Concorde, the solar eclipse that haunts the plane

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In 1973, a small group of astronomers from around the world had a secret weapon to watch and study the eclipse for longer than ever: the prototype of the Concorde supersonic plane.

The future commercial aircraft – developed in partnership between the French and British governments – first flew in 1969 and was on the verge of completing a successful test program.

While the French and British aeronautical engineers were preparing their Concordes for the passenger flight, the solar astronomer was preparing for his private tutor: The longest total solar eclipse in a lifetime, On June 30, 1973.

In theory, a supersonic transport (SST, or Super Sonic Transport) could give them more than 70 minutes to witness the eclipse, which is ten times more observation time than if they were on Earth in the longest eclipse in history at a fixed point, 7 or 8 minutes. And above any cloud and water vapor. Now they just had to have a Concorde.

Search for Concorde

In London, British astrophysicist John Beekman has used airplanes to make astronomy for years. Beekman requested the use of the British prototype Concorde “002”, but was rejected, possibly because the test program in the UK was lagging behind the French.

Then, in May 1972, just over a year before the celestial encounter, a Paris Observatory astronomer named Pierre Lena made his personal proposal to French test pilot André Turcat.

As a scientifically curious pilot, he gave the young researcher an hour of his time. During lunch at a restaurant inside Toulouse airport, Lena drew her vision on the paper towel.

The plan seemed very simple. The Concorde is approaching full speed, descending from the north and intercepting the moon’s shadow over northwest Africa.

Concorde travels together at roughly the same speed, essentially running a solar eclipse across the planet’s surface, giving astronomers an unprecedented opportunity to study the various phenomena made possible by the eclipse: the solar corona, the effect of sunlight on the dimming of the atmosphere, and the short red flash of the chromosphere, namely A narrow region around the sun that is often erased by the brighter photosphere.

I liked the Turcat. He presented the idea to his superiors at Aérospatiale, who were given the temporary green light and agreed to bear the cost of the mission. Turcat and chief navigation engineer Henri Perrier have begun work on all the details, keeping in mind the weather patterns and even the ground temperatures where the Concorde can take off, which could affect the amount of fuel.

Prepare for this historic achievement

After deciding on the Spanish island of Gran Canaria, off the coast of Africa, as a good starting point, the team planned a route south and then east along the eclipse line. Turcat and Perrier have considered which runways in Africa will be able to handle the aircraft. They advanced as much as possible west, to N’Djamena, Chad, with Kano, Nigeria, for support. The actual meeting will take place in Mauritania, which agreed to close its airspace to commercial air traffic at midnight the night before.

But there is still a lot to do. The first was the mechanical transformation of the aircraft. It occurs during the summer solstice and practically along the Tropic of Cancer, the eclipse will be at its zenith: directly above them. To view it properly, they will need to install skylight windows at the top of the fuselage and design a camera through them.

The windows will have to withstand the difference in pressure between the cabin and the outside, as well as the high temperatures – around 100 degrees Celsius – that are felt on the outside of the fuselage during supersonic flight, due to friction with air. If the window blew during the flight, this would not necessarily endanger safety, but would require an emergency landing and an end to the experiment.

Finally, in February 1973, just four months before the eclipse, scientists received news that the mission was underway. The researchers rushed to final preparations.

In addition to the temporal constraints of the Sun-Moon interference, each experiment must deal with the constraints imposed by the plane itself. Nothing could be short-range – a fire on board would be catastrophic – and everything had to be built to withstand the vibrations upon takeoff. Despite the aircraft’s clean safety record at that point, there were legitimate concerns on the minds of scientists about flying an experimental plane at hypersonic speeds.

Time to go

At 10:08 AM on June 30, the four Olympus 593 engines below Concorde Suites fired “001” on the runway at Las Palmas de Gran Canaria Airport. Thousands of kilometers to the east, the moon’s shadow was already crossing the Atlantic at speeds of more than 1,900 km / h, tracing a path towards the African coast.

Two minutes after take-off, the plane hit Mach 1, or about 1,140 km / h, and headed southeast toward the moving shadow. Further in the stratosphere to an altitude of 56,000 feet (17 km), the Turcat took the aircraft up to Mach 2.05, more than twice the speed of sound and slightly below the displacement velocity of the eclipse shadow, from about Mach 2.3.

With the help of the two inertial guidance systems on board the Concorde, the crew steered the aircraft along a carefully marked path and found the eclipse with an accuracy of one second of the planned confrontation.

With a solar eclipse in the sky, Turcat turned on its night-time navigation lights in the dark at noon, then decided later whether to record the flight day or night.

Flag and Concorde could have continued, but the landing site in Chad was rapidly approaching. Altogether, the experimenters observed the entire eclipse for a standard 74 minutes duration.

End of astrological journey

Heading south, away from darkness, Turcat began to line up to approach. There will be 10 tons of kerosene on arrival, giving you the surplus to wait forty minutes in case the approach gets lost. But the plane landed smoothly.

During the flight, Concorde gave astronomers more time to observe the eclipse than all previous expeditions in the past century combined, generating Three articles in nature And a wealth of new data.

This feat is still being repeated, but only 26 years later, in August 1999. However, The three business trips, Two British Airways and one Air France, all after an eclipse over Europe to observe through the same side windows, it will last for 4 to 5 minutes and everyone on board will hardly be frustrated by looking through the tiny windows of Concorde.