The new generation of supersonic aircraft could have severe environmental impacts, warns ICCT study
Boom Supersonic recently closed a $100m Series B investment round to develop its Mach 2.2, 55-seat Overture airliner (image: Boom)
Wed 30 Jan 2019 – A planned 2,000-strong international supersonic commercial aircraft fleet in operation by 2035 could have severe environmental and health impacts around the world, finds a new study by the International Council on Clean Transportation (ICCT). An estimated 5,000 supersonic flights per day could expose large regions of the globe to sonic booms at a frequency of more than once per hour, with the most heavily impacted regions experiencing between 150 and 200 sonic booms per day. The fleet could also consume five to seven times as much fuel per passenger as subsonic aircraft on the same routes, leading to emissions of 96 million tonnes of CO2 per year, more than the combined 2017 emissions of US carriers American, Southwest and Delta. International regulators meet next week at ICAO to discuss whether to apply existing subsonic standards to the new generation of supersonic aircraft or develop new standards that ICCT fears will be more lenient.
According to ICCT's modelling, the 5,000 supersonic transport (SST) flights would likely depart and land at around 160 airports located predominantly in Europe, North America, the Middle East, Asia and Oceania, with the two potentially busiest airports – Dubai International and London Heathrow – seeing in excess of 300 SST operations per day. Other airports expected to see more than 100 SST landings and take-offs (LTOs) per day include Los Angeles, Singapore, San Francisco, New York-JFK, Frankfurt and Bangkok, forecasts ICCT. The aircraft could double the area around airports exposed to substantial noise pollution compared to existing subsonic aircraft of the same size, it warns.
The most heavily sonic boom impacted regions include Canada, Germany, Iraq, Ireland, Israel, Romania, Turkey and parts of the United States, which may experience between 150 and 200 incidents per day, or up to one boom every five minutes over a 16-hour flight day. Parts of western United States, including Colorado, could be exposed to sonic booms approximately every 10 minutes, estimates ICCT.
The 2,000 SST fleet would emit an additional 1.6 to 2.4 gigatonnes of CO2 over a 25-year service lifetime, which would correspond to one-fifth of the CO2 that all flights could emit this century under a 1.5-degree C climate trajectory. It would also make even more challenging the industry’s goal of halving net CO2 emissions from 2005 levels by 2050, argues ICCT. Non-CO2 climate forcers – water vapour, nitrogen oxides, black carbon and aviation-induced cloudiness – are expected to be significant with the high cruise altitudes of SSTs.
Given that 87% of projected flights would depart one country and land in another, International standards will be needed. ICCT reports that ICAO is initiating work on SST standards for LTO noise, air pollution, sonic boom and cruise CO2, and a full set of standards may be finalised by 2025 and take effect before 2030.
“Regulators are faced with two choices: either to develop new SST standards that would allow those aircraft to produce more noise, air pollution and climate pollution than new subsonic designs, or to apply existing subsonic standards to SSTs,” suggest the authors of the study.
“Aspiring SST manufacturers could boost public acceptance for their designs by committing to meet existing LTO noise and cruise CO2 standards for subsonic aircraft and by supporting new en-route noise standards that would mandate low-boom technology. Lacking these commitments, manufacturers may find it difficult to access additional capital to finalise their aircraft designs.”
The ICCT analysis is based on an initial unconstrained modelling approach that assumes no overland flight bans or local airport restrictions.
“If those restrictions instead remain in place, some fraction of the actual noise and pollution impacts of the new SST designs will be mitigated for several reasons,” says ICCT. “First, noise-constrained airports may be unable to absorb the indicated flights. Second, overland flight bans would limit the viability of some routes, leading to lower overall share.”
Since 2016, says ICCT, advocates of supersonic flight have pushed to lift existing bans on overland flights in the US despite objections from environmental and health groups, with the Trump administration favouring permissive SST standards that have already led to clashes with Europe.
Commented ICCT’s Dan Rutherford, lead author of the study: “Current supersonic sales targets, paired with ongoing efforts to lift overland flight bans, imply severe environmental consequences. Manufacturers should commit to meeting existing standards for new subsonic jets and promise to adopt low-boom technologies before further developing their aircraft.”