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Ariane 5: Europe's heavy lifter

Ariane 5: Europe's heavy lifter

Who owns space? The Europeans do, or so they claim... Russia, America, China, and others go into space largely for defense or national prestige. But with two-thirds of the world's commercial space-launch business, Europe has quietly taken over as the leader in making space flight pay.

Underscoring its preeminence, the European Space Agency (ESA) will soon launch the first all-new, heavy-lift rocket since the Space Shuttle. The Ariane 5 promises a range of orbits, payload configurations, and reliability currently unmatched by any other booster.

If the future isn't what it used to be--no pinwheel space stations and single-stage-to-orbit aerospace planes--then the Ariane 5 represents the future that is. It will haul 39,000-lb, 15-ft-diameter payloads to low-earth-orbit or push three or more individual satellites of 12,000 lbs total weight to geosynchronous transfer orbit. Judging by experience, this is region in space where new generations of direct-satellite communications, earth-observation satellites, and fledgling space manufacturing will get their start.

Born amid promise. The Ariane 5 project began with the Long-Term Space Plan adopted at a meeting of European Space Ministers in Rome in 1985. The agreement called for the development of a winged, reusable space plane dubbed Hermes, an orbiting laboratory called Columbus, and a new heavy lifter to get them off the ground. Recession and technical uncertainty killed the space plane. Columbus' fate remains tied to the multinational space-station project. Only the new rocket came to be.

Given its original intent, Ariane 5 had to depart from the step-by-step approach taken in the development of earlier Arianes. Arianes 1 through 4 were, in a sense, classic designs with stacked cryogenic and hypergolic stages and a variety of strap-on boosters to increase lift capability. Their in-service reliability was good--over 95%, but not good enough to be called man-rated. Moreover, the desired jump in lifting capacity and payload size with a requisite 10% lower cost-per-lb-lifted precluded merely scaling up the existing blueprints.

"A great effort was made to gain reliability compatible with manned flights," says Juan de Dalmau, an Ariane ground facilities engineer with ESA in Paris. The most powerful Ariane 4 has 10 liquid-fueled engines, compared with only four engines on any Ariane 5. "This gives us more reliability and less cost," he explains.

Cost may seem a delicate issue to bring up in the context of a machine built to carry people into space, especially in light of the Challenger disaster. But over its development, cost became a critical matter to Ariane 5's designers. Funds for the program came from ESA's 12 member nations and were disbursed through the prime contractor, the French space agency CNES. As the European recession of the late '80s came on, money spent on development work became increasingly hard to justify. The program went ahead, but with a new constraint called "Design to Cost."

As opposed to a fixed-profit, cost-plus contract, Design to Cost required detailed planning up-front. Contractors, with oversight from CNES, established target costs based on program and market conditions, then worked to keep development costs below the target figure. "It certainly leads to a conservative approach when choosing technologies," says de Dalmau, "but it also allowed us to start with a full funding commitment from ESA's member states." The conservative design philosophy resulted in an expected 98.5 % reliability rating; solid funding allowed the consortium to plan for more-powerful Ariane 5 derivatives in the future.

New architecture. At first glance, the Ariane 5 resembles the Space Shuttle, minus the orbiter. Shorter and wider than previous Arianes, it comprises a lower "composite" that features a main cryogenic stage (known by the French acronym EPC) and two large solid-fueled boosters (EAP), and an upper composite that houses the payload, guidance and control bay, and the hypergolic third stage (EPS). The completed assembly stands some 167 ft high, with an overall launch weight of more than 1.6 million lbs.

The countdown to launch follows a relatively brisk 22-day assembly and check-out sequence. Part of the six-billion European-Currency-Unit ($6.28 billion U.S.) cost of the Ariane 5 project went toward construction of new facilities at ESA's Kourou, French Guiana launch complex. The new infrastructure can prepare two launchers simultaneously and fire the new rocket as often as 10 times per year. Included were liquid oxygen and liquid hydrogen production facilities that can produce 33 m3 of liquid hydrogen (LH) and 14 m3 of LOX or liquid oxygen (8,700 and 3,700 gal, respectively) per day. Also included was an on-site plant that can produce between 32 and 40 middle and aft segments for the solid-propellant boosters.

