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IN FOCUS: Europe's next rocket has high hurdles to clear

Despite no real surprises emerging from the 20-21 November meeting in Naples of European Space Agency member states - who agreed funds for ESA to essentially carry on as planned until 2017 - three of the programmes green-lighted are likely to redefine Europe's standing in spaceflight.

The highest stakes probably ride on the most visible programme of all, the Ariane launcher family. By formally authorising ESA to draw up detailed plans for a new generation of Ariane, subject to an effective preliminary design review when they meet again in Switzerland in 2014, ministers have recognised that, for all its strengths, Ariane 5 is due for replacement.

If Ariane 6 - a modular concept that will abandon proven liquid-propellant stages for solid rocket segments - turns out to be cheaper and faster to build and launch than Ariane 5, while maintaining its reliability and precision, then ESA will have ensured Europe's place as a leading spacefaring region. If not, it may be overtaken by a new generation of private sector - principally US - launch contenders, notably SpaceX with its Falcon 9 heavylifters.

The stakes are high. SpaceX founder Elon Musk, speaking in London a few days before the Naples conclave, declared: "Any variant of Ariane 5 is not going to be able to compete with Falcon."

When reminded of this quote, ESA director general Jean-Jacques Dordain wondered if Musk, whose Falcon 9 has only flown once, with partial success, might wish to contribute to Ariane 6? However, Dordain stressed in all seriousness that ESA's customers have made their expectations for the new launcher "very clear".

Ariane rockets have orbited more than half of the globe's communications satellites and Ariane 5 has chalked up 52 consecutive successful flights. Ariane 6 will thus be following one of the world's most reliable launchers. And it must be readily available to orbit individual payloads of 3-3.5t up to 6-6.5t while being cheaper than the Proton and Falcon 9 rockets in that payload range.

Underscoring the challenge ahead, ESA plans to develop Ariane 6 to fly from 2021 while finishing the so-called Ariane 5 ME, or Midlife Extension, for flight from 2017. ME is planned to increase Ariane 5's payload by a fifth, to 12t - giving it the ability to orbit two full-sized communications satellites - without increasing costs. The two projects are expected to share a new, restartable upper stage, which will improve Ariane 5's ability to place multiple payloads in precise orbits; Dordain will seek further commonalities as he pushes towards preliminary design review in 2014.

Antonio Fabrizi, ESA director of launchers, says the restartable Vinci engine would be the "common brick" between the two vehicles. However, he stresses that the so-called "PPH" architecture of Ariane 6 would represent a break from the cryogenic liquid main stages technology that underpins Ariane 5.

With solid fuel main stages and a liquid, restartable upper stage, Ariane 6 will bear more resemblance to Vega, ESA's small launcher which made its maiden flight in February. And, Fabrizi adds, ESA will search for commonalities between Vega's evolution and evolutions of Ariane 6.

The decision to co-develop the ME and 6 rockets was frequently referred to in Naples as a compromise, but that typically pejorative term may be inappropriate. As one ESA insider put it, even if all the resources going into the ME were put toward Ariane 6, the next-generation rocket could not realistically be ready any sooner - although given that preparatory work has begun, 2021 is realistic.

And, ESA adds, the upper stage is the important one when it comes to precise payload placement, so pushing that part of the project and sharing it between the two programmes makes sense.

However, he adds, new-generation satellites have their own electric propulsion systems, so they can push themselves to a final, precise orbit with little fuel. So the key to Ariane 6 is to lower costs and cut launch lead times by creating a modular system of solid fuel components that can be built in reasonable volume and stored for assembly in flexible configurations to meet the wide range of mission requirements.

Ariane 5, he notes, is reliable and precise - but not flexible. Each rocket must be custom-built to match its specific performance to the demands of a particular payload. This is relatively slow, and expensive. The smaller Ariane 4 was more flexible, but also very expensive to produce.

MANNED FLIGHT

ESA will also make its first foray into manned spaceflight vehicles by building on technologies underpinning its Automated Transfer Vehicle, the fully robotic resupply ship that has been bearing much of the load to the International Space Station formerly delivered by the now-retired Space Shuttle. The service module ESA will develop for NASA's Orion Multi-Purpose Crew Vehicle will have to be ready to fly in 2017 and, as Dordain likes to note, if international plans come to fruition it will ultimately venture as far as the Moon.

A promising strand of ESA research into re-entry technology is also worth keeping an eye on. The ministerial conference approved a continuation of work on the Intermediate Experimental Vehicle, or IXV, which is intended to pave the way for a small, reusable unmanned spaceplane. The IXV is completing a series of descent and landing tests, and ESA has a splashdown trial penned in for early 2013.

In 2014, if all goes well, the plan is to launch on a suborbital trajectory via the Vega rocket from Kourou, French Guiana, to qualify IXV's low-Earth orbit re-entry technologies, including hypersonic flight. The flight will end with a parachute-assisted Pacific Ocean splashdown.

Vehicles developed from the IXV programme might be geared to space transportation and servicing of orbiting infrastructure.

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