Ariane 6

Ariane 6 is a European expendable launch system operated by Arianespace and developed and produced by ArianeGroup on behalf of the European Space Agency (ESA). It replaces Ariane 5, as part of the Ariane launch vehicle family.

This two-stage rocket utilizes liquid hydrogen and liquid oxygen (hydrolox) engines. The first stage features an upgraded Vulcain engine from Ariane 5, while the second uses the Vinci engine, designed specifically for this rocket. The Ariane 62 variant uses two P120 solid rocket boosters, while Ariane 64 uses four. The P120 booster is shared with Europe's other launch vehicle, Vega C, and is an improved version of the P80 rocket stage used on the original Vega.

Selected in December 2014 over an all-solid-fuel option, Ariane 6 was originally targeted for a 2020 launch. However, the program encountered delays, with the first launch occurring on 9 July 2024.

Ariane 6 was designed to halve launch costs and increase annual capacity from seven to eleven missions compared to its predecessor, but the program has faced controversy over high costs and lack of reusability versus competitors' rockets, such as SpaceX's Falcon 9. European officials defend the program, saying it provides crucial independent space access for its member states.

Description
Two variants of Ariane 6 are offered:
 * Ariane 62 (A62), with two P120 solid boosters, weighs around 530000 kg at liftoff and is mainly for government and scientific missions. It can launch up to 4500 kg into geosynchronous transfer orbit (GTO) and 10350 kg into low Earth orbit (LEO). The first launch in 2024 used this variant.
 * Ariane 64 (A64), with four P120 boosters, has a liftoff weight of around 860000 kg and is intended for commercial dual-satellite launches of up to 11500 kg into GTO and 21500 kg into LEO. Like Ariane 5, it will be able to launch two geosynchronous satellites together.

First stage
The first (lower) stage of Ariane 6 is called the Lower Liquid Propulsion Module (LLPM). It is powered by a single Vulcain 2.1 engine fueled by liquid hydrogen (LH2) with liquid oxygen (LOX). The LLPM is 5.4 m in diameter and contains approximately 140 t of propellant.

Boosters
Additional thrust for the first stage will be provided by either two or four P120 model solid rocket boosters, known within Ariane 6 nomenclature as Equipped Solid Rockets (ESR). Each booster contains approximately 142000 kg of propellant and delivers up to 4650 kN of thrust. The P120 motor is also used in the first stage of the upgraded Vega C launcher. By sharing motors, production volumes can be increased, lowering production costs. The first full-scale test of the ESR occurred at Kourou, French Guiana, on 16 July 2018, and the test completed successfully with thrust reaching 4615 kN in vacuum.

Second stage
The second (upper) stage of Ariane 6 is called the Upper Liquid Propulsion Module (ULPM). It shares the same 5.4 m diameter as the LLPM, and is also fueled by LH2 and LOX. It is powered by the Vinci engine, which delivers 180 kN of thrust, burns for up to 900 seconds and is capable of up to three restarts. The ULPM carries about 31 t of propellant.

History
Ariane 6 was conceived in the early 2010s to be a replacement launch vehicle for Ariane 5, and a number of concepts and high-level designs were suggested and proposed during 2012–2015. Development funding from several European governments was secured by early 2016, and contracts were signed to begin detailed design and the build of test articles. In 2019, the maiden orbital flight had been planned for 2020, however by May 2020, the planned initial launch date was delayed into 2021. In October 2020, the European Space Agency (ESA) formally requested an additional €230 million in funding from the countries sponsoring the project to complete development of the rocket and get the vehicle to its first test flight, which had slipped to the second quarter of 2022. By June 2021, the date had delayed to late 2022. In June 2022, a delay was announced to "some time in 2023" and by October 2022, ESA clarified that the first launch would be no earlier than the fourth quarter of 2023, while providing no public reason for the delay. In August 2023, ESA announced that the date for the first launch had slipped again to 2024.

