Unit 7Unit 7The Hazards of Space TravelThe Hazards of Space Travell lA hazard is a situation that poses a level A hazard is a situation that poses a level of threat to life, health, property, or of threat to life, health, property, or environment.environment. earthquake hazard earthquake hazard 地震灾害地震灾害 Job Hazard Analysis Job Hazard Analysis and hazard identification and hazard identification 工作风险分析和风险识别工作风险分析和风险识别Richard B. SetlowRichard B. Setlowl lRichard B. Setlow is a Senior Biophysicist Richard B. Setlow is a Senior Biophysicist at the Brookhaven National Laboratory, at the Brookhaven National Laboratory, Upton, New York, USA. Upton, New York, USA. l lThe Laboratory is operated by Brookhaven The Laboratory is operated by Brookhaven Science Associated, LLC. for the US Science Associated, LLC. for the US Department of Energy. Department of Energy. I. Background informationI. Background informationl l1. International Space Station (ISS) is the largest and 1. International Space Station (ISS) is the largest and most complex international scientific project in history. most complex international scientific project in history. Led by the United States, the International Space Led by the United States, the International Space station draws upon the scientific and technological station draws upon the scientific and technological resources of 16 nation: Canada, Japan, Russia, resources of 16 nation: Canada, Japan, Russia, 11nations of the European Space Agency and Brazil. 11nations of the European Space Agency and Brazil. Background informationBackground informationl lOn-orbit construction of the station On-orbit construction of the station began in 1998 and is scheduled for began in 1998 and is scheduled for completion by late 2011. The ISS is completion by late 2011. The ISS is by far the largest artificial satellite that by far the largest artificial satellite that has ever orbited Earth. It serves as a has ever orbited Earth. It serves as a research laboratory that has a research laboratory that has a microgravity environment in which microgravity environment in which crews conduct experiments in crews conduct experiments in biology, chemistry, medicine, biology, chemistry, medicine, physiology(physiology(生理学生理学) and physics, as ) and physics, as well as astronomical(well as astronomical(天文学的天文学的) and ) and meteorological meteorological ( (气象学的）气象学的） observations.observations.Background informationBackground informationl l2. Cosmic rays are high energy charged 2. Cosmic rays are high energy charged particles in outer space that travel at nearly the particles in outer space that travel at nearly the speed of light. Most cosmic rays are the nuclei of speed of light. Most cosmic rays are the nuclei of atoms, ranging from the lightest to the heaviest atoms, ranging from the lightest to the heaviest elements in the periodic table(elements in the periodic table(元素周期表元素周期表). ). l lThe term “cosmic rays” usually refers to galactic The term “cosmic rays” usually refers to galactic cosmic rays (GCR), which originate in sources cosmic rays (GCR), which originate in sources outside the solar system, distributed throughout outside the solar system, distributed throughout our Milky Way galaxy. our Milky Way galaxy. l lAbout 85 percent of the GCRs are protons About 85 percent of the GCRs are protons (nuclei of hydrogen((nuclei of hydrogen(氢氢) atoms), with ) atoms), with approximately 12 percent consisting of alpha approximately 12 percent consisting of alpha particles (helium(particles (helium(氦氦) nuclei). The remainders are ) nuclei). The remainders are electrons and nuclei of heavier atoms. electrons and nuclei of heavier atoms. Background informationBackground informationl l3. Zero gravity (0g) is the weightlessness any 3. Zero gravity (0g) is the weightlessness any condition equivalent to experiencing little or no condition equivalent to experiencing little or no acceleration or gravitational attraction, e.g., far acceleration or gravitational attraction, e.g., far from a planet, star, or other massive body. from a planet, star, or other massive body. l lThe human body is adapted to the gravitational The human body is adapted to the gravitational field at the surface of the Earth, which is one field at the surface of the Earth, which is one gravity (1g)), and a weightless environment can gravity (1g)), and a weightless environment can have adverse effects on human health.have adverse effects on human health.Background informationBackground informationl l4. A supernova explosion is an extremely 4. A supernova explosion is an extremely energetic star explosion. Supernova are energetic star explosion. Supernova are extremely luminous and cause a burst of extremely luminous and cause a burst of radiation that often briefly outshines an entire radiation that often briefly outshines an entire galaxy, before fading from view over several galaxy, before fading from view。