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Human Space Flight Services

Human spaceflight is by necessity the least risk-tolerant activity in space. The health and safety of the crew must remain paramount at all times. The radiation environment is the main hazard, even in Low Earth Orbit where the benefits of the Earth's natural magnetic shielding remain strong. With more distant manned missions again on the horizon the additional risks encountered in interplanetary space call for careful consideration.

 ▶  In-flight Crew Radiation Exposure Under development.
 ▶  Cumulative Crew Radiation Exposure Provides an estimate of the past radiation dose accumulated by a person in space.
 ▶  Increased Crew Radiation Exposure Risk Under development.

Human Space Flight Background

Onboard the International Space Station (ISS), the astronauts are not protected by the Earth's atmosphere and are exposed to space radiation such as the galactic cosmic rays (GCRs) and solar energetic particles (SEPS). The GCRs are the cause of the 'flashes of light' reported by the astronauts during the Apollo Moon missions in the 1960s and 1970s. Beyond such short-term physiological effects, these ionising radiations can have long-term biological effects when reacting chemically with molecules inside human cells and damaging DNA or affecting cell replication. In just one week on the ISS, astronauts are exposed to the equivalent of one year's usual exposure at Earth's surface. Major SEP events increase the risk of higher exposure. After the solar flare on 18 October 1989, a powerful interplanetary shock directed towards the Earth caused SEPs as well as a large geomagnetic storm. During this event, the astronauts and cosmonauts onboard the Mir space station received their full-year recommended dose within a few hours.

Space radiation is a primary health concern to astronauts and is currently seen as a potentially limiting factor for interplanetary space missions. During such interplanetary space missions, astronauts lose the protection of Earth's magnetic field and are fully exposed to GCRs and SEPs. During the Apollo era, the risk of exposure was limited in time (less than 12 days), but for a Mars exploration it will be much longer (about 18 months) and solutions have to be found for the case when a life threatening event will occur.


The Matroshka experiment evaluates the radiation exposure level
during extravehicular activities (EVAs) outside ISS (© NASA)