Radiation, bone weakness, anxiety: Sunita Williams's next worry in ...

The Nasa astronauts on Boeing's maiden human spaceflight aboard Starliner were initially slated to return within seven days of their launch from Earth on June 5, 2024.

Nasa astronauts Suni Williams, wearing Boeing spacesuits, gestures as she prepares to depart the Neil A. Armstrong Operations and Checkout Building. (Photo: AFP)

Two months after astronauts Sunita Williams and Butch Willmore arrived at the International Space Station, Nasa announced that their return could be delayed until February 2024.

The Nasa astronauts on Boeing's maiden human spaceflight aboard Starliner were initially slated to return within seven days of their launch from Earth on June 5, 2024.

Nasa has now said that they might have to return to Earth on SpaceX's Crew Dragon instead of their existing vehicle, Boeing's Starliner.

This means that Boeing's maiden human mission could end up in a daring rescue mission by Elon Musk’s SpaceX, pushing the planned eight days in space to over eight months. That's a long time to be in space, and there is a concern about the impact of such a prolonged mission on the physical and mental health of the astronauts.

Although the ISS, a $150 billion flying laboratory above Earth, is well equipped with living facilities, sleeping quarters, and even a gym, an artificial environment away from the protection of the home planet is always challenging.

Astronauts who visit the ISS circle in an orbit about 400 km above the surface of Earth. This means they are no longer protected by Earth’s atmosphere and magnetic field from harmful solar radiation. In fact, near the eastern coast of South America, the ISS passes through a point where the radiation levels are over 30 times higher than those on Earth.

In other words, in one week on the ISS, astronauts experience the same radiation levels as one year on the ground.

To understand this better, we know that astronauts experience radiation somewhere between 50 to 20,000 milli-sieverts (mSv). A milli-Sievert is the unit in which radiation is measured. For comparison, 1 mSv is equal to the radiation of about three chest X-rays.

So, effectively, astronauts experience radiation exposure of about 150-6,000 chest X-rays. This increased exposure to radiation, especially over the long term, can be carcinogenic, degenerate tissues, and damage the nervous system.

High levels of radiation damage lymphocytes, cells heavily involved in maintaining the immune system; this damage contributes to the lowered immunity experienced by astronauts, and existing microbes in their bodies can flare up and cause infections.

The second major issue in space is long-term exposure to microgravity or zero gravity.

When we are on Earth, we are under the constant influence of Earth’s gravity—our body is in continuous exercise against this. Long-term exposure to microgravity removes this exercise, and this can lead to loss of bone and muscle mass.

The loss of bone tissue can be approximately 1.5% per month, especially from the lower vertebrae, hip, and femur (upper leg). This can impair astronauts' performance, increase their risk of injury, reduce their aerobic capacity, and slow down their cardiovascular system.

The human body consists mostly of fluids, and gravity tends to force them into the lower half of the body. Our bodies have many systems to balance this situation. But when released from gravity, these counterbalancing systems continue to work, causing a general redistribution of fluids into the upper half of the body.

This is the cause of the round-faced 'puffiness' seen in astronauts. It may contribute to observations of altered speech motor control, and loss of smell, taste, and balance in astronauts.

The third issue, which is more specific in the Boeing case, is psychological. Imagine going away from your family on an eight-day trip but ending up being stranded away for at least eight months.

Add to it the fact that the place you are stranded is 400 km upwards in space—much worse than the remotest islands you can think of. Adding to the anxiety is that the ship you came on is leaking helium and has unpredictable thruster issues.

This is the environment our stranded astronauts are facing. Both Sunita and Butch are seasoned astronauts and US Navy pilots, so being in unpredictable situations is part of their training and experience. But even for them, such a situation could be mentally stressful.

But there are reasons to be hopeful.

Foremost is that Nasa has multiple options to rescue the astronauts even if Boeing fails to rectify the Starliner. The American space agency not only has a fully functioning Dragon spacecraft operated by SpaceX, but it could also call in help from the Russian space agency, Roscosmos, to rescue the astronauts.

However, it would need a lot of technical adjustments and geopolitical arrangements given that Russian-American relations are at an all-time low.

Then we have history to lean back on.

It is not the first time an astronaut will spend months in space. Russian cosmonaut Valeri Polyakov spent 437 consecutive days in the Soviet-era space station Mir, and when he landed back on Earth, he chose to walk the short distance from the space capsule to his chair.

In doing so, he proved that humans could be physically capable of working on the surface of Mars after a long-duration journey from Earth.

On another note, Sunita Williams is currently going around the Earth at a speed of 27,000 kmph. At such high speeds, the theory of relativity kicks in, and time moves slightly slower for her than for the rest of us.

In a matter of eight months, when Sunita Williams begins her return to Earth, she would be 0.01 seconds younger than anyone on Earth born at the exact time and date as her.