The Obama administration’s $18.7 billion NASA budget request for fiscal 2012 continues the new policies started in last year’s request, with a stronger push into commercial space travel to low Earth orbit (LEO) and modifications to accommodate the three-year NASA authorization enacted in December.

In a bid to follow President Barack Obama’s overall science and technology policy, the new budget aims to create “a sustainable program of exploration and innovation,” according to Administrator Charles Bolden’s introduction to the strategic plan that accompanies the budget request.

“This new direction extends the life of the International Space Station, supports the growing commercial space industry, and addresses important scientific challenges while continuing our commitment to robust human space exploration, science and aeronautics programs,” Bolden states. “The strong bipartisan support for the NASA Authorization Act of 2010 confirms our essential role in addressing the nation’s priorities.”

The government’s effort to seed private development of commercial crew and cargo transportation to the ISS and other LEO destinations would be boosted to $850 million in the fiscal year that begins Oct. 1 — up from the $612 million authorized but not appropriated in the current fiscal year.

But the James Webb Space Telescope, which an outside panel has found faces a cost overrun of at least $1.5 billion, would get only $375 million to continue fabrication and testing while NASA conducts its own calculations. The budget request carries no launch date for the telescope, and says there will not be one until the fiscal 2013 request a year from now.

The independent review ordered by Sen. Barbara Mikulski (D-Md.), who chairs the appropriations panel that funds NASA, estimated that launch of the deep-space infrared telescope will have to slip more than a year from its old September 2014 target.

If the new budget is adopted by Congress, which has yet to fund NASA for the current fiscal year, commercial vehicles could start delivering crews to the ISS by 2016, with commercial cargo deliveries by Orbital Sciences Corp. and Space Exploration Technologies Inc. (SpaceX) starting in 2013.

But the NASA request does not commit to a date for the first flight of the heavy-lift Space Launch System (SLS) ordered in the authorization act. Instead, it calls for $2.81 billion in 2012 to begin work on the vehicle and the Multi-Purpose Crew Vehicle (MPCV) that would ride atop it on deep-space missions and — as a backup to the hoped-for commercial crew vehicles — to the ISS. Congress had ordered a first flight of the heavy lifter in six years.

In keeping with the approach started with last year’s request, NASA would embark on an open-ended program of technology development needed to enable human exploration beyond LEO. The new request also merges the enabling technology development and demonstration program that has been run under the defunct Constellation Program to the agency’s new technology office, which would get a total budget of $1.024 billion.

The technology office was set up last year, but has accomplished little actual research and development because Congress has not appropriated funds for it. The new request comes as budget hawks in the new Republican-controlled House make their voices heard in debate on a continuing resolution to fund the government for the rest of fiscal 2011. As a result, NASA acknowledges that out-year figures after 2012 are only “notional.”

In the constrained spending environment, the agency has maintained a flat funding line that falls below last year’s out-year projections in many instances. For example, Earth science missions in development that had been accelerated are slowed, while the Landsat Data Continuity Mission, Global Precipitation Mission and the replacement Orbiting Carbon Observatory are kept on schedule under an overall $1.797 billion request.

Plans to launch the big Mars Science Laboratory lander remain on track for this fall under the $1.54 billion planetary science budget, while the agency’s aeronautics program refocuses its hypersonics work on “foundational research” under a $569 million top line for the fiscal year.

Top-line figures in the fiscal 2012 request for NASA are:

Science at $5.017 billion; aeronautics at $569 million; space technology at $1.024 billion; exploration systems at $3.949 billion; space operations at $4.347 billion; education at $138 million; cross-agency support at $3.192 billion, and inspector general at $38 million.

Bolden plans to merge the exploration systems and space operations mission directorates later this year, but the budget accounts will be kept separate. The new request assumes a third space shuttle flight this year — STS-135 — before the fleet is retired. Sustaining and utilizing the ISS until at least 2020 will become the primary near-term focus of the merged mission directorate.