Everything you need to know about Themis
The history and where the programme is today.
Issue 61 Subscribers 2,332.
Firstly, a huge thank you to Latitude for sponsoring another issue of the Europe in Space newsletter. Latitude is developing Zephyr, a 17-metre tall launch vehicle capable of deploying 100 kg payloads to SSO at an altitude of 700 kilometres. If you’re interested in sponsoring the next issue, you can view the rate card here.
To my 42 new subscribers, I hope you enjoy your first issue and, if you have any comments, suggestions, or tips, you can reply to this email.
Everything you need to know about Themis
Last week, ArianeGroup announced that it had completed the first Themis-integrated hot fire test of a Prometheus engine. To celebrate the milestone, I decided to take a look back at the programme’s conception and development over the years.
Once upon a time
The story of Themis goes back as far as December 2014 with the approval of the Launcher Evolution Elements (LEE) programme at the ESA Ministerial council meeting. The programme was really the birth of Callisto and the cooperation between CNES, DLR, and JAXA on the project. However, the LEE programme also gave birth to the Prometheus methalox engine project that would be utalised for Themis and not Callisto.
The development of Prometheus began as a CNES project in 2015. The project's goals have remained relatively unchanged since its inception with the aim of reducing the cost of producing rocket engines by tenfold and the development of key technologies for reusable launch systems. That original design briefing also identified methane as a primary fuel and the 100 tonnes thrust target of the engine.
In its annual report for 2015, CNES set a target of 2020 for a full-scale demonstrator to be ready for a hot fire on the test stand. A maiden flight of a Prometheus-equipped vehicle was expected to take place between 2020 and 2022. Interestingly, the report states that the agency was examining a number of recovery methods including "some using winged flight."
Initial work on the engine was conducted by Airbus Safran Launchers (which was later renamed to ArianeGroup) and the CNES launch vehicle directorate. At the ministerial council meeting in Lucerne in late 2016, Prometheus was officially adopted by ESA under its Future Launcher Preparatory Programme.
Just prior to Airbus Safran Launchers becoming ArianeGroup, the company signed a contract with ESA at the Paris Air Show on 21 June 2017 to develop the Prometheus engine demonstrator. This was followed by the signing of a second contract in December 2017 that awarded ArianeGroup with €75 million to fund the design, manufacturing, and testing of the first two examples of the Prometheus engine. At that time, initial testing of the engine was scheduled for 2020, as was the maiden flight of Ariane 6.
What to do with Prometheus, though? If it was going to be ready as soon as early 2020, and it wouldn’t fly aboard an operational vehicle before 2030, it was going to have very little to do in the 2020s. Enter Themis.
It started with 171 views
One of the first introductions of Themis to the public occurred on 31 May 2018 during a conference held at Palais de la Découverte science museum in Paris in partnership with the Académie de l'air et de l'espace (the French national Air and Space Academy). Amazingly, thanks to the Palais de la Découverte museum’s YouTube channel, there is actually a recording of the event that has attracted just 171 views. For the purposes of this article, it was the presentation given by the head of the CNES launch vehicle directorate Jean-Marc Astorg that interested me.
During his presentation, Astorg revealed that a programme called Themis would be the next step in the agency’s push to develop a reusable launch vehicle following the work that was being done for CALLISTO. The next slide in Astorg’s presentation shows three possible configurations that the Themis booster demonstrator could take. The first option would be on the scale of micro-launcher first stage and would feature a single Prometheus engine. The next would be on the scale of an Ariane booster and would feature three Prometheus engines. Finally, the third option would be on the scale of an Ariane NEXT first stage and would feature seven Prometheus engines. However, he did stress that the project was in its earliest phases of development.
Interestingly, during a Q&A section, Astorg was asked where European reusable rocket stages would be refurbished, and his answer was at the launch site in Kourou. According to Astorg, it would be too expensive to send the stages back to Europe for refurbishment.
The next time the programme was mentioned publicly was on 21 February 2019 with the announcement that ArianeGroup and CNES were partnering to launch ArianeWorks. I have most often defined ArianeWorks as a skunkworks division of ArianeGroup dedicated to rapidly prototyping Themis. However, at the time that it was launched the man put in charge of the project, Jerome Vila, penned a LinkedIn article attempting to define it.
"ArianeWorks is not exactly a space startup nor an aerospace "skunkworks", or maybe it is actually a bit of both at the very same time," explained Vila. To explain the outfit's mission, Vila stated "cheaper, agile, flexible, building upon deeptech capabilities, a reshuffled ecosystem and new alliances: this is the plan, in short. And it starts with a cornerstone capability, a low cost and reusable multipurpose rocket stage called THEMIS."
