How does a scuba diver’s oxygen tank last for ~1 hour but an astronaut’s lasts ~6-8 hours when both tanks are around the same size?

Question

How does a scuba diver’s oxygen tank last for ~1 hour but an astronaut’s lasts ~6-8 hours when both tanks are around the same size?

In: Technology

Answer 1

You need about 2-3 liters of air to fill your lungs with every breath. The problem is that these are 2-3 liters at ambient pressure. If you breathe at a depth of 50 meters, the pressure is about 6 times higher than at sea level. So now you are using the equivalent of 12-18 liters of air per breath.