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Figure 9. Effective sound speed profiles, Boston, MA, June 20, 1979, 1200 hours. From Rickley and Pierce (1980).
ground only when the wind velocity in the direction of propagation and the sound speed, including the wind veloc- ity in the direction of propagation at an altitude above the flight altitude, exceeds the corresponding seen at the ground as shown in Figure 9. Examination of Figure 9 shows that strong winds at heights from 30 to 60 kilometers blowing east to west that are in the same direction as the Concorde incoming flight track will result in their being secondary booms in the Boston area. This hypothesis was tested and the results indicated that the probability of receiving a large amplitude event is small unless the east-to-west wind speed in the stratopause exceeds 16 meters per second. (The stra- topause is the region of the atmosphere where there is a local temperature, and hence, sound speed maximum; see Figure 6.)
Aircraft operations
Relatively minor variations in the incoming Concorde ar- rival flight paths and operating conditions can alter the loca- tion of impact of the secondary booms. Computed second- ary boom focus line sources using the TSC computational program (Rickley and Pierce, 1980) show that slight varia- tion in Concorde flights results in a shift in the secondary boom footprints by 40 kilometers. The measurements and ray-tracing computations demonstrated that the secondary booms frequently reported by New England residents were created by the Concorde flights off the New England coast en route to John F. Kennedy International Airport in New York. A brief set of measurements made in Applebachsville, PA, also correlated with Concorde flights into Washington Dulles International Airport in Virginia. These boom dis-
turbances, which are propagated upward to the stratosphere and lower mesosphere and refracted back downward to the ground, are an order of magnitude higher in amplitudes than the boom returns from the thermosphere and are ob- servable not only by persons located indoors but also by those located outdoors.
In every case of complaints about Concorde-generated secondary sonic booms, rerouting of the flight tracks, and changes in operational conditions depending on atmospher- ic and seasonal variations, mitigated the problem, especially in earlier deceleration to Mach 1 before the coastline was reached.
Concluding Remarks
The Concorde was a technological marvel that astounded the world with its beauty of design and speed, halving passen- ger flight times to distant destinations. However, it was not a financial success due to high operating and maintenance costs and low utilization. The low utilization was because its primary sonic booms and limited range confined its opera- tions to trans-Atlantic routes. Even for trans-Atlantic routes, low-amplitude secondary booms, reaching the ground from the upper atmosphere by refraction, resulted in further re- strictions on the operations of the Concorde.
The Concorde was absolved of responsibility for the east coast booms. Although it is agreed that the majority of the east coast booms were due to high performance military aircraft operating offshore, many of the events cannot be explained in this way (Eos, 1978). The East Coast Mystery Booms remain a mystery to this day.
biosketches
Peter H Rogers received an SB in physics from MIT in 1965 and a PhD from Brown 1970. He worked at the Naval Research Laboratory as a Re- search Physicist and at ONR as Sci- entific Officer for Underwater Acous- tics before joining the School of Mechanical Engineering at Georgia
Tech in 1983. He became the Rae & Frank H. Neely Chair in 1993. He is a fellow of the Acoustical Society of America and received its Biennial Award (now the R. Lindsay Award) in1980 based largely on the work reported in this article.
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