Geoff FordenWhy Would a 2 Stage Safir Be Surprising?

Dead weights are for the second stage plus satellite, the red line is the orbital threshold, required Isp for each dead weight is read off by looking where each blue line crosses the red line

I’m sure that anyone following ACW’s discussion of the Safir-Omid will have picked up that a number of us find it hard to accept that a two-stage Safir could put the Omid satellite into orbit. I thought I’d try to explain why, if it really only used two stages, this is so surprising/worrying. Fortunately, this can be done rather simply without worrying about the details of the trajectory if a couple of simplifying assumptions are made. Both of these make it seem easier for a two-stage Safir to get into orbit so if it still seems surprising then you know it is really surprising! These assumptions are

1) The second stage doesn’t lose any energy due to atmospheric drag
2) The total second stage burn time, regardless of how many times it is turned off and on or coasts before being lit, is short compared to the flight time to its orbital altitude. (Gravity is, of course, included during all of the “coast” period.)

The second assumption means we are ignoring the effects of gravity during the burn time of the second stage; this effectively adds an unknown Delta V (change in velocity) to the second stage. But, as I said, I am loading up the assumptions on the side of making the 2-stage hypothesis easier to accept because it will end up still being so surprising! My model for the Safir gives a first stage burn out at about 30 km altitude and a speed of 1.4 km/s. Thirty km altitude is pretty high but there should still be some aerodynamic drag. Again, however, I am giving this “bonus” to the two-stage hypothesis.

In order to put the Omid satellite into its observed orbit, the second stage needs to lift it to an 243.5 km altitude and give it a speed (relative to the Earth) of 7.54 km/s. Converting that change in potential energy into a change in speed and adding in the change in speed needed to boost it up to orbital speed means that the second stage needs to supply a total of 8.16 km/s. This is the threshold and is shown in red in the plot above.

That plot shows the change in speed (Delta V) supplied by various engine/propellant combinations that vary in strength ( specific impulse or Isp ) for several different dead weight fractions. This dead weight not only includes the engine masses and the propellant tank masses but also the navigation and control units and the satellite mass. Notice that even a 5% dead weight, which would be an amazing improvement in the stage’s structure, requires an effective Isp of 278 s while an optimistic SCUD-type rocket might have an Isp of 240! More “realistic” dead weights require an even greater improvement in engine/propellant power. This is why some of us have a hard time accepting a two-stage Safir. It is also why a two-stage Safir, which all the experimental data seems to point to, would indicate why the rocket would have to be so much more sophisticated and worrying than what we expected.


  1. Arash Chavoshi (History)

    Hello Mister Forden

    i am very very glad you talked about this question that i been thinking of since Omid Launch

    i am 4th year aerospace major in tehran Sharif University, my proffesor say that iran did two-stage launch and finally broke SCUD-stacking method but i am not believing him

    based on the magnitude brightness data from ground observer and your own expert opinion do you think it was real two-stage or maybe a solid-fuel SAM-style third stage?

    you article descibe the question but i want your personal expert opinion… two-stage or three?

    thank you very much sir

  2. Murray Anderson (History)

    Say the rocket has 20 tons of usable propellant in the first stage, 2 tons structure and residuals, and 4 tons upper stage. Then the vacuum delta-v is 2.6*1.466 = 3.81 km/sec, assuming a not-unreasonable figure of 2.6 km/sec for a Scud-derived missile, with improvements since the 1960’s.
    If the second stage has a residual weight fraction of .14 and exhaust velocity of 2.8 km/sec (similar technology, longer nozzle), then the vacuum delta-v is 5.5 km/sec. Total delta-v is then 9.3 km/sec.
    This is enough to get into low earth orbit. I’m assuming a residual mass fraction of about 9% for the engines, structure, and residuals of both stages, and 200 kg extra on the upper stage for guidance and control, and payload. The upper stage is shorter and fatter than the lower, giving better mass ratios for structure, but the nozzle on the engine will be longer, and it’s always harder to make a light structure on something small, because of minimum gauge thickness, etc.
    If vacuum delta-v of the first stage is about 3.8 km/sec, then it should attain about 2.6 km/sec at burnout, with a maximum cloudtop-to-cloudtop range of 675 km, so it might fall 700-800 km downrange, depending on the details of the trajectory.
    I don’t know why a two stage to orbit liquid-propellant rocket is so surprising. Sputnik was launched with a stage-and-a-half configuration.

    Murray Anderson

  3. Liviu (History)

    Greetings Geoffrey,

    Can you estimate what would be the ballistic range of this missile as an ICBM, carrying the Shihab known payload?


