Second “Safir-E Omid”
(Emissary of Hope)
Booster Orbital Launch Attempt
© By Charles P. Vick (All Rights Reserved)
Design Flaws Implicated
Back in February this author was able to identify at least ten recognizable potential design flaws in the Safir launch vehicle with only some of which I can confirm that have been addressed by this second flight test as the mock-up booster does not have these features (that this author has inferred the design flaws from). It is possible that several of the other potential design flaws noted have also been addressed with this flight. Several design flaws previously identified can be discussed. This booster did have the translation staging and retrofire rockets for the first and second stage and third stage separation payload and propellant stabilization but the mock up and engineering test models did not necessarily have all of these features. Previously seen – They are very obscure in the released imagery -- are the anti-vortex baffles for the second stage. From start to finish the second stage thruster stabilization attitude control system has been questionable with potentially only one axis gimbals mounted main thrust chambers to control both yaw and pitch axis regimes through repeated roll maneuvers? Where is the solid motor (required) third stage for orbital insertion? Which stage is used for the upper stage spin up required to be carried out (because spin up stages solid motors are not as easy as one may think and can get you in real dynamic trouble without an active attitude control system causing the total loss of the vehicle completely)? (8, 9) http://www.globalsecurity.org/wmd/world/dprk/nd-a-warhead.htm for reference information. This author decided not to reveal the rest of those potential recognized design short comings that would be a violation of the national security technology transfer rules. It is rather amazing to me that they have missed some of those design issues in the engineering models that experienced designer would immediately have recognize as required, but it could be that they are there for the flight models.
Engineering Model Estimated Performance
The Safir launch vehicle weighing in at over 26 metric tonnes with a length of about 22 meters and a diameter of 1.35 meters has about 10,000 parts in its design according to the Iranians aerospace organization. The first stage is assumed to have shut down somewhere in the 20-25 km distance down range at an estimated altitude of 22-28 miles with first stage impact 250-300 km down range. The first stage burn was perhaps less than 120 seconds. Shroud separation is presumable at 150 seconds in flight at greater than 100 km altitude [152 km’s (94.64 miles) is the altitude of failure (7)]. Its second stage step throttle probably operated at a higher rating for maybe 50 seconds and then went to a lower setting where thrust equal mass roughly 65% thrust rating at first for 120-125 seconds. Third stage burn perhaps was planned to be on the order of 25-30 seconds at most using a recognizable Chinese solid motor design Iran duplicated and produced. That is on the order of 300-315-325 seconds to orbit not including coast staging sequences times which is similar but better than Taep’o-dong-1’s, which took 293 seconds to achieve orbit. This tends to suggest that the Safir has and is indeed a highly redesigned improved compacted Taep’o-dong-1 design heritage. It is reasonably understood that the Iranians did indeed purchase a Taep’o-dong-1 class booster for engineering study but rejected using its failed design. The launch gee’s acceleration were indeed slower for liftoff on the order of 1.25-1.3 gee’s based on the launch video imagery. Both liquid propellant stages are assumed to be using the same Scud-B propellant combinations.
The TVC - thrust vectoring control - appears very limited in one axis before running into interference with surrounding existing hard and flexible piping and other apparatus equipment including throttle controls plus the apparent limited Soviet style attitude control thruster lines pipe roll control thrusters that are apparent in existing images. Unfortunately such a system offers very limited control of the second stage and probable contributed to the failure. The lack of an apparent two axis gimbals mounted thrust chambers capability is reasonable apparent. Where is the spin stabilization kick in on the second stage or the third stage or both?
The Apparent Second Stage Stabilization Regime
We have to understand this two thrust chamber vernier type control from the old Soviet SLBM control mode. That is two thrust chambers set in one pitch axis control which also can and are utilized for yaw control through a roll maneuvers to correct the directional errors which means it is constantly doing this kind of maneuver to correct both yaw and pitch direction and if the thrust chambers are not programmed to work together and fight one another it literally does tear the vehicle apart and sends it wildly out of control. At any time in flight if things are not right at payload separation or during or near the end of the second stage burn it can with an inadequate active attitude control totally loose it. If the Iranians had finished the burn of the second stage and tried to separate the third stage solid motor and do the spin up at the near same time it may indeed have gone wildly out of control. The Iranians may understand what went wrong and have immediate solutions available. The second stage may utilize two Scud-ER type SA-2 class step throttle altitude revised vacuum thrust chambers (or possibly two modified No-dong-B/Mirim vernier thrust chambers) with only one off set turbo-pump. The turbine exhaust and the two fixed thrust chambers straddle the stage center line in an off set configuration which means except for the active attitude control system there is no propulsion for propellant stabilization for start up without the solid motors doing the job at staging. This acts as three thrust chambers that is why it is configured as it is. This strongly suggests that the stage is not intended to carry out a long ascent coast before ignition of the main two altitude thrust chambers.
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