Everything you need to know about CALLISTO
And a little you probably didn't need to know.
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Everything you need to know about CALLISTO
The economic benefit of reusability in small launch vehicles is still very much in question. However, SpaceX has more than proven that reusability can drastically reduce launch costs in medium to heavy-lift launch vehicles. Europe was slow to accept this new reality.
In October 2017, ArianeGroup CFO Pierre Godart told SpaceNews that the company was "trying to see whether there is really a business case for reusability." This comment was made approximately two years after the first successful SpaceX recovery and the same year that the company relaunched its first five recovered and refurbished Falcon 9 boosters.
It is unlikely that an institutionally-developed launch vehicle with any degree of reusability will be launched before the late 2020s. Reusability may be integrated into Ariane 6 towards the end of the decade but for a truly reusable European launch vehicle, we’ll likely have to wait until 2030 and beyond. Small commercially-developed reusable launch vehicles may come into operation before that but as I stated earlier, the economic value of reusability in these vehicles is still in question.
As bleak as that outlook sounds, Europe is certainly not stagnant with its reusability efforts. Themis with its Prometheus engine is by far the most publicized of the continent’s reusability programmes. The smaller but no less capable CALLISTO project is, however, also interesting. This is especially true when you consider that it is not an ESA-driven project.
What is CALLISTO?
In what is probably one of the more ridiculous acronyms in the aerospace industry, which is saying something, CALLISTO stands for Cooperative Action Leading to Launcher Innovation in Stage Toss-back Operations. The cooperative action part of that mouthful refers to the fact that the project is a collaborative effort between CNES from France, DLR from Germany, and JAXA from Japan.
The project was launched in 2015 and appears to have originally been a joint project between DLR and CNES. According to this paper published in 2019, JAXA joined the international partnership in June 2017. However, this DLR paper from 2018 makes no mention of JAXA. This may indicate that JAXA agreed to provide the engine in June 2017 but didn’t sign on to be a full partner until sometime between 2018 and 2019. However, I have not yet gotten to the bottom of that mystery. The 2018 paper also has CNES and DLR completing the flight campaign for CALLISTO by the end of 2021 with the first flight taking place in late 2020. This timeline obviously never worked out, and the trio is now targeting 2024 for the first flight.
Following the completion of the preliminary design review, the vehicle configuration was frozen. The vehicle will stand at 13.5 m tall with a diameter of 1.1 m. It will have a dry mass of 1,520 kg and a take-off mass of 3,600 kg. It will feature four deployable fins as one element of its flight control systems and four deployable landing legs for propulsive recovery.
The engine selected for CALLISTO is derived from the 40 kN re-ignitable LOx/LH2 engine developed by JAXA for its Reusable Sounding Rocket programme. The adapted engine has 15% more thrust and the layout has been tweaked to allow it to fit within the aft-bay diameter. The engine, which is referred to as RSR2, will have a throttling range from 16 to 46 kN allowing for adequate control of the vehicle during the landing phase.
In addition to the four deployable fins, the vehicle's flight control system is also equipped with two electromechanical actuators that will gimble the engine, and eight hydrogen peroxide thrusters derived from those being developed by NAMMO for Vega E and Space Rider.
CALLISTO will conduct its entire flight campaign from the new commercial launch facility at the Guiana Space Centre, which is being built on the grounds of the old Diamant launch facility. The facility will also be utilized for Themis test flights. Landing points on land and at sea (sea barge) were considered with the former being selected in consideration of the mission objectives.
The development of different components of the CALLISTO demonstrator has been split between the three primary partners. DLR is responsible for the fairing, navigation system, fins and aerodynamic science, equipment bay (VEB) structure, the hydrogen tank, and the landing system. CNES will complete the VEB assembly and is responsible for the hydrogen peroxide thrusters, telemetry and telecommand, neutralisation system, and the ground segment. JAXA is responsible for the oxygen tank, aft bay structure, power supply system, and propulsion system. All three organisations will have a part in the onboard computer and flight software.
CALLISTO mission objectives
The mission objectives for CALLISTO have slightly evolved over the years, but the core objectives have more or less remained the same.
Vertically land on a designated landing zone following an ascent phase and a return phase which includes a boostback manoeuver and an unpowered aerodynamic manoeuver.
Demonstrate a large and rapid manoeuvre at low dynamic pressure while managing cryogenic propellant behaviours inside the tank.
Perform at least one landing with a minimum non-gravitational acceleration of 1.3g.
Optimise the inter-launch operations to reach an objective of at least 8 launches within 6 months.
Why have CALLISTO and Themis?
It’s important to remember that Themis isn’t a launch vehicle itself but rather a demonstrator of key technology that will enable future reusable launch vehicles. As a result, it’s not absurd to be working on multiple versions of a single technology to ensure a wide range of variables are explored. Additionally, CALLISTO has a key focus that I don’t often hear associated with Themis and that is the maintenance, repair, and overhaul of the vehicle between flights. The CALLISTO project is particularly interested in how quickly it can fly and reuse the vehicle over a series of eight flights and how much it will cost to do so.
