SLS Green Run
The core stage of the Space Launch System fires its four main engines during an abbreviated test Jan. 16 at the Stennis Space Center in Mississippi.

NASA remains cautiously optimistic that the first launch of the Space Launch System rocket can take place before the end of the year despite having to perform a second hotfire test of the rocket’s core stage.

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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...