Mid-September is the deadline for what may be regarded as the most important launch in the history of the European space programme - the Ariane 502. If the second European Space Agency (ESA) development flight of the Ariane 5 satellite launcher is successful, the $366 million loss of the 501 in June 1996 will be seen as merely an unfortunate hiccup. If it fails, then the 502 could well be regarded as "not only a catastrophe for the space-transportation industry but for the European space industry as well", says one leading space executive.

The reliability of the Ariane 4 launcher, operated commercially by Arianespace, is 96%, and the predicted design reliability of the Ariane 5 - because it was originally conceived as a manned launcher - is 98%, or one failure in 78 launches.

As it has already had one failure, the pressure is on to make sure that the Ariane 502 is successful. At the Centre Spatial Guyanais (CSG) at Kourou in French Guiana, however, the 502 is not being viewed in such a dramatic perspective. The launch date, for example, which has already slipped from April and which may be put back to November, is not seen as being as critical as the overall success of the mission.


Ariane 4 continuity

In addition, most of the satellites in the Arianespace orderbook can be launched by Ariane 4 boosters, which will now continue in service until 2000. A total of 16 Ariane 5s has been ordered, including two vehicles for the originally planned two-flight ESA demonstration programme. The remaining orders are for Arianespace. One will be the 503 vehicle, which has been sold to ESA for use as the third development flight, but which will also carry a commercial satellite from Arianespace's existing manifest, at a discounted launch price. An order for 50 Ariane 5s, expected to be confirmed if the 502 is successful, will ensure launch capability until about 2005, with a flight rate of eight a year.

The Ariane 5's timing is not yet critical, but further delays to the 503, scheduled for March 1998, and the first fully commercial Ariane 5 flight later the same year, will pile on the pressure. Both launches are already two years behind the original schedule, and extension of the Ariane 4/5 transition period will cost Arianespace at least $200 million, bringing the total cost of the change-over to $1 billion (Flight International, 9-15 April).

Ariane 5-specific payloads could also be threatened, including ESA's plans to launch the Envisat, the X-ray multi-mission telescope, and to provide the International Space Station with logistical support provided by the automatic transfer vehicle.

The launch programme for the 502 will begin in earnest in mid-June, when the first stage, upper stage, the vehicle equipment bay and the payload fairing arrive in containers at Kourou aboard the ship, the Toucan. "It all starts when we open the box," says Julio Monreal, Ariane range-operations director for French space agency CNES, which manages the CSG and its launches. The 502's solid-rocket boosters are already assembled.

The launch of the 502 "-will seem a very nervous event for people outside, but, for the team, it will be a special moment. All the problems will be behind us," says Arianespace's Charles Bruyer, chief of 502 launch operations, who is also working for CNES, the French space agency. The team has been making sure that there are no problems to the guidance system similar to those which caused the 501 crash, says Bruyer.

The objective of the Ariane 502 flight is to demonstrate the primary dual-satellite geostationary-transfer-orbit (GTO) capability of the Ariane 5 fleet, which could not be qualified by the 501. This means that the atmospheric-re-entry demonstrator, originally scheduled to be carried on the 502, has been delayed to the 503.


502 launches

The spacecraft which will be placed in orbit by the 502 as part of the payload-experiments APEX configuration are the Amsat P3D radio-amateur satellite and the Team spacecraft. The Amsat, mounted in the lower section within a Speltra container, weighs 550kg, and is attached to a lower satellite mock-up craft, with a total weight of 1,800kg. The Amsat has its own small engine, which will be used to boost it into a final 4,000 x 50,000km elliptical orbit.

The 350kg Team, mounted beneath the 2,000kg upper-satellite mock-up, is composed of five experiments proposed by different European universities, including a satellite experiment to study the behaviour and controllability of a tether system. It consists of 120kg and 20kg sub-satellites, linked by a 20km tether to be deployed after launch.

The Maqsat B and Maqsat H technology payloads, respectively, will measure the dynamics within different parts of the payload shroud during lift-off and the period of maximum dynamic pressure on the vehicle.

Once Arianespace is up and running with the Ariane 5, serious consideration will be given to the full development of proposed uprated versions. One of these is already in the pipeline: the ESA-funded Vulcain Mk2 cryogenic first-stage engine, to increase thrust from 100t to 130t. The first prototype of the liquid-oxygen turbopump of the Vulcain Mk 2 is being built. The first flight of this new Ariane 5 model is possible in 2003 - a delay of two years, caused by the 501 accident and the need to divert $400 million of Mk2 funds to the recovery programme.

Also continuing are other reviews of potential upgraded vehicles to meet projected market needs by Arianespace, including a model with a high-energy upper stage. This vehicle, which will be funded by Arianespace, could fly in 2000, increasing GTO performance to 7,400kg.

Source: Flight International