 However the Mars mission, along with all work related to the evolutionary successors of the Saturn V, was cancelled in 1972-3 by the Nixon Administration.The ground testing of the Nuclear thermal rocket engines intended for the Saturn C-5N's, in-space 3rd stage, still hold a number of combined rocket thrust and specific impulse records.The concept of nuclear thermal rockets serving as the in-space rocket stage influenced the 1990s Project Timberwind.