1946-1947: British Interplanetary Society manned rocket proposal "Megaroc" intrigued the British Government, causing the government to not deny the proposal outrightly. This is the divergence point from our main timeline.
1947: The British government attempted to propose to the government of the United States for a collaboration of the Megaroc project. Truman, who was the US president at that time, decided to turn the proposal down citing lack of funds, after some ponderings on the project made by him. Though the turn-down effectively kill off the project for good, Truman would have some realization of the implications if they had become the first country to launch a person to space, partly as a result of his ponderings and some lobbying done by the British Government. As in our timeline, USA launched a group of fruit flies into space, making them the first animals in space.
1957: In October, the Soviets launched Sputnik 1 satellite into orbit. This results in a "Sputnik Moment" as in our timeline and confirming some of Truman's convictions.
In an act of desperation, Von Braun's Project Adam proposal is accepted. This is the divergence point from the Alan Shepard, first man in space timeline. Astronauts from the "Man in Space Soonest " program would be included into the "Project Adam spaceflight program.
1958: Creation of NASA and DARPA.
1959: Astronauts Alvin White and Scott Crossfield is being launched into suborbital spaceflight via an Adam rocket. Alvin White is the first man in space.
1961: The bigger shock to the American public came in April when the Soviet Union responds by launching cosmonaut Yuri Gagarin into orbit, which prompt US president Kennedy to set a national goal for a manned Moon mission.
1969: On July, NASA astronaut Neil Armstrong landed on the moon with Buzz Aldrin in Apollo 11 mission. Armstrong is the first human to step his foot on moon, saying: "That's one small step for man, one giant leap for mankind".
1977: NASA's Voyager 1 and 2 is launched to flyby the outer planets and into interstellar space. The former spacecraft would become the first spacecraft to enter interstellar space eventually.
1981: American space shuttle "Columbia" is the first orbital space plane to be launched into space.
1986: Challenger space shuttle disaster. First parts of Soviet Union's MIR space station is launched into space.
1991: Dissolution of the Soviet Union, which brings the decades old Cold War to an end.
1998: First parts of ISS (International Space Station) is launched into orbit.
2001: MIR space station fall backs to Earth.
2003: Space Shuttle Columbia disaster.
2006: First robotic spacecraft mission to planet Pluto, "New Horizons" is launched by NASA.
2007: First robotic spacecraft mission to dwarf planet Ceres, "Dawn" is launched by NASA.
2010: Major completion of ISS.
2015: Both NASA's Dawn and New Horizons spacecrafts arrived Ceres and Pluto respectively. LIGO, with help and contributions from American scientists and international scientists who come from countries like Australia and Italy, detected the first gravitational wave.
2016: LIGO announced the gravitational wave discovery.