Problem Statement & Objectives

Nearly 15 years after the last commercial supersonic flight, the quick evolution of technology combined with the emergence of ambitious industrial projects indicate that a second era for environmentally friendly supersonic commercial flights is about to happen.

Since then “low boom” technologies have emerged, opening the door to regulatory evolutions.

One of the main obstacles remaining on the path to sustainable supersonic commercial flight is the issue of noise, specifically the loud and sudden sonic boom felt by the populations overflown during the entire cruise. The high level of sonic boom produced by supersonic aircraft at the time led to a complete ban of civilian supersonic flights over land in the United States and several other countries.

A precise quantification of the correlation between low sonic boom exposure and human response is beyond today’s knowledge for the following reasons.

  • Sonic boom accurate precision remains out of today’s routine procedure in several situations: lateral boom, turbulent atmosphere, non-flat ground.
  • Past studies have relied on either Concorde experience or flight tests with military fighters, whose ground booms are unable to reproduced the expected characteristics of a future low-boom civil aircraft (low amplitude, non N-wave shape, multiple small amplitude smeared out shocks, dampened high-frequency content).
  • Human response has been assessed mainly through exposure within boom artificial simulators, far from the conditions of ‘ecological validity’ of real boom experience (during daily life in usual home, work or social environment).
  • Most recent studies correlating human response to boom levels implied only subjects from Japan or USA exposed inside boom booth or « typical » American light-wooden houses, a population not necessarily representative of the world population / buildings, and especially of the European ones.
  • Studies on potential sleep disturbances are too old, too partial and implied to few subject people.

The high level objective of RUMBLE is to support the European contribution to a regulatory standard for low sonic boom at the United Nations' International Civil Aviation Organization, on an equal footing with other key countries.:

To reach this high level objective, RUMBLE addresses the following scientific and technological objectives:

  • To develop advanced numerical models and tools to predict the boom generation, its propagation through the atmosphere and the induced building vibratory response.
  • To provide quantitative information on the human response to outdoor and indoor low sonic boom.
  • To identify relevant flight procedures and instrumentation for low boom impact assessment.
  • To provide recommendations for a future low boom flying demonstrator.
  • To produce recommendations for future low boom standards.

The RUMBLE consortium gathers the best skilled organization in Europe and Russia, the only two industries ever able of designing and operating a civil supersonic aircraft, to achieve these objectives.

The RUMBLE project, in agreement with and in complement to ICAO/CAEP/SSTG roadmap aims at providing major breakthroughs to fill this gaps:

  • Take the international lead by joining ICAO (International Civil Aircraft Organization) roadmap: define the characteristics of a low boom flight demonstrator able to perform large scale, representative community surveys and prepare future low boom surveys adapted for European geography, air traffic and population.
  • Be innovative to obtain the pressure near field / shock waves patterns on a reduced scale mock up: advanced devices to measure pressures at different locations around the model in a supersonic flow facility – new specific wind tunnel mounting and open track facility where a model instrumented with microphones will be rocket-powered to reach supersonic speeds.
  • Predict with high fidelity future boom levels especially in cases little investigated up to now within SSTG works, but for which the European RUMBLE consortium has recently taken the lead by developing advanced operational simulations tools: lateral booms, propagation through turbulent atmosphere, temperature inversion, propagation over non-flat ground (topography or urban landscape).
  • Promote a rational way to account for sonic boom observed variability, develop an operational statistical approach to quantify ground sonic boom and define adapted margins, instead of a poorly operational worst-case approach.
  • Validate advances in simulation tools along with standard ray method with carefully monitored flight tests performed in a field site in Russia with different climate from specific sites used by US (Edwards AFB) and Japan (Northern Sweden) sites.
  • Strengthen the European point of view regarding flight procedures and instrumentation as means of compliance for a sonic boom standard through experience obtained during flight tests. The RUMBLE project will provide recommendations for the policy making process based scientific data on human response, validated numerical tools used to assess sonic boom levels in reference conditions, RUMBLE flight tests for flight tests procedures, instrumentation and test data processing.
  • Quantify sonic boom transmission through some carefully selected buildings of major interest for Europe and different from the typical American single floor light-wooden house.
  • >Assess quantitatively indoor human annoyance to low boom exposure taking into account building structural vibrations.
  • Prepare future community surveys by quantifying outdoor human annoyance to low boom taking into human activity performed at the time of perception, so as to reach ‘ecological validity.
  • Explore for the first time impact of low boom on sleep disturbances, a yet almost completely unknown issue with no announced plans to SSTG, using polysomnography, the gold standard for investigating sleep quality (by combining brain activity, eye movement and muscle tone).

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 769896.

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