Take A Deep Breath: Staying Alive In Space
The vacuum of space is immediately deadly to humans. In order to send manned missions into space, NASA had to develop ways of keeping them alive until they safely returned to Earth.
Museum Exhibit: Beckman O2 Analyzer
The unit displayed here served the vital function of measuring the quality of the air on space missions. Built by Beckman, this type of oxygen analyzer was developed during the Second World War and was intended for use in high altitude aircraft. In spaceflight, it proved it could work at much higher altitudes than any airplane can fly.
Monitoring Gas for Safety
An oxygen analyzer works by pumping air through an inlet valve into one side of a tightly sealed container. The gas is forced through an outlet valve, and on its passage through the unit, the air is measured. It’s important that the oxygen level be carefully monitored in space since the gas is an oxidizer that fuels fires. Oxygen itself does not burn or explode, but objects in the presence of oxygen burn faster than those that aren’t. During the space shuttle program, NASA allowed that the oxygen concentration in the vehicle be no more than 25.9 percent.
Fun Fact 1: Deep Space Missions
In the late 1960s, NASA entertained proposals to send men on flyby missions to Mars and Venus using Apollo hardware. Little about the spacecraft’s fundamental systems would have to change except for the environment. The agency recognized in 1967 that long duration missions would need a dual gas environment for crew safety.
Learning from Oxygen Fires
On January 27, 1967, a frayed wire sparked in the crew cabin of the Apollo 1 spacecraft during a pre-launch test. At the time, the spacecraft was pressurized with 16.7 pounds per square inch of pure oxygen, a level that mimicked the environment of spaceflight. With everything inside the spacecraft saturated in pure oxygen – including the crew – the fire spread in an instant and engulfed the cabin. The crew died of smoke inhalation; their space suits protected them from burns. The accident was a wakeup call for NASA, which had initially selected the pure oxygen environment for Apollo because it was simpler and lighter than flying with a dual gas system that mimicked the Earth’s atmosphere. As a short-term solution, all Apollo missions after the fire had a dual gas environment that was 60 percent oxygen and 40 nitrogen at launch. The nitrogen was slowly bled out as the spacecraft ascended until it was gone. The crew was exposed to a pure oxygen environment for the duration of the mission.
An Earth-Like Atmosphere in Space
The International Space Station provides crews with an Earth-like environment in space. It’s a mixed gas environment with nitrogen and oxygen pressurized to 14.7 pounds per square inch, which is equivalent to sea level pressure on Earth. The benefits of this environment are many. Not only is fire a lower risk in this mixed gas environment than in a pure oxygen environment, it’s safer for the crew. Breathing pure oxygen for extended periods of time can be incredibly harmful to humans. Some side effects include: fluid accumulation in the lungs, chest pains associated with deep breaths, mucus plugs in the alveoli (where gas is exchanged between the lungs and blood), and a decreased efficiency of the body to absorb oxygen. The Gemini and Apollo astronauts were exposed to a pure oxygen environment for up to two weeks but didn’t experience any problems, but NASA had no intention of risking its astronauts on longer missions. With the shuttle program came the new, safer environment for astronauts.
Clean Air in Space
We don’t often think about the air we breathe on Earth, but in space every breath counts. Apollo astronauts lowered their store of oxygen with every breath and relied on lithium hydroxide filters to keep toxic carbon dioxide out of their air. Modern astronauts rely on sophisticated systems that recycle oxygen constantly during a mission, though the systems can break and astronauts still rely on the old method of filtering out toxic gases to breathe the cabin air.
Fun Fact 2: Chemical Oxygen
Crews on the International Space Station have a backup supply of chemical oxygen, similar to the oxygen supply in the overhead compartment in an airplane. Oxygen is released through an inorganic chemical reaction, providing a limited amount of breathable air.