The Shenzhou XX crew arrived safely back on Earth on Nov 14 using the recently arrived Shenzhou XXI capsule. This has left the Shenzhou XXI crew with no immediate prospect of return if there was another emergency. The Shenzhou XXII capsule has just been sent up early, given the situation is an unprecedented event for the Chinese Tiangong (Heavenly Palace) space station. However, given that the crew of the last two Shenzhou missions have spent some EVA (extravehicular activity, aka spacewalk) time installing additional shielding against space debris, it was clear the risks were understood, and that further precautions were already being taken.
Given what has eventuated, this event will spur the Chinese space program to build more redundancy into the space station sooner than planned and to reevaluate the urgency that China, and indeed the world, attaches to the issue of and threat from space debris. I speculate that China will also plan to add an extra docking port. It would make the space station larger, which is part of the overall plan anyway, but they might now bring those plans forward. This event is sharply focusing the minds of the Chinese and indeed all space-faring nations on the profound impact of space debris.
At the moment, we have a 1 billion yuan ($141 million) space capsule stranded, attached to the space station, and unable to be used at all as a result of the impact of a small, worthless piece of space junk traveling at perhaps 10 kilometers per second. At such speeds, small pieces of debris, a few grams in mass and less than 1 centimeter in size, can have the explosive power of a grenade. It is not the mass of the debris particle that is the main issue; it is the velocity at which it is moving. This is because the kinetic energy of impact is given by the square of the velocity multiplied by the mass of the debris particle, then divided by two. The piece that affected the window on the capsule was likely even smaller, but still had a significant effect. This impact created fissures and cracks in the space capsule’s glass. In the searing heat of reentry and the attendant vibrations, these cracks would spread and easily blow the whole window out. This is why they haven’t risked it. It’s just too dangerous.
Furthermore, the window is not a component that can be fixed in situ because it is complex and critical, and the damage is too severe to be repaired on-site. The China Manned Space Agency has now announced that the spacecraft will remain in orbit and be deorbited after the current mission completes its tasks. An alternative is to keep it as a storage facility attached and for experiments, but the docking port is needed.
Despite this unprecedented saga, all is now well for the time being on board the “Heavenly Palace”. Though this issue has now grabbed all the headlines, there are still many positives and “firsts” for this mission worth noting.
China can take a global lead in tackling space debris for us all. At the same time, the Hong Kong Special Administrative Region could play a pivotal role by establishing a global space sustainability hub
To begin with, this was the quickest-ever docking between the rocket lifting off and the taikonaut entering the space station in just over three and a half hours, a new world record, and interesting to compare that with the equivalent timings for the International Space Station, which is typically 16 to 19 hours. There was also the youngest taikonaut ever on board, at 32. They also installed a special oven so they could have, effectively, the first barbecue in space, with viral images of the taikonauts tucking into chicken wings and steak. It is not just any oven, but one that filters out smoke and fat effectively, so as not to contaminate the pristine, almost zenlike space station environment characteristic of Tiangong. I am sure the barbecue aromas were still greatly appreciated.
Another fascinating snippet was the crew commander’s intention to improve the psychological and cultural well-being of the taikonauts, with plans for poetry, calligraphy, and tai chi to supplement the “gardening” already underway and to provide a few kilograms of lettuce and tomatoes. Interestingly, they also brought up four mice. These were not just any mice, but were selected from dozens of mice that were “specially trained”, and they picked the best, the fittest, and most physiologically suitable to be part of the space mission, two male and two female mice. So while this is interesting and even entertaining, there is a very serious side to study and experiment.
Given the saga of the Shenzhou XX-to-XXI changeover, the implications of what’s just happened will filter through to the highest levels of all spacefaring nations, and I think there may well be a very proactive approach going forward, and hopefully, greater collaboration and cooperation to solve the debris problem before it becomes too difficult. This event will lead to a much stronger, better-resourced, and more urgent global program to address the space-debris issue, and this is the silver lining we need. China can take the international lead in tackling this issue for all of us. This is also in the context of all the pushing and warnings from certain vocal quarters, including me, that have stressed the existential threat posed by space debris to the entire low earth orbit ecosystem and, by extension, the whole of the global space program. Space sustainability is included as a theme for the upcoming Asia-Pacific Regional Meeting of the International Astronomical Union, a massive megascience event to be held in Hong Kong in May. There will be talks addressing this very issue of space debris and the Kessler syndrome, and how it threatens all of space. The relevance to astronomy is that if that ecosystem is destroyed, the Chinese space station and the Chinese space station telescope for astronomical research will be gone as well.
In summary, China can take a global lead in tackling space debris for us all. At the same time, the Hong Kong Special Administrative Region could play a pivotal role by establishing a global space sustainability hub. It’s a very opportune moment with enormous potential — can we grab it?
The author is the director of the Lab for Space Research, the University of Hong Kong.
The views do not necessarily reflect those of China Daily.
