FB-22: Lockheed studying delta-wing bomber version

From janes

http://www.janes.com/defence/air_forces/news/idr/idr020524_1_n.shtml

“Lockheed Martin has briefed the US Air Force (USAF) on a radically modified version of the F-22 Raptor fighter with a delta wing, longer body and greater range and payload. A company-funded study of the so-called FB-22 will continue until the end of 2002.

The FB-22, as its designation suggests, is clearly a bomber. Operations over Afghanistan have driven home the fact that bases close to many potential targets may never be open to US combat aircraft. Apart from extreme-range operations by F-15Es, USAF fighters have been relatively little used in that theater, and much of the burden has been carried by B-52 and B-1 bombers.

Since early 2001, some members of Congress have pressured the USAF to buy more B-2s to reverse the ageing of the bomber force, but the USAF does not want to do this because the B-2 is expensive to buy and to maintain. Also, the problem of providing support facilities that can repair the B-2’s low-observable systems at forward operating locations has not yet been solved. One reason the service may consider the FB-22 is that it demonstrates that the service is taking the need for a new bomber seriously despite its lack of interest in more B-2s.

The USAF is showing interest at some levels in the Defense Advanced Research Projects Agency Quiet Supersonic Platform (QSP) project (see IDR 3/02, p60-62), which is directly aimed at long-range strike missions. The FB-22, however, could be available sooner and at a lower development cost than the more exotic, higher-performance QSP.

Details of the FB-22 are considered proprietary and some have not been settled as yet, but Lockheed Martin F-22 program manager Bob Rearden describes the aircraft as “very different, truly a derivative” of the F-22.

F-16XL revisited
The FB-22 recalls two earlier Fort Worth projects: the F-16XL, first flown in 1982, and the delta-winged F-16 proposed to the UAE in 1995. Both these aircraft were based on the F-16, but had no horizontal tail, a much larger wing and a stretched fuselage. The result in both cases was a heavier aircraft with a much larger fuel fraction (more fuel as a percentage of take-off weight) and greater capacity for external stores. Despite the airframe changes, many elements of the aircraft – avionics, cockpit and systems – remained very similar to the original.

If Lockheed Martin were to take a similar approach to the FB-22 design, some design features would fall into place logically. Dimensions would be influenced by the desired weapon load. The basic aircraft carries its main weapon load in a pair of side-by-side under-fuselage bays. A body stretch of 3-3.5m would accommodate longer bays, large enough to hold two Joint Direct Attack Munitions in line astern. The side bays, which accommodate AIM-9 missiles on the current aircraft, could be extended to hold AIM-120s, and the gun would almost certainly go.

One design goal, according to Rearden, is to ensure the aircraft fits in a standard hardened aircraft shelter, which is 14.6m wide. A 65º delta wing with a 14m span closely matches the root chord available on a stretched F-22 body.

The FB-22 could dispense with vertical tails as well as horizontal surfaces, Rearden suggests. Lockheed Martin has studied a tailless design under the Innovative Control Effectors (ICE) program, with a 65º-swept delta wing and a combination of slot-spoiler and conventional aerodynamic controls. An experimental tailless version of the F-22, known as the X-44 Manta (Multi-Axis No-Tail Aircraft) has been studied by NASA and the USAF Laboratory. Tailless technology could sharply reduce the bomber’s side-on radar cross section.

The FB-22 would offer a dramatic range increase. Higher fuel fraction is a major factor in improving range. Stretching the fuselage without increasing its girth gives the new aircraft a better fineness ratio, reducing wave drag at high speeds. Like the F-16XL, the FB-22 carries its additional weapons in tandem, increasing weapon load without adding frontal area or drag. Eliminating the large horizontal tails – and possibly the vertical surfaces as well – would further reduce weight and significantly reduce wetted area (the surface area exposed to airflow), cutting drag. Overall, the fighter’s unrefuelled range could be almost doubled.

Operationally, the FB-22 would probably be used in the same way as the USAF plans to use the F-22 in air-to-surface missions. The F-22’s value to the USAF resides in speed and altitude. The goal is to win a shoot-out against a surface-to-air missile (SAM) system by launching multiple guided weapons against the SAM site while remaining outside its lethal range. Speed and altitude help in two ways. Launching an inexpensive glide weapon at supersonic speed and 60,000ft (18,000m) increases its range, while speed, altitude and maneuverability combine to reduce the effective range of the SAM. Even if the supersonic attacker ventures inside the theoretical launch range of the missile, a supersonic turn can present the missile with a high-speed crossing target that it lacks the energy to intercept.

The FB-22 will have to make its way through political and budgetary defenses as well as technical challenges if it is to survive as more than a historical footnote. A prerequisite is the success of the F-22 program in meeting objectives between now and the end of 2003. So far, too, the FB-22 has not gathered any public support from USAF leaders; on the other hand, they have not committed themselves to any other long-range strike solution, whether supersonic, hypersonic or space-based. Another challenge is that, since the only logical way to produce the FB-22 is to start production as the F-22 line winds down, development will overlap with that of the JSF.

However, the FB-22 is the only aircraft proposed so far that offers the USAF substantially more range and more payload than the JSF for less than US$5-10 billion in development costs and before 2020. Perhaps Lockheed’s best bet, politically speaking, would be to offer leadership of the program to the company that already builds the F-22 wings and has recent experience with a transonic delta wing: Boeing.”

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Hmmmm.