Smoke and Mirrors
This column appears in the April 29 edition of Aviation Week & Space Technology.
Using secrecy to squelch debate is undesirable. Using bogus secrecy to do it is, to borrow the British civil service’s strongest term of opprobrium, unhelpful.
It’s reasonable, if misguided, to argue that the U.S. military has all theGrowlers that it needs. It does not make sense first to maintain that the Joint Strike Fighter will not need electronic-attack (EA) support, but then simply to cite “its combination of stealth and advanced sensors” in support of that statement, while withholding comment on any details. And that is what has been doing. (The JSF project office is not commenting at all on the issue.)
Two characteristics of the JSF that bear on this debate have been raised byand recent think-tank papers. One is the fighter’s susceptibility to detection by very-high-frequency (VHF) radars, and the other is the extent of its EA, or jamming, capability.
They are not secret at all. The F-35 is susceptible to VHF detection and—as Boeing’s charts suggest—its jamming is mostly confined to the X-band, in the sector covered by its APG-81 radar. These are not criticisms of the program but the result of choices by the customer.
To suggest that the F-35 is VHF-stealthy is like arguing that the sky is not blue—literally, because both involve the same phenomenon. The late-Victorian physicist Lord Rayleigh (photo) gave his name to the way that electromagnetic radiation is scattered by objects that are smaller than its wavelength. This applies to the particles in the air that scatter sunlight, and aircraft stabilizers and wingtips that are about the same meter-class size as VHF waves.
The counter-stealth attributes of VHF were discussed here a few months ago (AW&ST Sept. 16, 2013, p. 30). They were known at the dawn of stealth, in 1983, when MIT’s Lincoln Laboratory ordered a 150-ft.-wide radar to emulate Russia’s P-14 Oborona VHF early warning system. Lockheed Martin’s Fort Worth division should know about that radar—they built it.
VHF-stealth starts with removing the target’s tails, as on the B-2, but we did not know how to do that on a supersonic, agile airplane when the JSF specifications were written.
Neither did the technology to add broadband active jamming to a stealth aircraft exist in 1995. Not only did stealth advocates expect jamming to fade away, but there was an obvious and (at the time) insoluble problem: To use jamming, you have to be certain that the radar has detected you. Otherwise, jamming is going to reveal your presence and identify you as a stealth aircraft, since the adversary can see a signal but not a reflection.
We can be sure that onboard jamming has not been added to F-35 since. Had the JSF requirements been tightened by one iota since the program started, its advocates would be blaming that for the delays and cost overruns.
What the JSF does have is an EA function in the radar and an expendable radar decoy—’ ALE-70—which may be free-flying or towed, most likely the former. Both are last-ditch measures that would be used to disrupt a missile engagement, not to prevent tracking.
JSF’s planners, in the mid-1990s, were close to correct when they calculated that low-band stealth and limited EA, combined with passive electronic surveillance for situational awareness, would be adequate at service entry. But they expected that to happen in 2010, and China’s military modernization then was barely imaginable.
The threats of the late 2010s will be qualitatively different. Old VHF radars could be dealt with by breaking the kill chain between detection and tracking: They did not provide good enough cueing to put analog, mechanically scanned tracking radars on to the target. Active, electronically scanned array (AESA), high-power VHF radars and decimeter- and centimeter-wave trackers are more tenacious foes.
Russian developments have been covered here, but one worry for the U.S. Navy is that Chinese warships carry the Type 517M VHF search radar, which its maker says is an AESA.
None of this is to say that stealth is dead, but it is not reasonable to expect the cat-and-mouse game of detection and evasion in air combat has stopped, or that it ever will. EA and stealth still do not coexist very comfortably on the same platform, but offboard EA and stealth are synergistic: The smaller the target, the less jamming power is needed to mask it. The argument in favor of deploying the Next Generation Jammer system is that its greater precision and power will allow it to provide covering fire for stealth assets from a stand-off range outside the defender’s reach.
But the threat’s demonstrated agility drives home the lesson that there is no one winning move in the radar game. Excessive reliance on a single-point design is not a good idea, and using fictitious secrecy to squash the debate is an even worse one.