NORFOLK — The carrier Harry S. Truman sailed Wednesday in a test of the Navy's ability to have seven of its 12 carriers away from port simultaneously, a major shift from the way carriers have traditionally been used.

A second Norfolk-based carrier, the Enterprise, was expected to leave Thursday to participate in the exercise, dubbed "Summer Pulse 04."

"Summer Pulse 04" continues through August, with seven carriers conducting joint exercises and international exercises with allies from the Americas, Europe, Africa, Australia and Asia, officials said.

"The ability to push that kind of military capability to the four corners of the world is quite remarkable," Navy Secretary Gordon R. England said when he announced plans for the demonstration last week in Washington. "Several years ago, we could deploy only two" carriers at the same time.

"Summer Pulse 04" is the first exercise of the Navy's new Fleet Response Plan, announced last December, under which ships will move away from traditional, regularly scheduled six-month deployments and be prepared to leave as world events demand.

The Navy wants to be able to send six carrier strike groups in less than 30 days to handle a crisis anywhere in the world, plus have two more carrier strike groups ready within three months to reinforce or rotate with those forces and continue operations in other areas.

"Summer Pulse 04" is "a proof of concept that we can in fact make that happen," Capt. Michael R. Groothousen, the Truman's commanding officer, said Wednesday by telephone after the Truman left Norfolk Naval Station.

Groothousen said the Fleet Response Plan makes deployment schedules less predictable — a change necessary in a post-Sept. 11 world.

"Terrorists love predictability," he said. "If we can start putting some unpredictability into our schedule, it makes it more difficult for any threat out there to determine when to strike."

That also means more volatility in the sailors' schedules.

"When you're planning on being in port for a little while and then the schedule changes, nobody likes that," said Petty Officer 1st Class Tony Rice, 34, of Midland, Texas, a Truman crew member. "But you kind of get used to it as a sailor. You're taught to be fluid and expect the unexpected. "

The Navy demonstrated its ability to "surge" multiple carriers like this a year ago during the Iraq war, said John Pike, director of GlobalSecurity.org, an Alexandria research center on security issues.

However, the Navy wasn't really set up to deploy several carriers at once, so it wasn't easy, he said.

"Now they are demonstrating that they are set up to do it," Pike said. "If anybody anywhere gets any ideas — if North Korea gets frisky or the Red Chinese get too risky— they might have a half-dozen carriers show up on short notice."

This is "a fundamentally different way of deploying aircraft carriers than we had during the 20th century," Pike said.

Typically, a carrier deployed overseas for six months, then was at home for 18 months while sailors went back to school in the Navy and the ship was repaired and overhauled.

Under that arrangement, a carrier was combat-capable only for about six months during a two-year cycle, so generally only two of the stateside carriers could be deployed at a given time, Pike said.

The other carriers taking part in "Summer Pulse 04" are the Norfolk-based USS George Washington and San Diego-based USS John C. Stennis, which are already deployed; the USS Kitty Hawk, based in Yokosuka, Japan; the Mayport, Fla.-based USS John F. Kennedy; and the USS Ronald Reagan, which left Norfolk last week and is en route to its new home port of San Diego.