Future US Air Force missile: speeds up to Mach 6.5

In the hunt for Osama bin Laden and other individuals the military considers high-value targets, the US Air Force is pursuing a new program that could put a missile on a target in minutes instead of hours.

The Air Force is developing a "hypersonic" engine designed to fly bombs at Mach 6.5 speed, or more than 4,000 miles per hour, allowing commanders a chance to conduct long-range strikes on targets in a fraction of the time it takes now. The program, known as the X-51A scramjet, could be a valuable tool as a "manhunter" in fights such as those in Afghanistan or Iraq – or as a deterrent against more conventional enemies in industrialized nations, officials say. It all comes down to speed, and that could change the nature of the fight in the war on terrorism, military officials say.

"Faster is always better in air power," says Brig. Gen. Jim Poss, the Air Force's director of intelligence for its Air Combat Command at Langley Air Force Base, Va. "What we've found from combat experience is that people realize very quickly you have to move to survive on the modern battlefield. And the best way to counter that is to get there with the appropriate weapon in the appropriate size very quickly."

The program isn't a weapons program per se, but a demonstration of an engine that can move a weapon really, really fast. Unlike a rocket, which requires its own oxygen stored in heavy tanks, a scramjet engine mixes the oxygen already in the air with fuel at such a high rate that it can propel itself faster than anything else that can fly long distances within the atmosphere. Strap on a warhead, and the United States has a unique new weapon, analysts and military officials say.

It sounds ideal from a military commander's standpoint. There's just one problem: The X-51A doesn't quite exist just yet.

This spring, officials conducted an initial test of the SJX-61 Pratt & Whitney engine, which would drive the platform. An initial flight test could be held sometime in 2009. The platform wouldn't be operational for at least another eight years or so, the Air Force says. So far, the program is costing the service about $240 million, says Mark Lewis, the Air Force's chief scientist.

While the Navy is working on a similar "global strike" capability, it is the Air Force's initiative, with help from the National Aeronautics and Space Administration, that is getting the most attention. If and when it's fielded, the X-51A would allow the Air Force to contribute in a way that some think is more pertinent to the kind of ground operations in which the US is engaged.

"The [Air Force] today is looking for ways to become more relevant in the global war on terrorism beyond the smart bombs and the unmanned aerial vehicles it's already providing mainly in support of ground (counterinsurgency) operations," writes Guy Ben-Ari, a fellow at the Center for Strategic and International Studies, a Washington think tank, in an e-mail.

In the fight against terrorism, the US's most-wanted, such as Mr. bin Laden, are essentially moving targets. If bin Laden wants to have a meeting with his top lieutenants, for example, it will be called at the last minute and be short, intelligence officials say. That leaves the US military a small window in which to strike, posing a challenge to commanders and intelligence officials at the Air Force, which often oversees such operations. One option is to have missile assets in the area of the target already, perhaps by basing a bomber squadron in that region. Last year, when the Air Force zeroed in on a building where Abu Musab al-Zarqawi was meeting, it was able to get two F-16C Fighting Falcon jets near the target in time to get Mr. Zarqawi, considered the head of Al Qaeda in Iraq.

Other missiles, such as the Navy's Tomahawk cruise missile, which could be based farther away, require hours of planning. And once it gets in the air, it flies at less than the speed of sound – about 550 m.p.h. By then, the target could have slipped away.

"We've had some examples in Iraq where we've been able to do things quickly, but in other parts of the world where we'd be able to stand off at a distance and reach in, this would make an ideal weapon," Dr. Lewis says.

Because of the speed of the X-51A, it would dramatically compress the time needed for a commander to receive intelligence, prepare to deploy the weapon, and hit a target, analysts and military officials say.

"You're taking what could take a day and reducing it to a couple hours," says Chris Hellman, a military policy fellow at the Center for Arms Control and Non-Proliferation, a think tank and advocacy group in Washington.

The X-51A could also work as a deterrent, says Tom Ehrhard, a senior fellow at the Center for Strategic and Budgetary Assessments, a think tank in Washington. "If a terrorist group had to worry about something like that coming in on their meeting area, that is something they would have to consider," says Mr. Ehrhard, a retired Air Force colonel who specialized in strategy for the service. And for more industrialized nations with their own air defense systems, the X-51A could effectively negate such systems, allowing US air power to get past them.

But Ehrhard warns that a "persistent" surveillance system would have to be part of the X-51A platform to make it effective. "It's very sexy to talk about a Mach 6.5, but you have to ask a lot of hard questions about how you turn that Mach 6.5 into an effective weapons system," he says.