Ariane-501 Launch Campaign

A. González, E. Lefort, J. Gigou & P. Sartini

This article was written as the 501 launch campaign was in full swing, just before the launcher chronology review, while all concerned worked hard to prevent the smallest glitch that might postpone the launch. Reading this with hindsight leaves a wistful feeling for these efforts that were not rewarded by a success.

The Ariane-501 launch campaign began on 4 March 1996. This campaign would last longer than the nominal one whose normal duration was 23 days, due to the fact that some activities were performed for the first time with new flight elements and additional testing. The launch was planned for the end of May 1996.

The campaign can be divided into three main parts. The first one starts with the building up of launcher elements: the cryogenic stage, the vehicle equipment bay, the upper stage and the twin boosters on the launch table. It ends with the launcher chronology review. The main activities of this phase are performed at the launcher integration building (BIL, from the French: Bâtiment d'Intégration Lanceur). The second part comprises the combined operations between the launcher and the Cluster satellites at the final assembly building (BAF: Bâtiment d'Assemblage Final). The last activities take place at the launch pad (ZL: Zone de Lancement) where the final check-out is performed before lift-off.

Building up the launcher

The first part of the campaign is performed at the BIL (Fig.1). This building is the meeting point where the twin boosters coming from their integration building encounter the cryogenic stage, the vehicle equipment bay and the upper stage.

Fig. 1. The Launcher Integration Building (BIL) (photo CSG for ESA/CNES)

These last three launcher elements enter the BIL storage hall in their containers and the following set of operations is performed:

• removal of the main stage from its container;

• erection of this stage from the horizontal transport position to the vertical assembly attitude,

• installation in the integration hall with holding arms to keep the stage in a precise position (Fig.2);

Fig. 2. The cryogenic core stage in upright position (photo CSG for ESA/CNES)

• removal of the vehicle equipment bay from its container, hoisting and integrating it on the upper skirt of the cryogenic stage;

• removal of the upper stage from its container (Fig.3), hoisting of the stage and installation on the equipment bay.

Fig. 3. The third stage being removed from its crate (photo CSG for ESA/CNES)

The boosters are integrated and equipped in a special building located a few kilometers from the BIL after being individually rolled there in their pallets (Fig.4). When inside the BIL, the boosters are placed on the mobile launch platform and the main body is attached to them by the forward and rear links.

Fig. 4. A booster leaves its assembly building (photo CSG for ESA/CNES)

Afterwards, the following operations are performed:

• electrical, pneumatic and hydraulic connections,

• leak-tightness testing of fluidic circuits,

• pre-pressurisation of the hydraulic and high-pressure vessels,

• pressurisation of the cryogenic stage tanks.

There are two main milestones in this phase. The first one concerns the overall electrical check-out, where all the electrical functions will be tested following the chronology and flight sequence. The second milestone is the launcher chronology review for which the launcher will be rolled from the BIL to the launch zone (Fig.5). This activity includes the filling of the cryogenic tanks with liquid oxygen and hydrogen, the rehearsal of four chronological sequences, and an emergency cryogenic liquid draining.

Fig. 5. Launcher chronology review: Ariane-5 being rolled from the BIL to the Launch Zone (photo CSG for ESA/CNES)

After completing this review, the launcher is returned to the BIL in order to finalise some operations and it is then rolled to the BAF.

Combined A501/Cluster operations

The activities in the BAF begin in parallel to the ones in the BIL and concern the preparation and check-out of the upper structures: SPELTRA (multiple-launch structure), fairing and adapters for the launcher side and the Cluster satellites for the payload side.

When the launcher arrives at the BAF, the combined operations between the launcher and the payload can begin.

The activities in the encapsulation hall are the following:

• mating of the upper and lower Cluster stacks onto their adapters,

• mating of the Cluster upper stack onto the SPELTRA and closing the upper composite with the fairing.

In parallel, the launcher will be controlled and prepared to receive the payload in the integration hall as follows:

• the lower payload will be bolted to the EPS,

• the upper composite will be mated with the launcher at the upper interface of the vehicle equipment bay,

• finalising the mechanical assembly of the Ariane-501.

The remaining activities will include:

• installation of the flight batteries on the stages,

• payload checks and final inspections,

• loading the propellant of the upper stage and attitude control system,

• dry run of the general launch countdown,

• satellite and launcher arming,

• final pressurisation of all hydraulic and pressure vessels.

The rollout of the launcher to the launch zone ends this part of the campaign (Figs. 6 and 7).

Fig. 6. The launcher leaves the Final Assembly Building (BAF) (photo CSG for ESA/CNES)

Fig. 7. The launcher on its way to the launch pad (photo CSG for ESA/CNES)

Ariane-501 launch
The last operations before launch are performed at the launch zone by remote control (Fig.8). Their number has been limited so as to minimise the vulnerability of the launcher and of the launch area. The main activities are:

Fig. 8. Ariane-5 on the launch pad (photo CSG for ESA/CNES)

• remote controlled operations including purging, filling up and pressurising of the cryogenic stage with liquid hydrogen and oxygen; activation and last checks of the electrical system;

• synchronised sequence starting seven minutes before launch; final tasks performed by the on-board computer including the ignition of the Vulcain engine, verification of its functioning and ignition of the boosters;

• and liftoff of A501 with the four Cluster satellites on board, starting the flight part of the launch campaign. Approximately half an hour later, the separation and positioning of the spacecraft will achieve the main goal of the mission. In parallel, the main stage re-entry will be monitored from Clipperton Island and the boosters will be recovered.

The post-launch review meeting will allow a preliminary analysis of the launcher behaviour and performance ending the nearly three months of campaign effort.