Major reduction in Real Travel Time
May serve as Threat for Anti-noise Groups
Can NASA’s X-plane resurrect supersonic passenger air travel? is a headline which will stir the imagination of any aviator. As measured by real elapsed time, flight technology has not improved its speed in delivering passengers from A to B for decades— runway congestion at departures and arrivals, en route inefficiencies and other system limitations have inhibited the ability to reduce transit time.
The exception, the SST, produced a short jump in getting from here to there. It is well documented that the environmental effects of this magnificent bird limited its use to Transatlantic operations. There is some more dispute as to the economics of these flights, but it is clear that the combined impact of these factors resulted in the grounding of the Concorde.
This new X plane (the USAF has not issued its designator yet; maybe X-58) has been labeled the Low-Boom Flight Demonstrator by NASA and QueSST by the developer. NASA just issued a contract to the Martin Skunk Works to transform this from a conceptual model to an operational standard.
What are the design goals for the X plane?
SPEED Mach 1.42, or 940 mph, at an altitude of about 55,000 feet
CRUISE ALTITUDE 55,000’ (higher than 35,000’) for subsonic airliners
A/CT LENGTH 94 feet long
wingspan 29.5 feet
gross weight 24,300 pounds
POWERPLANT one General Electric F414 engine
TARGET NOISE 75 Perceived Level decibel (PLdB),
That last criteria is the most critical one and an element which mutes the enthusiasm. Lockheed says that the sound is comparable to “a car door closing.” If all goes according to plan, spectators on the ground should barely be able to hear the plane as it rips through the sound barrier high overhead. (The speed of sound, also known as Mach 1, varies depending on air pressure and temperature but is roughly measured at about 758 mph or 1,220 km/h.)
If the community response data collected during the QueSST shows a level of acceptability of the quiet sonic boom, then NASA will deliver that information to the FAA, likely also EPA and ICAO. If the history over the approval of the Concorde is any predictor, the battle over the standards for the commercial X-58 will consume years.
In the late 1960s and early 1970s, the anti-airport community was not as well organized as today’s. Community expectations as to acceptable noise has become more and more demanding. While the FAA data supports this statement:
“In 1975, there were about 200 million people flying in the United States, with about 7 million people exposed to what is considered significant aircraft noise. Since then, an FAA study conducted in 2015 showed that the number of people flying in the United States had almost quadrupled yet the number of people exposed to aircraft noise had dropped to around 340,000, or a 94% reduction in aircraft noise exposure. “
These objective numbers do not correlate well with the outcries from citizens around the country and perhaps that dissonance can be attributed to the fact that the measurement of human reaction to noise is called psychoacoustics . Sound is the most subjective of the human senses. Scientists and engineers have quantified the reaction of an ear to the noise of an airplane in decibels. With that logarithmic scale, a psychoacoustician issues precise estimates to the population’s response to a plane. Their numbers are expressed in tenths.
In that hearing is so subjective, raising or lowering expectations can result in auditory responses that are higher or lower than the mathematical projections of the reactions.
To add to this discernible trend, Recent research may have dovumented some correlation between certain sounds and “noise rage.” The phenomenon is called misophonia, literally “hatred of sound.”
In 2000 scientists defined misophonia as a “condition in which negative emotions, thoughts, and physical reactions are triggered by specific sounds.” Other labels include “select sound sensitivity syndrome” and “sound-rage.” Misophonia has not been classified as an auditory, neurological, or psychiatric condition; so far, no standard diagnostic criteria have been defined. Neither the DSM-IV nor the ICD-10 has included misophonia listed in their referenced problem. Unfortunately, there is little research on its prevalence or treatment.
All of these noise escalations are reviewed here to add a note of caution to the excitement about the QueSST’s promise. The current public policy debate about aviation noise is titled toward the opponents. Adding the foreboding new “quieter” SST to that crucible may add to the public’s skepticism about aviation noise progress and add to the size of the anti-aviation corps.
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