Launch of an Ariane 5 begins by starting the cryogenic "Vulcain" main engine. Designed by Soci't' Europe'nne de Propulsion (SEP), Suresnes, France, the Vulcain uses a gas-generator cycle. In other words, the engine is fed oxygen and hydrogen by dual turbopumps, themselves powered by LOX and LH bled from the fuel tanks and ignited in a separate combustion chamber.

LH and LOX, routed though 516 injection elements in the rocket's combustion chamber, are electrically ignited and produce a throat pressure of 1,600 psi at 5,800F. Liquid hydrogen, routed through the combustion chamber and nozzle walls prior to burning, keeps the structures from melting during the engine's 576-second nominal burn time. According to SEP documents, the cycle provides a reasonable performance level, while ensuring higher reliability and lower costs.

Producing about 180,000 lbs of thrust at sea level (256,000-lbs vacuum), Vulcain is the most powerful rocket engine Europe has produced. Nevertheless, once started and up-checked by controllers, it's instantly eclipsed by the ignition of the twin EAP solid-fueled boosters.

Rated at nearly 1.5 million lbs thrust each, the solids provide more than 90% of Ariane 5's initial lift capacity. Although smaller than the Space Shuttle boosters, they're still the most powerful rockets of any kind developed in Europe. The solid's bottom two sections are filled on-site in South America, with the casing segments, carbon-carbon composite nozzle and gimbal system, and the specially formed, topmost solid-propellant segment brought in from Europe. As a unit, they burn though their million lbs of polybutadiene, ammonium perchlorate, and aluminum propellant in just over two minutes, lofting the "stack" over 37 miles high before being jettisoned to be recovered at sea.

Multinational cooperation. During ascent and orbital insertion, trajectory and attitude control are maintained by computers backed by ring-laser gyros and hydrazine-fueled thrusters housed in the vehicle equipment bay (VEB) in the upper composite structure. Manufactured by Matra Marconi Space, Toulouse, France, the bay is assembled with a Spanish carbon-fiber chassis, Swedish computers, Belgian pyrotechnic controls, and batteries and attitude-reference equipment from France, Italy, Scotland, and Germany.

According to Francois Lopez, an integration engineer with Matra, the Ariane 5's VEB uses a digital data bus for communication. Although its increased diameter and possible man-rating called for complete redundancy in electronics, the data bus architecture reduces the weight of wiring compared to the parallel-communications of earlier Ariane VEBs.

Continuing the launch sequence, the Vulcain engine burns out at just under T+10 minutes at an altitude of 87 miles. Pyrotechnics jettison the German-made aerodynamic fairing covering the payload, then detach the lower composite from the nitrogen tetroxide-hydrazine-fueled upper composite. Depending on the payload and the orbit desired, the upper composite stack can then burn to create a highly elliptical geostationary transfer orbit, a heliocentric orbit, or any of several circular orbits around the earth.

All options are available for loading into the VEB computers prior to launch. With captive boosters, three or more separate satellites borne by a single Ariane 5 can have their pick of orbital slots.

Emerging market. The Ariane 5 debuts in a burgeoning commercial launch market. According to the Wall Street Journal, as many as 350 satellites, delivering world-wide paging, digital radio, telephone, and video transmission, are expected to be launched in the next five years. Given successful test flights and a hand-over to commercial-launch vendor Arianespace early next year, the short-term prospects for the newest heavy lifter seem bright.

Nevertheless, the end of the Cold War has brought forth a number of challengers to Ariane's preeminence. American missile manufacturers are working with Russian rocket-engine designers to create new, lower-cost chimeric launchers. Boeing has a project underway to launch Russian Zenit heavy-lift rockets from a floating platform in the North Sea.

Since most commercial satellites have a life expectancy of 10 years, the current feast of launch candidates may turn into a famine in the year 2005 or so. Increased competition and market vagaries make the Ariane 5's payoff less certain than its predecessors'. Still, Arianespace launches incur the lowest loss-insurance costs of any competitor in the business. And, according to ESA's de Dalmau, "The Ariane project has had many spin-offs in Quality Assurance and Configuration Management fields." For the Europeans, owning space means growing on Earth.

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