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The Mobile Service Platform Visitors to the Soyuz launch facility often do not suspect that a multi-floor maze is hidden below the pad's vast concrete surface. However a careful observer would notice that when the Soyuz rocket is erected onto its launch pad, the lower portion of the vehicle ends up deep below the pad. To service the business end of the rocket, a massive movable structure is located under the pad. It is known as the service cabin or the mobile service platform, but also nick-named a "balcony".
An isolated view of the Service Cabin, KO, for the Soyuz launch pad in Vostochny shown in deployed position. Credit: Roskosmos
Side view of the Service Cabin, KO, in retracted (left) and in stowed position. Credit: TsKBTM
Access bridges of the Service Cabin, KO. Credit: KBOM Following the delivery of the Soyuz rocket to the launch pad, the Service Cabin, KO (a Russian abbreviation for "Kabina Obslyzhnivaniya"), moves into position around the wide base of the rocket under the launch pad. A series of access bridges then are deployed and raised vertically with hydraulic mechanisms to form a three-level scaffolding just inches from the vehicle. The bridges provide access for the launch personnel to the first and second stage of the rocket at three levels, all located below the main concrete surface of the launch pad. Structurally, the mobile platform consists of four trusses, four pads and floor cover. Each raised level is made of four sections attached to telescopic hydraulic cylinders.
Personnel works at Level –0.6 meters of the Soyuz rocket pad in Plesetsk circa 1990. Credit: VKS (The access to a higher level just 0.6 meters below the surface of the pad is provided by a separate "service aggregate" designated 11T11.) The movable structure is used by fueling personnel to connect kerosene and liquid oxygen supply lines from the launch complex propellant storage to the multiple propellant tanks aboard the rocket. The service cabin also provides access to the lower support structures of the pad, which hold the fueled rocket at the tail. The platform's access bridges and upper levels are deployed with hydraulic cylinders and secured in place with mechanicals stops. A special hydraulic pump, driven by a dedicated electric motor and located on the main platform, feeds the hydraulic distribution system under control from a centralized console. The platform also has lighting and alarm systems. Shortly before liftoff, the access bridges of the structure are folded and it moves on rails into a large niche below the pad under a power of an electric motor. A special vertical shield protects the structure from the exhaust of the rocket at launch, while it is inside its shelter.
Evolution of the design First built in 1956, the movable service platform is common for all Soyuz pads in Baikonur, Plesetsk, Kourou and Vostochny. The original structure, designated 8U216, was developed at the TsKBTM design bureau in Moscow and manufactured at the Novo-Kramatorsk Machine-building Plant, NKMZ, in Ukraine. The factory provided the platform for a total of six R-7 pads (two in Tyuratam and four in Plesetsk). At least one back-up structure is known to be ordered in 1971 and delivered to what became Baikonur Cosmodrome in 2013. On the original platform, all access bridges formed a circular turntable, which could rotate along with other service systems to orient the rocket for a correct ascent azimuth depending on the flight direction of the ballistic flight or the orbital inclination of the upcoming mission. The rotation of the main ring was provided by four electric motors. This feature became unnecessary with the introduction of the Soyuz-2 variant, whose flight control system could perform the necessary roll maneuver in flight to attain the correct azimuth. The upgraded versions of the mobile service platform received designations 8U0216 and 8U0216M. In the 21st century, two new mobile platforms were built at Tyazhmash factory in Syzran, one for the Soyuz launch pad in French Guiana and another for Vostochny. Their hydraulic systems were controlled by electro-magnetic distributors activated by dedicated switches.
The mobile service platform in deployed position during testing at Tyazhmash factory in Syzran. |
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