Commercial Supersonic Technology The Way Ahead (2001) / Chapter Skim
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4. Areas Needing Continued Technical Development
4. Areas Needing Continued Technical Development
Pages 27-40
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From page 27... ...
Technology requirements include reducing propulsion noise and controlling emissions of carbon dioxide, various oxides of nitrogen, and, possibly, water vapor (at very high altitudes) ; structures and materials that can withstand the more hostile environment resulting from supersonic flight; cockpit displays and controls compatible with the special design features and operational requirements of commercial supersonic aircraft; and systems and procedures to address safety issues associated with cabin Repressurization and exposure to ionizing radiation during high-altitude flights.
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From page 28... ...
whereas a transport designed to fly at Mach 2.4 would ideally operate at about 60,000 ft. Three issues associated with engine emissions are particularly important for a commercial supersonic aircraft: stratospheric ozone, climate change, and local air quality.
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From page 29... ...
. Figure 4-3 shows the estimated impact on radiative forcing of a mixed commercial fleet of supersonic and subsonic aircraft in the year 2050, and Figure 4-4 compares the radiative forcing in 1992 with the radiative forcing in 2050 for both an all subsonic fleet and a mixed subsonic-supersonic fleet.
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From page 30... ...
Reducing this large uncertainty is essential to developing a better understanding of the environmental challenges posed by commercial supersonic aircraft. The disproportionate effect of the supersonic transport fleet on radiative forcing is primarily due to larger emissions of water in the stratosphere and the lack of vertical mixing between the stratosphere and troposphere.
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From page 31... ...
, a key difference between a supersonic aircraft and a subsonic aircraft with the same payload is that the supersonic aircraft will burn more fuel because aircraft designed for high-altitude supersonic flight are generally much less efficient during low-speed operations near the ground. Future supersonic aircraft are unlikely to receive exemptions from the environmental standards imposed on subsonic aircraft, so the need to minimize the impact on local air quality provides another reason to develop advanced supersonic propulsion technology.
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From page 32... ...
Also, although the energy density of hydrogen by weight is nearly three times as great as that of conventional aviation fuels, potential weight savings are offset by the additional weight of the high-pressure gas or liquid cryogenic systems needed to handle the hydrogen fuel and the additional aircraft structure needed to accommodate the large hydrogen fuel tanks and fuel handling systems. Two new means of storing high-density hydrogen may turn out to be useful as aviation fuel: slush hydrogen and gelled liquid hydrogen.
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From page 33... ...
However, none is applicable only to supersonic flight, and successful application to commercial supersonic aircraft would almost certainly have to be preceded by success in other applications, such as groundbased power systems (fixed or mobile) and subsonic aircraft.
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From page 34... ...
Casting with laser powder COMMERCIAL SUPERSONIC TECHNOLOGY: THE WAY AHEAD deposition to produce complex castings could lead to additional cost savings. Combustor Liner Materials and Coatings Current subsonic engines use state-of-the-art nickel-based superalloys with a thin ceramic coating for additional thermal protection.
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From page 35... ...
The lower limit is probably adequate for SBJs, and the higher limit is essential for higher-Mach-number airplanes. Materials to Meet Engine Noise and Weight Requirements The extent to which a commercial supersonic aircraft will require new materials to meet engine noise suppression requirements is highly dependent on the type of aircraft and the engine design concept.
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From page 36... ...
Advanced materials may be advantageous in some structures for commercial supersonic aircraft with cruise speeds below Mach 2.0, but they are essential for faster aircraft. Graphite epoxies and aluminum cannot sustain the temperatures expected at cruise speeds above Mach 2.0 for long periods of time, and titanium is too heavy to use as the primary structural material.
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From page 37... ...
For example, fuel could be stored in bladders inside each fuel tank, although this is probably not a viable approach for a new commercial supersonic aircraft because of increased weight and the difficulty of removing bladders for structural inspections and repairs. 37 Coatings Coatings are used for both appearance and thermal management.
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From page 38... ...
At sea level, Earth' s atmosphere provides an effective shield against primary and secondary cosmic radiation, with a mass thickness of over 1,000 g/cm2. The shielding mass drops off to about 200 to 300 g/cm2 at normal cruise altitudes for subsonic aircraft (30,000 to 40,000 ft)
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From page 39... ...
The FAA also established certification teams to support the future certification of new technologies under development by the HSR Program. Ongoing efforts to develop new supersonic technologies should proceed in parallel with the development of new regulatory standards to ensure that the regulatory approval process does not impede the development of a commercial supersonic aircraft.
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From page 40... ...
:526-544. .= COMMERCIAL SUPERSONIC TECHNOLOGY: THE WAY AHEAD IPCC (Intergovernmental Panel on Climate Change)
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