Europe copies SpaceX's approach to reusability

Recently a conference organized by the French Aerospace Academy was held in Paris. One of the speakers was Jean-Marc Astorg, the head of CNES (National Center for Space Research). He spent his entire career at the Directorate, working on Vega, Ariane 5 ECA, Soyuz in French Guiana, and in 2015 he was appointed director of work with launch vehicles. He revealed many technical details, shared his plans for the future, and spoke about the reaction of Europe to American reusable launch vehicles. This article is a translated interview, complemented by the slides that he showed during his presentation.

“When I started working at CNES in 1985, immediately after graduating from engineering school, reusable use had an extremely negative image. Mainly due to the US space shuttle, which was completely unable to achieve its original goals. Initially, the expected cost was 30 million dollars for the launch and with a frequency of one launch per week, in the end it cost about 1 billion dollars for the launch with 6 starts per year. In this way, we built the Ariane rocket based on the unsuccessful experience of the Shuttle. Today, Ariane 6 is the first European response to revived reusable US missiles.

Before we dive into the details, I’ll quickly remind you of the economic realities. From 2017 to 2018, the NASA budget increased, and this increase constituted the entire annual budget of CNES. As for the global launch market, it represents a lot of satellite launches per year, but only about 25 of them are open to global commercial competition. Most commercial launches are for geostationary communications satellites, but we do not know whether the market will remain the same.



A little story about the development of European launch vehicles: The Ariane 1 was an unexpected commercial success due to the failure of the Shuttle. She was commissioned at exactly the right time. Due to the evolution of Ariane 4, we have reached the ceiling for the Ariane 1 concept, so we developed Ariane 5. For 20 years, it has been the leading commercial launch vehicle (hereinafter PH) in the world. One of our strengths was the location of our Kourou launch site, in French Guiana.

We got a decent market share, given the relatively small funding in Europe. Currently, there is political will in the United States to return to the commercial market and regain lost ground. There has been a development of the LV worldwide, from state and commercial participants, due to the expected increase in the market. For PH it is important to be as cheap as possible. Currently, prices are about 10,000 euros per kilogram when put into geostationary orbit (GTO). Please note that most RNs in development are one-time, so Ariane 6 is no exception in this regard.

To give a brief overview of the global efforts to develop new launching capabilities, it suffices to recall that the Chinese have a space program with incredible progress on all fronts - these are new RN and spacecraft. It makes us turn yellow with envy. They announced that they are also developing reusable RN: Long March 8 to launch by 2028.

In the US, we should not oppose public and private space efforts: SpaceX is largely a creation of NASA, thanks to technical and financial assistance.

In Europe, the main reason for the existence of the space program and the possibility of launches is independent access to space. We realized this the same day that we wanted to launch our first communications satellite, Symphonie, on the American RN. They agreed to launch, but only on the condition that the satellite will not be used for commercial purposes. This shows that we must be confident in ourselves and in our capabilities. However, within Europe there is a need for no more than 4-5 launches per year. Therefore, it is important for us to have a share in the commercial market in order to keep our aerospace industry viable.



We expected a resumption of competition in the United States. Ariane 6 was originally proposed in 2009, when we realized that the Falcon 9 SpaceX was a good PH with high performance at low cost. Therefore, the main task of Ariane 6 was to reduce costs. However, the decision to finance the program was made only in 2014, which is very late. Low decision-making speed in Europe is a serious problem.

Ariane 6 is a one-time rocket, which is very similar to Ariane 5, but we reduce its cost by 50% thanks to three things: an increased frequency of launches, as it replaces the Soyuz launched from French Guiana, innovations (for example, instead of two 3- We will use 4 monoblock solid fuel boosters) and an improved production process with the implementation of lean management. The goal is the cost of 10,000 euros per kilogram on the TRP in 2020. There are few technological challenges, but many organizational ones.

Reuse is a rather old and obvious idea: it takes 3 years to manufacture a RN (due to long engine production), it costs more than 100 million euros, we launch it, and in less than 30 minutes it sinks into the sea. However, there are various ways to implement reusable: Falcon 9 is fundamentally different from the Space Shuttle in this aspect. Only the first step is saved, the easiest to reuse. It is separated at a speed of only 2 kilometers per second, and its cost is 50% of the cost of the entire rocket. This is a big difference compared to Shuttle. Falcon 9 has reasonable technical goals that it can achieve step by step. The shuttle had too many ambitions in the 1970s.

There are several reuse strategies. Since the goal is to minimize the negative impact on the stage, landing with a parachute into the ocean is not an option: salt water complicates repairs. For example, for the Falcon 9 SpaceX, the engine is used to return the engine forward along a looped trajectory with several brake impulses. We worked on this, with the national aerospace laboratory of France, and realized that it was quite difficult.

The key aspect is that this approach allows you to experiment with landing: after the second stage has separated, the first stage can try to change the trajectory and speed of movement without affecting the course of the main mission and without major changes in the design of the first stage. In solutions that use a winged return, on the contrary, non-drop wings must be set to a level during the entire flight of the first stage, which may interfere with the mission. Thus, the SpaceX method works, allowing you to experiment with one-time launches, while adding a minimum of rocket components. So this is the less expensive and most interesting option.



Reusable has pros and cons. The disadvantages are a reduction in the payload, up to -50% when using part of the fuel to return to the launch pad, increased danger when the step returns to the launch pad in Guyana - which is near the city of Kuru and the problem of accessibility of the landing pad in the ocean. To land on a barge, weather conditions must be suitable within a radius of 400 km and in case of bad weather, the launch may not take place.

