The stealth war: new threats, new technology

  • Even the newest stealth aircraft, such as this F-35B Lightning II, face radar and missile threats that opponents say can track and destroy them.
  • Bistatic radars. Illustrations by Timothy J. Reynolds
  • VHF target-aquisition radar. Illustrations by Timothy J. Reynolds
  • Phased-array engagement radar. Illustrations by Timothy J. Reynolds
  • Anit-aircraft missle. Illustrations by Timothy J. Reynolds
  • An anti-aircraft missile seeker displayed at an arms show outside Moscow. The 15 cmdiameter disc is studded with transmit/receive modules. The entire apparatus fits in the nose of a missile. Picture by Oleg Nikishin/Getty Images
  • B-2 Spirit. Illustrations by Timothy J. Reynolds
  • F-22 Raptor. Illustrations by Timothy J. Reynolds
  • F-35 Lightning II fleet. Illustrations by Timothy J. Reynolds
Date:1 November 2012 Author: Joe Pappalardo Tags:, ,

For the past 30 years, stealth technology has helped American warplanes maintain air dominance around the globe. Now Russian firms are designing and selling weapons they claim can shoot down the most sophisticated aircraft ever built. Think stealth means invisible? Think again.

There’s something unnerving about watching Iranians browse among weapons built to hunt down and destroy American warplanes.

The International Salon of Weapons and Military Equipment-2010, held at the famed Zhukovsky airfield outside Moscow, outwardly resembles US defence industry shows. Exhibits stand in rows inside a cavernous hangar converted into a convention hall. Engineers and sales people talk up their wares. Employees hand out pens tattooed with company names and logos. Clusters of visitors – on the first day of the show, mostly potential international customers – gather at the displays. Here, a couple of Eastern Europeans peer through the scopes of sniper rifles. There, a group of Asians gawk at a demo of small radio- controlled quadrotors.

This is all pretty standard defence industry fare. But some differences become more apparent when I reach the booth of the Russian firm AlmazAntey, one of the world’s leaders in anti-aircraft weaponry and the nation’s largest arms dealer. A promotional animation on a large screen hanging over the display shows an Almaz missile streaking toward an aircraft that looks a lot like a carrier-launched F-35C Lightning II. The missile closes in and the aircraft disappears in an orange explosion.

The image is shocking. I’m used to seeing American stealth warplanes prevail, in combat as well as in corporate promotional animations. The US government has invested 16 years and R3,2 trillion to ensure that F-35s can fly undetected through well-defended airspace. And the Russians are selling defence systems that can knock them out of the sky?

I notice a trio of men in nearly identical grey suits and close-cropped beards examining toy train-sized models of mobile radar and missile launchers. They are from the Sharif University of Technology in Tehran, a civilian institution that has ties to the military. Late last year, a scientist from Sharif visiting the United States was arrested for purchasing unspecified equipment that could be used in military programmes.

Almaz engineer Ivan Shalaev sidles up to them and they settle into a conversation in English. It’s a perfect opportunity to eavesdrop. The Iranians ask Shalaev questions about infrared sensors that can detect an aircraft by the heat of its engines and the air friction against its skin. But Shalaev tells the Iranians that infrared is just one tracking method the company offers to customers.

Behind him are seekers that use enhanced radar to chase down warplanes. Several are cut open to show a gimballed disc studded with a forest of tiny T-shaped transmit/receive modules. Under the disc is a small computer that can quickly process even the most subtle radar returns. This makes the missile responsive and difficult to outwit. Almaz-Antey is selling these upgraded warheads to fit on existing anti-aircraft missiles, including ones it sold to Syria, Venezuela, China and Iran.

The Iranians don’t answer any direct questions, beyond stating their university affiliation, when I introduce myself as an American journalist. But Shalaev is open, even friendly. He’s a hometown boy; his father was an engineer, too, who worked on advanced Russian aerospace programmes here at the Zhukovsky.

The young engineer is not shy about which aircraft are in his company’s cross-hairs. Asked if the new seekers could track and destroy an F-35, Shalaev grins and says, “Well, we’re going to try”.

Two years after the Zhukovsky arms show, sales of Russian anti-aircraft equipment are surging, and Almaz-Antey is at the head of the effort. Company officials, quoted in Russian media, say that the nation’s new defence plants – the first built in 20 years – will make anti-aircraft weapons.

