lecture_23 - Notes on Lecture #23: Life Support in Space We...

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Notes on Lecture #23: Life Support in Space We have had so many successful manned missions to space that we tend to forget how terribly dangerous a place space really is. Human spaceflight is inherently very costly and extremely risky. We must be particularly careful in evaluating the risks and benefits when deciding to pursue something as ambitious as a manned trip to Mars. On the one hand, it is much safer and cheaper to send robotic missions to scope out the surface and look for signs of life. On the other hand, no computer or robot today can come close to matching the combination of human brain, eyes, and hands. And certainly no robotic mission can satisfy the human desire for adventure the way a manned mission can. Any time we send human beings into space, we must provide them with all of the conditions necessary for survival which we take for granted here on the Earth: Food Water for drinking, hygiene, and humidification Atmosphere (with the correct composition, pressure, temperature, and humidity) Waste management The one item I didn’t list above is gravity . On all spacecraft to date, the astronauts live in a weightless environment. This is the one thing that we don’t attempt to duplicate in space (at least not yet). More on this later. The strategies that we use to meet these basic human needs will depend in part on the size of the enclosure that the people will inhabit. We can consider four different sizes of enclosure, from smallest to largest, with the duration of the stay increasing accordingly: Spacesuit (1 person, a few hours) Crew cabin of a small craft like the Space Shuttle (a few people, 2 weeks) Space station (a hundred people, a few months) Space colony or planetary colony (thousands to millions of people, a whole lifetime) Later on we will look at space stations and space colonies. For now we will focus on small spacecraft, particularly the crew cabin of our Space Shuttle, and also spacesuits. The planet Earth is not only our home; it is the place where we became what we are today, through billions of years of natural selection. Here are a few examples of our species’ inheritance from our planet: The chemical composition of our atmosphere governs our metabolism The pressure, composition, and density of our atmosphere determines the structure of our lungs The mass of the Earth determines the strength of the gravity we experience and through that the strength of our muscles and bones
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Our distance from the Sun and tilt of Earth’s axis determines the range of temperatures we experience The 24-hour length of the solar day sets our internal biological clock or circadian rhythm The tilt of the Earth’s axis of rotation determines the annual change of the seasons The list goes on and on. If any one of these factors were tweaked by even a little bit, any life forms that evolved on Earth would have been suited to a different environment, and would not have been human. We really are completely a product of planet Earth. Our planet is a closed ecological system except for the sunlight we receive from space
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lecture_23 - Notes on Lecture #23: Life Support in Space We...

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