Paleo-aero: an alternative low-carbon history of aerospace and aeronautics (Atelier 21, February 2023)

Paleo-aero: an alternative low-carbon history of aerospace and aeronautics (Atelier 21, February 2023)

Illustration from La Découverte australe par un homme volant, ou Le Dédale français, Nicolas-Edmé Restif de la Bretonne, 1781

The history of energy is far from continuous: it is full of fantastic innovations, precursor devices that were judged to be irrelevant or unreliable in their time, failing to find interested users or lacking a technical device to build a truly efficient system. But today, these forgotten inventions have the means to respond favourably and no doubt unexpectedly to the challenges of a rapidly changing world.

COP21 returned our attention to the urgency of reviving among the general public this overlooked technical heritage based on renewable energies. We launched the Paléo-énergétique participatory and citizen research program in order to collectively excavate social and technical inventions, patents, forgotten or abandoned practices that have fallen into the public domain – to collect potentially catalysing social visions and weak signals from the past.

This rewritten history of energy, which shines a light on the invisible margins, calls for a global vision that leads to other fertile phases of analysis and creation. As a collective commons, this intellectual material can be redistributed to and revived by creative and collaborative open source communities – where former inventions would no longer fall into the public domain, but instead rise to and emerge from it.

Since we first launched Paléo-énergétique, a number of projects for low-carbon flights and attempts to reach outer space have caught our attention, as our research has introduced us to various alternative flying machines. Meeting Tomás Saraceno and participating in his Aerocene initiative further motivated us to pursue our investigations into aeronautics and aerospace.

We have therefore decided to embark on a dedicated research project to collect all these counterfactual histories from the forgotten fringes of aviation and aerospace. Our current goal is to build a circular economy of knowledge about low-carbon flights by identifying and inventorying techniques and technologies that can be updated and adapted for today’s society.

This rich heritage and counter-history will be documented on a dedicated
website – – as a collaborative research tool that makes available to the general public the collective intelligence of experts and non-experts alike.

We all invite all Paleo-investigators to join us on this journey through time, to discover surprising stories, revolutionary machines, and inventors who just might have changed the course of history.

1784: First (involuntary) solar flight of a hot-air balloon

This flight took place on May 30, 1784, as described in the book Voyages Aériens by James Glaisher, Camille Flammarion, Wilfrid De Fonvielle and Gaston Tissandier, published in 1870. A hot-air balloon (104,000 square feet / 3,565 m3) was resting at Dijon Academy, inflated in order to let dry a recently applied layer of varnish. The guards had measured the temperature inside the balloon at 39°C, while outside, the thermometer only showed 23°C in the sun. A few days earlier, they had observed a temperature of 60°C inside the balloon under the same circumstances, without measuring the temperature outside. On May 30, around 12:30 p.m., a strong wind swept up the balloon, carrying along with it the net, ropes and equatorial ring – a total of 122 kilograms. The package even lifted off his feet a 34 kilograms boy who tried to pull it down. The balloon continued on its way, drifting along the first alleyway behind the Porte Bourbon, astonishing people who came running to get a closer look. The balloon fell more than 250 steps away, unfortunately ripped along its length by two trees.

Paleo-aero: an alternative low-carbon history of aerospace and aeronautics (Atelier 21, February 2023)

Illustration from Voyages aériens / by J. Glaisher, C. Flammarion, W. de Fonvielle, G. Tissandier; woodcuts and chromo-lithographs drawn from sketches by Albert Tissandier by Eugène Cicéri and Adrien Marie; Librairie L. Hachette et Cie, 1870

1881: The Tissandier brothers’s aerostat

By the 19th century, electric power had spread to all sectors of society: medicine, leisure and transportation. Contemporary citizens had become so fascinated with electricity that in 1881, the International Exposition of Electricity was held in Paris. Under the roof of the Palais de l’Industrie floated the aerostat of renowned French aeronauts Gaston and Albert Tissandier. It measured 3.5 meters long, was filled with pure hydrogen, had a lifting capacity of 2 kilograms, and was powered by electricity. Gustave Trouvé, brilliant engineer, the “French Tesla”, developed a small electric motor, made partly of aluminum and weighing only 220 grams. A rudder oriented the little aerostat to the left or right. At a good altitude, on a calm day, it could reach a speed of up to 25 km/h! Throughout the exposition, demonstrations were held twice a week before the astonished eyes of visitors.

