Progressin Siperian mahalaskun syyt alkavat tarkentua.

Sojuz-U / Progress mahalaskun syy liittyy todennäköisesti 3. vaiheen RD-0110 moottorin kaasugeneraattorin toimintaan.

RD-0110

1 - Heat Exchange Unit
2 - Flow Control Valve
3 - Turbopump
4 - Ignitor
5 - Hot Gas Generator
6 - Stabilizer
7 - Fuel Valve
8 - Combustion Starter
9 - Ignitor
10 - Combustion Chamber
11 - Steering Nozzle
12 - Fulcrum Pin
13 - Evaporator Converter
14 - Fuel Valve
15 - Pressure Regulator
16 - Fuel

Sininen = kylmä polttoaine eli kerosiini, keltainen = LOX / RG-1 kaasut, punainen = kaasuturbiinin pakokaasut ohjailusuuttimille ja polttoainetankkien paineistukseen.
 
Ignition and Staging Timing Chart for Block I:

After reaching the set speed measured by integrating accelerometer, a GK2 command is issued to start up engine of Block I; after delay of 1.25 seconds a command to shut down engine of Core Block A is issued. Before that, capping pins of gyroscopes are blocked. One second after command to shut down Block A, a SEPARATION 2 command follows to allow voltage on explosive connectors between Block A and Block I. Block A begins trailing behind and pulls out the interunit assembly and connectors. Fuel tank of Block I is pressurized by cooled down Turbopump exhaust, Oxidizer tank is pressurized by evaporated Oxygen. 5 to 25 seconds after GK2, the Block I's tail section halves jettison, and at 6 seconds after GK2 capping pins of gyroscopes are reactivated. 

Jotain häiriötä kaasugeneraattorissa todennäköisestin ollut, mutta vielä jää auki että onko vika itse laitteessa vai jossain muussa osassa. Moottori on itsessään aika monimutkainen ja samoja kaasugeneraattorin pakokaasuja käytetään ohjailusuuttimissa ja sitten myös polttoainetankkien paineistuksessa.

Sojuz-manuaalista: "The RD-0110 engine is powered by a single turbopump spun by gas from combustion of the main propellants in a gas generator. These combustion gases are recovered to feed four vernier thrusters that handle attitude control of the vehicle. The LOX tank is pressurised by the heating and evaporation of the oxygen, while the kerosene tank is pressurised by combustion products from the gas generator."

Lisätietoja moottorista: http://www.astronautix.com/engines/rd0110.htm