US space agency National Aeronautics and Space Administration (NASA) will take the first critical step towards manned mission to Mars with launch of spacecraft Orion, on its first voyage to space.
The spacecraft that could one day take astronauts to Mars will be lifted off aboard a Delta IV Heavy rocket from Cape Canaveral, Florida in the morning between 7:05 am and 9:44 EST. The Orion spacecraft, which has no crew, will embark on a 4.5-hour mission of orbiting the Earth twice before it splashes down in the Pacific Ocean, approximately 600 miles off the coast of Baja, California.
Orion will orbit 3,600 miles above Earth before splashing down in the Pacific.
The test flight, named `Exploration Flight Test-1' (EFT-1), will evaluate Orion's critical systems such as avionics, altitude control, parachutes, and heat shield.
A key part of the mission will be to see how Orion's heat shield withstands the 2,200 degree C heat of re-entry.
Orion is being designed to carry astronauts on exploration missions into deep space, including a trip to an asteroid and eventually to Mars.
Meteorologists had upgraded their outlook to a 70 per cent chance of acceptable conditions in the three-hour Orion launch window.
While today's launch comes courtesy the Delta IV Heavy rocket, future Orion test missions (possibly as early as 2018) are scheduled to hitch a ride on NASA's next-generation Space Launch System (SLS), which was specifically created to propel humans and heavy cargo all the way to Mars.
If all goes well with today's flight, the groundwork will be laid for the next big test, which is tentatively scheduled for 2018, NASA said.
The launch marks the first of a US spacecraft meant to carry people into deep space since the Apollo missions that brought men to the Moon in the 1960s and 1970s.
With no American vehicle to send humans to space since the space shuttle was retired in 2011, some at NASA said the Orion launch has re-energised the US space programme, long constrained by government belt-tightening and forced to rely on costly rides aboard Russian Soyuz spacecraft to reach the International Space Station in low-Earth orbit.
"We haven't had this feeling in awhile, since the end of the shuttle program, (of) launching an American spacecraft from America's soil and beginning something new," said Mike Sarafin, lead flight director at Nasa's Johnson Space Center in Houston.