The passenger jet of the future is taking shape. NASA and its industry partners have developed a concept for a next-generation supersonic passenger jet that would fly 300 passengers at more than 1,500 miles per hour (more than twice the speed of sound). As envisioned, the High-Speed Civil Transport (HSCT) would cross the Pacific or Atlantic in less than half the time of modern subsonic jets, and at a ticket price less than 20 percent above comparable, slower flights.
Technology to make the HSCT possible is being developed as part of NASA's High-Speed Research (HSR) program. The HSR program, begun in 1990, is supported by a team of U.S. aerospace companies. The international economic stakes are high. The projected market for more than 500 HSCTs between the years 2000 and 2015 translates to more than $200 billion in sales, and the potential of 140,000 new jobs in the United States.
In December 1995, a single aircraft concept was chosen to focus the intensive technological development planned for the next three years of the HSR program. This aircraft, the Technology Concept Aircraft (TCA), is not an actual design or airplane that will be built, but rather serves as a common reference point for HSR technology development.
The TCA evolved from separate Boeing and McDonnell Douglas HSCT designs. Computer modeling and wind tunnel tests were used to produce a single concept with superior aerodynamic performance and operational characteristics, which also satisfied environmental goals.
The technology focus also was significantly narrowed in the areas of propulsion and airframe structural components. Technical challenges remain in each area, however, though significant progress has been made.
New high-temperature materials and structural concepts were selected for fabrication and testing of various subcomponents in the TCA's fuselage and wings. Selecting the right structures and materials for an airframe designed to fly 60,000 hours in its lifetime, in temperatures approaching 350 degrees Fahrenheit, is critical to making a future supersonic transport economically feasible. Weight and manufacturing costs must be minimized, while strength and durability are maintained.
After much design, analysis and testing, the many different structural concepts studied early in the program were narrowed down to two types. This allows the program to focus on the lightest weight, highest performance designs and move from testing small coupons and elements to testing large panels. In recent tests, two 40 inch wide by 80 inch long composite panels were subjected to more than 400,000 pounds of force before they failed. Eventually the program will test two large fuselage sections, approximately 12 feet in diameter by 20 feet in length.
Imagine flying a supersonic passenger jet (like the Concorde) at 1,500 mph with no front windows in the cockpit. NASA engineers are working to develop the technology that would replace the forward cockpit windows in a future supersonic passenger jet with large sensor displays. These displays would use video images, enhanced by computer-generated graphics, to take the place of the view out the front windows. An eXternal Visibility System could provide safety and performance capabilities that exceed those of unaided human vision, while eliminating the need for a heavy, mechanically drooped nose such as that on the Concorde.
Laboratory tests of the proposed HSCT engines have confirmed that undesirable emissions of oxides of nitrogen produced by supersonic engines can be significantly reduced while maintaining efficiency and meeting future Federal Aviation Administration noise standards. A single HSCT engine design was selected for large-scale tests to demonstrate this efficiency, affordability and environmental compatibility.
The design of an advanced propulsion system for the HSCT must include noise reduction goals. The selection of the basic engine concept as well as the design of its propulsion components, such as the inlet, fan and nozzle, will all be impacted by noise reduction requirements. The designer's challenge is to produce a low noise propulsion system without seriously affecting engine performance. The HSR program is moving forward with the assumption that a future supersonic passenger jet must be as quiet as today's commercial subsonic aircraft.
Another form of noise pollution is the sonic boom. When an aircraft flies faster than the speed of sound it produces sound waves that can reach the surface of the Earth, creating an often startling and annoying noise - a sonic boom. Although studies have found ways to redesign supersonic aircraft to create less intense sonic booms, these methods seriously compromise the aerodynamic performance of the aircraft. To minimize the effects of sonic booms on humans, future HSCTs will fly at supersonic speeds only over the oceans.
The atmospheric effects of the HSCT are also being studied because its engines will emit gases and small particles directly into the Earth's upper atmosphere. Scientists have been assessing the atmospheric effects of a proposed fleet of HSCT aircraft since the HSR program began in 1990. The Atmospheric Effects of Stratospheric Aircraft project has aided in the development of environmental standards for HSCT exhaust emissions. The current atmospheric models developed by this program show a negligible impact on stratospheric ozone concentrations from a fleet of 500 HSCTs using the advanced technology engine components.
To properly characterize the radiation environment in which the HSCT will operate, NASA began a program to measure high-altitude cosmic and solar radiation. Using the NASA ER-2 aircraft, researchers have measured cosmic and solar radiation at altitudes between 52,000 and 70,000 feet. This data is being used to characterize and define the radiation environment for both crew members and the frequently flying public on future HSCTs. Although the exposure levels are higher at the HSCT cruise altitudes than for current subsonic flight altitudes, the typical flying public will actually receive less radiation exposure than on today's subsonic transports because of the higher speed of the HSCT (less time in the air).
These environmental principles are now firmly rooted in the HSCT development process. As new aeronautical technologies are introduced into the evolving HSCT design, the engineering team must test each new concept for its ability to meet the environmental constraints. At the conclusion of the HSR Program, there will be high confidence that HSCT will be an environmentally compatible airplane.
HSR program team members include aircraft manufacturer Boeing, engine manufacturers General Electric and Pratt & Whitney, flight deck partner Honeywell, and more than 40 major subcontractors.
The High-Speed Research Program is a key element of NASA's Office of Aeronautics and is managed by the NASA Langley Research Center, Hampton, Va. The NASA HSR team includes NASA Lewis Research Center, Cleveland, Ohio, NASA Ames Research Center, Mountain View, Calif. NASA Dryden Flight Research Center, Edwards, Calif., NASA Goddard Space Flight Center, Greenbelt, Md., and the Jet Propulsion Laboratory, Pasadena, Calif.
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