Concept and early development: 2010–2015
Following detailed definition studies in 2012, ESA announced in July 2013 the selection of the "PPH" (first stage of three P145 rocket motors, second stage of one P145 rocket motor, and H32 cryogenic upper stage) configuration for Ariane 6. It would be capable of launching up to 6500 kg to Geostationary transfer orbit (GTO), with a first flight projected to be as early as 2021–2022. Development was projected to cost €4 billion. A 2014 study concluded that development cost could be reduced to about €3 billion by limiting contractors to five countries.

While Ariane 5 typically launches one large and one medium satellite at a time, the PPH proposal for Ariane 6 was intended for single payloads, with an early 2014 price estimate of approximately US$95 million per launch. The SpaceX Falcon 9 and the Chinese Long March 3B both launch smaller payloads but at lower prices, approximately $57 million and $72 million respectively as of early 2014, making the Falcon 9 launch of a midsize satellite competitive with the cost of the lower slot of a dual payload Ariane 5. For lightweight all-electric satellites, Arianespace intended to use the restartable Vinci engine to deliver the satellites closer to their operational orbit than the Falcon 9 could, thus reducing the time required to transfer to geostationary orbit by several months.

Ariane 6.1 and Ariane 6.2 proposals
In June 2014, Airbus and Safran surprised ESA by announcing a counter proposal for the Ariane 6 project: a 50/50 joint venture to develop the rocket, which would also involve buying out the French government's CNES interest in Arianespace.

This proposed launch system would come in two variants, Ariane 6.1 and Ariane 6.2. While both would use a cryogenic main stage powered by a Vulcain 2 engine and two P145 solid boosters, Ariane 6.1 would feature a cryogenic upper stage powered by the Vinci engine and boost up to 8500 kg to GTO, while Ariane 6.2 would use a lower-cost hypergolic upper stage powered by the Aestus engine. Ariane 6.1 would have the ability to launch two electrically powered satellites at once, while Ariane 6.2 would be focused on launching government payloads.

French newspaper La Tribune questioned whether Airbus Defence and Space could deliver on the promised costs for their Ariane 6 proposal, and whether Airbus and Safran Group could be trusted when they were found to be responsible for a failure of Ariane 5 flight 517 in 2002 and a more recent 2013 failure of the M51 ballistic missile. The companies were also criticised for being unwilling to incur development risks, and asking for higher initial funding than originally planned – €2.6 billion instead of €2.3 billion. Estimated launch prices of €85 million for Ariane 6.1 and €69 million for Ariane 6.2 did not compare favorably to SpaceX offerings. During the meeting of EU ministers in Geneva on 7 June 2014, these prices were deemed too high and no agreement with manufacturers was reached.

Ariane 62 and Ariane 64 proposals
Following criticism of the Ariane 6 PPH design, France unveiled a revised Ariane 6 proposal in September 2014. This launcher would use a cryogenic main stage powered by the Vulcain 2 and upper stage powered by the Vinci, but vary the number of solid boosters. With two P120 boosters, Ariane 6 would launch up to 5000 kg to GTO at a cost of €75 million. With four boosters, Ariane 6 would be able to launch two satellites totaling 11000 kg to GTO at a cost of €90 million.

This proposal, unlike Ariane 6 PPH, offered a scalable launcher while retaining Ariane 5's dual-launch capability. The proposal also included simplification of the industrial and institutional organisation along with a better and cheaper version of the Vulcain 2 engine for the main stage. Although Ariane 6 was projected to have "lower estimated recurring production costs", it was projected to have "a higher overall development cost owing to the need for a new, Ariane 6-dedicated, launch pad".

The Italian, French, and German space ministers met on 23 September 2014, in order to plan strategy and assess the possibility for agreement on funding for the Ariane 5 successor, and in December 2014, ESA selected the Ariane 62 and Ariane 64 designs for development and funding.

At the 2022 International Astronautical Congress, ArianeGroup announced the proposed "Smart Upper Stage for Innovative Exploration", a reusable upper stage for the 64 (or later) variant, capable of autonomous cargo operations or carrying five astronauts to LEO.

