New-Jack Radars for Old-School Jets

The Air Force has been saying for years that it needs 380 Raptor stealth fighters to fill out its fighter force, but Congress has capped the program at 180 to keep costs around $60 billion. To make up for the shortfall, the Air Force is considering upgrading 180 of its youngest F-15s with new "electronically scanned" APG-63(v)3 radars roughly comparable to the Raptor's APG-77. What you get is a "Raptor Lite" lacking only the Raptor's stealth and more powerful engines.

Traditional radars are mechanically steered. In other words, you've got one antenna that literally sweeps back and forth, emitting radio waves to detect targets. That creates blind spots. In the new "Active Electronically Scanned Array" radars, by contrast, there are hundreds of individual emitters all packed together, each capable of shooting its beam in a different direction. With an AESA (pronounced "ay-ee-suh," you can scan a whole lot of airspace with just one jet -- and there are all sorts of fringe benefits. AESAs can be focused to jam other radars or even to transmit data.

"Are there any drawbacks to the AESA?" Air Power Australia asks:

Two issues are of key importance with this technology. The first item of interest is power dissipation. Due to the behaviour of microwave transistor amplifiers, the power efficiency of a ... module transmitter is typically less than 45%. As a result, an AESA will dissipate a lot of heat which must be extracted to prevent the transmitter chips becoming molten pools of Gallium Arsenide. ...

Another issue of concern with AESAs is the mass production cost of the ... modules. With a fighter radar requiring typically between
1,000 and 1,800 modules, the cost of the AESA skyrockets unless the modules cost hundreds of dollars each. With early module builds yielding unit costs of around USD 2,000, the cost penalty of using an
AESA over a conventional design was prohibitive. The good news in this respect is that the ongoing trend has been downward.

And as AESAs get cheaper, more fighters are being retrofitted or having them installed on the production line, especially in the U.S. Eighteen
Alaska-based F-15s received early-model (v)2 AESAs in the 1990s (these jets are now cascading down to Kadena, Japan, as Alaska get Raptors) and new Super Hornets got APG-79s beginning last year. The Air National Guard is next. The 180
AESA-equipped "Golden Eagles" will equip U.S.-based fighter squadrons, assuming Congress keeps the cash coming. The F-35's radar will be an
AESA, too, of course -- and the European Typhoon might get AESA sometime down the line.

UPDATE: Noah here, with a question. One of the biggest arguments for the Raptor was that China was starting, barely, to catch up to America's fighter jet force, building planes that might be considered in the same ballpark as old-school F-15s. But now that these U.S. jets are getting an AESA upgrade, doesn't that only undermine the case for the Raptor even further?

-- cross-posted at War Is Boring