As NASA takes steps to make it easier for researchers and companies to use the International Space Station, some of those potential users want more guidance about how long the station will be around and what might replace it.

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Jeff Foust has more than a decade of experience writing about space policy, entrepreneurial ventures and regulatory affairs. In 2001, he established spacetoday.net to aggregate and summarize the day's space-related news stories. In 2003, he started The...