What do Harpoon missiles and Led Zeppelin music have in common? After more than 30 years, they are still relevant. The Harpoon remains a key element in the U.S. Navy arsenal and Led Zeppelin music is being used to sell Cadillacs. Go figure.

"There's definitely more life left in the Harpoon program, and I'm as surprised as anybody," said Steve Morrow, a manager on Boeing's Naval Weapons Advance Development team.

Developed to fill a "blue ocean" requirement in the 1970s against large adversarial navies, the Harpoon met the requirement of being able to sink an enemy ship at a significant distance, but over three decades, the surface navy has never embarked on a program to upgrade, or replace, the Harpoon for an anti-surface warfare role.

"The question is do they still need to maintain that capability or can they, in effect, operate at risk?" asked Mark McGraw, director of Naval Weapons for Boeing. "If they give up that capability they end up relying on the tactical aircraft to protect surface combatants, which is fine for carrier battle groups, but expeditionary strike groups, or individual ships on their own may find themselves at a tactical disadvantage."

McGraw and Morrow don't expect the Navy to give up the ability to wage a sea battle, but they say the Navy continues to look at alternatives, such as Harpoon Block II, or a further enhanced version that would include a data link.

"Our analysis, and what we have seen from the Navy, indicates that there is a gap in surface warfare capability for the Navy," declared McGraw.

Morrow agrees. "I don't think the gap requires a new weapons system per se, which bodes well for Harpoon, because we can modify it to meet the Navy's capabilities needs, so I'm encouraged."

"In our discussion with the Navy, they want to have even more positive control over the weapon while it's in flight," McGraw said. "The Navy wants to be able to command retargeting, abort if necessary, or let the weapon do its thing."

From the air, the Navy has that capability with the Standoff Land Attack Missile Expanded Response (SLAM-ER), the only anti-surface warfare weapon produced by Boeing that can be used to hit a moving target. Despite its effectiveness, its 10th birthday in 2006, may be the SLAM-ER's last.

"We've got a production decision coming up on SLAM-ER," McGraw stated. "If the Navy does not secure more assets, and if we are unsuccessful in some of our international campaigns, we may be forced in the 2006 timeframe to shut down the SLAM-ER production line."

A close relative of the Harpoon, the 14-foot, 1,500-pound SLAM-ER can travel more than 150 nautical miles, carrying a 500-pound warhead. It packs a punch, but how many of these highly versatile, but high-cost weapons does the Navy need as lighter and more affordable upstarts, like the Joint Direct Attack Munition (JDAM) and the Small Diameter Bomb (SDB) come into the inventory?

"There's definitely a trend there," McGraw says. "As the accuracy of the weapons' systems improves you don't need as big of a warhead to take out the target in most cases."

The Navy dropped its first 500-pound JDAMs in combat in November and has asked Boeing to accelerate production of the 500-pounders because they are finding them to be an extremely effective weapon in Iraq.

"Who's the enemy? Who's the guy you're designing to go to war with in the future?"

Those are the questions Steve Morrow says the war planners at the Pentagon struggle to answer every day.

"It's the Holy Grail to develop one weapons system and then not have to develop another one because it will always transform itself to meet the new requirement as threats and needs arise. That's impossible, because no one has a crystal ball," says Morrow.

The 250-pound SDB, Boeing's newest weapon, which is scheduled to go into production for the U.S. Air Force in April, may some day fill a gap for the Navy by being launched from a ship next to a 30-something-year-old Harpoon.

"We've been looking at a boosted SDB on surface combatants," said McGraw. "It could be an effective weapon against small boat threats because with SDB's Increment II (moving target) seeker technology, you just have to get it in the basket and it will find the target and engage at pretty decent ranges."

What about long-term? What does the future hold? Long range. Smaller. Faster. Definitely faster.

"We're putting a lot of effort into high-speed strike weapons working along with our advanced tactical missile folks," McGraw said. "We're involved in a bunch of programs demonstrating propulsion technology going all the way from Mach 2.5 to Mach 6 and this could be a revolutionary weapon for the Navy, both for ships and aircraft."

As they say in the Navy...stand by.