Imagine a structure as big as a football field and moving at a speed of close to 29,000kmph doing backflips about 400km above the surface of the Earth. Scary, right? Well, that is what happened to the International Space Station (ISS) after the docking of a Russian module on July 29. The entire episode that lasted 47 minutes was deemed not to have posed any threat to the seven-member crew on board, but how safe is it on ISS, mankind’s home in the sky for more than 20 years.
What Happened With The Russian Module?
Hours after the Russian Nauka module docked with the ISS, its thrusters accidentally began to fire, causing the space station to “roll backwards". While Russian controllers scrambled to bring the situation under control, firing thrusters on other modules to counteract the spin, the situation came under control only after the Nauka module’s thrusters shut down, on their own. The episode lasted about 15 minutes.
The somersaults ended with the ISS fully upside down, which meant it had to do a 180-degree forward flip to regain its original position, the New York Times said. Nasa had initially reported that the margin by which the ISS had been thrown off its normal position was 45 degrees, but an official later said that the the space station had made 1.5 backflips, spinning a total of 540 degrees.
The spin caused by Nauka’s misfiring thrusters was at the rate of about 0.5 degrees per second, which Nasa said was too minor for the ISS crew members to notice. But astrophysicist Jonathan McDowell told Gizmodo that the event represented “one of the more serious incidents in the 24-year-history of the ISS" and such episodes could end up in the disintegration of the structure.
What Are The Threats That ISS Faces?
A 2007 report of the ISS Independent Safety Task Force said that the ISS “is robust and, to the extent practicable, meets a two failure-tolerance requirement to minimise the likelihood of catastrophic events". Which means, that for a host of contingencies, “time is available to mitigate vulnerabilities by switching to redundant systems, performing maintenance/repairs by the crew, or relying on consumables reserves until a future logistics flight can be launched" to the ISS.
However, the report listed nine “primary factors" that were regarded as “potential threats to the ISS crew and the Station". Chief among these is micrometeoroid and orbital debris (MMOD) penetrating the living quarters or damaging critical equipment". But the report noted that the risk of MMOD penetrating the ISS “is 55 per cent with a 9 per cent risk of a catastrophic result over a 10-year period". Reports suggest that debris levels in low-Earth orbit have increased by 50 per cent since 2008, including through events like when China blew up its own weather satellite in a 2007 missile test.
Among the other major threats are a catastrophic collision with a visiting vehicle or robotic arm — the Nauka module would qualify as a visiting vehicle although the July 29 episode did not amount to a collision, although it could be described as “a catastrophic system failure" or a “hardware or software design flaw", which are also counted as critical threats to ISS.
Have There Been Cases Of Critical Crises On ISS?
Amid the pandemic, the ISS was described as the “safest place to be" to beat the novel coronavirus, but it can be faced with issues more critical than Covid-19. Even though space is regarded as having claimed no human lives — any tragedies have occurred on the way to space or during the return, like the Space Shuttle Columbia disaster in which Indian-origin astronaut Kalpana Chawla was among the seven crew members who died.
Last year, Russia had reported that there was an air leak in its section of the ISS although it was not considered to be “dangerous for the life and health of the ISS crew and does not prevent the ISS continuing manned flight". A similar case had occurred in 2018 as well when astronauts found a hole in the wall of a Russian-made Soyuz space capsule that had docked with ISS.
There have been instances of scares involving leaks, short-circuits and space debris. Astronauts can use Soyuz capsules that are attached to the ISS for evacuation in the event of a serious crisis although most incidents have only been of a minor nature.
Among other potential threats for ISS are on-board fires, a toxic spill, or a crew member drifting off during a spacewalk. While there are fallback options and redundancies for such scenarios, the Nasa Task Force had noted that “regardless of the efforts put forth, operating in space is, and will be for the foreseeable future, inherently risky and requires continuing discipline and diligence to maintain safe operations".
What About The Astronauts’ Health?
Apart from wear and tear and issues that may crop up with the ISS, space poses its own challenges for the health of the astronauts themselves. Astronauts can be exposed to high levels of radiation while low gravity on board ISS can result in the loss of muscle and bone mass, to avoid which, astronauts have to work out at least two hours a day. In fact, the six-bedroom sized living quarters on ISS also houses a gym.
When Does ISS Retire?
The ISS has been cleared to operate at least till the end of 2024, Nasa has said, adding that it is technically fit to continue in its orbit around Earth till the end of 2028. “Additionally, our analysis has not identified any issues that would preclude us from extending beyond 2028 if needed," they told space.com.
In the meantime, taikonauts from China are already at work assembling the country’s very own space station — called Tiangong, or Heavenly Palace — and it is expected to be ready by the end of 2022.