From a distance, the concrete bulk rising out of the arid landscape surrounding Livermore, Calif., could be mistaken for an indoor sports stadium. The huge building being erected at the Lawrence Livermore National Laboratory for the National Ignition Facility (NIF) is two football fields long. Its glassed-in atrium is cluttered with posters and plaques, and upper observation tiers let spectators gaze into the interior through panoramic windows.

But instead of teeming with activity, the cavernous NIF is nearly deserted, silently awaiting either distinction or obsolescence.

When the U.S. Department of Energy first conceived of the NIF in 1994, the project sounded like something out of an Isaac Asimov novel. Its crowning glory, planners said, would be a high-powered array of 192 lasers, each capable of emitting a beam wider than a dinner plate. Mirrors would reflect all 192 beams into a 9-meter-wide aluminum target chamber, where they would converge at a single, infinitesimal point, smashing hydrogen atoms together in a nuclear fusion reaction like those that fuel the sun.

If that reaction ever takes place, NIF scientists claim, it would represent a critical breakthrough in nuclear weapons testing. A facility that could produce fusion in controlled conditions could allow weapons specialists to simulate the detonation of different types of bombs, helping them assess the status of aging atomic stockpiles without conducting the risky test explosions that international law is trying to ban.

More than a decade after the NIF's inception, however, its future is in limbo. Many scientists and lawmakers question whether the facility can achieve its stated scientific goals—and whether such a money-draining marquee project was really necessary in the first place.

In the project's defense, NIF officials point out that they achieved several important milestones last year, including installation of more than 1000 of the facility's 6000 optical and instrumentation units—precision electrical and optical devices that guide the laser beams into the target chamber [see photo, "On the Spot"]. Eight of the 192 planned beams are up and running, and a series of experiments last August verified that the eight-beam "bundle" can produce 153 kilojoules of targeted infrared laser light, making it the most powerful laser array in the world.

Nevertheless, detractors in high places have kept up a steady barrage. Last summer, a congressional committee led by Sen. Pete Domenici (R-N.M.) proposed axing the facility's funding altogether on the grounds that it has sucked money from the federal government's coffers every year with no definite indication that its scientific goals will ever be fully met. NIF officials currently figure the facility will achieve fusion ignition in 2010, eight years behind the origi-nal schedule, and the project's cost is now projected to exceed US $4 billion, up from the initial estimate of $2.1 billion.

NIF advocates chalked up a much-needed victory in November. A Senate joint committee ignored Domenici's recommendations, granting all but $10 million of the Bush administration's $337 million 2006 budget request for the project. Hearing the facility's funding had come through "was like a revalidation," says Bruce Warner, the NIF's deputy associate director. "This tells us that the government believes we've managed the project well and they like what they see."

Despite the triumph, questions remain about the project's ability to live up to its larger-than-life billing. "Although we've settled on continuing construction at NIF, I remain skeptical that [the Department of Energy] will be able to deliver on its promises regarding schedule, cost, and scientific capability," Domenici said in a statement released after the budget vote. Now that the facility's physical construction is almost complete, the 2007 budget request for the NIF is $29 million less than the year before, but even so, Congress's attitude is uncertain.

Doubters such as Domenici see the NIF, despite the formidable home being built for it, as a ramshackle, multibillion-dollar house of cards. And they have some support from qualified experts. A panel of the Jason group—leading scientists with top security clearances who regularly give the government advice about cutting-edge military technologies—recently released a report detailing technical difficulties that could stymie the NIF's goals and questioning the validity of some of the scientific principles underlying the facility's planned fusion experiments.