With the announcement, it was revealed that ArianeGroup and CNES intended to present the project for adoption at the 2019 ESA ministerial council meeting in Seville, Spain that November. Of course, ArianeGroup wasn’t quite so blunt with its intentions, stating “ArianeWorks is being created in the lead up to the 2019 Ministerial Conference and its results will be made available to ESA.”
A year after its launch, ArianeGroup posted an article examining the work done by the ArianeWorks team over the preceding 12 months. The article stated that "it took the ArianeWorks team just a few months to sketch out the first design for this 30-metre high biomethane-fueled vehicle which will be powered by three new-generation Prometheus motors." Considering the content of Astorg's presentation in 2018, this appears to be a little misleading. CNES, at the very least, came up with the general design concept and I would have to assume that some work on the design was completed before ArianeWorks was launched in February 2019.
After that slight push into the future, we’re going back a bit to May 2019 with a contract awarded by ArianeWorks to MyCTO. The contract would see the company tasked with creating a prototype of the Themis recovery system based on FROG, a small booster demonstrator created for CNES for its Callisto programme. MyCTO was at some stage renamed to Sparkmate. According to a project page dedicated to its work with ArianeWorks, the company was briefed to "design and construct a prototype for a rocket stage-recovery concept." The prototype was to be used to test several elements of the system including landing algorithms, automated operations, and avionics architecture. The prototype was completed and delivered to ArianeWorks within six months. Sparkmate states that the exact form and function of the prototype are “confidential”. According to ArianeGroup, ArianeWorks, and MyCTO "showcased their fruitful collaboration at several industry events." So, someone out there may have a picture and/or some information.
In November 2019, ESA member states met in Seville, Spain for the Space19+ council meeting. At the meeting, two major decisions were made regarding the future of Themis. Firstly, the agency’s member states agreed to provide full funding to bring the current Prometheus engine design to technical maturity. And secondly, member states agreed to provide funding to begin testing the Prometheus engine aboard the Themis reusable booster demonstrator. ArianeWorks would, however, have to wait another year before the contract for Themis would be awarded.
In the meantime, ArianeGroup conducted combustion chamber tests for Prometheus, and on 4 November a propellant tank test model for Themis code-named Strike was raised into position at the PF20 test zone at the ArianeGroup test site in Vernon, France. The test model was used to complete a series of fill tests that were designed to test several key components including a transverse internal fuel line and a common bulkhead between the oxygen and methane tanks.
The first contract for Themis would finally arrive on 15 December 2020 with €33 million in funding for the project's “initial phase.” This first phase of the Themis project was to include the preparation of the flight vehicle technologies, the test bench, and static firing demonstrations at Vernon. It also included the preparation of the ground segment at the Esrange Space Center in Sweden, the facility that will host the vehicle’s first hop tests.
When the contract was awarded in December 2020, initial engine tests were set to take place in 2021 with low-altitude hop tests from Sweden occurring in 2022. Suborbital flight tests would then have taken place in 2023 and 2024, followed by a "full flight envelop test" in 2025.
In March 2021, ArianeGroup signed what is one of the more out-there elements of the Themis system with a French startup called Flying Whales. The company was founded in 2012 with the aim of developing a large-capacity airship capable of carrying up to 60-tonne payloads in its 96-metre cargo bay. ArianeGroup signed the contract with the goal of utilising a Flying Whales LCA60T airship to transport a Themis demonstrator from a recovery barge located off the coast of French Guiana and return it to the Guiana Space Centre. To achieve this, the airship would hover above the recovery barge and deploy its "lock-on and hoist system" to acquire the stage. The airship, with Themis on board, would then return to the launch facility where the stage would be refurbished for its next flight. According to a press release published at the time, "the objective is to install a competitive solution that can make significant time-savings between two launches."
In May 2021, ESA awarded ArianeGroup with €135 million in additional funding for a pair of Prometheus engine demonstrators. According to a press release at the time, the new funding was to be used "to finalize the demonstration phase with hot-fire testing of the first two prototypes at the DLR site in Lampoldhausen. The contract also stated that ArianeGroup would utilise the funding to begin work on a "liquid hydrogen-oxygen version of Prometheus that could be used aboard an upgraded Ariane 6 variant by 2025” and an "improved version" of the methalox engine that would be capable of delivering 120 tonnes of thrust. Finally, the contract called for the production of "a pre-series of engines to begin the pre-industrialization phase."
On 1 December 2021, ESA announced that ArianeGroup had recently performed six tests of a pair of propellant tanks at its Vernon test site. The tests were conducted to validate the fluidic and electrical operations of these test cryogenic tanks and ground equipment. The goal of this series of tests was to reduce risk going forward into integrated hot fire tests of the Prometheus engine utalising the same propellant tanks. A year later, in November 2022, the next major milestone of the programme was completed when an initial ignition test of a Prometheus engine was completed.
