The previous blog entries have given an overview of the activities of the last few weeks: from the arrival of the spacecraft in Kourou to the successful test of the Launch and Acquisition Mode (LAM) – the initial operational mode of the spacecraft during and after launch up to the contact with the ground stations.
Another recent activity was the inspection of the Soyuz facilities and especially the VS06 rocket (Soyuz Flight number 6), which will now launch Gaia, after the switch with the O3B project.
The first thing that catches your eye is a depot with 40 massive containers that are shipped from St. Petersburg by boat. The Soyuz facility stores up to four launchers at the time and ten are required for a single launch.
When entering the MIK (the Soyuz integration and test facility), the cool dry air replaces the sweltering tropical heat outside: from a very humid 32oC to a welcoming 20oC. As the next door opens, what lies ahead is a hangar filled with the different stages of the Soyuz-Fregat. Commanding attention on the left side is the second stage with the four integrated first stage boosters. Meanwhile, the smaller third stage and the Fregat upper stage sit on the right.
To give an impression of its size: the fully integrated launcher is 46 m tall and more than 8 m wide, with a dry mass of around 25 tons. Once fully loaded, the launch mass will be well in excess of 300 tons. Knowing this is the actual Soyuz that will propel Gaia towards L2 at the speed of more than 8 km/s after 10 years of development makes it even more remarkable.
The propellant of the main engines is a mixture of liquid oxygen and kerosene, which is a relatively safe combination. However, the engines’ turbopump system and the Fregat upper stage use highly concentrated hydrogen peroxide, which is very corrosive (a few drops would burn right through your hand). Hence, fuelling is a delicate process in a special facility with operators in full body suits, which wouldn’t look out of place on a spacewalk!
Once the Fregat is loaded with propellant, it will be mated with the payload and the fairing. The other stages of the launcher are integrated in the MIK and are transported by rail towards the launch pad (or ELS), which is about 600 m away. There it will be placed upright and suspended above the launch pad with four booms, which will open up like petals once the engines generate enough thrust after ignition.
A lift that is fitted on the launch tower brings you to the platform at a height of 45 m where the upper composite (Fregat, spacecraft and fairing) will be placed onto the third stage. This is also where the umbilical will be connected to provide power and telemetry to the launcher and spacecraft. The tower also protects against thunderstorms that frequently occur in Kourou. The entire building is rolled away shortly before launch, avoiding the engine’s exhaust plumes.
The launch pad does not only consist of the visible gantry but also of a vast array of tunnels and control rooms underground, beneath the platform, housing all the required systems supplying the launcher with propellant, electricity, communications, etc. Walking through this labyrinth truly makes you appreciate the complexity of the platform.
Completing the Soyuz-Fregat requires meticulous preparations and rigorous testing to be ready on the appointed date. Thus in a bid against time, two teams are working non-stop to prepare both Gaia and the launcher for the big day: the 20th of November 2013.
This entry was submitted by Alessandro Atzei, Gaia spacecraft System Engineer, reporting from Kourou.