F-22 enters production

Assembly of the first operational F-22 Raptor fighter has begun at Lockheed Martin Aeronautics Co. During an inaugural ceremony at the plant in Fort Worth, TX, mechanics began assembling the aircraft's mid-fuselage, one of the largest and most complex structural components of the F-22. The aircraft carries its weapons, fuel, and a large number of sub-components, such as the Raptor's electrical, hydraulic, landing gear, and flight control systems, in the mid-fuselage.

Production of the first operational F-22 Raptor has begun at Lockheed Martin.

Assembly of the mid-fuselage for this Raptor, unit 4018, will take approximately 11 months. Once completed, the section will be delivered to the company's facility in Marietta, GA, where the F-22's forward fuselage, wings, aft fuselage, and vertical and horizontal tails will be attached and its F119 engines installed. First flight and delivery of this aircraft to Tyndall Air Force Base are tentatively scheduled for early 2003. Tyndall AFB is home to the 325th Fighter Wing, the training unit for the F-22.

The Raptor will serve as a stealthy air dominance fighter capable of multiple missions. According to Lockheed Martin, the aircraft will be unseen at long range, unmatched at close-in air-to-air combat, and a force in air-to-ground combat with precision ground attack capabilities.

The F-22 is being built by principal subcontractors Lockheed Martin and Boeing, with the engines supplied by Pratt & Whitney. To date, Lockheed Martin has built 19 F-22 mid-fuselages, the first 11 of which were used by the program's flight or ground-test aircraft. Three more mid-fuselages were built for the program's Production Representative Test Vehicles (PRTVs), test aircraft that will later join the USAF's operational inventory. Lockheed Martin is currently assembling five additional PRTV mid-fuselages, which will be completed this year.

If fully funded, the Air Force will field 339 Raptors during the next decade to replace its fleet of F-15 aircraft. The first Raptor squadron is scheduled to be operational by 2005.

- Frank Bokulich

Nuclear-powered aircraft

Ian Poll, Director of Cranfield College of Aeronautics in the UK and new President of the Royal Aeronautical Society, believes that the environmental and socioeconomic challenges now facing the aerospace industry call for some fundamental re-thinking of established systems for the propulsion and design of passenger and freighter aircraft. "The projected growth in air traffic worldwide for the next several years is expected to be 5-7% per annum," he said. "If that growth rate continues for 25 years, it would involve the trebling of current aviation consumption levels of kerosene. I believe it is time to consider all the alternatives—and one is the use of nuclear power."

Although Poll said that he fully appreciates the complexities with respect to public concern about nuclear power—not least from those very environmentalists who are worried about the use of fossil fuels—he believes it should be considered as a serious and viable alternative. "If the world continues as it is now, conservationists will cry out for better implementation of our resources," he said. "To achieve that in the area of air transport, the alternatives are limited without radical and potentially unacceptable changes to its structure and pattern."

Ian Poll, Director of Cranfield College of Aeronautics in the UK and President of the Royal Aeronautical Society, believes that the environmental and socioeconomic challenges now facing the aerospace industry call for some fundamental re-thinking of established aircraft systems.

It is the efficiency and cleanliness of the thermodynamic process that he sees as offering a potential solution to many problems. "By using nuclear fuel to power what is essentially a closed-cycle steam engine driving propellers, there would be no atmospheric emissions to cause concern," said Poll. "There would probably be some degradation in airliner cruising speed—about Mach 0.7 would be typical—but the efficiency of the aircraft, without the need to carry an enormously heavy fuel load on take-off, would be very high."

Savings in terms of operating costs would be extensive. Without the need to carry a large fuel load, the aircraft would have greatly enhanced passenger or payload carrying potential, and range would no longer be a limiting factor.

Of course, the problems of nuclear-fueled airliners are obvious, not the least of which is likely public concern about possible leakage of radioactive material both in service and as the result of an accident.

As far as is known, nuclear power, applied successfully to naval surface ships and submarines for decades, has not been used to power an aircraft. In the 1950s, the U.S. Air Force flew a Convair NB-36H, which carried an operational nuclear reactor, but the technology was not used to power the aircraft's engines.

Poll said that while he fully understands that public and political unease about nuclear-powered aircraft would be considerable, he nevertheless feels that the use of nuclear power should be considered as a serious alternative aviation fuel. "I am not pretending the nuclear issue is easy, but an assessment could be made today—the physics are proven, so it would just be a matter of examining the engineering issues," he said. "I do not believe the use of nuclear power per se would necessitate radically different aircraft configurations or structures." This is somewhat surprising because, as already reported in Aerospace Engineering, he is an advocate of the flying wing or blended wing body (BWB) as offering a major step forward in overall efficiency. There is no apparent reason why nuclear power would not be equally applicable to a flying wing or BWB. However, Poll explained that "without the use of nuclear power, other solutions or aircraft configurations should be considered; but with it, these would be unnecessary because we would then be solving the problem twice."

Another of the possible solutions to the problem of achieving enhanced efficiency concerns laminar flow. This is an interesting element of aerodynamics that moves in and out of fashion, said Poll. "In the 1930s, it was seen as a promising route to obtaining high speeds, but that problem was solved with the invention of the jet engine," he said. "But early jet engines used a great deal of fuel, and laminar flow was then regarded as a possible route to achieve greater range. To counter this, the aero-engine makers designed more fuel-efficient powerplants, so again the interest in laminar flow faded. Now it is being taken seriously once more because it might be used to help us get from A to B more efficiently without damaging the environment."

The possible use of nuclear power and the potential of flying wings represent the more esoteric, philosophical side of aerospace activity at the College, which is part of Cranfield University. This year the College of Aerospace has been reorganized to be integrated far more closely with the University as a whole, especially with departments such as the School of Industrial and Manufacturing Sciences and the School of Management, to engender a more effective relationship with industry and specialist aerospace organizations, including the UK Civil Aviation Authority. Poll said that Cranfield is also focusing on specific areas such as unmanned air vehicles (UAVs) and the particular technology they require, including communications systems. Cranfield has already designed and is flying an autonomous UAV, the Cranfield A3 Observer, in association with Defense Evaluation Research Agency (DERA) at Farnborough. The observer has military and civil applications, including environmental monitoring and Earth observation roles.

Another important area of Cranfield's research involves air safety. Construction has begun on a two-deck aircraft simulator for research into emergency evacuations from very large aircraft (VLA). The simulator is understood to be the first of its kind in the world and replicates the probable interior layout of such aircraft as well as facilitating research into optimum cabin layouts. Now in the final stages of construction, it has been built in response to the aerospace industry's shift toward large, wide-bodied airframes that have the potential to carry 1000 passengers. The simulator will allow complete flexibility of layout and can be configured to demonstrate designs and requirements of different manufacturers and operators. Parameters that can be varied include aisle widths, seating plans, legroom, and exit position.

However, particular importance is being placed on the development of rapid, reliable, and efficient evacuation procedures for VLA. The College of Aeronautics has been involved in aircraft evacuation procedures for several years using a narrow-body simulator. Although Cranfield has not yet released any details of its plans for an evacuation program for the VLA simulator, with some exits about 8 m above the ground when the aircraft is parked, consideration must be given to the angle and length of escape slides and the material used for their construction. The possibility of injuries being caused to and by passengers accelerating rapidly down the slides is obvious. The risk of falling over the side from such a height is also certain to be considered. The VLA simulator will be officially opened in July.

- Stuart Birch