Atmospheric reentry a success for the IXV

On February 11th, in the first stage of the development of a European reusable space shuttle, the IXV* demo vehicle (Intermediate eXperimental Vehicle) executed a flawless atmospheric reentry. This flight made it possible to validate the effectiveness of its thermal protection. Thierry Pichon, Director of thermostructural composite materials programs at Herakles (Safran) explains.

Could you remind us: what is the IXV?

The IXV is a flying space vehicle five meters in length, developed under the auspices of the ESA. It was conceived to validate the precision of the guidance system and to demonstrate the effectiveness of thermal protection on an aircraft performing a gliding atmospheric reentry**. This is a major step towards the development of a reusable spacecraft. With this demo vehicle, it was a case of controlling the heat build-up that the vehicle undergoes during this kind of reentry, in such a way that we no longer have to change the thermal protection in between flights. In this way, the spacecraft can quickly return to space to carry out further missions.

 

How was Herakles' involved in this program?

Nose thermal protection

With its 35 years of experience in extreme heat-resistant composite materials, and as a partner of the ESA and CNES over many programs, including Ariane 5, Herakles was naturally called upon to provide the thermal protection for the IXV. This program was a genuine technological challenge as we had to devise, design and qualify these parts as well as the systems needed to attach them to the vehicle. We therefore supplied Thales Alenia Space Italia, the program's prime contractor, with the thermal protection for the lower surface and the leading edge (a total of around 30 panels), as well as the protection for the nose – a single 1.3m diameter part, for a total surface area of 10m2.

In order to manufacture these parts, we used CMC materials (ceramic matrix composites), capable of resisting temperatures of up to 1,650 ºC whilst retaining very good mechanical properties. Qualification testing enabled us to validate the excellent performance of these parts. For the leading edge, we designed panels consisting of a 1.5mm layer of CMC and 100mm of layered silicon and aluminum insulation. During the atmospheric reentry of the demo vehicle, these absorbed the thermal flow that results in temperatures of almost 1,500 ºC, providing effective protection for its carbon/epoxy structure, which itself only had to withstand temperatures of around 130 ºC!

The installation of these parts was particularly complex as a result of the presence of 300 sensors (temperature, movement, warping...) that had to be integrated into the thermal protection.

 

What are the next steps?

In the short term, we will be analyzing the flight data provided by the IXV in order to optimize our products. These results will then be used in the context of the PRIDE program, which aims to produce a spacecraft capable of landing on a runway, as the US X-37B has already. In the longer term, this type of future craft will make it possible to carry out experiments in microgravity, for example, then bring the results back to Earth, at a far lower cost than that of a mission on board the ISS (International Space Station).

Recovery of ESA’s Intermediate eXperimental Vehicle in the Pacific Ocean just west of the Galapagos islands.

* The IXV (Intermediate Experimental Vehicle) is an experimental spacecraft designed to validate atmospheric reentry technologies that will be used in the framework of reusable launcher projects by the European Space Agency (ESA).

** Gliding atmospheric reentry, as opposed to a ballistic or free-falling reentry, involves making the spacecraft enter more horizontally than vertically, by resting on the layers of the atmosphere.

Optimal flight for the IXV

Launched on February 11, 2015, at 10:40 from Kourou, in French Guiana, by the Vega rocket, the IXV performed a flight of 99 minutes through the Earth's atmosphere. Having reached an orbit of 412 km, the demo vehicle began its descent back to Earth, at speeds of 7.5km/s on entry into the lower atmosphere at 120km in altitude. In under 20 minutes, it went from hypersonic to supersonic speed (mach 1.4 - 476 m/s), before being slowed by a series of parachutes. After reentering without sustaining damage, it splashed down in the Pacific Ocean, where it was retrieved a few minutes later by the ESA.

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