That’s not good news for US pilots and American allies. The Pentagon strives to hold any place in the world, no matter how well defended, under threat of air attack. Modern US warplanes are designed to evade enemy radar, electromagnetic snoopers and heat-seeking missiles. The Pentagon calls this low observable (LO); the rest of the world calls it stealth.

LO aircraft enable precision strikes against protected targets, allow military containment of rogue states and curb the geo political appetites of potential adversaries. Their existence creates diplomatic leverage. Selling anti-aircraft weapons to anyone who feels threatened by the US and Nato is a way of making Russia a global power player.

“Russia still believes it has an important role to play in the world,” says Travis Sharp, an analyst with the Centre for a New American Security. “Producing and selling advanced military equipment is one way to signal to other states that you are not someone to mess with; nor are your allies someone they should mess with.”

Selling these weapons is also lucrative. In a recent R16 billion deal, Almaz-Antey delivered 15 batteries of S-300PMU-2 mobile anti-aircraft missile systems to China. Each battery has two or three radar units and four missile launchers. The radar can simultaneously track 100 targets; each launcher can shoot four missiles that speed towards their targets at Mach 6. That’s about 60 missile- launching vehicles for the price of four F-22 Raptors. The S-300’s keen radar and fast-moving missiles guard the Taiwan Strait and form an umbrella that would protect a Chinese invasion of Taiwan.

Scary as the missiles might be, it’s the radar systems that pose the gravest threat to stealth airplanes. Post-Cold War engineers in Russia breathed new, deadly life into VHF radars that have been around since the 1970s by digitising their signals. Increasing computing power has improved the system’s ability to glean coherent information from a jumble of data. Faint VHF radar returns that once would have been construed as random background noise can now be detected and identified.

“These VHF radars can detect aircraft constructed using stealth technology,” Viktor Ozherelev, a division head at Almaz-Antey, claimed at a 2007 arms show. “The Americans know their stealth programme has failed.” Most experts say this is an exaggeration, but it’s not unfounded.

The interplay between radar and aircraft is a physical one. Stealth aircraft are shaped to deflect radar waves away from the receivers – but not every radar scans at the same wavelength. Increasing the frequency of a wave decreases its wavelength (the distance between its peaks). The shorter the wavelength, the more detailed the return and the better the resolution.

Aerospace engineers designed stealth aircraft primarily to beat the detection equipment that poses the greatest threat – X-band radar. Surface-to-air batteries use this band because it operates at wavelengths that give the optimal compromise between the range and resolution needed to identify and track a target. But when stealth aircraft are exposed to radar waves longer than this wavelength range, they generate stronger radar returns.

For this reason, well-equipped defenders have more than one kind of radar protecting the same airspace, set up at different angles. For example, a defender protecting a fixed target (such as a uranium- enrichment facility) could share data from a network of several radars to get enough information to accurately launch a missile. A VHF radar could detect incoming aircraft while lower- frequency S-band or L-band radars on the flanks could paint the target from the sides. Russia sells such counter-stealth radar combinations as package deals.

These integrated-air-defence systems, as the Pentagon calls them, complicate any war plan. Pilots of stealth aircraft are expected to dismantle these networks, as B-2 Spirit bombers have done over Iraq, Serbia and Libya.

The upper echelons of the military warn that there are limits to stealth in these networked environments. “The rapid expansion of computing power ushers in new sensors and methods that will make stealth and its advantages increasingly difficult to maintain,” Admiral Jonathan Greenert, chief of naval operations, wrote in the July 2012 issue of Proceedings magazine, published by the US Naval Institute. “Maintaining stealth in the face of new and diverse counter-detection methods would require significantly higher fiscal investments in our next generation of platforms.”

America’s newest stealth aircraft, the F-35 Lightning II, is the most advanced warplane ever built. It’s set to enter service in 2016, and at least eight nations are buying it, making this stealth warplane the most likely one to face Russian radar and missiles.

The F-35 diminishes its visibility to radar with internal weapons bays, carefully aligned edges and embedded antennas. Yet the aircraft is accused of being more vulnerable to detection than earlier stealth aircraft, such as the F-22 Raptor, due to its more conventional airplane shape. The Air Force Association president, retired Lt-General Mike Dunn, slighted the F-35 when he stated that “only the F-22 can survive in airspace defended by increasingly capable surface-to-air missiles”.

