"More than 6,300 individuals applied to become a NASA astronaut between Nov. 15, 2011 and Jan. 27, the second highest number of applications ever received by the agency. After a thorough selection process, which includes interviews and medical examinations, nine to 15 people will be selected to become part of the 21st astronaut class."
Keith's note: According to NASA PAO, NASA received 8,000 astronaut applications in 1978. Hmm ... It was during 1977 that NASA used Nichelle Nichols to help encourage a broader range of applicants. According to Memory Alpha: "After meeting Nichols at a Star Trek convention in 1975, scientist Dr. Jesco von Puttkamer suggested that the actress take part in NASA's recruitment drive. Nichols took up the role in 1977, making recruitment and training films, and supervising astronaut recruits and hopefuls. She noted that the applicant count went from fewer than 100 a year to 1,649 within six months."