The European Space Agency’s (ESA) Space Rider program has officially begun its validation and testing phase, as it prepares for a maiden flight in the third quarter of 2025. Space Rider is Europe’s reusable uncrewed robotic laboratory that will provide an “end-to-end integrated space transportation system” for commercial customers. After launching into space, Space Rider will spend two months in orbit while customers complete experiments and technology demonstrations onboard, before returning to Earth.
Space Rider was originally set to begin flights end of this year after having received funding in 2019; however, several delays have pushed back its inaugural launch. Yet, entering into Phase D marks a significant step toward launch as ESA is preparing for several drop tests to validate the capability of Space Rider’s autonomous landing algorithms.
NSF sat down with Space Rider program manager Dante Galli, to discuss the reasons for the delay, the challenges involved in an autonomous landing, and its success so far.
What is Space Rider?
According to ESA, Space Rider aims to give Europe access to “affordable” and “independent” access to space by providing an end-to-end launch service. With the ability to transport payloads to several orbital altitudes and inclinations, customers will be able to complete technology demonstrations and science experiments, whether it’s within pharmaceuticals, biomedicine, or robotic exploration, and have the ability to bring them back to Earth.
The spacecraft will be about the size of two minivans, according to ESA, massing approximately 4,900 kilograms at launch. With the ability to carry up to 800 kilograms of payloads in mass, Space Rider will remain in orbit for two months, while customers complete their missions utilizing microgravity to validate technology.
Payloads will be integrated into the re-entry module cargo bay and will launch into orbit atop a four-stage Vega C rocket from Centre Spatial Guyanais in Kourou, French Guiana. The re-entry module is coupled with the AVUM orbital module, which is an extension of Vega C’s fourth stage and supplies the power, data-handling, and telemetry capability to maintain the two-month mission. Coupled with AVUM is AVUM Life Extension Kit (ALEK), which is the adaptation kit required for orbital life extension, acting as the service module during the orbital phase and providing power with two solar arrays, guidance and navigation, and propulsion. AVUM and ALEK will stay attached to Space Rider during the two-month orbital phase of the mission and will finally provide the de-orbiting boost for the re-entry module to come back to Earth.
When the mission concludes, Space Rider will complete a re-entry through the Earth’s atmosphere going 28,000 kilometers per hour and softly land on a runway. At about five kilometers from the landing strip, Space Rider will release a parafoil and steer itself to a soft landing with 150-meter accuracy.
Following its landing, Space Rider will be refurbished for re-use, as each vehicle is designed to make at least five re-flights.
Dante Galli explained that there was a multitude of reasons to develop the spacecraft, including the shift toward increasing in-orbit services, and the desire for ESA to offer services that are commercially viable. “One of the main objectives of the program is to address so-called reusability,” Galli said. “When we think about the stage of the Falcon 9 reused several times, it was told that the capability of having a spacecraft that can land autonomously on the ground and be refurbished in a limited amount of time… was something that had to be addressed by ESA.”
While the program was initially conceived in 2016, Space Rider was officially approved at the ESA Ministerial Council held in Seville in November 2019, and is a follow-up from the intermediate experimental vehicle mission which performed a perfect suborbital flight and atmospheric re-entry with a sea landing in February 2015.
In December 2020, ESA signed two contracts with Thales Alenia Space Italy and Avio to deliver the Space Rider flight model, including the re-entry module and AVUM module. A further contract was inked with Telespazio and Altec to deliver the ground segment.
Two landing sites were being considered, including French Guiana or Santa Maria in the Azores archipelago in Portugal. French Guiana was seen to allow maximum mission performance, whereas Santa Maria was considered more suitable for high-altitude inclination orbits.
Delayed to 2025
In late June, ESA announced it received the green light to enter Phase D of the program, which is focused on building and testing the spacecraft. Other than developing the system, this phase will primarily involve the completion of several drop tests to refine the autonomous landing technology and the capabilities of the parafoil.
Tests on a smaller parafoil began in July, in preparation for a full-scale test later in 2023 using a 70 square meter parafoil, ESA explained. “The smaller tests will allow engineers to tweak the algorithms that will pilot the spacecraft using winches to pull and release the canopy — just like a human parapente [paraglider] pilot does,” the agency said. A drop test amid the worst weather conditions is also slated to take place, to determine the spacecraft’s landing system, software, and parafoil regardless of wind.
