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European Flexible hEat Shields: advanced TPS design and tests for future in-Orbit demonstration

Periodic Reporting for period 1 - EFESTO (European Flexible hEat Shields: advanced TPS design and tests for future in-Orbit demonstration)

Reporting period: 2019-03-01 to 2020-12-31

Fully in line with the European Union H2020 call SPACE-11-TEC-2018, EFESTO provides advances in the three areas of thermal control, materials and structures through the design and testing of innovative inflatable TPS solutions for re-entry vehicles. It enables new space mission concepts, which require bringing a payload from space to ground of a planetary body with an atmosphere beyond the current limits imposed by launcher fairing size or rigid heat shields geometrical and structural aspects. Morphing solutions allow for example landing bigger or heavier payload on Mars or enable the reusability of launchers’ upper stages enhancing European reusability and cost reductions in the access to space industry. Non space applications in the areas of materials and structures are also considered.
The project contributes to improving the current European TRL of inflatable heathshields through design and ground testing of the most critical elements. In pariticular, innovative flexible TPS samples have been designed in RP1 with current state of art materials and they will undergo intensive heat in arcjet facility in RP2. The application limits will be understood and the capability of numerical tools to predict materials performance will be validated and enhanced, with a focus on thermal properties. Beyond arcjet testing, ground testing of the inflatable structure is ongoing. In RP1 the design, based on an innovative annulus concept, has been completed and the first hardware prototypes have been built. The final demonstrator will be built in RP2 and it will undergo dynamic (morphing during inflation) and static (external pressure) load tests. Again, application limits will be understood and the capability of numerical tools to predict materials performance will be validated and enhanced, in this case with a focus on mechanical properties.
The inflatable heatshied has been the focus subsystem of the study, but its design has been performed in coordination with the overall mission and system design. Two sets of applications have been covered in the project: Mars Robotic Exploration and Reusable Small Launchers Upper Stages (Earth).
During this first Reporting Period, the “Future requirements and needs” have been analysed, resulting into two applications cases, one for Mars scientific robotic exploration and one for Earth reusability of launcher stages. For both applications, the technical activities progressed as planned over the four main disciplines covered in the project: Materials, Structures, Aerodynamics and Aerothermodynamics, Missions and Systems.
In particular the first element “Mission and system and prototypes design” has been extensively covered by the work performed in the work packages WP2, WP3 and WP4 from a conceptual to a preliminary and a detailed design of both applications (Mars exploration enabled by inflatable heatshield and Supersonic Retro Propulsion, SRP; Earth reuse of VEGA AVUM upper stage enabled by inflatable heatshield and parafoil with mid-air-retrieval, MAR).
The second element “Prototype manufacturing” plus “Thermal and structural ground testing” is ongoing, with key significant results already obtained from the work performed so far in WP5 (materials for thermal testing have been selected according to design, purchased and prepared for tests; samples holder for arcjet tests have been designed and the facility has been prepared including a definition of the test campaign) and WP6 (Test article designed for a 1:2 scale; test article manufacturing is ongoing; inflatable structure test conditions have been established and sensors have been selected).
The third and fourth elements (“Numerical tools validation and extrapolation to flight” and “IOD mission preparation”) will both start in 2021.
In parallel to these 4 elements, a “Technology Roadmapping” activity is ongoing, with the objective of placing the results of EFESTO in a mid-long term perspective useful for Europe and with future exploitation options for the consortium. The first steps identified are the need for a consolidated business case analysis and the need for In-Orbit-Demonstration (IOD) flights to raise the TRL in preparation to a future product or service (return of launcher elements or in general “payloads” from orbit).
Several progresses beyond the European state of art are expected by the end of the project.
In particular the following ones are already in good progress with the work performed in RP1:
1) innovative F-TPS solutions have been designed as multi-layer combinations of different advanced materials. The current designs are expected to sustain heat fluxes in the range of 500-600 kW/m2. FTPS samples are under preparation and the design validation will be completed in RP2, through dedicated arcjet test campaigns, in air and in Martian atmospheres.
2) innovative inflatable structures have been designed introducing the annulus concept in the overall design. This solution is expected to outperform the classic stacked-toroid inflatable heatshield solution providing a better strength/weight, improved aeroshape stability propertied during re-entry, simplified manufacturing and improved scalability. A first prototype of the inflatable structure has been manufactured and the design validation will be completed in RP2, through dedicated ground test campaigns.
3) innovative applications have been considered, in two areas: Mars exploration and reusability of launchers' stages. In the first application, inflatable heatshields, in combination with supersonic retro propulsion will enable landing heavier payloads to Mars areas never explored by past or current missions; in the second application, inflatable heatshields, in combination with parafoil for descent and landing, will enable recovery of launchers upper stages or other launcher hardware elements, reducing costs of access to space and reusing valuable hardware that by today is expended at the end of the launch mission becoming a debris. Design validation will be completed beyond EFESTO, through a dedicated In-Orbit-Demonstration mission (that will be designed in RP2 but not performed within EFESTO). This future step will bring the technology to a TRL of 6/7.
Both missions are of fundamental importance for the society: the first will help in the exploration of planet Mars, and could find its ultimate application in supporting not only robotic but also human exploration of Mars; the second contributes to the reduction of both access to space cost and number of space debris generated by a space mission. Beyond these direct impact on the space sector, advances in modelling and understanding of materials and structures can introduce innovative solutions to non-space applications, such as fire protection or, more in general, applications for high temperature protection.
Mars EDL: recipe for a mission!
EFESTO Study Logic