President Obama's proposed $18.5 billion budget request for NASA is good news, the space agency's head says, keeping it and its current projects on track.

The budget would fully fund initiatives including the Orion crew capsule, the Space Launch System rockets, and the James Webb Space Telescope, set to replace the aging Hubble Space Telescope in 2018.

The president's budget, with a $500 million increase over the 2015 number, is a "clear vote of confidence," NASA Administrator Charles Bolden says.

The budget would put $1.2 billion into NASA's Commercial Crew Program, which would see American commercial spacecraft take crew members to the International Space Station after years of NASA having to depend on Russian spacecraft after the retirement of the agency's Space Shuttle fleet.

Boeing and SpaceX have been awarded NASA contracts to develop such spacecraft.

"This initiative, where we hand off low Earth orbit transportation to the private sector, is critical to our journey to Mars," said Bolden.

A controversial project, the space agency's Asteroid Redirect Mission, will also retain its funding under the president's new budget.

The mission, which has its share of doubters, would see a small robot probe latch on to a small asteroid and drag it from its normal orbit into an new orbit around the moon, where it could be visited and studied by astronauts in one of the first missions of the Orion capsule.

A pet project of the president, the asteroid mission has seen continual opposition from Republicans in Congress.

Although the asteroid project does not appear as a specific line item in the president's budget request, it could be funded under NASA's Space Technology Research and Development budget, which would be boosted from $370 million to $491 million if Obama's budget is approved by Congress -- likely to be an uphill battle.

Space science has $5.3 billion tagged in the budget which would be earmarked for the next rover to go to Mars, as well as a robotic space probe to be sent to Jupiter's moon Europa, where the possible existence of a subsurface ocean has long fascinated astronomers.

Not directly addressed in the budget but firmly on NASA's mind is a crewed mission to Mars by the 2030s, Bolden said.

"NASA is firmly on a journey to Mars," he said. "Make no mistake, this journey will help guide and define our generation.

"I couldn't be more excited about our future. We're making steady progress and continuing to reach for new heights."

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