Answer: There is no way for an average person to know what it feels like to be on space.
Explanation: Their is used to refer to someone's belonging or associated with some other person whereas there is used to refer to attract someone's attention regarding and issue. In the given sentence there is the suitable word.
Since average starts with the letter a which is a vowel, an should be used instead of the. So the sentence would be : an average person.
Therefore, the correct sentence can be written as : There is no way for an average person to know what it feels like to be in space.