Chéngwéi yī míng tàikōngrén shì hěnduō háizi de mèngxiǎng.
Becoming an astronaut is many children's dream.
Tips
usage
太空人 is used in Hong Kong and Taiwan. Mainland China uses 宇航员 or 航天员 for Chinese astronauts specifically. All three mean 'astronaut' but reflect regional preferences.