The Pentagon’s prototype Airborne Laser is not likely to be of much use as an operational missile-defense weapon and is expected to cost $5.1 billion through 2009, or several times its original price tag. Nevertheless, now is not the time to derail the program.

That is what the House of Representatives has effectively proposed in the Defense Authorization Act for 2008. The bill, which passed overwhelmingly in the House May 17, recommends providing about $300 million next year for the Airborne Laser, or just over half of the $549 million requested by the Missile Defense Agency (MDA).

Although that mark is far less onerous than the $400 million cut originally recommended by the House Armed Services strategic forces subcommittee, it still would have a dramatic impact. According to the MDA, it will delay by up to three years a planned flight demonstration in which the modified Boeing 747 aircraft will attempt to shoot down a target missile with a high-powered laser. It also probably would require a restructuring of the program that would add hundreds of millions of dollars to its cost.

There is much to be skeptical about when it comes to the Airborne Laser, which is billed as the MDA’s primary means of destroying missiles during their boost phase, when they are most vulnerable. Among the burning questions are whether such a large, lumbering aircraft could get within effective range of enemy launch sites without being shot down and how much it would cost to build, deploy and maintain an operational version of the system.

The MDA has developed a cost estimate for a second aircraft that the agency says would have some operational utility, but refuses to disclose the number. That suggests that the number is so high as to be politically unpalatable. The Boeing-led Airborne Laser industry team, which includes Northrop Grumman and Lockheed Martin, is preparing its own cost estimate, but

the companies have every incentive to be overly optimistic in their assessment; Congress should take with a grain of salt the number they come up with.

The project, which a Boeing official has likened to putting a Hubble Space Telescope inside an aircraft, is incredibly complex – some say it is the most sophisticated optical system ever built, and there is little reason to doubt that. Like almost all advanced technology development programs, it has seen its share of delays and cost growth. The original value of Boeing’s prime contract was $1.1 billion. The value is now $3.6 billion and expected to rise to $3.8 billion when the contract is modified to account for the latest slip of the shoot-down demonstration, now scheduled for August or September of 2009.

What’s more, nobody knows whether the system will even work.

But if it does, the implications are huge: An air-mobile system capable of generating a directed-energy beam powerful enough to destroy ballistic missiles at distances of hundreds of kilometers – the exact range of the Airborne Laser is classified – has the potential to revolutionize not just missile defense but warfare itself.

Almost all of

the hardware for the prototype Airborne Laser is built.

The aircraft is currently undergoing a series of tests to demonstrate its low-power beam control/fire control laser, and installation of the high-energy laser, which has been tested on the ground, is expected to begin later this year. The bulk of

the investment in this program has already been sunk; the MDA has just under $1 billion budgeted for the effort for 2008 and 2009 combined, and Boeing says this will be sufficient to carry out the test.

Given what is now known about the Airborne Laser’s cost, along with the unanswered questions about its practical military utility, it is debatable as to whether the MDA should have undertaken the project when it did. But slashing the program’s budget with the demonstration just over two years away will accomplish only one of two things: drive up the cost, or minimize the knowledge that can be gleaned from the funding that

already has been invested.

Rep. Ellen Tauscher (D-Calif.), who chairs the strategic forces subcommittee, wants the MDA to focus on deployment-ready programs such as the Aegis sea-based system. That is her prerogative and generally speaking is not an unreasonable position to take. And there is nothing wrong with demanding that the MDA be more forthcoming with information about its programs, an area where the previous Congress was often lacking.

Congress would be wise not to approve funding for a second Airborne Laser aircraft before it has seen both an independent estimate of its cost and promising test results with the first unit. But barring some unforeseen technical snag or a major cost overrun, it would be wasteful and imprudent to disrupt work on the first aircraft anytime between now and the shoot-down demonstration.