  4. Paul

    Can somebody summarize key dates (and more or less consensus opinions) on Iranian “space” launches since 2007 (vehicles used, purpose, failure or not, why, distance traveled, …)?

  5. Geoff Forden (History)

    Hello Arash,
    I just dont know yet, whether or not it was a two or three stage rocket. I am hoping that the amateur satellite observers will have more data soon. There is also the possibility that the beta_star or drag term in the satellite orbital parameters might give some additional information on size to mass ratio of the rocket body. Until I get more information, however, I cannot make up my mind. I promise to post my conclusions here as soon as I do!

  6. Paul

    Why was the Omid launch carried out at night?

  7. Geoff Forden (History)

    Sputnik makes an interesting comparison. It was launched on the R-7 which was 34 m long, 3 m in diameter and weighed 280 metric tons, it was two-stage, and powered by rocket motors using liquid oxygen (lox) and kerosene. For comparison, my model of a two stage Safir (which, since I have only modeled it with SCUD-type technologies, does not make it into orbit) weighs about 21 tons. If anything, this makes the Safir that much more surprising.

  8. Nahang (History)

    Just as surprising as the Americans and Russians managing to build their launch vehicles from a german WWII ballistic missile? Or actually, it was more surprising that the Russians built everything before the Americans even though they didn’t have all the top nazi scientists working for them, building everything in their name.

    This rocket is definately a two stage, there is no indication what-so-ever of another (hidden) stage.

  9. Hairs (History)


    After re-reading the interesting post and discussions about Safir in the 21 Aug 2008 ACW I’d like to ask:

    1) Do you believe it is technically plausible that Safir could have reached orbit with: two-stages; zero coast time between the first and second stages; and a kerosene / IFRNA propellant?
    2) If not, and if we assume two stages is correct, does the unambiguous fact that they did reach orbit imply that there must have been a coast time between 1st and 2nd stage and / or that there must have been a change of propellant? Or could some other technological advance (e.g. lighter casing materials) have been sufficient on its own to get them there?

  10. Geoff Forden (History)

    these are exactly the questions I think still need answering. When we get some more definite answer about the size of the final stage, then we can start to draw conclusions. Until then, I would rather not speculate. However, the analysis shown here is independent of any coast time, though I do believe there must have been some such time regardless of the number of stages.

  11. Geoff Forden (History)

    One possibility not considered here but mentioned in the discussion on the previous post is the possibility that the first stage has been improved. If so, that would certainly reduce the requirements on the second stage but would, in turn, be equally surprising/worrisome.

  12. wise

    I am no expert in this area. But I can read Farsi and all material from different sources say it was a two stage rocket. I see no reason why they would lie about that. There is no reason and I have not seen any lies in any of the material posted. They also tell you that the first stage went up to 67 kilometer and crashed some 700 kilometer south east of Tehran in a desert. I have no idea where it was launched other than guess the desert south of Tehran.

  13. Hairs (History)


    I don’t wish to sound argumentative, but why should the necessary improvements be “surprising”? Rocketry requires good engineering, but no more or less so than (in their own way) nuclear reactors, aeroplanes, or communications networks.

    My non-expert impression is that Iran’s rocketry may be moving from early fifties technology to late fifties technology; and if the Americans and Soviets could do it in 5 – 10 years, when they had to invent everything from scratch, why should the Iranians not be able to cut the timeline to 1 – 2 years, when they have the advantage of more modern materials, tools and computing power, to say nothing of the huge amount of data in the open literature?

    At the risk of repeating myself from another thread, I’m sure that for the Iranian leadership rocketry development is quite as much an issue of national security / national pride as the Manhattan Project or Apollo Programme were for America.

    “Worrisome” it may be; but from my point of view it shouldn’t be too surprising if the launch really did include some technological jumps.

  14. Geoff Forden (History)

    Fortunately, we can wait for objective data to decide the issue.

  15. pedram (History)

    one way to solve this mystery is to send shuttle on a special mission to catch Omid and bring it to earth for furher analysis.

    After 2 months, Iran is done with it and americans can have it for cheap

  16. Jochen Schischka (History)


    Isn’t a burnout height of the 1. stage of only 30km a little bit low? I get something more like 60+km according to my own simulation (assuming
    a) an improved NoDong-engine with ~34 tons of thrust and
    b) an estimated height-optimized trajectory;
    But admittedly, data on both is only guesstimated, as are some other things in my model like the aerodynamic data etc.); and that figure could match up nicely with the “official” 67km that wise mentions in his comment.

    What Isp-vac/Isp-SL or dm/dt did you use for the first stage?