Test vehicle development: 2016–2021
In November 2015, an updated design of Ariane 64 and 62 was presented, with new nose cones on the boosters, main stage diameter increased to 5.4 m, and the height decreased to 60 m.

The basic design for Ariane 6 was finalised in January 2016 as an expendable liquid-fuelled core stage plus expendable solid-rocket-boosters design. Development advanced into detailed design and production phases, with the first major contracts already signed. Unlike previous Ariane rockets, which are assembled and fueled vertically before being transported to the launchpad, the Ariane 6 main stages were to be assembled horizontally at the new integration hall in Les Mureaux and then transported to French Guiana, to be erected and integrated with boosters and payload.

The horizontal assembly process was inspired by the Russian tradition for Soyuz and Proton launchers – which had more recently been applied to the American Delta IV and Falcon 9 boosters – with a stated goal of halving production costs.

The industrial production process was completely overhauled, allowing synchronized workflow between several European production sites moving at a monthly cadence, which would enable twelve launches per year, doubling Ariane 5's yearly capacity. To further lower the price, Ariane 6 engines were to use 3D printed components. Ariane 6 was to be the first large rocket to use a laser ignition system developed by Austria's Carinthian Research Center (CTR), that was previously deployed in automotive and turbine engines. A solid state laser offers an advantage over electrical ignition systems in that it is more flexible with regards to the location of the plasma within the combustion chamber, offers a much higher pulse power and can tolerate a wider range of fuel-air mixture ratios.

Reorganisation of the industry behind a new launch vehicle, leading to the creation of Airbus Safran Launchers (ASL), also started a review by the French government into tax matters, and the European Commission over a possible conflict of interest if Airbus Defence and Space, a satellite manufacturer, were to purchase launches from ASL.

While development was initially slated to be substantially complete in 2019, with an initial launch in 2020, the initial launch date has slipped several times: first to 2021, then to 2022, then to 2023, and then to 2024. In October 2022, Arianespace expected the maiden flight to occur in 2023, although in December 2023, Arianespace once again set the flight to occur on 15 June 2024. In June 2024, ESA Executive said its first launch was postponed to July 9th 2024. The maiden flight took place 9 July 2024 and successfully orbited some satellites even though the mission did suffer some problems.

Future development options
CNES began studies in 2010 on an alternative, reusable first stage for Ariane 6, using a mix of liquid oxygen and liquid methane rather than liquid hydrogen that is used in the 2016 Ariane 6 first-stage design. The methane-powered core could use one or more engines, matching capabilities of Ariane 64 with only two boosters instead of four. , the economic feasibility of reusing an entire stage remained in question. Concurrent with the liquid fly-back booster research in the late 1990s and early 2000s, CNES along with Russia concluded studies indicating that reusing the first stage was economically unviable as manufacturing ten rockets a year was cheaper and more feasible than recovery, refurbishment and loss of performance caused by reusability. It was suggested that with a Arianespace launch schedule of 12 flights per year, an engine that could be reused a dozen times would produce a demand for only one engine per year, making supporting an ongoing engine manufacturing supply chain unviable.

In June 2015, Airbus Defence and Space announced that Adeline, a partially reusable first stage, would become operational between 2025 and 2030, and that it would be developed as a subsequent first stage for Ariane 6. Rather than developing a way to reuse an entire first stage (like SpaceX), Airbus proposed a system where only high-value parts would be safely returned using a winged module at the bottom of the rocket stack.

