How Long Could You Live In The ISS If Earth Was Destroyed?

Key Concepts:

• International Space Station (ISS) survival
• Resource management in space (food, water, oxygen)
• Altitude decay and reboosts
• Electrolysis for oxygen production
• Water recycling

Resource Availability and Longevity:

The video addresses the hypothetical scenario of the ISS crew becoming the last humans alive after a global catastrophe. It posits that the ISS could sustain the crew for a considerable period, primarily depending on the crew size and the timing of the last resupply mission. Rationing strategies for food and water could extend their survival beyond initial estimates. The video highlights the ISS's closed-loop life support systems, specifically water recycling, exemplified by the phrase "yesterday's coffee is today's coffee," and oxygen production via electrolysis, which breaks down water (H2O) into hydrogen and oxygen. The mass ratio of water being nearly 90% oxygen is mentioned as a benefit of this process.

Altitude Decay and Reboosts:

The most critical limiting factor for long-term survival on the ISS is not the immediate depletion of resources like food, water, or air, but rather the gradual loss of altitude. The ISS orbits at approximately 415 kilometers above Earth, where a small amount of atmospheric drag exists. This drag causes the ISS to lose about 100 meters of altitude per day, resulting in a monthly drop of 3-4 kilometers. Periodic "reboosts" are necessary to counteract this altitude decay. These reboosts require propellant delivered by resupply missions.

Propellant Depletion and Descent:

Without resupply missions to provide propellant for reboosts, the ISS would gradually descend into the Earth's atmosphere. The video estimates that approximately 15 months after becoming the last humans, the ISS crew would also perish due to atmospheric reentry, even before exhausting their food and water supplies.

Conclusion:

The video concludes that while the ISS has sophisticated life support systems capable of sustaining a crew for an extended period, the dependence on external resupply for propellant to maintain altitude is the ultimate limiting factor in a scenario where the ISS crew becomes the last surviving humans. The gradual altitude decay, leading to eventual atmospheric reentry, would occur before the depletion of essential resources like food and water.