“CALLISTO has its place in the roadmaps for access to space, both French and Japanese,” Michel Illig, CALLISTO project manager at CNES told Europe in Space. “The objective is therefore to acquire a certain number of technologies and information to prepare the development of reusable launchers in Europe and Japan. Examples are the landing system, the control and navigation algorithms, the localization system, the flight control systems, the use of variable engine thrust, and more. But beyond that, information on MRO (Maintenance, Repair, and Overhaul) that is needed between flights, as well as the operational aspects of integration into the activities of a busy space base, will be invaluable in preparing the Guiana Space Center for the launchers of tomorrow.”
Despite the project being a valuable demonstration of key technology along a separate path from the Themis project, I do get the feeling that CALLISTO would have been more valuable as a preamble to Themis instead of the projects being worked on concurrently. This is, however, from a purely European standpoint with Japan likely having its own view of the project’s place in its future launcher strategy.
Contributing programmes
A fascinating aspect of CALLISTO is how many different programmes the project is drawing inspiration, insight, and key technology.
I have already spoken about how the engine is being pulled from the Japanese Reusable Sounding Rocket project and the thrusters from the Vega E and Space Rider programmes, but there’s more.
If you thought the CALLISTO acronym was bad, wait until you hear the recursive acronym for the FROG project. The FROG, a Rocket for GNC demonstration (FROG) project was initiated by the CNES Launchers Directorate in 2017 to test landing algorithms for reusable launchers. The three-metre-tall turbojet-powered vehicle completed its first powered flight in May 2019.
Interestingly, the CNES information page for the FROG project lists an ArianeWorks (a now-closed skunkworks division of ArianeGroup) employee as the contact point for the project. This seems to indicate that the FROG was part of the secretive ArianeWorks activities. Even more interestingly, the employee in question, Jeremie Hassin, states on his LinkedIn profile that during his time at ArianeWorks, he was the product owner of the Morpho reusable mini launcher, a project that would later become MaiaSpace where Hassin is now employed. This shows how much of a head start MaiaSpace has gotten in the development of its vehicle and why its 2025 maiden flight target isn’t nearly as ambitious as it first seems.
The Environment for Autonomous GNC Landing Experiments (EAGLE) is a DLR project that was focused on developing and testing guidance, navigation, and control technologies for exploration vehicles that are required to land on the Moon, planets, and other celestial bodies like asteroids. The vehicle is 2.7 metres tall with a lift-off mass of just 30 kg. It is powered by a jet engine with a maximum thrust of 400 N. The first flight of EAGLE took place in 2017.
The DLR Reusability Flight Experiment (ReFEx) might be one of the most interesting European space projects you’ve likely never heard anything about. The project was initiated to provide flight and design data for aerodynamically controlled reusable launch vehicle stages. The agency also hopes to gain operational experience from the programme. The vehicle being developed for the programme looks like a 2.7-metre scale model of the SpaceX Starship launch vehicle. It will be launched aboard a Brazilian VSB-20 sounding rocket and will perform an unpowered gliding touchdown much like the Space Shuttle. The ReFEx vehicle has a wingspan of 1.1 metres, a mass of approximately 450 kg (not sure if that’s dry mass or take-off mass), and will be equipped with a nitrogen cold gas reaction system. The maiden ReFEx flight is expected in 2024.
Although ReFEx and CALLISTO are being developed concurrently, there is some overlap. According to DLR, the programmes overlap in the following areas: real-time multicore processing, guidance, navigation and control, health monitoring, aerodynamic design, and controlled transonic flight.
In addition to the above, I also found references to a project called METRO. I have, however, not been able to find any information about that particular project.
Latest CALLISTO updates from CNES
Getting updates on Callisto from CNES, DLR or JAXA was… interesting. JAXA has a contact form that sent my requests into the ether never to be seen again. I managed to find some people responsible for the programme at JAXA who very politely told me to fill in the contact form - one more desperate plea into the ether. DLR was mostly responsive once I called on a friend to share a contact. The German space agency, however, thanked me for my interest and said they would be ready to talk to me about the programme in April. CNES, who I traditionally have had a very hard time communicating with, were my saviors on this one. The below responses to my very brief questions (I was desperate) are from the CALLISTO project manager at CNES Michel Illig.
How far along is the development of CALLISTO?
CALLISTO successfully passed its System Design Key Point in 2021 which confirmed the definition presented previously during the preliminary system design review. This made it possible to carry out the preliminary definition review of the products and subsystems in 2022 and to carry out the development tests for these products (deployable landing system, environmental tests of avionic equipment, flight control system tests, etc.). Long-term supplies for flight hardware have been committed, in particular for the manufacture of tanks and the engine. The avionics validation platform is in place and the first tests have begun. Finally, on the ground side, the infrastructure work has progressed well, and the contracts for the ground support means have been notified (control bench, fluid networks, cryogenic arms, robot, etc.). Proof of concept tests for the robot, which should assure reconnection of helium, nitrogen, and electrical supply after landing, was carried out in 2022 which validated the proposed concept.
What is the next major milestone expected to occur?
