Good photos M-ATF, are there any more on that website?
Regarding the difference between the Simorgh and the Unha:
The 120 tons thrust of the first Unha stage fits to the clustering of four Nodong engines minus the 6-8% loses due to the use of the jet vane thrust vectoring system.
The 142 tons of the Simorgh is strange at first but makes sense if the take the four Shahab-3/Nodong engines to get 128 tons of thrust and add the remaining 14 tons to the reported "control engine"
So, what could those control engines be? One of you photos tells it. On the third photo in this thread http://www.iranmilitaryforum.net/space-technology-and-news/unha-4simorgh-2/
, there is a smaller engine, which has just been seen in Iran until now. The nozzle expansion ratio tells us that it has to be part of a first stage. If the Simorgh is fitted with two of them in a similar way as the Safirs second stage the source of the remaining 14 tons of thrust would clear.
Each of those engines would have to produce 7 tons of thrust, about four times the amount of the Safirs upper stage engines. This fits with the thrust increase and would make one of the Safirs upper stage turbopumps necessary for each of the venier engines.
We will have to wait and see of the Simorghs nozzle section really has those necessary changes. The most obvious change must be the removed thrust vector jet vanes on the Simorgh as compared to the Unha-2/3.
The second stage of the Simorgh, rated at 7.2 could use four of the Safir-1 upper stage engines. For two of the new engines it would appear to have no not enough thrust at 7.2 tons.
The Simorgh-2 is likely going to benefit from the technologies developed in the Safir-1B and the R-27 main engine.
The first stage is going to use the uprated Shahab-3/Ghadir engines with 37 tons thrust which would result in 148 tons without venier/control engine and with accordingly uprated venier engines in about 165 tons first stage thrust.
The new second stage is likely to be a vacuum optimized variant of the R-27 missile, not only its venier engines like on the Safir but also its main engine because Iran has already copied it. the 1.5m diameter fits perfectly here (if the nozzle extensions fit. With the fuel combination of the Safir-1B, the second stage of the Simorgh-2 should be able to produce more than 35 tons of thrust five times more than the planned Simorgh-1 second stage. This would also easily enable a third stage and approach the 1000kg payload goal of the Simorgh-2.