President Barack Obama has cancelled the American project designed to take humans back to the Moon.
The Constellation programme envisaged new rockets and a new crewship called Orion to put astronauts on the lunar surface by 2020.
But in his federal budget request issued on Monday, Mr Obama said the project was "over budget, behind schedule, and lacking in innovation".
It was draining resources from other US space agency activities, he added.
He plans instead to turn to the private sector for launch services.
Read more: BBC