NASA will not fly astronauts on the first integrated flight of the Space Launch System (SLS) rocket and Orion spacecraft, a part of exploration missions that will take humans to deep space, and eventually to Mars.
In February, NASA began an effort looking at the feasibility of putting crew aboard the first launch of the SLS rocket and Orion - for its Exploration Mission-1, or EM-1.
After weighing the data and assessing all implications, the NASA will continue pursuing the original plan for the first launch, as a rigorous flight test of the integrated systems without crew, the US space agency said.
NASA will also adjust the target launch date for the EM-1 mission to 2019, and will execute its normal process in the coming weeks to determine an official revised launch date.
Engineers will apply insights gained from the effort to the first flight test and the integrated systems to strengthen the long-term push to extend human presence deeper into the solar system.
NASA said it is technically capable of launching crew on EM-1, however, after evaluating cost, risk and technical factors in a project of this magnitude, it would be difficult to accommodate changes needed to add crew at this point in mission planning.
The agency confirmed that the baseline plan to fly EM-1 without crew is still the best approach to enable humans to move sustainably beyond low Earth orbit.
"We appreciate the opportunity to evaluate the possibility of this crewed flight," said NASA acting Administrator Robert Lightfoot.
"The bi-partisan support of Congress and the President for our efforts to send astronauts deeper into the solar system than we have ever gone before is valued and does not go unnoticed. Presidential support for space has been strong," said Lightfoot.
Exploration Mission-1 is the first in a broad series of exploration missions that will take humans to deep space, and eventually to Mars.
"We are considering additional ground testing of the heat shield prior to EM-1 as well as the possibility of advancing the ascent abort test for the Orion launch abort system based on findings from the study," said William Gerstenmaier, associate administrator for NASA's Human Exploration and Operations Mission Directorate.
"Conducting these tests in advance of EM-1 would provide additional data that will advance our systems knowledge faster and possibly improve the robustness of the overall plan for sending humans into deep space," said Gerstenmaier.