Human In Space

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> Manned Space Programs

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> Hubble Space Telescope

> Recent & Future Developments

Space is a hostile environment for human beings in a number of ways. It contains neither air nor oxygen, so human beings are unable to breathe. The vacuum of space can destroy an unprotected human body in a few seconds by explosive decompression. Temperatures in space in the shadow of a planet approach absolute zero; on the other hand, temperatures can become fatally high under direct solar radiation. Energetic solar and cosmic radiations in space may also be fatal to an unshielded person who is not protected by the atmosphere of the Earth. These environmental conditions can also affect the instruments and devices used in spacecraft, so the design and construction of these materials are dictated by the space environment. Experiments in weightlessness for long periods of time have been studied intensively to discover what adverse effects this condition will have on travelers in space.

Spacewalker with Manned Manoeuvring Unit

Astronaut Bruce McCandless floats freely above the earth, wearing a manned manoeuvring unit (MMU) during a shuttle mission. McCandless helped design the MMU and was the first to fly one. The MMU is propelled by small nitrogen thrusters controlled by the astronaut’s hands. Because no umbilical cord attaches the astronaut to the spacecraft, the MMU gives much greater mobility than was available to earlier spacewalkers.

People can be protected against the space environment in several ways. At present, they are enclosed inside a hermetically sealed cabin or space suit, with a supply of pressurized air or oxygen to approximate conditions on Earth. Air conditioning controls the temperature and humidity. Absorbing and reflecting surfaces on the outside of the spacecraft regulate the amount of heat radiation affecting the craft. Furthermore, space journeys are carefully planned to avoid the intense radiation belts around the Earth. On long interplanetary voyages of the future, heavy shielding might be necessary to protect against solar radiation storms; or crews might be sheltered in a central position within the spacecraft with supplies and equipment to surround and shield them. For lengthy space journeys, or for prolonged stays in an Earth-orbiting satellite, the effects of weightlessness might be reduced by spinning the craft to provide artificial gravity. For this purpose, the spacecraft might be shaped like a large wheel that spins slowly around its own axis, or like a dumbbell, rotating end over end.

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