astronauts. That will finally come in 2012, if all goes well.

Source: Space Daily.
Link: http://www.spacedaily.com/reports/Time_Enough_for_Tiangong_999.html.