  17. Jochen Schischka (History)


    I can’t help but wonder if this all isn’t about “more modern materials, tools and computing power”, but rather “expert russian rocket scientists working in their iranian-financed north-korean exile-design-bureau on improving ancient soviet technology secretly provided by modern-day russia”…

    And i don’t have any doubt that if someone would actually invade North Korea and/or Iran or even Russia itself to check this out, there’d of course NEVER be found ANY trace of such a collaboration, so please consider this a strictly unofficial opinion of somebody highly frustrated by the blatant failure of all international non-proliferation treaties.

  18. Ben (History)

    Perhaps the Safir-2, is simply a 2 stage Taepo-dong 2c/3 variant that 2 uses no-dong B (ss-n-6)engines. Is this current thinking?

  19. spectator (History)


    Going forward, is it likely the Iranians will now strap a 2,4 or even 6 scud-cluster to the 1st stage to act as a booster, in order get a much needed imrpovement in payload capacity.
    I mean I’m very impressed they haven’t had to do this in the first place to put anything at all into orbit: Hats off to the Iranians , this is what the iraqis did before the first gulf war they strapped a dozen scuds together and allegedly managed to sort of orbit something but they been bombed back to stone age so we’ll never know

  20. Jochen Schischka (History)

    To Paul:

    I suspect that one of the reasons for a launch at night-time was to “mask” a higher thrust of the first-stage engine (aka a considerably longer exhaust-gas plume as on the standard NoDong-engine) in the publicized photographs/videos by means of overshining (higher difference in brightness against a black sky – can anybody identify anything more than a bright yellow, star-shaped blotch in the official footing?).

    But of course there are also other reasons imaginable, for example lower levels of crosswinds or ambient temperatures. A burning rocket is also easier to track optically at great heights at night. Etc., etc., etc.

  21. Pedro

    It should not be forgotten that the official payload/range numbers of the original Shahab-3 were way higher than what western intelligence estimated and which is nearly considered fact today.

    And if the Safir uses Ghadir/Shahab-3B technology significant improvments in the performance over the Shahab-3 are very likely.

  22. Jochen Schischka (History)


    The really surprising part is that the Iranians obviously not only used Ghadr-1/NoDong-B (which, in itself, is a completely reworked and additionally improved Shahab-3/NoDong-A with bigger tanks in a different configuration, compacted guidance-system and a much lighter warhead) as a first stage, but completely reworked and additionally improved that missile all over AGAIN to create a first stage with even bigger tanks AND lighter structure (aka not simply a stretched version of the Ghadr-1/NoDong-B!) PLUS a completely new upper stage PLUS a completely new staging-technique (at least to the Iranians and North Koreans), and i haven’t even mentioned the new upper-stage- and a possibly uprated lower-stage-engine or a modified guidance package yet!

    I think most people grossly underestimate the effort and money creating all this simultaneously, all the necessary infrastructure included, must have cost (and i for my part, comparing this to the indigenous missile programs of other countries, can’t help but wonder if the Iranians had additional professional help from some sort of “A.Q.Kahn-network for missile technology” to make this possible in such short a time with so few accidents/constructional defects).

    Maybe all of us missile maniacs got duped by the fact that this new missile presumably isn’t built like a surface-to-surface-missile (as we obviously all expected), but more like a highly specialized space launcher (and thus perhaps even quite difficult to convert to SSM-mode due to some system-inherent operational constraints like low structural integrity, small feasible payload and considerable bulkiness).

  23. Paul (History)

    Inside Iranian mission control


  24. Jochen Schischka (History)

    BTW, Pedro:

    I’m not so sure if the nower-day broadly accepted payload/range figures for the Shahab-3/NoDong-A are anywhere near correct (sometimes i think somebody mixed up kilometers and statute or even nautical miles while completely neglecting basic requirements like minimum aerodynamic stability); Just consider: At what maximum ranges has this missile actually been tested? What are the maximum ranges countries like North Korea (NoDong-A), Pakistan (Hatf-5 Ghauri) or Iran (Shahab-3) have at their disposal? Over land? Without violating the airspace of other countries? Or endangering their own population (let’s pretend that Kim-Yong-Il would care…)?

  25. Azr@el (History)

    At what point does “rework” become “indigenous developed”? I would call this a case of “NoDong Syndrome” but that term seems to be censored on this site.

