On March 8, NASA recently signed a contract with SpaceX, a space exploration technology company, with a total amount of nearly $3.5 billion, allowing SpaceX to provide three more manned space missions to send astronauts to the international space station < p > it is reported that the contract includes three manned space missions: crew-7, crew-8 and crew-9, of which the first mission may be launched at the end of 2023. NASA says it may send more astronauts into space in the future < p > SpaceX has been sending NASA astronauts to the international space station with Falcon 9 rocket and manned dragon flying ship since 2020. Its first launch is also the first time to send American astronauts from the United States to the international space station since the retirement of NASA space shuttle in 2011. For a long time before that, NASA astronauts took the Russian Soyuz spacecraft to and from the international space station < p > last October, NASA submitted an application to allow astronauts to carry out new manned space missions after the completion of the 12 manned space missions originally awarded to SpaceX and Boeing. The contract signed with SpaceX is the first manned space mission arranged by NASA after submitting the application < p > NASA said in a statement that the new mission obtained by SpaceX will enable "NASA to maintain the ability to continuously send people to the international space station" < p > SpaceX's crew-6 mission is the last manned space mission previously ordered by NASA and is expected to be launched in early 2023. At present, crew-3 crew members are on mission on the international space station, including NASA astronauts Raja Chari, Kayla Barron, Thomas marshburn and European Space Agency astronaut Matthias Maurer. Crew-4, composed of NASA astronauts Kjell Lindgren, Robert Hines, Jessica Watkins and European Space Agency astronaut Samantha cristoforetti, is expected to travel to the international space station in mid April, The mission is scheduled to launch on April 15 < p > NASA said in a statement that the new procurement mission will continue until March 31, 2028. "The only source of supply at present does not rule out that NASA will modify the contract in the future because of the additional transportation services necessary," NASA said < p > in 2014, NASA chose SpaceX and Boeing to send astronauts to the international space station. However, the spaceship "Starline" developed by Boeing has not completed a successful test flight. In December 2019, due to software and communication problems, the first unmanned flight test of "Starline" failed to reach the space station. The second attempt has been postponed several times. The test flight of Starline is expected to take place later this year, but the specific launch date has not been announced. (Chen Chen) < / P > < p >