“We have technologies that exist today that had to be invented back in the ’60s. We don’t have to invent technologies today to make this work,” said Doug Loverro, NASA associate administrator for human exploration and operations, contradicting the assessment NASA made in its review of the proposals.

A planned reorganization of the NASA mission directorate responsible for human spaceflight programs has been put on hold after its leader abruptly resigned last month.

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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...