Pros are an opportunity to have a higher frequency of starts and to have more flexibility when planning paid starts, since we do not need to wait for a long time to start. In addition, reuse saves money if repair costs are low. This is a key factor for the entire formula of reusability. For example, prior to the introduction of the Falcon 9 Block V in the Merlin engine, there were instances of cracking in the turbo pump, which meant that it had to be replaced and limited to starting without significant repair to two uses.

The problem of reusable use is that if you no longer need to create the first steps, then you close your production lines. However, if at some point you need to build a stage, you need to reopen them and start production, which will require a huge amount of money. Therefore, it is important to use the same engine for the first and second stages so that production does not stop.



What could be a reusable Europe strategy? First, we will not do only reusable launches. Missions to geostationary orbits and missions to other space bodies would be one-time missions. For a mission in Earth orbit, we will use the trajectory of the return to the launch site. This would allow us to re-start the first stages and save production volumes, while reducing costs by 30%. Such partial, reasonable reuse is quite realizable. However, this requires a lot of development, because we need to master many complex physical phenomena. Nevertheless, it is interesting, even in today's realities. If the market expands, it even becomes necessary.

One of the technologies to be developed is engine thrust modulation. This can cause problems with burning instability, and we have not studied it in detail because it was not necessary. Therefore, in the short term, Ariane 6 is the only solution to reduce costs and start up costs. In the long run, reusable and other technologies, such as 3D printing, will further reduce them. 3D printing can revolutionize the production of combustion chambers, which currently takes a very long time.



We aim to introduce a phased experimental approach. We need to check how it works. As for the engines, we are currently using the Vulcain, which is a hydrogen engine based on the old design. We are developing a Prometheus methane-oxygen engine whose goal is to reduce costs. This does not mean that we abandon the hydrogen industrial base, we will see. The advantage of methane is that it is located in the middle between hydrogen and kerosene. It is much easier to handle it than with hydrogen, having a better specific impulse than kerosene, so the engine can be cheaper, much cheaper. Methane is also denser than hydrogen, which makes tanks smaller and cheaper. We are building two prototype Prometheus for fire tests by 2021.



Prometheus can be used in the new architecture, which we call Ariane Next. This booster will have 7 engines in the first stage and 1 in the second stage and can be used in a
disposable or reusable version, which makes it easy to experiment with reusability. The goal is to learn from tests that are not the strength of the European aerospace industry.



Before implementing Ariane Next, we have previous steps, one of them is Callisto. For this first-stage reusable demonstrator, we do not have a reusable engine in Europe, so we cooperate with the Japanese. After that, we will move to a larger scale - a prototype of the first stage of the new generation Themis with Prometheus engines. The concept is still in the definition phase.



Ultimately, we will need to make a choice between the evolution of Ariane 6 and the new launch vehicle, which will be ready in the years 2028-2030.

Questions and answers

Question : Where would you like to repair the first stage?

Answer : In Kuru, because otherwise delivery to Europe makes the whole enterprise too expensive. And the repair should be minimal for the concept to work.

Question : Callisto is very similar to the Grasshopper vertical landing demonstrator, the technology of which was then used to land the first stage of the Falcon 9.

Answer : Callisto has the same design as the Grasshopper from SpaceX. The Chinese are also building a similar prototype, we have no problems, saying that we have not invented anything new.

Question : Prometheus looks cheap in production, why not put more engines on the launch vehicle to further increase thrust-to-weight ratio?

Answer : Our design is based on market analysis. Although I cannot predict what the situation will be like in 2030, 7 Prometheus engines are optimal for the current market.

Question : Are you planning to go to Mars?

Answer : We are already going to Mars - the device, aboard NASA Insights Mars, is a seismometer manufactured by French SEIS.

Question : It seems that we are 5-8 years behind the USA, are we going to catch up?

Answer: Although Ilon Musk wrote a new chapter in the history of the creation of launch vehicles, his model of full reusable use is not the only one. I expect the launch market to be half reusable and half one-time in the future. For example, the United States Air Force is currently funding the development of disposable launch vehicles.

Q : What about 3D printing?

Answer : I visited the Relativity Spacein April, and thanks to 3D printing, they developed a methane engine with a load of 10 tons for 2 years and tested it at NASA Stennis. They want to print the entire rocket. Although I do not believe that they will achieve this, I think it can be a breakthrough as significant as reusable launches. On the Ariane 6, for example, the auxiliary power unit of the second stage will be 3D-printed, otherwise it will be too complicated to create. Therefore, I expect a very significant reduction in costs due to 3D printing.

Question : What are the limitations of the weather conditions for landing barges?

Answer: High waves force the barge to tilt heavily and may turn the set step. That's why SpaceX developed the Octograbber rocket capture system. Blue Origin has a different concept; they will use a vessel with a hydrodynamic stabilization system.

Question : What do you think, what impact will the mega constellations of satellites such as Oneweb have on the market?

Answer: I do not have a crystal ball. But I see that since all satellite operators have taken a waiting position and are watching the introduction of these groupings, they have suspended some orders for new satellites, and the commercial market has declined. Now it is 17 satellites per year, while earlier there was about 30 on average. They will have to face competition from geostationary orbit satellites and terrestrial networks, so it is possible that they will fail, as in the 1990s. Then the market, of course, will not grow 10 times.

Question : What do you think about the elasticity of market demand?

AnswerA: Until now, elasticity has been low. The cost of launching the GTO decreased from 20,000 € / kg to 10,000 € / kg, and this did not have a large effect on demand. If we reach € 5,000 / kg, I'm not sure that this will have a big impact. The problem is that the cost of access to space still remains high. Therefore, we do not base our models on market elasticity.

Question : How do you guarantee a safe first-step return for the population?

Answer : It is hard to say. We will use Callisto to show that we can provide safe trajectories.

Question : What about re-use of the second stage?

Answer: We believe that the effect on the mass of the output load is prohibitively high, so we are not working very hard on this.

Original article