Nuclear power will be a big part of the United States' space exploration efforts going forward, a new policy document affirms.

President Donald Trump on Wednesday (Dec. 16) issued Space Policy Directive-6 (SPD-6), which lays out a national strategy for the responsible and effective use of space nuclear power and propulsion (SNPP) systems.

"Space nuclear power and propulsion is a fundamentally enabling technology for American deep-space missions to Mars and beyond," Scott Pace, deputy assistant to the president and executive secretary of the National Space Council, said in an emailed statement Wednesday. "The United States intends to remain the leader among spacefaring nations, applying nuclear power technology safely, securely and sustainably in space."