NASA's smaller but still-costly - $30 billion - space station Freedom will require half the spacewalks to build as once envisioned, but it will not be ready for full-time science operations until the year 2000, agency officials said Thursday.

Formally unveiling the new space station design for the first time, William Lenoir, NASA's associate administrator for space flight, said the laboratory will provide an "excellent forum to support our space sciences."Under the new plan, part-time, man-tended operations are scheduled to begin in mid-1997, one year after the start of assembly. Full-time, permanently manned status, using four astronauts instead of eight as originally planned, is now scheduled for 2000.

Lenoir said the number of spacewalks required to build and maintain the station, a major question mark in the past, had been cut in half by a decision to shorten the station's laboratory modules from 44 feet to 27 feet, allowing them to be launched aboard space shuttles fully outfitted with lab gear.

Likewise, the bridgelike truss forming the backbone of the station also will be launched in smaller, already assembled and checked out sections.

On the downside, less electrical power will be available initially than NASA had hoped. But on the whole, Lenoir said, the new station design will meet the needs of the science community and national policy.

"It's inherent in our destiny and it's the character of the United States to want to explore," Lenoir said. "The space station is one of the elements in that."

Vice President Dan Quayle, who heads the National Space Council, sent a letter Wednesday to NASA Administrator Richard Truly praising the new design and authorizing him to forward the plan for space station Freedom to Congress.

Truly issued a statement saying he was "delighted" with Quayle's letter.

After questions were raised about the original proposal's feasibility, Congress last fall ordered NASA to redesign the station to reduce the size, cost and complexity of the project.

Prior to the redesign effort, NASA expected the outpost to cost some $38.3 billion, including development, on-orbit operations and shuttle transportation. The project now is expected to run some $30 billion, which includes the $4 billion already spent.

Critics, including the National Research Council, have charged that the science possible with the new design will not justify its cost.

Sen. Al Gore, D.-Tenn., said he would hold hearings on the proposal next month to "address some of the questions" about the station.