Chief designer of the Soviet space program, Sergei Korolev, decided that the cosmonauts must be male, between 25 and 30 years old, no taller than 1.75 meters, and weigh no more than 72 kilograms. The final specifications for cosmonauts were approved in June 1959. By September interviews with potential cosmonauts had begun. Although the pilots were not told they might be flying into space, one of the physicians in charge of the selection process believed that some pilots had deduced this. Just over 200 candidates made it through the interview process, and by October a series of demanding physical tests were conducted on those remaining, such as exposure to low pressures, and a centrifuge test. By the end of 1959, 20 men had been selected. Korolev insisted on having a larger group than NASA's astronaut team of seven. Of these 20, five were outside the desired age range; hence, the age requirement was relaxed. Unlike NASA's astronaut group, this group did not particularly consist of experienced pilots; Belyayev was the most experienced with 900 flying hours. The Soviet spacecraft were more automated than the American counterparts, so significant piloting experience was not necessary.