On 8 Jul 2022, CNES announced the agency and ArianeGroup had made the decision to disband the ArianeWorks team, bringing the initiative to an end. According to CNES, the 14-person team completed 25 projects and fully fulfilled its mission by "reducing the time between ideas and their realization and by acting as a catalyst for the European industrial ecosystem."
"We started at an old Ariane 1 facility at ArianeGroup's Vernon facility," explained ArianeWorks chief Jérôme Vila at the time. "Today, the Themis project is pushing forward with tests at two facilities allowing the commencement of real propellant tests. We have gradually handed over to the ArianeGroup industrial team as project manager, a fundamental step for the continuity of the project."
The most recent round of funding received on ArianeGroup for Themis and Prometheus came in July 2022 when the European Commission awarded funding for two ArianeGroup projects. The company received €39 million for SALTO, reuSable strAtegic space Launcher technologies & Operations (which is a ridiculous acronym), and €17.4 million for ENLIGHTEN, or European iNitiative for Low cost, Innovation & Green High Thrust Engine (which is only marginally better). SALTO is aimed at validating the landing phase of Themis. ENLIGHTEN was focused on strengthening "new propulsion system initiatives that ESA has entrusted to ArianeGroup in order to create a family of reusable, high-power engines using bio-methane or green hydrogen."
2023 kicked off with an interesting look at an ArianeGroup contractor working on a key element of the Themis demonstrator. Almatech SA is a Swiss aerospace structures and mechanisms, and thermo-optical hardware specialist that has been contracted by ArianeGroup to build the Themis landing legs. In February of this year, the company revealed that it had successfully delivered the first landing leg of the Themis 1H (more on the different variants of Themis later) reusable demonstrator.
Where we are now
On June 22, ArianeGroup successfully carried out the final test ignition campaign of a Themis demonstrator equipped with a Prometheus engine at its Vernon site. The test campaign was concluded with a 12-second burn of a single Prometheus engine. The engine did, however, lack a number of key elements including its engine bell. Additionally, it’s important to understand where this version of Themis fits into the vehicle’s development campaign.
The Themis project will utilise three separate booster demonstrators. The recent test campaign utalised Themis 1G which features one Prometheus engine and will have the geometrical characteristics and use materials close to those of an operational stage. It would appear that this version of the vehicle has completed its mission. The second version of the Themis demonstrator is Themis 1H and will also feature one Prometheus engine and have just enough equipment to achieve liftoff and recovery. This will be for the so-called hop tests that are currently targeted to commence in 2024, a full two years behind schedule. Finally, Themis 3 will feature three Prometheus engines and will be utilised for the rest of the programme's scheduled flights. This includes the first tests at the Guiana Space Centre all the way up to the "full flight envelop test."
Before the initial hop tests commence in Sweden, additional Prometheus engine testing is scheduled to continue at the DLR testing facility in Lampoldshausen towards the end of the year. Interestingly, when the initial ignition test was completed in November 2022, ESA stated that the additional testing at Lampoldshausen would commence "in the coming months." This would appear to indicate that this testing is possibly as much as half a year behind schedule.
Another significant development to arise following the 12-second test last week is the announcement that ArianeGroup would be setting up a "Prometheus User Club." The project will see the company begin to market the engine "to all interested European parties." This could potentially allow European startups to quickly shift from micro and small launch vehicles to medium to large vehicles without having to develop the engines themselves. The exact cost that ArianeGroup will market the engines at is currently not known. The company has stated that it is hoping to produce Prometheus engines for approximately €1 million a piece. It remains to be seen how much of a makeup will be placed on the engines and if ESA will impose pricing restrictions on ArianeGroup.
At the 2023 New Space Summit in Munich, head of liquid propulsion at ArianeGroup Gerald Hagemann gave a presentation regarding the company's road map for Ariane. The road map includes multiple potential upgrades to Ariane 6 utalising Prometheus and the technology developed for Themis. A hydrogen-oxygen version of Prometheus is envisioned as replacing the Vulcain 2.1 engine on the rocket's core stage and boosters powered by the methane-oxygen version of Prometheus would replace the vehicle's solid fuel P120+ boosters, which are a proposed upgrade of the current P120 boosters. The boosters will also be recoverable to enable multiple uses.
In addition to Ariane 6 upgrades, Hagemann's presentation also has Themis and Prometheus as the first steps toward developing the Ariane Next family of launch vehicles. ArianeGroup is already in the process of creating the first elements of this launcher family with MaiaSpace, a subsidiary launched in late 2021. MaiaSpace is developing a microlauncher with a reusable first stage powered by Prometheus engines and taking advantage of the technology developed for Themis. The maiden flight of Maia is expected to take place in 2026.