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Suddenly, All Eyes Are On Stealth

Science & Technology


One by one, the matte-black F-117A jets roared down a Saudi Arabian runway, kicking up the first gusts of sand in Operation Desert Storm. Over Iraq minutes later, the stealth planes would atone for their combat debut in the 1989 invasion of Panama, when one bombed the wrong target. On the gulf war's first night, just 50 stealth planes--5% of the air armada massed against Saddam Hussein--flew 40% of the bombing runs. The damage they did helped give the allies mastery of the skies, and seal Saddam's defeat.

During the six-week war, in fact, F-117s flew 80% of the missions against the most heavily defended targets, and hit 97% of them. Yet not one of the planes was even damaged. "If there's one lesson out of the gulf conflict," Defense Secretary Richard B. Cheney told the House Armed Services Committee last month, "it is the value of stealth."

That could be the byword for a decade of military lobbying. There's no talk of adding to the fleet of 56 Lockheed F-117s, which cost $106 million apiece. But Northrop Corp. hopes to build 75 B-2 stealth bombers, including 15 already ordered, for what the General Accounting Office puts at $865 million each. Teams led by Lockheed Corp. and Northrop are jockeying to build 750 stealthy Advanced Tactical Fighters (ATFs), starting around 1996, for about $65 million each. And the U. S. Navy still wants a stealthy successor to the A-6 attack plane. Early this year, Cheney killed its replacement, the A-12, for being behind schedule and over budget.

'CHEAPER.' The quest for stealth doesn't stop there. The Navy will soon put in service the Arleigh Burke, the first of a new class of stealthy guided-missile destroyers. General Dynamics Corp. is working on a stealthy cruise missile. The Pentagon wants stealthy spy satellites. And even the U. S. Army envisions hard-to-detect tanks, armored personnel carriers, and helicopters.

Air Force Secretary Donald B. Rice laid out the rationale for all this before the House Armed Services Committee on Feb. 26. The cost of stealth is misleading, he argued, unless compared with the cost of the "force package" needed for a given job. He calculated that eight F-117s armed with smart bombs and accompanied by two refueling tankers can deliver the punch of75 nonstealthy planes. Those extra planes would be needed mainly to hit enemy air defenses and jam radars so conventional bombers could go to work. In theory, stealthy planes wouldn't need such support, since they are so hard to spot. Desert Storm, Rice declared, was "a demonstration that stealth is cheaper" overall. The question is whether that idea will sell in Congress, given the thaw in the cold war.

Stealth is a combination of efforts to make a plane harder to find. John F. Bashen, Northrop's chief scientist, says eluding radar is only half of stealth's job. The heat of jet exhaust must be masked so that infrared missiles can't home in on it. The plane must be made quiet to avoid acoustical detectors and small to make it hard to spot visually. Still, the main objective is reducing the radar cross section, a measure of the echo that bounces back from the front of the plane. Make the cross section small enough, and you can sneak in, bomb, and escape with little risk. Or circumvent ground radar, whose transmissions are easy for a stealth plane to spot before it is detected.

The technology involved in all this is what makes stealth so expensive, starting with the design of the plane's shape and structure. Right angles, especially, reflect radar--even gun barrels or the blades on a jet's turbofan. Rockwell International Corp. shrank the cross section of its B-1 bomber from 10 square meters to less than one by eliminating an antenna housing along the plane's spine and by tucking turbofans inside curved inlets that hug the fuselage. Concern over shape explains the origami design of the F-117 and its lack of normal fighter weapons, such as guns or underwing missiles. The B-2 is also toothless in air combat, relying solely on stealth to evade enemy fighters. Keeping both planes airborne is the trick: Lacking a conventional tail, bat-shaped designs are inherently unstable. So on-board computers adjust the flying trim long before a pilot can detect the need, let alone react.

PLASTIC FRAME. Materials are the other big cost. The F-117's body is built mostly of aluminum panels, cloaked by a secret coating that absorbs and dissipates radar signals. But plastics are better, especially reinforced composites containing carbon fibers, which are stronger than steel and soak up radar energy. The B-2 has a composite airframe, covered with a coating that's related to the one on microwave oven liners. Now, research is being done on even better coatings, including a multilayer design that would trap radar energy, convert it to heat in a subsurface layer, then channel it to air-cooled outlet slits on top of the wings.

Improved coatings and other stealth tricks can help hide planes with more conventional shapes, and even ships. And they help prepare for the day when counterstealth technology emerges. For instance, some scientists argue that so-called impulse radar could overpower today's technology. Impulse radar, which hasn't been built yet, would transmit short, high-power pulses of energy while hopping around a frequency spectrum much broader than that of current radar. Stealth defenders doubt that this could provide the accuracy needed to track a B-2 at long ranges. "The truth is probably in between," says a Defense Dept. insider. But "no one appears willing to spend the money on a demonstration" that could put "programs costing billions in jeopardy."

