12. Monitoring of Launch Platform Drift Parameters during Zenit-3SL Integrated Launch Vehicle Prelauch Processing

Annotation: Under the Sea Launch program when developer of the Zenit-3SL ILV control system issued the permission to launch in the conditions of drift from the design launch point of the Odyssey launch platform, the problem of drift parameters monitoring at the Sea Launch Commander ACS appeared. To ensure the payload orbiting accuracy the following maximum permissible values of platform drift parametres were determined: • maximum velocity of platform drift – no more than 0,32 m/s; • maximum acceleration of platform drift – no more than ±0,05 m/s2; • maximum distance of platform drift from design launch point – no more than 1950 m. The article includes the computation algorithm of the platform drift parametres to calculate velocity and acceleration of the drift, as well as distance from the design launch point to the actual point of the platform location. Geographical coordinates – latitude and longitude of the platform according to the GPS sensor, installed on the platform are used for calculations. These values during prelaunch processing of the ILV are transmitted to the assembly and command ship’s workstation for calculation of loads in the ILV root section at the rate of once in a second. During one of the Sea Launch missions, C++ program was developed and installed on the loads calculation workstation, realizing the computation algorithm offered by the authors of this article. This program displayed in real time the monitored parametres of the platform drift, and monitored the tolerable limits. During the same mission, the correctness of the developed algorithm and program were confirmed during the special experiment on the launch platform drift in the launch point. In future, they were used during the subsequent missions of the Sea Launch program.