Facing unpredictable White House decision-making and delays in appointing a new NASA leadership team, Boeing Co., Lockheed Martin Corp. and their supporters are taking extra precautions to safeguard deep-space exploration programs.

The Boeing-led Space Launch System, a 212-foot, heavy-lift rocket carrying on the tradition of the storied Apollo missions to the Moon, is intended to be the most powerful booster ever built. Lockheed Martin’s Orion spacecraft is designed to sit on top and ultimately protect humans from the ravages...