ESA Science & Technology - Launch Vehicle

Cutaway diagram of Soyuz-Fregat launch vehicle. Image courtesy of Starsem

The Soyuz rocket was first launched in November 1963 and has since flown more than 1500 times. It is one of the most reliable launch vehicles, with a 98% success rate. The Soyuz rocket usually comprises three stages:

• stage 1: four conical boosters grouped around the central core stage;
• stage 2: a cylindrical core;
• stage 3: an upper stage with a payload adapter and fairings;
• and for very demanding payloads, a fourth stage is added.

For Mars Express the Fregat fourth stage was used, but other, smaller stages are also available − for instance, Starsem uses IKAR stages for Globalstar launches.

The four side boosters and the core (first) stage ignite at the same time before liftoff, but the lateral boosters shut down and separate first. After the first stage has used all its fuel, it separates and the second stage continues to burn. All three stages use liquid oxygen and kerosene fuel.

The main engine on the fourth stage, the Fregat, was ignited twice for Mars Express. The first ignition put the Fregat into a circular orbit after separation from Soyuz. The second, a few hours later, injected Mars Express into its interplanetary flight trajectory. The Fregat uses UDMH and nitrogen tetroxide as fuel and is capable of up to 12 restarts. Mars Express required the Fregat as it can accommodate a larger fairing (3.7 m diameter) than the other fourth stages available for Soyuz. The resultant higher aerodynamic forces during liftoff required the rocket's inter-tank section to be strengthened.

The third stage of Soyuz also carried a flight control system, slightly modified to match the larger Fregat fairing. The separation system was the standard Ariane version procured from Saab.

Soyuz facts

• liftoff weight: 304 tonnes
• (of which) propellant weight: 279.5 tonnes
• height: 43.5 m
• maximum diameter: 10.3 m
• thrust (in vacuum):
  • 1st stage: 4964 kN
  • 2nd stage: 997 kN
  • 3rd stage: 298 kN
  • 4th stage: (Fregat) 19.6 kN
• payload capability (to 400 km): up to 6 tonnes

Baikonur Cosmodrome

Baikonur Cosmodrome is located at 45.6^oN 63.4^oE in the flat grasslands of the former Soviet republic of Kazakhstan. The area has a continental climate, with long, cold winters and hot, dry summers. Construction of the secret missile site began in 1955. The first artificial satellite, Sputnik 1, and first human in space, Yuri Gagarin, were launched from Baikonur. All subsequent Russian manned missions have lifted off from there, as well as geostationary, lunar, planetary, and many ocean surveillance missions.

Until recently, the name Baikonur was misleading. The former Soviet Union used the name and co-ordinates of a small mining town, Baikonur, to describe its secret rocket complex. This was done intentionally to hide the true location of the launch complex. In fact, the launch complex is about 230 miles south-west of Baikonur town, near the railway station and village of Tyuratam and close to Leninsk city. However, in 1998, Leninsk city was renamed Baikonur city.

The Mars Express spacecraft was delivered to the cosmodrome by air in March 2003. It was then housed in a cleanroom and integrated with the Fregat stage inside a modern payload processing facility. The strap-on boosters and stages of the Soyuz booster were assembled horizontally in the large Vehicle Assembly Building. The entire launch vehicle, with its payload, was then transported by rail to the launch pad, where it was vertically erected over a large flame deflector pit.

The Fregat upper stage

Flight qualified in 2000, the Fregat upper stage is an autonomous and flexible upper stage that is designed to operate as an orbital vehicle. It extends the capability of the lower three stages of the Soyuz vehicle to provide access to a full range of orbits (MEO, SSO, GTO, escape). In order to provide the Fregat with high initial reliability and to speed up the development process, several flight-proven subsystems and components from previous spacecraft and rockets are incorporated into the upper stage.

The upper stage consists of 6 spherical tanks (4 for propellant, 2 for avionics) arrayed in a circle, with trusses passing through the tanks to provide structural support. The stage is independent from the lower three stages, having its own guidance, navigation, control, tracking, and telemetry systems.

The stage uses storable propellants (UDMH/NTO) and can be restarted up to 20 times in flight, thus enabling it to carry out complex mission profiles. It can provide the customer with 3-axis stabilization or spin-up of their spacecraft.

• diameter: 3.35 m
• height: 1.5 m
• liftoff weight: 6415 kg
• (of which) propellant weight: 5350 kg
• propellant:
  - fuel Unsymmetrical dimethyl-hydrazine (UDMH)
  - oxidizer Nitrogen tetroxide
• main engine thrust: 19 620 N
• main engine specific impulse: 328s

NPO Lavotchkin (Lavotchkin Research and Production Association) was founded in 1937 as an aircraft manufacturer. It later became one of the leading Soviet design bureaux for planetary exploration, participating in the Luna, Venera, Vega and Mars programmes. The centre has extensive experience in building rocket upper stages.