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ESA’s Future Launcher Systems

Published by Sigurd De Keyser on Mon Nov 28, 2005 12:17 am
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By Klaus Schmidt and Stephen Deisher, Space Fellowship counsilors; Which will be the future launcher systems for Europe? To answer this question ESA started in 2004 the Future Launcher Preparatory Program (or FLPP). But let us first look on the current situation.

Currently ESA has access to space through the Ariane-5 launcher, operated by its commercial offset Arianespace. Developed as a cheaper and more powerful successor of the very successful launcher family Ariane-4, the Ariane-5 is available in three models. The generic version G (currently upgraded to Ariane-5 GS), the heavy-lift model ECA and a modified vehicle for transporting the ISS supply craft ATV, called Ariane-5 ES-ATV.

Through the alliance, called Starsem, of Arianespace, EADS, and Russian partners, ESA can and does also use the Soyuz launchers, especially for interplanetary probes. Currently, the Kourou spaceport gets an additional launch pad for the Soyuz rocket, so in future it will possible to launch the Soyuz from the equator-near Kourou with an increased payload.

For smaller payloads ESA develops the Vega launcher, consisting of three solid propellant stages and one liquid propellant stage. The solid rocket engines are based on the Ariane-5 booster engines. It is planned to first-launch the Vega in 2007.

Recently ESA announced a cooperation with the Russian Space Agency to build the Kliper spacecraft together. As this craft needs a new launcher or at least a modified launcher, ESA could also use that launcher for future payloads. The rockets currently in consideration are a modified Soyuz launcher, called Soyuz-3, a Zenit with a new upper stage, named Onega, or another launcher currently in development, the Angara-3.

These launchers will give Europe space access for the next several years. As the private launcher business is yet unclear, Europe will need a new launcher family around 2015 to 2020.

The FLPP calls for a future launcher to be operational around 2020. Currently the first studies are conducted. Now we will take a look at the potential launchers, reusable and expendable both.

One important condition for the whole program is the use of matured technologies and concepts. Designs like Single Stage to Orbit (SSTO) vehicles or air-breathing propulsion systems like scramjets are not considered because they are not yet proven and sufficiently developed.

The most conservative concepts are expendable launchers. Aside from a payload increase, they would incorporate better and especially cheaper manufacturing and components like low cost engines. But as the launchers would be rather conventional, the launch costs would be not very different from today’s. If that would be (on the background of a potential emerging private rocket market) enough to compete with others, that is likely to be a question. The advantages clearly would be no dependancies on new breakthrough technologies and a manageable budget.

On the other side, reusable concepts are investigated. The first idea are semi-reusable rockets with so called Liquid Fly-Back Boosters (LFBBs) or Reusable First Stage (RFS). As the Russians explore the capabilities of Fly-Back Boosters since several years, a cooperation between Europe and Russia is considered from the start on. As these designs, mainly the Fly-Back Boosters, are somewhat conventional, the cost reduction is not for sure. In contrast, the more complex reusable technology is still a major barrier. That’s why ESA will also investigate and test technologies to reduce this complexity. For example there are already structures in evaluation and testing with embedded fiber-optic health monitoring systems.

The most advanced concepts are certainly fully reusable Two Stage to Orbit (TSTO) concepts. Especially for this kind of launchers, as also for a Reusable First Stage for a semi-reusable concept, investigation in high performance reusable engines are seen as a key objective. Up to today, only the Space Shuttle and the Energia/Buran spacecrafts used reusable engines. Both are seen as robust but also as technically demanding and relatively expensive. If SpaceX with its Merlin engine, which also should be reusable, can achieve a successful complexity and cost reduction, time will still have to tell. The potential cost reduction is surely the highest but the development costs will also be the highest. Another key objective would be the development (and maturing) of light-weight reusable stage structures with cryogenic propellant tanks. Also the second stage would need a reentry system, which would add structural mass. Additionally reentry systems showed to be complex and very labor-intensive for reuse.

Structural mass and additional operational costs for inspection and re-qualification of the system after a launch are the main difficulties to handle with reusable systems, as compared to an expendable vehicle. As the reusability adds structural mass, e.g. increasing the structural and engine robustness for withstanding several launches or adding health monitoring systems, it’s necessary to focus on materials and systems science. Inspection and particularly re-qualification of the hardware is an expensive area as this work is very labor-intensive. Also new procedures are necessary to be developed. How much of damage to a certain part is tolerable before it will be necessary to replace it? In aviation we have this expertise today, we can predict for example how a small crack will develop and when it’s necessary to replace or repair it. In the aerospace sector we nearly have no such experience yet. The clear advantage if all these challenges are mastered is a low-cost high-performance launcher system which will strengthen Europe’s future role in spaceflight.

So ESA has a lot of work to do, they have to investigate several concepts and must predict how the technologies will develop in the next 15 years. As private spaceflight stands on the swell, cooperation with not only governmental agencies but also private companies will be needed. Arianespace already took a first step by admitting interest in talks with SpaceX.

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