Buoyed by this success, Gaston Tissandier registered a patent for the conquest of air: “New application of electricity to aerial navigation […] “Electric motors offer the following advantages: 1. Their weight is stable, so the balloon remains balanced in the air […] 2. There is no need for fire, which is a certain hazard on a hydrogen-filled aerostat […] 3. The electric motor has the advantage of being easy to start up and shut down, and the mechanics are relatively simple to operate.”

In order to develop the prototype into a dirigible capable of transporting passengers, the Tissandier brothers founded a company in 1881. They spent two years with collaborators building a new dirigible: 28 metres long, with a diameter of 9.2 metres, a volume of 1060 cubic meters, and a 2.8-meter propeller that could spin at 60-80 rotations per minute.

On October 8, 1883, the balloon was inflated in seven hours. At 3:20 p.m., the dirigible rose on a light east-south-east wind with the two brothers on board. At an altitude of 500 meters, it flew at a speed of 1 km/h. Taking off from the aerostatic workshops of Auteuil, the dirigible reached a cruising speed of 10 km/h as it flew over the Bois de Boulogne. However, once the wind had risen, the airship with its rough rudder could no longer advance. The motor was stopped for a moment. After 20 minutes of flight, over a distance of almost 3.5 km, the dirigible landed without incident in a large field near Croissy-sur-Seine. The Tissandier brothers would continue to improve their electric dirigible in the following years.

Paleo-aero: an alternative low-carbon history of aerospace and aeronautics (Atelier 21, February 2023)

Illustration of the Tissandier brothers’ airship with accumulator batteries, engraving extracted from Gaston Bonnefont’s book, Le Règne de l’électricité, published in 1895

1884: “La France” dirigible at Hangar Y, the world’s first return flight

Charles Renard, a French military engineer and inventor, aeronaut and
aviation pioneer, became director of the Central Establishment of
Military Ballooning at Chalais-Meudon in 1877. It was the first
laboratory for aeronautical testing in the world. In 1879, he
established Hangar Y for building and storing balloons and dirigibles.
On August 9, 1884 at 4 p.m., one year after the Tissandier brothers flew
their airship over Boulogne, Renard’s own dirigible “La France” rose
into the air over Meudon. The cigar-shaped airship measured 52.4 meters
long, with a diameter of 8.4 metres and a volume of 1,864 cubic metres,
all propelled by an electric 8-horsepower engine. On board were Charles
Renard and the infantry captain Arthur Krebs. They launched the
dirigible on an easterly wind, first against the wind and then across
it. In these conditions, the airship traveled 7.6 kilometres in 23
minutes, before landing softly in a relatively small forested space. It
was the first time that an aerial device had returned to its point of
departure. And it was this flight that showed the general public that
the airways were wide open for navigation.

April 22, 1959: First stratospheric flight in France by Audouin Dollfus with a bunch of 105 balloons

On April 22, 1959, the French astronomer and aeronaut Audoin Dollfus reached an altitude of 14,000 meters in a pressurized capsule. The objective of this flight was to detect the presence of water on the Moon and Mars. This unprecedented method for attaining this altitude was validated by Professor Auguste Piccard, who, along with Paul Kipfer, had been the first in 1931 to have penetrated the stratosphere at a height of 15,781 metres, but in an exploit that was more athletic than scientific.

Tied to 105 balloons spread over a distance of 500 meters, the capsule that contained Dollfus for the duration of the flight consisted of an aluminium sphere measuring less than 180 centimetres in diameter and 1.2 millimetres thick, covered by 20 millimetres of polystyrene. It had 7 windows and a 460-centimetre opening. Its total weight, including all scientific appendages, was 800 kg. The polystyrene balloons were inflated simultaneously with bottles of hydrogen. Tests for dilating the envelopes had previously been carried out inside Hangar Y in Meudon. Using a large number of probe balloons was also financially viable, as the meteorology industry was already an important consumer.

After 2.5 hours of flight, Dollfus reached 14,000 metres and made his observations using a Cassegrain telescope with a 500 mm fixed lens on top of the capsule. To come down, the balloons were gradually released from the cable using explosives controlled by radio waves. After 5 hours of flight, Dollfus landed at night in a prairie in Nivernais. If this flight on April 22, 1959 enabled the observation of the Moon and Mars, it also led to the first precise measurements of water content in the stratosphere.

