Update at 8:35 a.m. ET
NASA's Orion spacecraft, which could one day send astronauts to Mars, is waiting to liftoff at Cape Canaveral as part of an unmanned test of the new vehicle in Earth orbit. But a hold has been called over a stuck liquid-oxygen drain valve on the Delta IV Heavy rocket's left booster engine.
After multiple delays caused by gusty conditions, the latest glitch followed an alarm over an engine temperature issue that was quickly resolved. The vehicle perched atop the Delta rocket, known officially as Orion Multi-Purpose Crew Vehichle, or MPCV, is designed to carry up to 4 astronauts.
As NPR's Geoff Brumfiel reported earlier this week, Orion is expected to make two orbits at a distance of 3,600 miles from the Earth's surface on its second lap, before conducting a re-entry burn and splashing down in the Pacific Ocean.
The flight is meant to validate the vehicles basic systems, including avionics, heat shielding and parachutes.
According to Geoff: "It's designed for deep space, but Orion's first mission will be back to the neighborhood of the moon. The plan is to have a robot capture a small asteroid and drag it back to lunar orbit. Then Orion will carry up to four astronauts to meet it. It's all supposed to happen in the 2020s, though some say the mission is too complicated and not much of an advance."
Although unmanned, the stakes are high for the space agency, which sees this test flight as a first step towards the exploration of deep space.
By the year 2040, NASA hopes Orion will be a key piece of a manned mission to Mars — considered the next logical, if not extremely ambitious target following the Apollo moon shots of the 1960s and 1970s.
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