In the following items, each passage consists of six sentences. The first sentence (S1) and the final sentence (S6) are given. The middle four sentences in each have been removed and jumbled up. These are labelled P, Q, R and S. You are required to find out the proper sequence of the four sentences and mark accordingly on the Answer Sheet. 

S1: John Young, the astronaut, piloted the 75-ton space-shuttle, Columbia. 
P: The Columbia, however, landed safely at the Edwards Air Force base in the Mojave desert. 
Q: The space-shuttle circled the Earth 36 times. 
R: It was dangerous because a re-usable craft was being used now. 
S: This flight was fraught with dangers. 
S6: And it moved smoothly to a stop as the crew rushed to greet it.