Boost rockets or solid fuel rockets are rockets that sit on opposite sides of the space shuttle to make it take off at take-off.
SpaceX has been noted for its progress in reusing the boost rockets by bringing them down safely to a designated location on the ground.
The crew is scheduled to arrive at the space station early on Saturday, after a flight of about 23 hours.
It is the third manned flight made in collaboration between NASA and the commercial rocket company SpaceX, which is owned by the billionaire entrepreneur and Tesla founder Elon Musk.
Friday's astronaut team consists of two NASA astronauts, Shane Kombrough and Megan McArthur, the Japanese astronaut Akihiko Hoshide and Thomas Pesquet from the European Space Agency.
See parts of the flight to the International Space Station in the clip above.