Hoping to settle the issue, Congress earmarked $25 million in 1989 to investigate impulse radar's prospects. But the initiative boomeranged. The funding windfall touched off a wild scramble among radar researchers, and when the Air Force convened experts last year to assess research progress, some proponents of impulse radar withheld key data for fear of tipping off potential rivals. Partly as a result, the panel's report slammed the antistealth capabilities of impulse radar. That triggered outcries of foul play, cronyism, and political pressure. By November, the controversy was so acrimonious that the Air Force inspector general launched an investigation of the ruckus.

Questions have also surfaced about other potential stealth-decloaking technologies. For example, some experiments have shown that the exhaust "plume" from a jet engine affects certain radio-wave frequencies in a way that can betray the identity of the engine. If this is true, then the right sensors might track a stealthy plane from a distance of 100 miles or more. Evaluating such claims is the job ofthe Red Team, a group of outside experts funded by the Pentagon. So far, says the Air Force, the Red Team has studied 50 stealth-busting schemes and uncovered "no Achilles' heel."That's not to say a stealth plane can't be spotted. But seeing it isn't the same as shooting it down. That requires computing its distance, course, speed, and altitude, shuttling the data to a missile-guidance system, and firing a missile--all while the plane is in range. But stealth, the Red Team says, enables a B-2 to zip past radar sites before being hit. That's apparently what happened when F-117s launched Desert Storm, says Technical Sergeant Bobby Shelton of the 37th Tactical Fighter Wing: They didn't draw fire until their bombs hit the ground. Moreover, the radar on board fighters isn't powerful enough to be good at picking up stealth planes. In the recent war, Shelton adds, one U. S. pilot found himself above an Iraqi MiG fighter, wondering if his earthbound bomb would hit the oblivious enemy. The MiG banked away just in time.

MOVING TARGET. Despite such tales, the B-2 faces a tough fight on Capitol Hill. Many B-2 boosters were shocked when Air Force brass conceded, in 1987, that the plane can't hunt down the mobile ICBM launchers it was supposed to kill. It could be directed to these by a spy satellite. But so could cruise missiles carried by B-52s parked outside enemy airspace. Suddenly, the B-2 became an expensive weapon with no special purpose. That's why Congress may not buy more planes than those already ordered from Northrop.

By contrast, an ATF contract that could approach $80 billion over 20 years may be let by the end of April. This plane will replace the Pentagon's prefighter, McDonnell Douglas Corp.'s F-15, which has been in service for 16 years, longer than any of its predecessors. If the ATF matches its billing, it will combine agility, speed, and stealth.

That's a challenging recipe, since the things that enhance maneuverability and speed are bad for stealth. For instance, while a tail section with large horizontal and vertical stabilizers makes for quick maneuvers, it can be a major source of radar echoes. And to reach speeds above Mach 1, conventional planes have to use afterburners that give their location away. That's why the F-117 and B-2 fly at subsonic speeds--and aren't agile.

Still, as a result of their previous stealth work, both Lockheed and Northrop, the competitors on the ATF, have unprecedented computer-aided design tools. Ben R. Rich, who retired last year as head of the supersecret Skunk Works, where Lockheed developed the F-117, says a stealthy ATF can be built with just a 10% loss in performance. Either Lockheed's prototype, called the YF-22A, or Northrop's YF-23A will become the first fighter that can fly at up to about Mach 1.5 without the use of afterburners. And stealth technology shrinks their apparent radar size to something on the order of a robin.

SILENT SHIP. Attempts to transfer this technology to weapons such as ships will be less impressive. Still, if an 8,300-ton destroyer such as the Arleigh Burke looks no bigger on radar than a yacht, it should gain an element of surprise and be harder to attack. So right-angle joints on the ship have been eliminated wherever possible or shrouded by panels coated with radar-absorbing materials. A secret sound-dampening "bubble system" between the walls of the hull cuts down the distance over which subs can hear the ship's diesel engines. And to thwart heat-seeking missiles, the funnels have extra-thick insulation and suck in outside air to cool engine exhausts before the gases exit the stacks.

The Burke, the first ship of its kind, will cost more than $1 billion, but copies should be 30% cheaper. The Navy wants to buy more than two dozen, with construction split between Bath Iron Works Corp. in Bath, Me., and Litton Industries Inc.'s Ingalls Shipbuilding Div. in Pascagoula, Miss.

Until Jan. 17, a debate still raged over how effective stealth technology would be. The war provided an answer--and probably set off a new race between nations in warplane design. That's the spectre that defense lobbyists can now be expected to raise, along with a proposed solution: to stay on top, stay ahead.Otis Port in New York, with Seth Payne and John Carey in Washington and Eric Schine in Los Angeles

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