The development tests for the majority of the components and sub-systems should be completed soon. For example, environmental and acoustics tests of the equipment vehicle bay will be conducted this summer, which will make it possible to hold critical definition reviews. This will pave the way for the critical launch system definition review in the second half of 2023. In 2024, a series of flight-worthiness reviews will follow. However, CALLISTO being a demonstrator, a proto flight logic is retained for certain sub-assemblies, such as the hydrogen tank. The commitment to manufacture these sub-assemblies will therefore be carried out in parallel with the traditional reviews with a certain number of key points to correct the definition if necessary.
The ground support systems should be gradually implemented at the launch site from the middle of 2023, for a technical qualification scheduled for 2024. Everything will therefore be in place to receive the elements of the vehicle before the end of 2024 at the Guiana Space Center. Then combined test and finally the first test flight will follow.
Conclusion
I’m excited about Themis. I am, however, somehow more excited about CALLISTO. I think one of the reasons for this is how holistic the approach to CALLISTO is. Developing a reusable launch vehicle is only a small piece of the puzzle with the ground segment including the refurbishment of the vehicle being just as important. The targeted launch rate is also interesting with the goal of eight flights in six months likely to push the team to come up with some creative solutions. All of this will, however, count for very little unless it can’t be implemented to solve what ESA Director General Josef Aschbacher has referred to as a “crisis in the launcher sector.”
If there’s no press release, did it even happen? - In a LinkedIn post, CNES chairman and CEO Philippe Baptiste appeared to announce that an Ariane 6 upper stage had recently successfully completed a second hot fire test. ESA announced the successful first hot fire test of an Ariane 6 upper stage in October 2022 at Germany’s DLR test centre in Lampoldshausen. I haven’t seen this second test announced anywhere outside of the Baptiste LinkedIn post. It should be noted that the post is in French and the automatic translation feature may be misleading me.
Europe wants to clean up its act - Speaking at the World Economic Forum in Davos, ESA Director General Josef Aschbacher said he was discussing introducing a new space debris policy with member states that would require satellites to be deorbited immediately after their mission came to an end. “We want to establish a zero debris policy, which means if you bring a spacecraft into orbit you have to remove it,” said Aschbacher. “This policy should be in place in a couple of years.”
A legend steps down - UK ESA astronaut Tim Peake announced that he would be stepping down as an astronaut to take on an ambassadorial role for space. “I’ve always believed in moving forward and embracing new challenges, even if you don’t know what’s around the corner - it keeps things interesting,” said Peake in a statement on Twitter. “My years with ESA have been a fantastic phase of my life and I look forward to remaining part of the ESA family as an ambassador.” Peake spent 186 days in space aboard the ISS during which time he became the first UK ESA astronaut to complete a spacewalk.
The space janitors are coming - Swiss-based in-orbit servicing and active space debris removal startup ClearSpace closed a €26.7 million Series A led by OTB Ventures and Swisscom Ventures. The round included participation from the Luxembourg Future Fund, Lakestar, In-Q-Tel, Happiness Capital, and 600 T Space Investments. As part of the financing, ClearSpace will establish an operational presence in Luxembourg. The company intends to launch its first debris removal mission ClearSpace-1 in 2026.
No time to cry over spilled milk - Swedish space tech company AAC Clyde Space has received a €234,000 order from the UK-based in-space manufacturing startup Space Forge. The order is for an integrated attitude determination and control system and a Kryten OBC to be used as a ground reference for the ForgeStar-1 mission, forming a complete attitude and control system for the spacecraft. AAC Clyde Space expects to have completed delivery of the order during the second quarter of 2023.
A cryptic announcement - Italian launch startup Sidereus Space Dynamics signed an agreement with US-based space tech company Space Tech. The announcement was a little vague simply stating that the partnership would “push the boundaries of space technology.” Further updates regarding the partnership are expected. Sidereus Space is developing a small single-stage-to-orbit rocket called EOS that is designed to be capable of delivering 15 kg payloads to low Earth orbit.
A 10-year commitment - The EU Agency for the Space Programme (EUSPA) has awarded the Search and Rescue (SAR) Galileo Data Service Provider to CNES. According to EUSPA, the renewed cooperation with the French space agency will ensure the seamless continuation of the SAR service while paving the way for new Galileo emergency management services. The 10-year contract is valued at €137 million.
Wait, is it three keys or four? - In an article published on LinkedIn ESA director of space transportation, Daniel Neuenschwander outlined the three keys to unlocking Europe’s independent access to space. Although it’s not entirely clear in the article itself, the title states that the three keys are sustainability, flexibility, and innovation. However, in the conclusion, Neuenschwander also adds competitiveness… so, four keys? Despite the confusion, the article does give a nice overview of the work being done by the agency’s space transportation division.
Commemorating the man who saw it first - ESA’s JUICE (JUpiter ICy moons Explorer mission) spacecraft received a commemorative plaque during a press event at the Airbus facility in Toulouse. The plaque honours Galileo who was the first to view Jupiter and its largest moons through a telescope in 1610. The spacecraft is expected to leave the facility to be shipped to the Guiana Space Center in early February. It is expected to be launched in April aboard the final Ariane 5 flight.
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