NASA is set to launch an unmanned spacecraft that is designed to help get humans to Mars, in a mission touted as the first step in deep space exploration.

The tiny Orion spacecraft was scheduled to blast off at 12:05 GMT on Thursday with the help of a Delta 4 Heavy rocket, known as the biggest booster rocket in the US fleet. However, the weather conditions forced delay and the launch window was extended to 14:44 GMT.

The conical spacecraft looks similar to the Apollo capsule that took astronauts to the Moon in the 1960s and 1970s, but slightly larger and with modern electronics.

NASA hopes to send an Orion crew to an asteroid corralled in lunar orbit in the 2020s and to Mars in the 2030s.

"We haven't had this feeling in a while, since the end of the shuttle program,'' said Mike Sarafin, the lead flight director stationed at Mission Control in Houston.

"Launching an American spacecraft from American soil and beginning something new, in this case exploring deep space."

The space capsule is aiming to travel for a distance of 57,800km, 14 times higher than the International Space Station.

This high altitude will give it the momentum it needs for a 32,200-kph, 4,000-degree entry over the Pacific. Those crucial 11 minutes to splashdown is the critical part NASA calls the "trial by fire".

The heat shield at Orion's base, at five metres across, is the largest of its kind ever built. Orion will land in the Pacific Ocean, 1,000km off the coast of Baja, California where recovery teams will retrieve the shuttle.

"For the first time in more than 40 years, this nation is going to launch a spacecraft intended to carry humans beyond low-Earth orbit. That's a big deal,'' said NASA’s Administrator Charles Bolden Jr.

NASA wants to experiment with the capsule’s most critical parts before it carries out astronauts.

This $370m trial includes the heat shield, parachutes and all the sections jettisoned during ascent and entry.

The capsule will also pass through extreme radiation in the Van Allen belts surrounding Earth, as engineers want to estimate the effects on the on-board computers.

Lockheed Martin Corporation is managing the test flight for NASA.

Sarafin's entire team at Johnson Space Center in Houston is comprised of former shuttle flight controllers.

Gene Kranz, known as the legendary flight director of Apollo 11 and more, will be on hand in Mission Control on Thursday.

Source: Agencies