On September 27, the international space station has been in operation for more than 20 years. Members of Congress are paying attention to the details of NASA's low earth orbit plan after the international space station, but they are worried about NASA's plan to build a commercial space station < p > last Tuesday, the House subcommittee on science, space and technology held a two-hour hearing to discuss how long the international space station can continue to operate and how to promote low earth orbit activities in the future. International space station partners are currently committed to continuing operations until 2024. NASA has always believed that the international space station can be safely used until at least 2028. NASA Director Bill Nelson supports the operation of the international space station until 2030 < p > NASA said at the hearing that it would either postpone the operation of the international space station or develop multiple small commercial space stations in low earth orbit. But members of Congress expressed concern about the future of the international space station. Some lawmakers are worried that the international space station will lead to disaster if it runs far beyond its design life. A series of events show that the facility has begun to age. Others worry that the commercial operation of the low earth orbit space station will keep NASA on the ground. Because NASA astronauts rely on Russia's Soyuz spacecraft to go to the international space station nearly a decade later, they will use SpaceX's manned dragon spacecraft to regain the opportunity to go to the international space station in 2020 < p > Robyn Gatens, director of NASA's international space station, said at the hearing: "when we retired the space shuttle, there was indeed a gap in our space transportation system. We don't want this to happen again in the low earth orbit space station." < / P > < p > she stressed: "NASA is committed to an orderly transition from the international space station to a commercial low earth orbit space station." < / P > < p > NASA has long believed that no matter how long the international space station itself can be maintained, reliable access to low earth orbit is very important for NASA's operation. Low earth orbit provides a low-risk environment for NASA to test manned spaceflight technologies and procedures to deep space and assess the possible health risks faced by astronauts. < / P > < p > however, the annual operation cost of the international space station is as high as 3 billion or 4 billion Dollars. Gartens said that preliminary estimates show that if NASA can commercialize the space station project and only pay the admission fee for research, it can save more than $1 billion a year. < / P > < p > gartens revealed that NASA plans to transition the international space station to a smaller commercial space station, so that NASA astronauts can continue to carry out various research in the microgravity environment. But at present, NASA No transition plan was submitted. At the hearing, members of Congress urged NASA to come up with a strong outcome plan, but the two sides did not reach an agreement. < / P > < p > gartens said that the report should be submitted to the U.S. Congress "in the next few weeks". As part of the plan, NASA will outline a series of so-called transition indicators in the new plan. < / P > < p > "The first and most important indicator is that we have a transitional commercial low earth orbit destination," gartens said. "This is a prerequisite so that we won't have a gap in low earth orbit projects." She said that other indicators include the structural health of the international space station and the development of the commercial market. < / P > < p > members of the committee also heard about the current NASA astronaut Kate Rubins and William shepherd, one of the first astronauts of the international space station Testimony from the CEO of nanobacks, a participant in aerospace companies and the space station, and an expert from a think tank focusing on space. < / P > < p > Shepard said that if private enterprises are not effectively guided, the system integration of the space station will become a big problem. The recent lawsuit filed by blue source and its delay to the moon landing program are typical examples. He also warned that, The crack in the international space station is "a serious problem that needs to be solved if the international space station is planned to operate until 2028" < / P > < p > the international space station itself has been in orbit for 20 years, and some of them have shown signs of aging. Facts have proved that it is difficult to add even a new module. When the Russian science experiment module docked at the end of July this year, due to improper ignition of the thrusters, the attitude of the entire international space station deflected, which may put pressure on the overall structure. < / P > < p > the overall structure of the international space station may be under pressure He said that at present, NASA still doesn't know how Russia first noticed the problem and how to try to solve the problem and other details. < / P > < p > Shepard said: "we didn't have a detailed discussion, but it was very common 20 years ago." < / P > < p > he stressed: "The primary task for the space station to continue to operate is to work closely and sit around the table to solve problems." < / P > < p > gettens said that NASA's transition plan also includes international cooperation in low earth orbit projects. (Chen) < / P > < p >