ESA’s mysterious reusable fairing study

Issue 1.
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ESA’s mysterious reusable fairing study

Credit: ESA - M. Pédoussaut

I recently came across a SpaceNews article from 2017 discussing the possibility of utilizing Prometheus aboard Ariane 6. In the article, author Caleb Henry briefly mentions a project RUAG Space (which is now Beyond Gravity) is working on to develop reusable fairings that could be utilized aboard Ariane 6. I had never heard about this project before and there appeared to be little if any additional details available online. So, what happened to this project, and will Ariane 6 utilize reusable fairings?

Although the SpaceNews article describes the program being initiated as far back as 2017, there seems to be no mention of it until 2019. At this stage, RUAG Space was joined by DEIMOS Space in performing some early studies regarding the feasibility of the concept under the ESA Future Launchers Preparatory Programme. At this point, ESA moved ahead with these early studies and requested a study examining a preliminary design and assessing the potential cost savings of such a project. The agency also laid out a long-term objective for the initiative that would see the development and qualification of a flight model of a reusable payload fairing.

The most recent development in the program was the Reusable Payload Fairing Feasibility Study that commenced in April or May 2022 (ESA and Beyond Gravity seem to have different recollections of when exactly the study commenced) and was concluded in late November with a final presentation occurring on 9 December 2020. 

The Reusable Payload Fairing Feasibility Study

When I asked ESA to describe the original brief for this study I was told that it was “limited in distribution on a need-to-know basis due to industrial interests.” Luckily, those industrial interests, which in this instance is Beyond Gravity, were kind enough to supply the project’s goals.

Project goals:
1. To investigate and assess the business and market analysis of a reusable payload fairing.
2. To investigate and assess the technical feasibility and the preliminary requirements and design of a reusable payload fairing, including the most important phases of the Payload Fairing lifecycle. This work addresses the following points:
- mission analysis, flying quality analysis, and GNC (guidance, navigation, and control).
- the preliminary sizing of equipment (e.g. sensors, actuators, parachutes, etc.).
- the preliminary concept of the life cycle for several successive reuses.
3. To propose a plan for future development and demonstration of the recovery and reuse of a reusable payload fairing.

Neither ESA nor Beyond Gravity shared the presentation of the results, however, I was able to find a paper prepared by Beyond Gravity and the ZHAW School of Engineering that appears to outline the approach of the study. The paper describes a very basic “blunted-cone” fairing with no capacity for a payload that is referred to as the conceptual payload fairing (PLF). The reference vehicle used for the study was an Avio Vega rocket hinting at a broader application for the technology than just Ariane 6.

The structure of the fairing would be constructed from aluminum alloy facesheets over an aluminum alloy honeycomb core. The choice of aluminum over the more standard carbon-fiber-reinforced polymers was made due to the more favorable cost of an aluminum construction. The material used for the thermal protection system (TPS) was cork which would be adhered to the outer facesheet. The cork is described as being a key element in defining how cost-effectively the fairing could be refurbished and reused and for how many missions it could be reused.

“After each launch, a refurbishment of the TPS must be considered. The extreme cases are with no TPS present (zero costs), and with single-use TPS (high costs, as the entire cork must be replaced and reinstalled). If the TPS can survive multiple flights, the cork can be refurbished with resurfacing.”

A number of different recovery options were also explored. The team proposed the use of a parachute or a parafoil to arrest the last of the fairing’s momentum on its way back to the ground. The fairing would then either be captured midair by a helicopter, splashdown in the ocean, or fall into a net stationed in the ocean (it’s not clear exactly what this would look like, but it’s likely in the same vein as the early SpaceX recovery ships).

Conclusion

According to a statement to European Spaceflight from Rüdeger Albat, ESA head of Ariane 5, and future preparation, a reusable fairing concept is still being explored in the frame of the Space Transportation reusability roadmap of ESA. The roadmap includes the Prometheus, Themis, and CALLISTO programmes. The below is outdated but is a nice illustration of the complexity of the agency’s reusability roadmap.

Interestingly, Beyond Gravity seems to have put the concept on a shelf until there is a “business case” for reusable fairings. “There is yet no business case for reusable fairings, but overall new conditions could change the business case in favor of reusable fairings,” EVP of Beyond Gravity’s launchers division Paul Horstink said to European Spaceflight. “And Beyond Gravity is well-prepared for such a situation. We know exactly how to adapt our existing fairings to make them reusable and thoroughly analyzed the effects of reusability on our fairing’s performance, quality (e.g. less shock protection, more weight), and price.” The company also told me that it needs “customers willing to buy a reusable fairing and accepting the impact on performance of this solution.” It would be interesting to see how large a performance hit a launcher would have to absorb to make use of reusable fairings.

It’s kind of astonishing how little is known publicly about this series of reusability studies. ESA is typically quite vocal about its reusability efforts talking extensively about projects like Prometheus and Themis. However, there doesn’t appear to be a single mention of the Reusable Payload Fairing Feasibility Study on the agency’s website. The little public information I did find was buried in dry academic papers published on the European Conference for Aeronautics and Space Sciences website. I would suspect that these papers haven’t been downloaded more than a dozen times since they were uploaded.

Additional reading: 

• Reusable Payload Fairings:  Mission Engineering and GNC Challenges

• Preparing the Future of European Space Transportation: Reusable Technologies and Demonstrators