  26. spectator (History)

    congrats to the uranium bros, they really cracked it & it’s absolutely non-reversible, they don’t even need to improve ISP, they might simply make it bigger, this is one way to improve on dead weight, the dead weight ratio is not a design constant at all because as the tanks volume increase the D/W ratio can only decrease (even though structural mass naturaly goes up) so they might big it up or strap some solid fuel missiles round to boost it, also they obviously mastered the non-trivial technological issue of attitude control outside the atmosphere, if the west is concerned about the obvious advance, it needs to be because Mahmood big boy is no puppet serving united israel

  27. Amir

    I had a visual observation of OMID satellite using binoculars (12*50). Its magnitude was changing rapidly (each 3-4 second) in quite a wide range of 3 to 7 or even 8. Also, I saw two flashes one as bright as mag 1 to 0. I think (more of a guess) it does one rotation each 8-12 seconds.
    Note: max elevation was 57°.

  28. Pedro

    @Jochen Schischka

    Iran solved the problem with the maximum test range by increasing the payload and thus bringing the missile at its maximum capability.

    Btw. Does someone here really think that all this zero-gravity maneuverability /control/guidance technology came for the first time in form of the Safir? I remember how everyone said “ah.. the Kavoshgar-1 they tested is just a repainted Shahab-3B, launched for propaganda reasons”, today its clear to me that the Kavoshgar-1 was a testbed for Safir upper stage technology.

  29. Jochen Schischka (History)


    As long as the diameter of the missiles remains the same, you can still use more or less the same tooling and infrastructure to build your missile, and thus it’s only a “rework” (aka stretch or reduction in wall-thickness etc.). Building missiles with a new diameter now requires a completely new production line with tooling adapted to the new diameter (since when is it possible to produce tubes with different diameters on the same tool? Or stiffening rings?).

    There are also other aspects of “rework” vs. “indigenious design” to consider:

    One of the hardest parts of a missile to design AND produce is the engine. If a proliferator starts designing (or even producing!) its own engines, you’ll characteristically notice this by the rate of accidents going straight up (not much room for errors in that discipline). There will also be significant differences in design features like general dimensions, thrust levels, propellant combinations or general construction methods (compare for example the chinese engines with their russian counterparts: although both use the soldered corrugated steel method that the russians invented, there are significant differences in many other respects), since all this can be adjusted to a different missile, individual industrial cultures or personal preferences.

    And let’s not forget something else very difficult: the guidance system. There are two aspects of this system: the guidance (aka inertia platform/electronics) itself and the steering elements (aka air- or jet-vanes, gimballed nozzles etc.), the former almost never and the latter seldomly observable in good detail (but there are tell-tale signs, like the numbering on the fins)…

    As long as iranian (and presumably also north korean) missiles still use the same old diameter of 1.25m (there are some people that obviously add the cable ducts to this to obtain a “new” diameter of 1.35m – but that can to a certain extent be invalidated by photo-measurements) as the russian R-13/SSN-4/Sark or R-21/SSN-5 (yes, i know, the “official” figure accepted in the west is 1.3m – simply rounded up due to uncertainties in reconaissance! You’re all invited to proove me wrong by measuring examples of mentioned missiles in russian museums) and engines that look exactly like they were genuinely designed by Isayev (there can even be found cross-sectional drawings VERY closely resembling the NoDong-chamber in 40-year-old soviet textbooks!), albeit maybe tinkered-with (nozzle-extensions, higher chamber-pressure – the latter is particularly problematic), and point with the fin number “I” in the direction of the target on the launching table, this all is still only a “rework”, however impressive the outcome.

  30. Jochen Schischka (History)


    That was exactly my point: It is NOT POSSIBLE to reduce the payload any further on the Shahab-3/Ghauri/NoDong-A (otherwise the missile will unfortunately get considerably aerodynamically instable around Mach 1 – flying with the rear end ahead is a particularly disadvantageous way of breaking the sound barrier if you ask me!), so the higher (untested) ranges are pure fantasy!

    Considering Kavoshgar-1:

    You are absolutely right, maybe this was in fact actually a subscale-test of the modified (height-optimized) lower-stage guidance and perhaps also of the telemetry system (did anybody else notice the pair of small antennas on the warhead? There is a pair of very similarly-looking antennas directly below the payload-shroud of the Safir), although i think that, as a side-effect, it was probably also a “non-military” test of the triconic reentry vehicle of the Ghadr-1/NoDong-B with additional telemetry.

