Periodic Reporting for period 2 - RUMBLE (RegUlation and norM for low sonic Boom LEvels) Reporting period: 2019-05-01 to 2020-12-31 Summary of the context and overall objectives of the project The first era of supersonic passenger flight started in 1976 and ended in 2003, and was symbolized by two iconic aircraft: the European Concorde and the Russian Tu-144.Apart from economic considerations, the main barrier that limited the expansion of supersonic flight at that time was the sonic boom phenomenon, which generated such an intense and sudden noise that supersonic flight was soon banned over populated areas in many countries, hence shrinking down the supersonic market to overwater routes only.This eventually proved to be insufficient to run sustainable and profitable operations and, since 2003, no supersonic commercial aircraft is in service anymore.However, over the past years, the quick evolution of the “Low Boom” technologies, combined with the emergence of ambitious industrial projects indicate that a second era for “environmentally friendly” super-sonic commercial flights is about to happen. Actually, the question is not if this second era will happen, but how and when it will.To answer this question, one essential obstacle to clear is of course the elaboration of a new international regulation that would allow supersonic flights over land. Much effort is currently ongoing in a dedicated working group (WG1 / SSTG ) at ICAO to progress towards this regulation.Over the past 10 years though, the European presence in this central organization has been quite weak, leaving the lead, both scientifically and industrially, to the US players (NASA, Gulfstream, Lockheed-Martin …) with some contributions from Japan (JAXA).In the perspective of this new supersonic era opening up, it is now essential that European and Russian play-ers come back into the race: • to avoid a “regulation driven monopoly” to the sole benefit of the American aircraft industry, • to prepare Europe to take part in an international demonstration program from the very start• to ensure our competitiveness in this to-be market.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 Organisation, 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. Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far In the RUMBLE project, models and tools have been enhanced for near- and far-field validation, including the effects of ground and of atmospheric turbulence, and for structural transmission. An additional task on the SonicBAT exercise has been agreed with ICAO/CAEP/WG1/SSTG and performed. Low-boom shape R3 has been designed and validated in extensive wind-tunnel tests.The human response to sonic boom has been studied, with requirements identified and metrics evaluated. A broad numerical study of low frequency sound transmission induced by sonic boom was carried out on different building styles across Europe. Indoor and outdoor sonic boom simulators have been designed and realized, and the corresponding studies on the perception of low boom performed.In order to prepare the flight tests and determine the relevant flight procedures and instrumentation for low boom impact assessment, weather simulations were performed and recommendations of procedures and instrumentation were produced. The sensitivity effects of weather have been studied and the results presented to ICAO/CAEP/WG1/SSTG. Several RUMBLE partners have participated in the "schemes" exercise proposed within ICAO to obtain reference day sonic boom levels from test day measurements.Two flight test campaigns were prepared and performed in Russia, involving flights at various supersonic speeds. Sonic boom was recorded both indoor and outdoor and analyzed.Studies on the RUMBLE Low Boom Flying Demonstrator concept have yielded a potential reference mission and a design.Several RUMBLE partners attended all ICAO/CAEP/WG1/SSTG meetings and workshops and the associated bi-weekly teleconferences, making regular communication on the objectives and progress of the project. Available information on sonic boom has been collected and analyzed.In addition, communication actions on RUMBLE have been performed through a dedicated website, active presence on social media and presentations at various scientific events. Two international open workshops have been organized, with presentations and attendance from NASA, JAXA and TsAGI in addition to the dissemination of RUMBLE results. Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far) 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 rather 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.In consequence, the RUMBLE project, in agreement with and in complement to ICAO/CAEP/SSTG roadmap, aims at providing major breakthroughs to fill this gaps:Societal and environmental:RUMBLE will provide the necessary data and procedure for a future, internationally-agreed standard on low sonic boom supersonic flights overland.Numerical tools:• Enhancement of near-mid- and far-field simulation tools.• Simulation of the influence of topography on sonic boom.• Simulation of building vibrations.• Application to low, shaped booms.Wind tunnel tests:• Near-field pressure measurement equipment and methodology validated in ONERA S2MA and TsAGI T109 supersonic wind tunnelsFlight tests:• Dedicated flight tests for measurement of sonic boom in conditions relevant to a future certification.Sonic Boom Perception by population:• Two sonic boom simulators: indoor and outdoor • Around 100 persons surveyed (25 indoor, 25 outdoor, 50 sleep) • Sleep disturbance • Correlation with SSTG metrics• Low frequency indoor transmission for various types of buildings. rumble.png