The teams are also preparing to complete a series of autonomous landing tests by dropping a scaled mock-up of the re-entry module from a helicopter at different altitudes to test its ability to land by itself. ESA will first test the mock-up by dropping it from 1.5 kilometers in altitude, and then eventually from three kilometers.
Space Rider was initially scheduled to complete its maiden flight in 2023, however, several delays have pushed the date back. According to Galli, the new target date is now the third quarter of 2025.
“As an outcome of the previous ministerial council of 2019, the Space Rider received quite significant financial support to cope with Phase C and D activities. However, the participating states contributed in a way that was not possible — due to the need to comply with the Geo-return mechanism — to keep the industrial consortium as it was operating up to that moment [end-2019],” Galli said.
ESA’s Geo-return mechanism was established to boost fairness among member states, ensuring that the nations that invest in the agency will generate a “fair return.” In a nutshell, participating states in an optional development program should receive industrial contracts in a proportional way with respect to their contribution to that program to ensure that money invested benefits the countries that actually contributed to that program. That is to say for example, if you put 30% of the funds into the program, you are expected to receive as close as possible to industrial contracts accounting for 30% of the overall program.
As the program must abide by the Geo-return mechanism, Galli explained that the initial consortium involved was required to significantly be rebuilt “in compliance with the available funds and their member state relevant origin.”
“This caused first a not negligible delay in setting up the new industrial consortium… that was finally concluded only in late 2020 with the signature of the new contract with the prime contractors. And then, a so-called bridging design phase was needed on the subsystems affected by the change of industrial supplier, resulting in a longer-than-expected completion of the design phase.
“Some other challenges were instead technical challenges, that arose, as it is natural in complex development programs with a lot of novelties when digging more and more into the detailed design phase,” Galli continued. “One of them for sure is the autonomous landing with 150 meter precision under a parafoil, a really complex and challenging objective to be achieved and for which we are indeed preparing an extensive test campaign for validation of the guidance and navigation control algorithms”.
Challenges to face
There are several challenges involved in developing an end-to-end space service. However, Galli said that the “autonomous landing on the ground under a parafoil with a precision landing of 150 meters” will prove to be the most difficult.
— ESA Space Transport (@ESA_transport) July 28, 2023
Unlike many missions that are piloted by astronauts, the spacecraft will land completely on its own. “In our case, we need to ensure this precision in a fully autonomous way by relying on weather predictions. However, weather predictions by definition are unpredictable… a human being is able to feel and see the wind to understand it and follow it, but an autonomous system has to make predictions based on some extrapolation of data provided by the system, and this is a real challenge.”
Galli said this requires a specific algorithm of guidance that can not only succeed on paper but can also be tested successfully.
Another challenge that could grow in the future is the Vega C’s current grounding. In late 2022, a Vega C rocket launched from French Guiana carrying two satellites onboard. But just under three minutes into the flight, an anomaly occurred on the Zefiro 40 — the second stage — and therefore prematurely ended the mission, destroying two satellites in the process. Since then, the Vega C has been grounded, and Arianespace, the operator of the rocket, has not disclosed when it will return to the skies.
Despite its unclear future, Galli said the grounding has not impacted Space Rider so far. “I expect that the issues will be resolved before the inaugural flight,” Gallis said. “Industry and the prime contractors and the industrial chain shall work regardless of the Vega C situation,” Galli continued. “This shall not be used in any way as an excuse… we are already in a delay with this program… now it’s time to move on and really see the concrete results of our design”.
Seeing success despite the delay
While the delay of the program presents issues of its own, Galli said the interest in Space Rider has been “huge” so far. In October 2021, ESA announced it was offering the opportunity for customers to ride on board the first flight. The agency released a dedicated announcement of opportunity with no restriction on nationality for commercial or institutional customers, and Galli said this generated over 40 applications.
At this time, there are 16 payloads slated to ride onboard the maiden flight. “Most of these payloads that are trying to demonstrate some technologies or applications in microgravity have already signed a memorandum of understanding,” Galli said. “It is not a binding contract, but upon a successful outcome on the first flight, [the customers] could commit to future flights.” According to Galli, there is still room for more payloads to join the inaugural flight depending on size.
Although ESA has previously said customers will pay roughly $40,000 per kilogram, Galli said they are still considering how the pricing will work, as Space Rider will provide end-to-end launch solutions, rather than only sending payloads into orbit.
(Lead image: Artist’s interpretation of Space Rider module in orbit for two months. Credit: ESA)