Aviation Week & Space Technology
July 3, 2000
Pg. 35

JSF And F-22 Refocused On Electronic Warfare

David A. Fulghum/Washington

The sophisticated sensors, unfilled spaces and radar-evading potential of the Pentagon’s two new stealth fighters are being reanalyzed with an eye to adding electronic warfare capabilities, thereby pushing their usefulness well beyond the primary air-to-air and air-to-ground missions.

The F-22 Raptor—designed as an air superiority fighter—is nearing approval for the Wild Weasel role of attacking antiaircraft missile sites. The ability of its passive systems to locate and identify electronic signals makes it an ideal platform to search out and attack enemy radar.

At the same time, aerospace industry officials are being asked to study the Joint Strike Fighter’s suitability for the task of penetrating enemy air defenses to jam radar and critical communications from relatively close ranges. JSF’s basic mission is air-to-ground strikes.

However, there are technological difficulties to overcome in adding the new capabilities.

The F-22 is expected to close—without being detected—to within about 15 mi. of the current generation of radar that controls the Russian-built S-300 family (designated SA-10/12 by NATO) of surface-to-air missiles (SAMs), Air Force officials said. The problem is that 15 mi. is the extreme range of the F-22’s standard air-to-ground weapon, the 1,000-lb. JDAM, when launched from about 40,000 ft. An F-22 pilot would either have to risk detection by SAMs or use a different weapon.

Both the new Navy-developed JSOW glide bomb and the Air Force-developed Jassm standoff missile provide the necessary standoff range. But neither fits inside the F-22’s weapons bays. If they are carried externally, it greatly increases the radar reflectivity of the F-22. However, solutions may be in the works. The Navy has just tested a combination millimeter-wave radar/RF-homing seeker for a follow-on to the current Harm radar-killing missile called the Advanced Anti-Radiation Guided Missile. In addition, USAF appears to have a black program working on its own smaller, "next-generation, Harm-like missile that fits in F-22’s weapons bays," the Air Force official said.

The S-300 family has a range of 85-120 mi. The next-generation S-400 is being touted by the Russians as having a range of 250 mi. U.S. lawmakers also have recently mentioned an even newer S-500 missile concept in congressional hearings, but so far the design is regarded as primarily an antimissile weapon.

With an offensive counter-air capability added to the F-22—which includes striking airfields, hardened hangars, command centers and communication nodes— and the projected ability to replace the F-15E and F-117, USAF hopes to increase the stealth fighter’s production run to about 600 aircraft from the current total of 333.

The Pentagon is also looking at a derivative of JSF for the electronic warfare, radar/communications-jamming mission currently conducted by the Navy and Marine Corps EA-6B squadrons.

JOINT STRIKE FIGHTER IS ALREADY designed to jam enemy electronics with its advanced radar, a little-talked-about capability it shares with the F-22. This ability will be limited in power-and-frequency range and will be primarily effective against radar of enemy aircraft and communications to and from these aircraft.

However, Lockheed Martin planners foresee a JSF derivative that carries a second radar-jamming package, probably on pallets in the main weapons bay, that can jam a wider range of frequencies with much greater power including long-range early-warning radar and those that direct antiaircraft missiles and guns. Other targets are the communications that link aircraft, missile sites and command posts.

"We’ve had a lot of interest in how this aircraft would compare to an F/A-18G [Growler radar jammer] in terms of the EW role," said Frank Cappuccio, Lockheed Martin vice president and JSF program manager. "You would need another AESA (active electronically scanned array) [antenna] in addition to the standard radar on the JSF to do the jamming. You could do a lot of directed, narrow-beam jamming." However, jamming coverage would only be in a 30-deg. field-of-regard, which would indicate operational limitations. "But from 40,000 ft., that would be a lot of targets. The Raytheon [AESA] radar has some very good features. You’d have to [add] a special radome" to carry the second antenna, he said. Company officials point out that there is no government requirement for a jamming aircraft and the study was done on the initiative of Lockheed Martin engineers.

Boeing officials would say only that they were involved in studying electronic attack alternatives. "There is a lot of functionality already in the basic [JSF] system that would allow you to do... a lot of the [jamming] mission," a senior Boeing JSF program official said. "There would be additional hardware... required to meet all the parameters."

