The disaster on 1 February 2003 (during STS-107, a non-ISS mission) resulted in a two-and-a-half-year suspension of the US Space Shuttle program. Another one-year suspension following STS-114 (because of continued foam shedding on the external tank) led to some uncertainty about the future of the International Space Station. All crew exchanges between February 2003 and July 2006 were carried out using the Russian Soyuz spacecraft; a STS-114 visit in July 2005 was purely logistical. Starting with Expedition 7, caretaker crews of just two astronauts were launched, in contrast to the previously launched crews of three. Because the ISS had not been visited by a space shuttle for over three years, more waste had accumulated than anticipated, which temporarily hindered station operations in 2004. Automated Progress transports and the STS-114 mission were able to eliminate this waste build-up.