Unmasking the Stealth Radar : Defense: The “invisible” radar for the B-2 is a machine like nothing experts have seen before--and so is its high cost.
In the summer of 1984, while the attention of Los Angeles was riveted on the Olympics, the engineers at Hughes Aircraft in El Segundo had something quite different to occupy their minds.
The radar antenna they had designed for the B-2 Stealth bomber--like no other antenna ever imagined before--would not work, though only a handful of people at Hughes and B-2 prime contractor Northrop knew it.
The radar program was one of the most secret parts of the top-secret bomber project. The fact that Hughes was even building the radar had become public knowledge only when one of the firm’s engineers was caught selling the design to Soviet spies a few years earlier. And like the rest of the B-2 program, it wasn’t cheap--the cost of each aircraft’s radar system would eventually grow to $32 million.
Why all the mystery? Hughes was building the world’s first “Stealth radar,” a device that could let the B-2 bomber locate enemy targets without being detected. Absent such a radar, the B-2 wouldn’t truly be stealthy. So, the radar project--while only a $2.4 billion component of the $62.5-billion B-2 program--was critical to the bomber’s success.
Usually, a radar acts like a radio beacon when it is turned on, announcing itself to enemies hundreds of miles away. This one was supposed to be so “quiet” that it would not reveal itself to enemies, but still use powerful radio waves.
To help solve the problem, the engineers at Hughes proposed in part to use a highly unconventional antenna--the details of which have never before been disclosed. It would contain 25,000 individual parts, most produced to the tolerance of a Swiss watch. It would have hundreds of moving parts, operated by magnetic switches. It would get so hot from electrical energy that it would require a liquid cooling system. And the entire radar system would weigh more than a ton--as much as a compact car.
It was one of the most technically risky elements of the whole B-2 program, meaning that much could, and eventually would, go wrong. Back in that summer of 1984, the Air Force convened a secret blue ribbon task force, made up of top military officers, academics and even competitors, to find a solution to Hughes’ problems.
A decade after the program began, internal Hughes sources and some congressional experts say the radar remains troubled. The estimated cost of the radars, including the antennas, has almost tripled from the original projections, excluding the effects of inflation. And just this week, Hughes replaced its longstanding production manager for the radar system, though the company insists the move was not a signal of problems.
Indeed, Hughes asserts that the program is going well and that past problems have been solved.
“The radar as a system works extremely well,” said Theodore W. Olson, a Hughes group vice president who is the program manager for the radar. “The Air Force is very pleased. Northrop is very pleased. Obviously, we’re very pleased. When you put all the pieces together, they do what they’re supposed to.”
No one argues that the task, from the start, hasn’t been a daunting one. The B-2 is called a stealth aircraft, because it is supposed to escape detection from enemy radars. The Lockheed F-117A used in the Persian Gulf War is also a stealth aircraft, but it has no radar.
The B-2 radar is supposed to perform 21 different functions, including helping the aircraft avoid terrain in low-level flight, find targets and even avoid nuclear debris after bombing runs. It can reportedly create detailed, photograph-like images of ground features, buildings and even small vehicles at ranges of more than 50 miles.
After receiving about half of the $2.4 billion in funding for the radar program, Hughes has delivered radars for five aircraft to Northrop and manufactured them for four others, Hughes executives said. (Each bomber carries two complete radar systems.)
Even though Olson and other company officials say the program is going well, they acknowledge periodic production problems. Olson said the system is over its specified weight and not meeting all of its specifications that might affect its Stealth capability.
“The antennas are not falling apart, but I don’t know how to quantify the effects you would consider a problem but that we would consider aggravations,” he said.
He added later in a lengthy interview: “We push everything right to the limit. That’s like if your car specification is 130 m.p.h. and you get to 125, you don’t worry about it.”
But some experts are not so sanguine, asserting that doubts remain about its stealth capabilities and whether Hughes has fully overcome its production problems.
