Scene Context: Prior to launch, the crew undergoes a low-residue diet and bowel-clearing protocol. Les and Sarah discuss how even a minor amount of gas in the body during a pressure drop can cause sharp pain, according to the Boyle-Mariotte law.
Essence of the Phenomenon: The Boyle-Mariotte law describes the inversely proportional relationship between the absolute pressure and volume of a gas at a constant temperature: as external pressure decreases, gas volume increases. In the event of a pressure drop within a spacesuit or cabin, trapped gases inside the body (specifically in the gastrointestinal tract, paranasal sinuses, and dental cavities) expand, which can cause severe pain or barotrauma.
Scientific Basis: The Boyle-Mariotte law is a fundamental gas law in classical thermodynamics. In aerospace medicine, it explains phenomena such as barotrauma and high-altitude flatus. For instance, the operating pressure in modern spacesuits is roughly 30% of atmospheric pressure, resulting in a proportional volumetric expansion of gases within the body. These effects are well-documented during high-altitude flights and space missions.
Current Limitations: Before a flight or EVA, astronauts adhere to a low-residue diet and undergo desaturation procedures (purging inert gases, particularly nitrogen, from the bloodstream). However, entirely eliminating gas formation in the human body is impossible, making discomfort during pressure changes physiologically inevitable.