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CNES: use of hydrazine for rockets

Date de l'actualité

On April 5, 2022, Arianespace signed a contract with Amazon to launch 18 Ariane 6 rockets, to help launch its Kuiper constellation into orbit. Ariane 6 is a program 52% funded by France, through CNES.

CNES, Centre National d'Études Spatiales, is always looking for more efficiency for its spacecraft, and less damage to the environment. In the perspective of a "cleaner" future, the development of new propellants (propellant is a homogeneous substance used to provide energy to spacecraft) is considered. Denser and more energetic propellants would be efficient to optimize the performance of launchers. Today, the most common propellants are hydrazine.


What is the CNES?


The Centre National d'Etudes Spatiales (CNES), was created in 1961 by the French government. It is a public establishment of an industrial and commercial nature (EPIC) which is in charge of the development of space activities in France. CNES's mission is to propose to the French government the orientations of its space policy and to implement, with the help of its partners in industry, research and defense, the decided programs.

Today, it is a major player in the space field. With its four centers (two in Paris, one in Toulouse and one in Kourou, French Guiana), CNES currently employs more than 2,350 men and women who work together to achieve excellence and meet the challenges of tomorrow.

CNES has a very strong CSR policy, built around five key areas

  • Acting as a responsible employer
  • Promoting a protective and sustainable space
  • Creating shared value through space
  • Reducing our environmental footprint
  • Supporting the resilience of territories

At CNES, every day is a new challenge for the environment and its future.

The current situation


Satellites and space stations usually stay in orbit for a very long time. During this time, they spread propellants. Ergol is a fuel used to provide energy to spacecraft. Since it is a substance not present outside the Earth's atmosphere, propellant ignites if it is in the presence of a gas other than oxygen.

Today, the most common propellants are made of hydrazine. This chemical compound of nitrogen and hydrogen is highly toxic and unstable. Typically, hydrazine fuels are so dangerous and carcinogenic that they require special clothing to handle them, like astronauts. Even if measures are taken to limit its presence in the atmosphere, it is still more than 10,000 tons of hydrazine-based fuels that are released each year.

Objective 2040

"The goal may seem far off, but we are already preparing for it today. By 2040, several technological breakthroughs should make it possible to develop radically different launchers with strong ambitions in terms of cost, performance and uses. CNES, notably through the Ariane Ultimate initiative, is involved in the emergence of these future innovations, which will concern both launcher structures and the engines and propellants that power them. On this last point, the advanced concept of HEDM (high energy density material) propellants is of particular interest. These molecules, which do not exist today, would have the advantage of being more energetic (high energy) and denser (density material)." CNES

What is hydrazine?


Hydrazine is, at room temperature, a colorless liquid. Its odor is comparable to that of ammonia. Hydrazine is a flammable, corrosive and irritating compound.

The aerospace sector, including CNES, is the largest consumer of pure hydrazine. Indeed, pure hydrazine and its derivatives have been used for more than 50 years as propellant, in association with dinitrogen tetroxide in rockets (in particular Ariane); hydrazine is generally used alone as propellant in low-thrust (but high precision) engines allowing the positioning on orbit of satellites and space probes.

The effects on humans are:

  • Inflammations and burns when in contact with the eyes and the epidermis.
  • Ingestion, even of short duration, is likely to attack the nervous system and cause death.
  • Repeated contact can cause liver and kidney damage.

To learn more, read this article: Hydrazine, what to expect with the changing standard?


How will launchers work in the future?

lanceurs cnes

> First of all, do you know where the energy comes from that allows a rocket to rise and reach space?

The energy is produced by a combustion, that of a fuel (or reducer) and an oxidizer (or oxidizer). These substances are called propellants. Several types of liquid fuels exist, but at CNES, on Ariane launchers, hydrogen at -250°C is used. For the oxidizer, it is most often liquid oxygen.

On Ariane 6, these propellants, put in tanks just before the launch, will feed the Vulcain 2.1 engine of the main stage (156 tons of propellants) and the Vinci engine of the upper stage.

> What about the future?

On future launchers, a new propellant could be used as a fuel to replace liquid hydrogen. This is liquid methane, which has the advantage of being liquid at a temperature close to that of oxygen (-160°C) and of having a higher density (440 kg/m3, compared to 70 kg/m3 for liquid hydrogen). These characteristics would make it cheaper and easier to use.

Source :

Titre du push

The equipment used for the launches

SPM FLEX et Chemcassette

SPM FLEX gas analyzer

Détecteur monogaz X-AM 5100

Single gas detector X-AM 5100