Free_Astronomy_-_SeptemberOctober_2019

44

ASTRONAUTICS

higher than that absorbed in the same pe-

riod on our planet. During the journey to

Mars, assuming about 6 months long, as-

tronauts could be exposed to at least 60 %

of the total radiation dose limit recom-

mended by space agencies for their entire

careers. Adding to the journey to Mars

both the stay on the planet and the re-

turn journey (almost 2 years in all), an as-

tronaut would have the certainty of being

exposed to enough radiation to probably

cause serious or even lethal diseases.

This problem could conceivably be solved

by reinforcing the shielding of space-

crafts, but this is not feasible, as current

spacecrafts already possess shields at the

limit of mass compatible with the power

of the available carriers. Take, for exam-

ple, NASA’s Orion, the most technologi-

cally advanced spacecraft in existence

today, currently at an advanced stage of

testing and designed for both short mis-

sions (nearby asteroids and the Moon)

and journeys to Mars. In its case, the best

solution adopted against particularly in-

tense and unpredictable flows of high-en-

ergy charged particles (typically of solar

origin) is to protect the crew by using the

W

hen a high-energy particle hits the Earth’s atmosphere, it can

produce a cascade of secondary particles of lower energy, as

shown above. This phenomenon, called spallation, occurs in a similar

way when a charged particle hits a spacecraft hull, generating a flow

of intravehicular particles, whose potential effect on the astronauts’

bodies is almost unpredictable.[A. Chantelauze, S. Staffi, and L. Bret]

space radiation EN_l'Astrofilo 29/08/2019 15:44 Page 44