NEW : Faster engines , better shielding under pressure , NASA official says . A long trip will be like getting abdominal CT scan A question of physics , a question of biology . every five minutes , study finds . Radiation exposure on NASA 's trip to Mars approaches NASA 's career limit for astronauts .
NEW : Faster engines , better shielding under pressure , NASA official says . A long trip will be like getting abdominal CT scan every five minutes , study finds . Radiation exposure on NASA 's trip to Mars approaches NASA 's career limit for astronauts .