Gaylord National Convention Center, National Harbor, MD - MARCH 7: Mark Sirangelo Corporate Vice President, Space Systems, Sierra Nevada Corporation.

Mark Sirangelo, the longtime leader and public face of Sierra Nevada Corporation’s space business, has resigned from the company for personal reasons but as part of a “friendly transition,” the company confirmed July 2.

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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...