People often talk about “long-term research”; for ONERA today, this is not a fashion statement when it comes to environmental concerns. Its vast, tried and tested work is the basis necessary for taking the sharp turn towards decarbonised aviation.
While the aeronautics recovery plan announced by the government provides ONERA with the resources it needs to prepare for green aviation by 2035, and although this is a huge catalyst for ONERA, ONERA had been exploring innovative ways to make aircraft less polluting for many years.
Previous studies as interim steps
As far back as 2008, it analysed innovative engine integration configurations with the NOVA project, the novelty of which was to design the airframe and the engine at the same time. Starting with a medium-haul aircraft, the idea was to mount the engines at the rear in a half-buried configuration: this partial integration makes it possible to ingest the boundary layer of the fuselage and thus reduce the required power and consequently fuel consumption.
Other innovations envisaged pertained to the shape of the sail, and winglets directed downwards to reduce drag. NOVA also featured Ultra High Bypass Ratio engines, which reduce noise emission and fuel consumption. In the same vein, the E2IM project "Study of innovative engine-integration concepts" also came up with a different engine position in relation to the rest of the structure. The idea is to better integrate the engine into the wings or fuselage. The question is how compatible is the airflow around the aircraft with sufficient air inlets into the nacelle to properly power the engine, and what is the resulting drag gain?
Wind-tunnel tests will be conducted in Modane's large wind tunnel by the end of 2020, in preparation for tests on even more breakthrough formulas by 2022/2023.ONERA is a real technology pace-setter, since as early as 2017 it was working on the AMPERE project: a regional demonstrator of aircraft with distributed electric propulsion. Thanks to this project, an important experimental database has been acquired. Analysing the results of this data will make it possible to best prepare for the integration of this technology on a future aircraft for use after 2035.More recently ONERA presented its DRAGON aircraft concept at the 2019 Paris Air Show, to evaluate the benefits and drawbacks of distributed electric propulsion for an airliner. The concept: distributing the thrust via a large number of electric ducted fans placed under each wing, to improve propulsion efficiency. These electric motors are powered by the electricity produced by turbines situated at the rear of the aircraft. This is hybrid propulsion technology since the on-board fuel is transformed into electricity.
The flying wing
However, traditional levers are no longer sufficient to compensate for the growth in air traffic: today, it is all about decarbonising air transport.
ONERA is working on the flying wing, which is expected to open up the possibilities to work on new sources of energy, such as hydrogen.
This aircraft configuration is a complete departure from existing conventional aircraft configurations: all the traditional functions of an aircraft are concentrated on a single geometric element, the wing. In a conventional aircraft, the fuselage contains the passengers and the cargo compartment, while the wing generates lift and allows for flight, and the empennage provides the stability and directional control of the aircraft. In a flying wing configuration, there is no fuselage or empennage, all functions are performed by the wing which becomes the central element.
This results in better aerodynamic performance, lower mass, and therefore a very huge decrease in fuel consumption.
ONERA has some obvious assets to lead the reflection: its ability to work on cross-functional issues, since all the aircraft-design disciplines will have to be involved: aerodynamics, materials, propulsion, etc. It also has further experimental and digital facilities to test the concepts. Moreover, ONERA has developed multidisciplinary design and optimisation methods to take into account all the interactions between these different disciplines.
In addition to its scientific skills, ONERA enjoys the renewed confidence of State authorities: while the Ministry of the Armed Forces granted an exceptional subsidy to ONERA in 2020 (€4.4 million in addition to the €110 million subsidy for public service charges), the DGAC's order-taking has reached €14.5 million.