The F-35 is a multi-role aircraft; it must fight other aircraft, bomb targets and conduct recon; and each mission requires specific payloads. For that reason, its design has trade-offs that make it less stealthy and less manoeuvrable than the Raptor, which was designed first and foremost to win air superiority over other fighters.

The F-35 does not have the radar-shunting curves of the Raptor that help mask it from radar at all angles. Engineers designed the F-22 and the B-2 to be unseen at many wavelengths and directions. The Lightning II does not offer many radar returns when the waves strike it from the front, but when they come from the side, the returns are stronger.

Persistent F-35 critic Carlo Kopp, an analyst with the group Air Power Australia, has written that the Lightning II is “demonstrably not a true stealth aircraft”. He also claims radar waves will bounce between the juncture of wing and fuselage in a way that can be detected if the aircraft is scanned from any direction but the front. He is not the only person who has pointed out possible sources of trouble. For example, rival aircraft-makers in Europe claim that powerful aircraft radar can spot an F-35 coming, even head-on, if multiple opposing aircraft are co-operatively scanning.

Radar waves do not just reflect off objects; they also flow across surfaces, scattering only when they hit a rivet, gun barrel or other feature that breaks the smoothness of the skin. Aviation Week reporter Bill Sweetman notes that the F-35A’s gun is located internally, but it is housed in a “hideous wart” on the aircraft’s surface – one of several features he says could betray the aircraft’s position.

Lockheed Martin won’t confirm or deny these alleged flaws, saying the information is classified. Still, the criticisms are plausible, even if they come from known F-35 sceptics using only public information. But Lockheed vice-president and former F/A-18 pilot Steve O’Bryan pointedly notes that there is more to being low-observable than just shape. “I reject the notion that the F-35 is an inferior stealth airplane,” he says.

The F-35’s approach to radar-absorbent material (RAM) is more reliable than that of any earlier warplane. The F-22’s surfaces are made of aluminium, which are covered in RAM that must constantly be reapplied. This is, of course, a nightmare for maintenance crews. But the F-35 is made of carbon-fibre composite; Lockheed engineers bake RAM into the aircraft’s edges in an effort to soak up inbound radar.

But the Lightning II’s key to survival is its own radar, the Active Electronically Scanned Array (AESA) installed in its nose. Conventional radar systems turn their gaze mechanically – imagine a dish spinning or a fl at surface tilting to aim radar beams. Electronically steered radar does not move, but its beams can broadcast in different directions, thousands of times a second and across many frequencies. This agility allows AESA to map terrain and track hundreds of targets.

AESA is built to do more than scan; it can reach out to enemy radars and scramble their signals. A combination of radar and electromagnetic warning sensors alert an F-35 pilot to the threat of enemy radar; he can then dodge the threat or use the AESA to jam the signal, no matter what frequency the radar is transmitting.

And, if a missile is launched, the F-35 can track it with 360-degree infrared-sensor coverage and then, in some cases, overwhelm the missile’s guidance system with the AESA. “Stealth works in conjunction with all those other techniques to make the F-35 what is probably the most survivable airplane of all time,” O’Bryan says.

But there’s a double edge to this sword. AESA radar is great at protecting stealth aircraft, but it can also detect them. Foreign military engineers are placing electronically steered radar arrays in their own warplanes and advertising them as stealth hunters. Putin’s radarmen are building several AESA radars for existing and future warplanes. Last year, Yury Bely, director of the Tikhomirov research institute, said in Takeoff, a Russian aerospace magazine, that the L-band AESA radar his staff is developing is “as good as any foreign radar of its type”. This year, flights of an X-band AESA radar began in prototypes of the Russian-Indian PAK-FA stealth airplane.

Air dominance is now being fought in a greater swathe of the electromagnetic spectrum. The critical part of any 21stcentury air combat will be the first invisible duel of flickering AESA beams dancing across each other hundreds of kilometres ahead of any aircraft. It’s the same old dogfight rules: the first pilot to spot the other shoots, and whoever is in the other aircraft probably dies.

Improved defences are already influencing Pentagon attack strategy. No one is saying stealth designs should be abandoned, but military planners must reckon with the advances of opponents. This is another part of the game – one that experts call the cost-exchange ratio. “There’s a real risk that a lot of the high-tech investments are going towards things our adversaries want us to invest in, because they can neutralise them – and spend far less money to do so,” Sharp says.

