Much has been made of the impending gap in U.S. human space-flight capabilities when NASA retires its space shuttle fleet next year in the absence of an operational follow-on program. But ferrying people to and from the international space station is not the only capability at risk in the coming years: Development of commercial vehicles for delivering cargo to the orbital outpost also is behind schedule.rnOrbital Sciences Corp. and Space Exploration Technologies Corp. (SpaceX) are developing space station logistics vehicles under NASA's Commercial Orbital Transportation Services (COTS) program and are under contract to begin resupply-ing the outpost within the next year.
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