Ariane 5

The Ariane 5 is an expendable launch system, designed and manufactured under the authority of the European Space Agency (ESA) by EADS SPACE Transportation, the Prime Contractor, leading a consortium of many sub-contractors and is operated and marketed by Arianespace as part of the Ariane programme. EADS SPACE Transportation builds the rockets in Europe and Arianespace launches them from a space port at Kourou in French Guiana.

It succeeds the Ariane 4, but it does not directly derive from it. Its development took 10 years and cost EUR 7 billion. The ESA originally designed Ariane 5 to launch the manned mini shuttle Hermes too, and thus intended it to be "human rated" from the beginning. After the ESA cancelled Hermes the rocket became a purely commercial launcher.

The main use of Ariane 5 is for delivering satellites into Geostationary transfer orbit.

Components

Ariane 5’s cryogenic H158 main stage (H173 in the case of Ariane 5 ECA) is called the EPC from the French, Étage Principal Cryotechnique. It consists of a large tank with two compartments: one for liquid oxygen and one for liquid hydrogen, with at the base the Vulcain engine.

Attached to the sides are two solid propellant boosters, P238 (P241 for Ariane 5 ECA).

The second stage is on top of the main stage and below the payload.

Variants

The original version is dubbed Ariane 5 G, for "generic". Its payload capability to Geostationary transfer orbit (GTO) was initially specified as 5970 kg, but was increased after the qualification flights to 6200 kg.

The Ariane 5 G+ has an improved second stage, with a GTO capacity of 6950 kg for a single payload. It flew three times in 2004 and will be replaced by the Ariane 5 GS.

The Ariane 5 ECA is a more powerful variant, with a GTO launch capacity of 10,000 kg for dual payloads or 10,500 kg for a single payload. This variant uses an ESC-A second stage, powered by an HM-7B engine, weighing 6,500 kg and carrying 14,000 kg of cryogenic propellant and previously used as the third stage of the Ariane 4, and a new Vulcain 2 first stage engine.

It must be noted that the ESC-A cryogenic second stage does not improve the performance to Low Earth orbit, with respect to Ariane 5 G, and that for this reason the Ariane 5 ECA will not be used to launch the ATV.

Future developments

The Ariane 5 ES ATV has been designed for launching the Automated Transfer Vehicle. It consists of the improved Vulcain 2 powered first stage and the upper stage from the Ariane 5 G.

The Ariane 5 ECB was planned to have a ESC-B upper stage using a new engine "Vinci", an expander cycle type engine which is to increase the GTO capacity to 12,000 kg, but it was put on hold indefinitely due to budget cuts.

Launch history

Ariane 5's first test flight (Ariane 5 Flight 501) on June 4, 1996 failed, with the rocket self-destructing 40 seconds after launch because of a malfunction in the control software, which was arguably one of the most expensive computer bugs in history. A data conversion from 64-bit floating point to 16-bit signed integer value had caused a processor trap (operand error). The floating point number had a value too large to be represented by a 16-bit signed integer. Efficiency considerations had led to the disabling of the software handler (in Ada code) for this trap, although other conversions of comparable variables in the code remained protected.

The second test flight, L502 on October 30, 1997 was a partial failure, with a roll problem causing premature shutdown of the core stage. The upper stage operated successfully but could not reach the intended orbit.

A subsequent test flight on October 21, 1998 proved successful and the first commercial launch occurred on December 10, 1999 with the launch of the XMM-Newton X-ray observatory satellite.

Another partial failure occurred on July 12, 2001, with the delivery of two satellites into an incorrect orbit, only half the height of the intended GTO. The ESA Artemis telecommunications satellite was able to reach its intended orbit on 31 January 2003, through the use of its experimental ion propulsion system.

The following launch did not occur until March 1, 2002, when the Envisat environmental satellite successfully reached an orbit 800 km above the Earth in the 11th launch. This was the rocket's heaviest payload to date at 8500 kg.

Ariane 5 lifts off with the Rosetta probe on 2nd of March, 2004.

The first launch of the ECA variant on December 11, 2002 ended in failure when a main booster problem caused the rocket to veer off-course, forcing its self-destruction three minutes into the flight. Its payload of two communications satellites (Stentor and Hot Bird 7) valued at about EUR 630 million was lost in the ocean. The fault was determined to have been caused by a leak in coolant pipes allowing the tail nozzle to overheat. After this failure, Arianespace delayed the expected January 2003 launch for the Rosetta mission to February 26, 2004, but this was again delayed to early March, 2004 due to a minor fault in the foam that protects the cryogenic tanks on the Ariane 5.

On September 27 2003 the last Ariane 5 G boosted three satellites (including the first European lunar probe, SMART-1) in Flight 162. On July 18 2004 an Ariane 5 G+ boosted the heaviest telecommunication satellite ever, Anik F2, weighting almost 6,000 kg.

The first successful launch of the Ariane 5 ECA took place on February 12 2005. The payloads were the XTAR-EUR military communications satellite, a small scientific satellite 'SLOSHSAT' and a payload simulator MaqSat B2. The launch had been originally scheduled for October 2004, but additional testing and the military requiring a launch at that time (for an Helios 2A observation satellite) delayed the attempt.

Ariane 5 flights

Upcoming flight

The next flight, V-166 was first foreseen on April 14, 2005 with the payloads Syracuse 3A and Telkom 2. In early March 2005, this launch target was abandoned, with a flight date now to be confirmed but expected in May-June. This will be the first flight of Ariane 5 GS, which shares the same improved P241 solid rocket boosters as the Ariane 5 ECA.

External links and references

• ESA description of the Ariane 5
• Ariane 5 technical notes, available as PDF from http://www.arianespace.com