Performance specs for stealth versus radar remain a carefully kept secret, for obvious reasons. But Breaking Defense did speak to (among others) two of the leading experts on the subject: F-35 booster
Deptula, a retired three-star general with decades of experience planning and flying combat missions; and long-time stealth skeptic Friedman,
an award-winning military analyst and author with a degree in theoretical physics. The two men have very different takes on the future viability of stealth – but both agreed, to start with, that it’s not the magic invisibility cloak from
Harry Potter.
“People need to understand stealth is not invisibility,” Deptula told Breaking Defense. As current sensor technology improves, he said, “you’re going to be able to detect aircraft with current levels of low-observability at further distances.” That said, non-stealth planes are much bigger targets, he said: “It’s a piece of cake for an adversary with a sophisticated air defense system to engage and kill a 4th generation aircraft; it’s very difficult for them to do that with a 5th gen aircraft. Will it get easier in the future? Possibly.”
“You can’t make something disappear, all right?” echoed Friedman. “What you can do is reduce the signature you get back [on the enemy’s sensor screens]. More powerful processors buy you back part of the signal” – and thanks to Moore’s Law, the processing power available to do that doubles every 18 months. The more powerful the processors and the more sophisticated their algorithms, the more effectively they can sift meaningful data out of the static. And no matter how stealthy an aircraft is, it still makes some noise, it still emits some heat as infra-red radiation, and – most critically – it still reflects back some portion of an incoming radar beam.
Not that all radars are created equal. Even back in the 1980s,
author Andrew Cockburn warned that, ironically, the Soviet Union’s oldest, crudest radars might detect stealth bombers that newer systems missed. Stealth aircraft rely on carefully designed shapes and thin surface coatings to baffle incoming radar beams. But the lower the frequency of the incoming radar, the longer the wavelength, which means the less it reflects such subtleties at all: It’s essentially too stupid to be tricked.
The upside is such relatively crude radars may detect a stealth aircraft is out there somewhere, but not accurately enough to shoot it down. The low-frequency, long-wavelength radars that are most likely to see through stealth are, for the same reasons of physics, the least precise. They’re also too big to fit in anything but a ship or a fixed ground installation, where they are typically used to give warning that aircraft are in the general area. Actually tracking and hitting a target depends on smaller, shorter-wavelength radars which can fit in, say, an interceptor aircraft or surface-to-air missile and which offer more precision but are also more easily baffled by stealth technologies.
“Just because you can see someone now doesn’t mean you can kill them,” said Deptula. “Acquisition radars, which are what people generally tend to focus on, are only one element in an adversary’s air defense equation.” After a target is initially “acquired,” he went on, “you need to be able to track the asset to then get to a firing solution; then you need to transfer that tracking data to the missile, which then needs to be able to acquire and track the aircraft [after it launches]. Presuming that the missile can track… now the fuse needs to be able to detect the aircraft” in order to detonate at the right time.
Break any link in that “kill chain,” and the stealth aircraft survives, even if it’s seen. So while stealth can’t defeat all the radars all the time, it doesn’t need to.
The problem is what happens when all the radars are working together in parallel instead of in a series. Rapid advances in computing technology don’t just improve the individual radars. They also make it easier to share data among multiple sensors of multiple types – radar, infra-red, visual, acoustic – and thus put together scattered clues into a picture that’s clear enough to kill.
“If you have a lot of radars working together, then you add up all of those very momentary detections and you get a track,” said Friedman. With a command-detonated or time-fused missile instead of a radar-homing one, he went on, you can then fire at the predicted position of the target, without needing a radar lock on its precise location. This technique is less precise – the equivalent of shooting at a strange noise in the dark instead of having the target in your sights – but it can be effective. It may, for example, have been how the Serbians shot down an F-117 stealth fighter during the Kosovo air war in 1999.
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