Roscosmos announced the preliminary results of the commission investigating the causes of the crash of the Luna-25 interplanetary station on August 19.
On that day, during an attempted landing, the station experienced an error in the operation of the correction engine: instead of 84 seconds, it ran for 127 seconds. Therefore, "Luna-25" did not switch from a circular orbit to a landing elliptical orbit in time and collided with the lunar surface.
The failure of the correction engine was called by the General Director of Roscosmos, Yuri Borisov, as one of the preliminary causes of the crash in the immediate aftermath of the disaster.
But now, Roscosmos has named the new domestic angular rate measurement unit "Bius-L," which is part of the station's onboard control system, as the "most likely cause of the accident."
The device was designed at the Scientific Production Center of Automation and Instrument Engineering named after Academician N. A. Pilyugin (NPCAAP) from completely Russian components.
It was responsible for determining the station's orientation in space and its speed. Shortly before landing, the "Bius-L" accelerometer units failed to operate due to possible "entry into one data array of commands with different priorities for their execution by the device."
At the same time, the distribution of commands in data arrays is random (probabilistic) in nature. In this regard, zero signals from the accelerometers of the "Bius-L" device were coming to the onboard control system. This did not allow to record the moment of reaching the required speed when issuing a corrective impulse and to timely turn off the propulsion system of the spacecraft, as a result of which it was turned off according to the time setting.
Information that the cause of the station's crash lies in "Bius-L" appeared long before the end of the official investigation. According to a version voiced to journalists unofficially, the device was not tested in space before the mission, although it was considered a development for conquering the Moon.
There is no official announcement yet that "Bius-L" will be excluded from the equipment of the following Russian interplanetary stations. But Roscosmos notes that, based on the results of the investigation, they have already formed recommendations for conducting "additional measures" for subsequent lunar missions.
According to experts, repeating the "Luna-25" mission will cost Russia 5 billion rubles. Before the crash, the launch of the following stations was planned for 2027, 2028 and 2030.