26 April 2014

Imagine That, Military Technology Developed Over 20 Years Sees Countermeasures Developed

Bill Sweetman, writing in Aviation Week, observes that the F-35's stealth capabilities, when juxtaposed with its limited jamming suit are inadequate: (Paid Subscription Required)
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 the EA-18G Growlers that it needs. It does not make sense first to maintain that the F-35 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 Lockheed Martin 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 by Boeing and 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—BAE Systems’ 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.
Potential opponents have known of stealth for over 30 years, and the mathematics of this technology have been public for even longer, so the use of lower frequency radars (as is the case of the confusingly name VHF) along with advances in computer power and phased array radars, imply that the effectiveness of stealth has been mitigated.

This is why the USAF putting its eggs in on basket, stealth, is concerning.


Post a Comment