The models for the Concorde, Rafale, Airbus 380, and all of France’s nuclear missiles are said to have been tested here.
In a quiet valley in the French Alps, hidden by giant domes and grey tubes, engineers are testing cutting-edge aerospace technology.
The research centre in Modane, in the Maurienne valley, features gigantic wind tunnels, which have been used for the past 75 years to assess how new plane and missile designs will perform in flight.
Wind tunnels are research devices with large tubes reproducing continuous or gusty winds to simulate the effects of movement and resistance of an aircraft in flight.
The models for the Concorde, the Rafale, the Airbus A380, the Mirage and the Falcon have all been tested in these tunnels.
Here they can be exposed for hours to winds of up to Mach 12, or nearly 15,000 km/h, to measure acoustics and resistance to pressure.
As the aviation industry tries to slash its carbon emissions, and as the French government advances new military projects fuelled by the war in Ukraine, the order books of these wind tunnels have filled up.
The facility, run by the French national aerospace research centre (ONERA), is at full capacity, with almost all of its “flights” booked for the next four to five years.
"There isn't a single missile from the nuclear deterrent force that hasn't passed through here," said Bruno Sainjon, ONERA's Director General.
"These days, when both civilian and military sovereignty have regained importance, (the site) has become even more indispensable," he said.
Testing new fuselages
One of the site’s four wind tunnels, the S1, is 24 metres wide and 400 metres long, making it one of the biggest in the world.
It’s also considered unique because it’s powered exclusively by hydraulic power thanks to two dams.
ONERA says that these trials of aircraft components allow designers to find and solve problems early on.
The tunnels are also big enough to fit large aircraft and missile models. ONERA says this allows detailed simulation of aerodynamics.
"It allows us to experiment with new engine test benches, new models, new test configurations in dimensions that allow us to have a very high measurement precision and resolution because the wind tunnel is large," said Olivier Guillerme, Head of Experimentation and Development Unit at ONERA.
Engineers can also probe the fuel efficiency of nuclear missiles and new fuselages here.
The tunnels’ advanced transonic systems capable of reaching the speed of sound enable experts to gauge whether the aircraft in development will be able to meet noise regulations when flying in the air.
The S1 tunnels were initially built by the Nazis in the Austrian Alps in 1942. When the Allies discovered the tunnels at the end of World War II, they dismantled and transferred them to Modane, France, in 1948.
Since then, many aircraft models of the largest French and European aeronautical programs have been tested in the tunnels before entering service.
For more on this story, watch the video in the media player above.