Scuba Divers vs. Astronauts: The Battle of Breathing Under Extreme Conditions

The Challenges of Breathing Underwater

Scuba diving and space exploration both involve extreme conditions that require careful consideration of breathing techniques. While scuba divers rely on regular air or slightly enriched air, astronauts utilize 100% oxygen tanks. However, the way these two groups breathe and manage their air supply differs significantly.

Scuba divers typically use regular air or slightly enriched air with up to 40% oxygen. Breathing pure oxygen underwater at depths deeper than 6m/20ft can be toxic to the central nervous system, leading to convulsions, seizures, and even drowning. The deeper a scuba diver goes, the faster their gas supply is depleted. At 30m depth, each breath consumes twice as much air as at 15m depth and four times more than at the surface.

The volume of air needed for each breath remains the same at any depth, but the pressure doubles with each 10m of depth. This causes the same volume of air to hold a different amount of air, making the gas supply diminish more rapidly as the depth increases.

Astronauts: Breathing in Space

In contrast to scuba diving, astronauts breathe air at the same or slightly lower pressure as we do on the surface of the Earth. Their space suits are pressurized to about normal atmospheric pressure, allowing them to breathe comfortably. They rely on a rebreather system, which is highly efficient in utilizing their air supply.

Astronauts use a closed-loop rebreather system that turns carbon dioxide back into oxygen and filters the air, ensuring that they can use all the air and make it last longer. This system is much more efficient than the open-loop system used by scuba divers. With a rebreather, astronauts can dive for 6-8 hours, significantly longer than scuba divers.

The Importance of Pressure

The pressure in a scuba diver's tank needs to match the pressure of the water around them. Higher pressure results in more gas volume being used, further reducing the available air supply. On the other hand, astronauts do not have air tanks like scuba divers. They rely on their rebreather system, which effectively uses all the air and makes it last longer.

Additionally, astronauts have equipment to scrub carbon dioxide and recover additional oxygen, resulting in a slower rate of oxygen loss compared to scuba divers. If scuba divers had access to a scrubber, similar to those used by military divers, they could significantly extend their air supply.

The Role of Oxygen Concentration

Diving air typically consists of regular air with 21% oxygen or Nitrox with up to 40% oxygen. Scuba divers cannot use 100% oxygen because it becomes poisonous under high pressures. In contrast, astronauts use tanks of 100% oxygen during spacewalks. The lower pressure in space suits allows for comfortable breathing without the risk of oxygen toxicity.

Astronauts receive approximately five times more oxygen per tank compared to scuba divers, further contributing to the extended duration of their air supply.

Breathing Techniques and Risks

Scuba divers need to be cautious about holding their breath while diving, as the air in their lungs can expand and cause serious issues. They must breathe out while ascending to avoid the expansion of air in their lungs, which can lead to lung overexpansion injuries.

In contrast, astronauts face different risks. The lower pressure in space can cause decompression sickness if they ascend too quickly. However, with proper equipment to scrub carbon dioxide and recover oxygen, astronauts can effectively use all the air in their tanks and make it last longer.

While both scuba divers and astronauts face unique challenges in breathing under extreme conditions, their methods and equipment differ significantly. Scuba divers rely on regular air or enriched air, while astronauts utilize a closed-loop rebreather system with 100% oxygen tanks. The ability to efficiently use all the air and manage oxygen concentration plays a crucial role in extending the duration of their air supply.