How ESA is paving its own way to reusable launchers

If a technology was suggested today that could would litter and pollute its surroundings it would seem old fashioned and the antithesis of everything people are working hard to achieve – a clean environment. But this is exactly what we do as we propel satellites and other missions into Space, leaving debris behind.

"Re-usability is exponential, it opens space for all" - Samir Bennani, Technical Officer in charge of ADAMP, ESA.

Reusable technologies, which are not discarded after just one use, are just one way that we can help become more sustainable equipment. Not only does it save the planet, but by not requiring a new version for each use, it also saves buying new materials and the time of rebuilding them.

The space shuttle was one such example of reusable technologies for space. Yet, in Europe, such rockets are only just entering the landscape. While overseas reusable launch vehicles are currently in use, Themis, ESA’s first relaunch-able rocket, is planned to take off for the first time in 2023. Themis will be powered by Prometheus, developed by ESA’s Future Launchers Preparatory Programme. Prometheus is ESA’s ultra-low-cost rocket propulsion system, which is designed to be used across a range of different types of launch vehicles.

"Bringing back a vehicle, in a fully autonomous way is possible in Europe. We know how to do it." -David Perigo, Technical Officer on the ADAMP engine activity.

One way ESA can meet the demands as space technology rapidly advances, is by developing high performance engineering that is more robust, through an evolving process of building and testing many iterations of similar products. This extensive prototyping means designs can be tested, and what works and what does not can be adjusted into the next prototype. With the rapidly accelerating pace of technology today, this would mean that new elements such as electronics and computing could be easily implemented into the design without constantly having to begin a new programme from scratch.This idea of incrementally maturing a technology is being implemented successfully into one GSTP activity, called ADAMP. ADAMP is helping ESA to master one of the more critical aspects of reusability – a smooth return and landing.

ADAMP is testing the limits of flying, landing precisely and avoiding hazards, all autonomously. The more autonomy onboard missions, such as Themis, the less human intervention, ground, and operational infrastructure is necessary, which means the craft can figure out and decide some carefully chosen things on its own, through a lot of online computing.

The culmination of more than 10 GSTP and TDE activities, developing technology little by little, ADAMP is just the current stage in a long line of vertical take-off and landing systems GSTP has advanced through this process of building, testing, learning from failures and trying again. As problems arise, the team hacks them, using their knowledge from a multitude of industries and inside ESA itself to gradually progress all of the different technologies that go into one reusable system. Ultimately, these advances in a huge range of never-before-used-in-Europe technologies will ensure that the next generation of launchers will have everything available, ready and at the right maturity, just when it is needed.

The first phase, builds on an earlier demonstration vehicle, imaginatively named the Demonstrator Technology Vehicle (DTV), which built on an even earlier design, the EAGLE.

Originally one of GSTP’s de-risk activities, which aims to unblock the difficult technologies that can preventive advances in larger critical technologies, the first phase say two initial designs proposed and possible propulsion systems narrowed down.

Now, the 3 million Euro activity, in a consortium with several Romanian entities, including ATD, the National Institute of Aerospace Research (INCAS), and the Romanian Space Agency, has just passed the critical design review. This means the design, after a series of analysis, simulations and tests, is now approved.

With the intention to make the final product airborne in 2022, time is vital, and with that in mind hardware is already being built, prototype test engines have been fired and the fuel tank design is almost final. The design is extremely simple and modular, so that parts can be replaced and upgraded easily as improvements are made or advances are made across the industry, whether that’s in engines or materials. Aerodynamically, the structure is incredibly advanced to take into account how heat flow on re-entry affects the engine. The tanks and engines are also built to be interchangeable and three different engines are being designed to be test and benchmarked on the vehicle. Beyond that, the flight software is also fully re-programmable to test various guidance, navigation and control strategies.Eventually, the vehicle will be able to mimic various scenarios, such as a moon landing meaning it can also act as an in flight simulation tool for other programs.The activity saw the development of three 1 kilo Newton (kN) engines, with the intention now to build a 6kN engine.

Now, developments are beginning to understand how operations and ground support will be able to work with the launcher. Alongside that, infrastructure is now being built to make sure a suitable testing platform exists, including a runway, vehicle integration and testing facilities, a refuel station, ground command and telemetry and tracking systems. There are also ongoing considerations for all safety and logistics procedures being put into place.

While each of the developments helps the activity reach closer to ADAMP-II and a fully tested autonomous reusable vertical landing and take off systems. The individual incremental advances are already having a wider impact on space R&D and expect to eventually see new space-qualified start-ups and companies, a permanent customer base for testing in-flight technologies, on top of the new infrastructure and activities it prompts.