Paleo-aero: an alternative low-carbon history of aerospace and aeronautics (Atelier 21, February 2023)

The stratospheric device of Audouin Dollfus before the last rope is cut for lift-off

1977: CNES infrared hot-air balloon

Since 1977, the CNES (Centre National d’Études Spatiales) has been developing the MIR (Montgolfière Infrarouge) hot-air balloon for long-duration scientific flights in the stratosphere. By day, the MIR balloon flies at an altitude of 28 kilometres to 32 kilometres, and by night, between 18 kilometres and 22 kilometres depending on the quantity of infrared rays rising in the flight zone and the temperature of the air at the flight level. The balloons can then carry a payload of about 50 kilograms for several weeks. The trajectory follows the circulation of stratospheric winds, enough to circle the Earth more than once...

MIR is an “open” hot-air balloon with a helium complement at takeoff. Thanks to their aluminum covering, these 35,000 to 45,000-cubicmeter balloons are heated exclusively by the sun during the day or by terrestrial infrared rays at night. This phenomenon follows the Earth, which is heated in its mass during the day by solar radiation, and gives back this heat at night in the form of invisible infrared radiation (this infrared radiation from the ground or clouds provides only a very weak thrust, estimated at 4 gr/m3). This “passive” heating system allows the air inside the balloon to remain hotter than the surrounding air, which gives a certain lift to this flying object.

Assembled by Zodiac International, the MIR balloon is composed of two distinct hemispheres made of materials that offer an adequate compromise between their thermo-optical properties and the balance of their mass: The upper part is made of aluminized Mylar of 12 to 16 µm forming a cavity to absorb rising infrared radiation and preventing any re-emission towards the sky. The lower part is made of 15 µm linear polyethylene, a material that is transparent for infrared rays and resistant when the balloon is exposed to a cold environment (temperature below -80°C) during its flight.

The average lifespan of a hot-air balloon is 15 to 20 days. On December 8, 1988, an infrared hot-air balloon took off from Pretoria in South Africa. It successfully circled the Earth twice in 50 days. More recently in 2001, a hot-air balloon circled the Earth three times in 70 days. Infrared hot-air balloons are powerful instruments for scientific measurements, and their low-carbon flights could inspire many other applications in aeronautics or outer space.

Paleo-aero: an alternative low-carbon history of aerospace and aeronautics (Atelier 21, February 2023)

MIR – Upper part of a Mongolfière Infrarouge, CNES

2014: SolarStratos, towards the first 100% solar-powered stratospheric flight

Initiated in 2014 by the Swiss pilot Raphaël Domjan, the SolarStratos project aims to achieve a technological exploit: to reach the stratosphere at an altitude of 25,000 metres with an airplane powered exclusively by photovoltaic solar energy. The goal of this adventure is to prove that, using today’s technology, it’s possible for vehicles to perform beyond the potential of fossil fuels. Electric and solar-powered vehicles are among the greatest challenges of the 21st century, and the SolarStratos project paves the way for tomorrow’s mobility.

SolarStratos is a two-seat airplane designed by Calin Gologan from the company PC-Aero GmbH. It is powered by two electric 19 kW motors that rotate a three-blade propeller with a 1.75-meter diameter. The wings are covered with 22 m2 of the latest-generation solar cells, whose conversion rate is between 22 and 24%. They charge lithiumion batteries with a total capacity of 14 kWh, extendable to 21 kWh.

But for the record-setting flight, the plane will leave the hangar with uncharged batteries, which will be recharged by solar energy before departure and upon landing. At the end of the flight, they should have stored at least as much power as at take-off in order to attest that the entire flight was effectively 100% powered by solar energy. A new propeller will also be installed, optimised for the ascent into the stratosphere.

The stratospheric flight is scheduled for 2023. In the meantime, SolarStratos aims to beat the current record for a fully electric and solar flight set by Solar Impulse in 2014 at an altitude of 9,400 meters. According to the website, the mission in the stratosphere should last approximately 6 hours, including a 3-hour ascent toward space (“15 minutes with our head in the stars”, then 3 hours to come back down to Earth). Both the aircraft and the pilot Raphaël Domjan will be subject to extreme temperatures, in the region of -70°C.

The last example cited in this article for this handbook and the launch of Paleo-Aero shows that many adventurers are innovating, pushing the limits of the impossible, even risking their own lives, to advance science and the energy transition toward low-carbon flights.

Paleo-aero: an alternative low-carbon history of aerospace and aeronautics (Atelier 21, February 2023)

Solarstratos, 3D image