RASTAS SPEAR

RAdiation-Shapes Thermal protection investigAtionS for high-SPeed EArth Re-entry

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 Obiettivo del progetto (Objective)

'In the frame of Activity 9.2.1 – Strengthening of Space foundations / Research to support space science and exploration - SPA.2009.2.1.01 Space Exploration, the actions proposed on RASTAS SPEAR project try to enlarge the basic capabilities on few known topics with low Technology Readiness Level and to strengthen European Industry and Research for coming or future Space Exploration missions with focus on Sample Return Missions like Marco Polo or Mars Sample return. The project does not analyse a specific mission but deals with crucial “bricks” to be well mastered for the design of a Capsule entering in the atmosphere with high speed (more than 10 km/s). These necessary bricks are: 1) To investigate on the available ground facilities and elaborate a proposal to improve these facilities in order to simulate in-flight conditions on ground. 2) to investigate and develop new and innovative methods, materials and systems for joining ablative blocks (tiles) together to produce a complete Thermal Protection System (TPS) for sample-return missions and validate them by tests with CIRA's Scirocco and DLR arcjet facility. 3) to identify and test damping, energy-absorbing systems to allow survival of the Capsule Payload (collected Samples from planets…) 4) to analyse the impact of ablation (and thus Capsule shape change) on the flight mechanics. 5) to investigate and test impact of surface roughness on the heat transfer between the flow field and the capsule heat shield. The return of invest for the European Community is a European capability to design carefully a Re-entry capsule with focus on mass and thus on mission cost.'

Introduzione (Teaser)

The atmosphere surrounding Earth protects life on our planet, but makes coming back after a visit to a planetary neighbour difficult. Scientists with the support of the EU have developed technology that is essential for the successful Earth re-entry of capsules bringing back research samples for analysis.

Descrizione progetto (Article)

Air resistance is helpful in slowing down the rate at which re-entry capsules of space missions are pulled back to the Earth by gravity. But the friction generated by the capsules hurtling earthwards results in extremely high temperatures. As they re-enters the Earth's atmosphere at supersonic speed, heat is released by the surrounding gas moving against the vehicles' surface.

To keep them from burning up, like meteorites when they fall to earth, re-entry capsules fly backwards to slow themselves down and enter the atmosphere at the correct angle. Furthermore, they need to be the correct shape and be covered in the appropriate material. The heat shield needed to survive re-entry has helped drive the development of several new technologies.

The aim of the EU-funded 'Radiation-shapes thermal protection investigations for high-speed Earth re-entry' (RASTAS SPEAR) project was the maturation of some key technologies. The initiative was also successful in providing strong technological bases for the preparation of future sample return missions. In addition, project results feed into the design of ESA's MarcoPolo-R Mission to a primitive near-Earth asteroid.

To provide a better understanding of phenomena that play a role in the supersonic entry, the RASTAS SPEAR project reviewed the capabilities and limitations of testing facilities. The shock wave formed ahead of the re-entry vehicles and the flow of gas around them can be reproduced in supersonic plasma wind tunnels.

The review addressed operation principles of the existing facilities with the testing methodologies applied, as well as all equipment used for collecting measurements. Based on the results of these comparisons, the RASTAS SPEAR partners designed new equipment and methodologies to simulated pressure changes encountered during re-entry.

Theoretical models based on computational fluid dynamics were developed for the analysis of impact to the thermal protection system (TPS) of the capsules. The RASTAS SPEAR researchers also combined and tested new crushable materials that can absorb the impact forces and adhesives for joining blocks of a TPS with improved performance.

A demonstrator representative of the thermal shield of sample-return mission was designed for testing in plasma wind tunnels. The tests were carried out at Italy's Scirocco plasma wind tunnel in Capua, near Naples, one of the few sites worldwide where such testing is possible. The demonstrator proved that it indeed functions as planned and mathematical modelling is accurate, opening new exciting opportunities for space exploration missions.