Answer:
The main idea of President Kennedy's "Address at Rice University on the Nation's Space Effort" was to let know American people of the government's plan to land a man on the moon.
Explanation:
When John F. Kennedy became president in January 1961, many Americans believed that the United States had lost the space race with the USSR, which launched the first artificial satellite four years earlier. The situation worsened on April 12, 1961, when Yuri Gagarin became the first man in space, ahead of American Alan Shepard, who after 23 days made a suborbital flight. At the same time, a full-fledged space flight had not yet been accomplished - this happened only in 1962, when John Glenn went into space. Kennedy believed that in this case, the United States should take a step that would demonstrate their superiority in space. After negotiations with NASA, on May 25, 1961, Kennedy spoke to Congress, stating that "The country should make every effort to send a man to the moon before the end of the decade and return him alive to Earth". With this decision, Kennedy initiated the Apollo program.
On September 12, 1962, John F. Kennedy delivered a speech in front of 35 thousand people at the Rice University Stadium, to tell them the news about the Apollo Program and about landing the first man on the moon.