In his essay in Proceedings, Greenert suggests the way to keep US aircraft safe is to make smarter choices in equipping them. Instead of investing massive amounts of money in aircraft that can defeat every new threat, he advocates purchasing weapons that existing aircraft can fire from longer ranges, safely away from radar.

He also suggests adopting UAVs and missiles that can jam enemy radar before manned aircraft even arrive. “We need more numerous electronic warfare and cyber payloads to thwart detection and targeting,” he wrote. “US forces can…employ long-range sensor, weapon and unmanned vehicle payloads instead of using only stealth platforms to reach targets.”

The drones, cruise missiles and decoys may lead an attack, spewing radar beams and flooding computer networks with viruses. But they will have to be built to defeat powerful radar networks and fast missiles with can’t-miss seekers. Years of fighting low-tech insurgencies have increased military reliance on UAVs that are easily spotted on radar.

“We’ve got to start planning to build systems and to field capabilities to fight in a contested environment again,” the Air Force’s new military deputy for acquisition, Lt-General Charles Davis, said in a recent interview with the Air Force Times. So, in one form or another, the duel will continue.

As of now, no S-300 surface-to-air weapon has ever been fired at a target in anger. The Lightning II is still in testing, and the debut of its style of networked warfare is years away. Their match-up awaits. Only then will the war of words between detractors, engineers, salesmen and journalists be settled – in combat, with lives at stake and history in the balance.

Warplanes at risk

Integrated layers of defence work together to spot and destroy attacking warplanes.

Bistatic radar

Alerts defenses to an intruding aircraft.

Emissions from civilian transmitters, such as phone or TV towers, reflect off a target moving through them. These bistatic radar systems can triangulate a target and measure Doppler shift to determine its heading and speed.

Example: VERA-E (Czech)

VHF target-aquisition radar

Tracks an aircraft and provides information to other radar.

Ever since stealth aircraft became public during the first Gulf  War, Russia has tried to thwart them by digitising the signals of its older VHF radars to increase range and improve resolution. Russian firms now claim their systems can detect stealth aircraft by bathing them in long wavelengths.

Example: 1L119 Nebo SVU (Russian)

Phased-array-engagement radar

Gives a missile direction as it soars towards its target.

Digital transmissions from other radars are delivered to this phased-array radar, which tracks the target and helps steer a missile before it gets close enough to home in on the intruder.

Example: 30N6E (Russian)

Anti-aircraft missle

Delivers 147 kg of explosives.

Single-stage, solid-propellant missiles launch vertically from the vehicle. Seekers in the 7,6 m-long missile have their own radar, enabling the weapon to close in without help from the launch vehicles, which are at risk of counter-attack while their radars are on.

Example: S-300PMU-2 (Russian)

 

Assessing America’s Stealth fleet

B-2 Spirit

Pros: The flying wing shape, with no vertical control surfaces, lowers the long-range B-2’s radar cross section dramatically. The engine and air intakes are embedded inside the air frame, reducing its radar signature.

Cons: This bomber’s design reduces its speed and manoeuverability, so much so that it doesn’t fly on daytime missions, when it might encounter enemy fighters that could see it.

RCS*    -40 dBm2 (equivalent to a marble)

F-22 Raptor

Pros: This fighter can reach supercruise speeds without using an afterburner (which would boost its thermal signature). Swept wings divert radar returns as it approaches, making it a deadly air-to-air combatant.

Cons: The aircraft is covered with a coating that absorbs radar but adds cost and effort to maintenance crews.

RCS*    -40 dBm2 (equivalent to a marble)

F-35 Lightning II

Pros: This warplane, still in testing, fuses information from many sensors to get warning of threats while remaining unseen. It has a powerful, electronically steered radar that can jam enemy radar and missiles.

Cons: The more conventional shape of the airplane gives it a larger signature on enemy radars that strike it from the sides, while the low wing-surface area makes it less manoeuvrable in high g’s.

RCS*    -30 dBm2 (equivalent to a golf ball)

* Radar Cross Section – widely reported, unconfirmed figures of head-on RCS, measured in decibles.

Video: F-35 Lightning II variant takes flight for the first time
Video: How Lockheed Martin builds the F-35