In addition, "you could make a Wild Weasel replacement" which would need to operate at lower altitudes, Cappuccio said. "You get rid of the weapons and load the electronics down in the weapons bay." To alleviate the antiaircraft-missile threat while operating at lower altitudes, a decoy could be towed to attract missiles away from the aircraft, he said. Boeing officials say they too have space in the undercarriage area "for huge growth," although they would not discuss derivatives.

The F-22 and JSF derivative could reintroduce two capabilities lost by the Air Force—those of the now retired F-4G Wild Weasel and EF-111 Raven. The Wild Weasel could identify, pinpoint and attack air-to-air missile radar. The Raven could penetrate enemy airspace to provide standoff or escort jamming of radar in support of bomb-carrying aircraft. The Raven was used to protect F- 117s during the 1991 Persian Gulf war and their absence contributed to the first loss of a stealthy aircraft during the 1999 Kosovo air campaign.

The JSF radar’s versatility in providing tracking, jamming, communications and several other functions at virtually the same time is made possible by the AESA radar. Each array is made up of about 1,000 transmitter-receiver elements on the F-22 and several hundred in the JSF. The number of elements dictate the power output and range of the radar which equates to about 125 mi. on F-22 and 90 mi. on JSF. Each transmitter/receiver module in the synthetic aperture radar cost about $1,000 for the 10-year-old F-22 design, but costs for JSF’s modules have dropped to about $350 each, and there are projections that the cost will eventually drop to about $100.

A DEDICATED JAMMING AIRCRAFT must cover a wide range of frequencies. It’s necessary to jam very-low-frequency radar because those can pick up tracks of stealthy aircraft. It’s equally important to jam very-high-frequency radar such as those used by the S-300 family of antiaircraft missiles (SA-10/12/20) and the emerging S-400 system. These high-frequency radar provide the most accurate location of a target aircraft.

An electronic warfare version of JSF, as now envisioned by Lockheed Martin, would not broadcast an indiscriminate, omnidirectional signal, said Cappuccio. Instead, it would jam with great power concentrated into pencil-like beams. The narrow beamwidth focuses jamming power and prevents the JSF from being easy prey for jam-following missiles. Those are powerful, high-speed, long-range missiles that track an electronic signal back to its source to destroy the transmitter. JSF’s engineering and manufacturing development program—currently being delayed for various technical and budgetary problems—is estimated to cost $16-18 billion. The total program, which is expected to produce 3,000 U.S. aircraft and up to 3,000 for foreign sales, is projected to cost more than $300 billion. By comparison, Cappuccio said the 100th Block 60 F- 16 built for the United Arab Emirates is to cost $40 million per aircraft while the 100th JSF (the cheapest CTOL variant) is to cost around $32 million. The F/A-18E costs $55 million, he said.

While the F-22 requires 2.5 million lines of computer code, primarily to make it the premier air-to-air combat aircraft, JSF will have twice that amount. A similar 2.5 million lines for aerial combat and another 2.5 million for the air-to-ground mission are anticipated, Cappuccio said. The aircraft will offer target identification and all-weather recognition even in a complex, urban environment, he said.

Combat radius of JSF variants was plotted against existing aircraft. USAF’s CTOL at 700 mi. is to have 2.4 times the range of the F-16. The Marine Corps’ STOVL at 500 mi. is to have 1.7 times the range of the AV-8. And the Navy’s carrier version, with a whopping 900-plus-mi. range, is to be 1.9 times that of the F/A-18C.

CAPPUCCIO RELEASED A FEW details about JSF’S electro-optical targeting systems for which there is no equivalent in the F-22. The system can now locate targets with enough acuity to identify the type of tank at 6.5 mi., he said. The radar already has a moving-target-indicator mode which is expected to locate ground targets at about 50 mi. The advanced AESA radar can spot air-to-air targets at 90 mi. JSF will have no head-up display. Instead, data will be projected on a pilot’s helmet visor.

JSF allows for the introduction of new weapons by having various-size weapons bay doors that can be quickly changed to accommodate carriage of larger, 2,000-lb.-class bombs and missiles. Cappuccio said Lockheed Martin engineers are looking at a range of weapons for JSF including Britain’s Brimstone, a millimeter-wave radar-guided antitank missile.