Air Force officials declined to be interviewed on the radar program, but they responded to a list of written questions submitted by The Times. The service asserted that Hughes has “overcome the major challenges in developing a high-quality B-2 radar system” and that “whatever lesser challenges remain can be overcome with relative ease.”
Test results are not yet in. Flight testing of the radar, which began only last month, are the first opportunities for the equipment to operate in real life conditions--crammed inside the B-2’s wing and having to work in concert with all the other B-2 systems.
On the Rockwell International B-1 bomber program, it was not until long into the flight test program that severe problems with its avionics systems became known. Northrop, Hughes and Air Force officials are confident that the B-2 will not repeat the failures of the B-1.
One indication that the radar program has technical and manufacturing problems may be its escalating cost.
In current dollars, each aircraft’s radar system costs $32 million, including the research, spare parts and ground equipment. Moverover, Hughes will have to substantially cut its production costs to build the remaining 60 radars for the $1.2 billion left in the program.
If the radar indeed works as it is intended, even an average cost of $32 million might not seem like much, given the megabucks of today’s defense business. But it is more than an entire F-16 jet fighter’s cost--including its radar.
In many ways, the Hughes radar suffers from the same problem as the entire B-2 bomber program: sticker shock.
Hughes officials note that the radar’s cost has simply kept pace with the overall program. The radar accounts for about 6% of the B-2’s production cost--less than the relative cost of Hughes radars for the fighter jets, according to Jim Uphold, deputy program manager. Olson also blamed the high unit cost on the B-2’s low production rate and schedule changes.
The Air Force said in a statement that the near-tripling of the costs “are not categorized as cost growth because they were changes directed by the Air Force to improve upon or enhance the original design.”
Critics are less certain. Staff members on the House Armed Services Committee dispute that the radar’s capability has improved at all, let alone by an amount that would justify a tripling of the cost. And a senior defense adviser in the Reagan Administration asserts that both the Air Force and Hughes “over-promised at the start of the program.”
A Hughes Aircraft executive, William Schumer, alleged in a 1989 federal civil lawsuit that Hughes improperly charged costs for other radar programs onto the B-2 radar, driving up its price tag by a substantial amount. Hughes denied his allegations, and the Justice Department declined to join in the case.
Still, the Pentagon is withholding $15 million from Hughes, based on a 1986 audit that found the firm improperly allocated development costs between the B-2 and three other radar programs that shared much of the same technology.
One Hughes insider privately asserted that the program is still dogged by cost problems and that the radar will become a maintenance nightmare once the B-2 enters service. Another expert, a former Hughes consultant on the B-2, said company officials have been on the verge of a “nervous breakdown” over cost and technical problems.
Olson, however, rejected such anonymous criticism and said Hughes has significantly advanced the art stealthy radars. The company, he added, will reduce the radar’s cost by substituting key plastic parts for complex metal ones.
During a two-hour interview, Olson described far more about how the radar works than has ever been disclosed before:
* Unlike any radar before, the radar beam is electronically steered, in part by moving strips of “dilectric material” roughly analogous to semiconductors. Their purpose is to alter the phase of the radar wave. The unusual feature of movable semiconductor strips adds significantly to the complexity of the antenna, since the strips must move precisely within channels inside the antenna body.
* Each radar antenna is made up of 52 carefully machined assemblies, called “phase shifters,” which are assembled into the rectangular block. The front face of the antenna is a flat plate with several thousand tiny square openings where the radio energy is emitted. The openings, arranged in perpendicular columns and rows, must be precisely positioned and shaped to maintain stealthiness.
“You can talk to all the antenna experts in the world, and they will think you are crazy if you start describing this antenna,” said one official intimately familiar with the program. Indeed, discussions with radar experts from government and academia said they were unfamiliar with any design resembling the Hughes radar and expressed doubts about such a design.
* Another unusual feature of the antenna is its extensive use of magnesium, a light-weight, highly flammable metal that is seldom used in aircraft structure.
But the potential flammability caused concern within the Air Force. At one point, the service wanted Hughes to toss an antenna out of an airplane to see if it would explode when it hit the runway.
