The main problems are:
I. Space sickness
II. Effects of weightlessness
III. Conditions resulting from exposure to radiation
IV. Many unwanted side effects
V. Disposal of rocket parts
VI. Pollution caused by burning of rocket fuel
1. Deaths in space missions
Many deaths have resulted during the manned space flights. Space scientist needs continuous work to improve safety in space mission.
2. Fell of space crafts
In 1979 skylab fell from its orbit to earth. This type of incidents very dangerous for populations
3. Very costly space programs
Space programs are very costly. Involvement of private sector in mission could be a possible solution.