Responding to NASA's claim that it cannot build a new rocket under the time and budget constraints, congressional members say they won't take no for an answer.
"The production of a heavy-lift rocket and capsule is not optional. It's the law," U.S. Sen. Bill Nelson, D-Fla., and three other members of the Senate Commerce Committee said in a joint statement.
Earlier, NASA told Congress that a Dec. 31, 2016 target date could not be achieved.
