The ISS Wonder: How Station’s Life-Support Systems Let Sunita Williams, Butch Wilmore Survive 9 Months

After a historic stay of around nine months at the International Space Station, Sunita Williams, Butch Wilmore, and two other astronauts are en route back to Earth in a SpaceX Crew Dragon, Freedom. The splashdown, expected in Florida’s coast around 3:27 am IST, will mark the conclusion of their unprecedented extended stay at the ISS, which was possible because of the station’s marvellous life-support systems.

Designed to sustain human life in an extremely harsh gravity-less vacuum of space, the life-support systems of the ISS, collectively called the Environmental Control and Life Support System (ECLSS), were crucial to the survival of Williams, Wilmore, and other astronauts. It is a self-contained environment that simulates an atmosphere similar to that on the Earth. While it lacks the gravitational pull and is the opposite of natural cycles, it is claimed to be perfectly suited for prolonged missions. The ECLSS has an oxygen generator, water recycler, temperature and humidity control, pantries, and vacuum-based toilets that allowed the astronauts to tackle the mission extensions triggered by the failure of Boeing’s Starliner thruster.

Oxygen Generation

The ECLSS has an Oxygen Generation System (OGS) which works on the principle of electrolysis to split water (H₂O) into oxygen (O₂) for breathing and hydrogen (H₂) into space. A Russian Elektron system works as a backup to ensure redundancy, giving about 5-10 litres of fresh oxygen per person daily. This matches the daily requirement of a person’s oxygen intake. The carbon dioxide (CO₂) is removed using a Carbon Dioxide Removal Assembly (CDRA).

Water Recovery

Through a Water Recovery System (WRS), the astronauts were able to drink 3-4 litres of water daily, matching their regular requirements considerably. The system can efficiently recycle 93 per cent of water onboard, including urine and sweat, with the help of processes like distillation, filtration, and chemical treatment.

Temperature Control

The International Space Station’s Common Cabin Air Assembly (CCAA) can regulate the station’s temperature between 20-27°C — typically the room temperature. This is done using heat exchangers and condensers, which work with external ammonia-based cooling loops for heat dissipation. During their nine-month stay, the astronauts performed routine checks to prevent mould growth and overheating caused due to the station’s orbiting.

Food and Waste Management

With the help of eight solar arrays, which can generate 75-90 kilowatts of power and lithium-ion batteries, the ECLSS runs all life-support systems. The amount of power the arrays generated during the stay of the astronauts allowed consistent output to keep systems operational. Although they require frequent monitoring, done by Williams and Wilmore.

Additionally, the ISS’ multilayered hull, made of aluminium and Kevlar, prevented solar and cosmic radiation, which helped the ECLSS to run smoothly for about nine months. Its built-in redundancy, along with the help from Williams, Wilmore, and the crew, allowed them to adapt to their extended stay. NASA intermittently carried out resupply missions to deliver consumables and other necessary items to ensure their stay came through without a hiccup.

The NASA astronauts are expected to enter the Earth’s atmosphere at around 2:15 am IST.

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