In August 2016, ASL gave some more details about future development plans building on the Ariane 6 design. CEO Alain Charmeau revealed that Airbus Safran were now working along two main lines: first, continuing work (at the company's own expense) on the recoverable Adeline engine-and-avionics module; and second, beginning development of a next-generation engine to be called Prometheus. This engine would have about the same thrust as the Vulcain 2 currently powering Ariane 5, but would burn methane instead of liquid hydrogen. Charmeau was non-committal about whether Prometheus (still only in the first few months of development) could be used as an expendable replacement for the Vulcain 2 in Ariane 6, or whether it was tied to the re-usable Adeline design, saying only that "We are cautious, and we prefer to speak when are sure of what we announce... But certainly this engine could very well fit with the first stage of Ariane 6 one day", a decision on whether to proceed with Prometheus in an expendable or reusable role could be made between 2025 and 2030.

In 2017, the Prometheus engine project was revealed to have the aim of reducing the engine unit cost from the €10 million of the Vulcain2 to €1 million and allowing the engine to be reused up to five times. The engine development is said to be part of a broader effort – codename Ariane NEXT – to reduce Ariane launch costs by a factor of two beyond improvements brought by Ariane 6. The Ariane NEXT initiative includes a reusable sounding rocket, Callisto, to test the performance of various fuels in new engine designs.

The European Space Agency is exploring human-rating certification for Ariane 6, awarding Arianespace a contract to explore potential options for enabling crewed missions to be launched aboard the vehicle.

Production
In a January 2019 interview, Arianespace CEO Stéphane Israël said that the company would require four more institutional launches for Ariane 6 to sign a manufacturing contract. Launch contracts would be needed for the transitional period of 2020–2023 when Ariane 5 will be phased out and gradually replaced by Ariane 6. The company would require European institutions to become an anchor customer for the launcher. In response, ESA representatives said the agency was working on shifting the 2022 launch of the Jupiter Icy Moons Explorer from Ariane 5 ECA to Ariane 64, further indicating that there are other institutional customers in Europe that must put their weight behind the project, such as the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) or the European Commission.

, Arianespace had sold three flights of the Ariane 6 launch vehicle. One month later, they added a satellite internet constellation launch contract with OneWeb to utilize the maiden launch of Ariane 6 to help populate the large 600-satellite constellation.

On 6 May 2019, Arianespace ordered the first production batch of 14 Ariane 6 rockets, for missions to be conducted between 2021 and 2023.

Rocket components are transported by sea from Europe to the Guiana Space Centre aboard the Canopée, a cargo vessel that uses sails to assist with its propulsion, reducing fuel use.

Development funding
Ariane 6 is being developed in a public-private partnership with the majority of the funding coming from various ESA government sources — €2.815 billion — while €400 million is reported to be "industry's share".

The ESA Council approved the project on 3 November 2016, and the ESA Industrial Policy Committee released the required funds on 8 November 2016.

In January 2020, two EU institutions, the European Investment Bank and the European Commission, loaned €100 million to Arianespace, drawing from the Horizon 2020 and Investment Plan for Europe corporate investment programmes. The 10-year loan's repayment is tied to the financial success of the Ariane 6 project.

Criticism
Ariane 6 has been subject to criticism for its cost per launch and lack of reusability.

When initially approved by ESA in 2012, the rocket was envisioned as a modernized version of Ariane 5, optimized for cost. At the time, commercial competitors like SpaceX were already putting downward pressure on launch costs. However, these companies had made few successful flights and had not yet proven that reusability would be economically beneficial, with the reusable Space Shuttle cited by some as an example to the contrary. In the more than a decade that Ariane 6 was in development, the project was delayed and went over budget.

During that same time, SpaceX continued to iteratively develop its Falcon 9 rocket, nearly doubling its payload capacity and successfully landing rockets for reuse, making it more capable and far less costly than Ariane 6.

European officials have defended Ariane 6 stating that its governments need access to space, independent from other states or private companies. They point to geopolitical events that cut off Europe's access to Russian Soyuz rockets in as an example of that need. They also defend the rocket's lack of reusability, arguing that it would not be economically viable given the rocket’s fewer planned launches.

The ESA's member states agreed to subsidize the rocket with up to €340 million annually from its 16th to its 42nd flight (expected in 2031) in return for an 11% discount on launches.