How different aircraft of the fourth and fifth generation

The return of the supersonic aircraft should be sustainable

Almost two decades after the Concorde's last flight, supersonic commercial aircraft could soon be on the move again. Several manufacturers are announcing a launch of commercial supersonic aircraft in the next few years. That is why the German Aerospace Center (DLR) is working with international partners to investigate the environmental impact of a future fleet of supersonic aircraft. The aim is to evaluate both the noise emissions and the climate impact of these aircraft. The research results should help to reduce the environmentally harmful effects of the aircraft.

“Aviation regulations still applied to the Concorde, which allowed higher emissions compared to subsonic aircraft. The new generation of supersonic jets will now have to be measured against conventional aircraft, ”explains Prof. Lars Enghardt, head of the engine acoustics department at the DLR Institute of Propulsion Technology. In order to define new certification rules, the authorities are dependent on extensive data. The EU project SENECA (noiSe and EmissioNs of supErsoniC Aircraft) makes an important contribution to the collection of this data.

Two new supersonic aircraft classes are being planned: business jets and scheduled aircraft

The scientists first design and analyze two different classes of supersonic aircraft on the computer: business jets for around ten passengers and scheduled aircraft for up to 100 passengers. The scheduled aircraft thus have roughly the capacity of the Concorde. The business jets can reach speeds of sound (Mach numbers) of 1.4 to 1.6 when cruising. The supersonic range begins from a Mach number above 1. At cruising altitude, an aircraft has to be around 1000 km / h fast. The currently fastest business jets are on the move with a Mach number of 0.9. The planned supersonic airliners should even achieve Mach numbers between 1.8 and 2.2 when cruising. This would make them more than twice as fast as current airliners.

“It is difficult to reconcile the efficiency of the aircraft when cruising and the noise emissions in the vicinity of the airport,” explains Dr. Robert Jaron from the Institute for Propulsion Technology discusses the challenges in aircraft design. “Because of their better flow behavior, supersonic aircraft are particularly long and narrow and have small engines. To reduce noise during take-off and landing, however, engines with larger diameters would be preferred. ”In the opinion of the DLR team, in which the Institute for Atmospheric Physics also works, there is still scope for the take-off procedure. The poor gliding properties in subsonic flight are compensated for in supersonic aircraft by a particularly powerful engine. A higher take-off speed with an early reduction of the engine thrust could reduce the noise pollution in the vicinity of the airport. This possibility is also being investigated in the project. Another research focus of SENECA: Pollutant emissions and their influence on the climate. Supersonic traffic will fly significantly higher than current air traffic and is therefore likely to have different effects on the atmosphere.

The project partners are currently assuming that the first new supersonic aircraft will not fly at supersonic speed over land because of the bang problem, but only over water. The sonic boom is being analyzed in detail in the EU project MOREandLESS, in which DLR is also involved. Here the scientists determine how different aircraft shapes affect the volume of the bang.