Why does the flight altitude of manned spacecraft not exceed 300 km?

Above an altitude of about 250-300 km are the Earth’s radiation belts, flying through which cosmonauts can acquire radiation sickness and even die.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.