NASA delayed the launch of the world's largest rocket Tuesday so it could check upper-level winds and other last-minute conditions, the agency said.
The Ares I-X was to launch at 8 a.m. ET, but officials said liftoff was now anticipated to be about 9:24 a.m. at Kennedy Space Center in Florida.
The launch is a test flight for the vehicle that may be used to return astronauts to the moon.
The unmanned, 327-foot rocket will help NASA collect information for future missions.
"Ares I-X will bring NASA one step closer to its exploration goals to return to the moon for ambitious exploration," NASA said in statement.
The launch, which NASA is calling a test, is among four test launches of Ares I-X that will go on until 2012.
The space agency hopes the rocket eventually will replace the aging space shuttle and conduct voyages to the moon and Mars.
NASA researchers have said that a trip to the moon could not happen before 2015.
The launch comes at a critical time, when NASA is waiting for President Obama to decide future funding for the agency.
An independent committee reviewing the future of space flight recently reported that the U.S. space program appears to be pursuing goals that exceed current funding.
The committee also recommended to the White House that funding for NASA's under-construction international space station should be extended until 2020.
If weather conditions do not improve, NASA will launch Wednesday.