“There were a lot of naysayers at the beginning,” Olson acknowledged.
The radar achieves it stealthiness through a “collection of individual . . . techniques” to confuse and elude the enemy, Olson said. But the Hughes executive said he could not discuss the techniques in much detail, for security reasons.
“To a large extent, what you read about low-probability-of-intercept radars is implemented (in the B-2)--and a lot more,” Olson said.
Academic experts at UCLA and the University of Southern California, along with several government experts, said a Stealth radar would undoubtedly use a number of techniques, including:
* Precision shaping of the antenna. The antenna, a large block of magnesium in the wing, must not become a target itself of enemy radars. To prevent the antenna from reflecting enemy radar signals, it must be precisely shaped, with tolerances as tight as 0.0005 inches--about half the average width of a human hair.
* Controlling energy leakage. A radar points a burst of radio energy at targets and then listens for an echo. If radio energy is prevented from leaking off the main beam, enemies will have a harder time detecting the radar. This leakage, called the “side lobes,” ideally would be held to 1-millionth of the energy of the main beam
* Pseudo noise. The B-2 would attempt to disguise its radar signal as random radio noise, which would make it difficult for an enemy to identify the signal and even harder for the enemy to use the signal to jam the B-2’s radar.
* Energy control. Reducing the total amount of radio energy used will help prevent detection. All radars operate by broadcasting pulses of energy and listening for an echo. By lowering the peak power or by decreasing the duration of the pulse, there will be less total radio energy that the enemy can search for.
* Special software techniques. The radar will have software believed to be the most advanced and most secret aspect of the system.
Critics of Stealth question the viability of these techniques. In the shaping of the antenna, for example, the Reagan Administration expert said that while such precision can be built at the factory, it will be lost due to vibration and distortion of the aircraft, he said.
But Olson said the tests verified the system could perform as designed.
The equivalent of 700 full-time workers work on the program, mostly in a top secret facility. But the antenna is produced in a non-classified area.
Hughes, using $4.2 million provided by the Air Force to reduce technical risks on the program, developed an innovative machining system for the antenna parts in the early 1980s. “The conventional machines available at the time were ridiculous,” said Adolph Stroibl, a supervisor in the machine shop. “We would have had to have a huge factory just to build the antenna.”
Stroibl, a 22-year veteran of building precision radar antennas at Hughes, said the scrap rate on the B-2 antenna parts is 0.5%, low by aerospace standards.
“When we first started, I didn’t think we could do it,” Stroibl said. “But they are coming out great.”
Unmasking the Stealth Radar
1. Side Lobes: If radio energy can be prevented from leaking off the main radar beam, an enemy will have a harder time detecting the B-2 radar. This leakage, called the “side lobes,” ideally would be held to one- millionth of the energy of the main beam (a level technically designated as 60 decibels) and certainly no higher than one-thousandth the energy of the main beam (30 decibels).
2. Pseudo noise: The B-2 would attempt to disguise its radar signal as random radio noise, which would make it difficult for an enemy to identify the signal and even harder for the enemy to manipulate the signal to jam the B-2’s own radar. Although the enemy might know a radar is operating, it would be difficult to locate and identify the source.
3. Energy Control: Reducing the total amount of radio energy used will help prevent detection. All radars operate by broadcasting pulses of energy and listening for an echo. By lowering the peak power or by decreasing the duration of the pulse, there will be less total radio energy that an enemy can search for. The B-2 radar is a “mono-pulse” radar, capable of finding its targets with just a single pulse of energy.
4. The Antenna: The antenna must not become a target itself of enemy radars. To prevent the rectangular-shaped antenna from reflecting enemy radar signals, it must be precisely shaped, with tolerances as tight as 0.0005 inches--about half the average width of a human hair. The antenna face is a flat surface with thousands of precisely-positioned square holes that emit radio energy.
5. Special Software: The radar will utilize software techniques that are believed to be the most advanced and most secret aspects of the radar. Very little is publicly known about this capability.