    On the other hand, i must say that i’m not sure if i understand your comments on “zero-gravity maneuverability” (the satellite, if really the 40cm-cube, evidently has no attitude control system at all and the upper stage IS subject to earth’s gravity until reaching orbital velocity) and “testbed for Safir upper stage technology” (since there clearly was no upper stage on Kavoshgar-1 which in essence was almost identical to a standard Ghadr-1/NoDong-B)…

  31. Hairs (History)


    You commented: ‘…rather “expert russian rocket scientists working in their iranian-financed north-korean exile-design-bureau on improving ancient soviet technology secretly provided by modern-day russia”…’

    I agree about external assistance, though I neglected to put it in my original comment. And with so many Russian technical experts connected to Iran (e.g. Bushehr) I think it’s just as likely that the Russians would be actually in Iran as in NK.

    More generally:
    Back in November 2008 in response to Geoff Forden’s illuminating series about rocketry, I suggested that it might be helpful to put together a timeline of the major advances needed in order to develop successive generations of rockets. I think it is a plausible assumption that the Iranian development is going to follow a well-worn track, if for no other reason than that’s how their “assistants” developed their own capabilities; so getting a feel for how quickly Iran has crossed, say, the first few technical hurdles, might give an indication of how quickly they’re likely to progress on the next problems. If we assume that the Iranians are getting assistance, then knowing how long it took Russia et al to solve problems in the past could at least give something of an upper limit on how long it will take Iran.

    I don’t have the necessary knowledge of rocketry to do such a timeline / historical comparison, but I offer to (modestly) sing the praises of he (or she!) who does. Certainly it would be very helpful for those of us who can’t assess the relative importance of advances in different propellants, “zero-gravity maneouverability”, gimballed engines, and the like.

  32. Gridlock (History)

    Wonder what the CRS has to say about Iranian programmes?

    Entire CRS catalogue online for the first time. Amazing coup for Wikileaks.

  33. Gridlock (History)

    EG – China and Proliferation of Weapons of Mass Destruction and Missiles: Policy Issues
    January 07, 2009

  34. Paul (History)

    Official web site of Omid by the Iranian Space Agency.

  35. Tal Inbar

    From the official website – a lot of new information. for example – pictures of the satellite – never seen before:

  36. Tal Inbar

    If this image is NOT intended to misguide us, then the weight of the satellite is 27.270 Kg.

  37. Jochen Schischka (History)


    Interesting point. Maybe you’re right, it is quite possible that russian “technical mercs” are also at work directly in Iran. But wherever they’re working, they bring their own production-line tooling with them for sure…

    And let’s not forget that there will certainly be a growing number of iranian “rocket scientists” with first-hand experience themselves!

    Considering a “timeline of the major advances”:

    I think this is more complicated than perceived at first glance, because there are many different possible ways that may all lead to more or less the same result in a wide variety of timeframes. To make matters worse, there will always be some sort of outside help (the only notable exception being the german missile program of 1934-45), willingly or unwillingly. What is more, all depends on the time, effort and money the particular administration is willing or able to invest in that project. Of course, it’s also a question of the ultimate technical goal of the program (e.g. SRBM, ICBM, SLBM, symbolical LEO-launcher, manned landing on the moon, liquid or rather solid propellants etc.). Last but not least, the general level of education and industrialization of a country also matters in this context. All in all, quite an impossible mission leading to rather doubtful results (since not all of the necessary data will be available or reliable) in the order of approximately 5-20 years…

  38. Azr@el (History)

    I think we have to move beyond “NoDongism” as an outdated way of looking at the Iranian puzzle. The NoDong engine has roughly one third the sea level thrust of the Safir 1st stage and an ISP of ~232 sec. This is obviously beyond a simple or otherwise rework.

    The Soviets never managed to coax more than an ISP of ~230 sec out of production engines burning Nitric Acid >70%/Kerosene, this seems a tad too low for the Safir first stage. If the N2O4 concentration of the nitric acid were brought closer to 50% this would bring the SL ISP closer to 270. This would of course require new plumbing for the turbo. Afterall if they are using the RD-27 engine from the R-27 on the 2nd stage of the Safir then they already have experience using a UDMH/N2O4 engine. And ‘IF’ they can use N2O4 as oxidizer on the 2nd stage why not 50/50 nitric acid/N2O4 oxidizer on the 1st stage.

    Does anyone have an opinion on this test being a partial failure? Was the carrier meant to take the payload higher or into a more circular orbit?

    Ad Amir;

    Did you observe the the second stage booster as well? According to an other poster it may be changing magnitude as well indicative of tumbling. It’s albedo should dwarf the Iranian cubesat2^2 Omid.

  39. David Wright (History)

    There was an article from Newsweek I just saw that said US government analysts claimed that the the Iranian launcher used 50-year-old technology. This could mean Scud-like technology, but it could also mean cryogenic engines. While this seems unlikely, I put the numbers in my model to see if that would give a high enough Isp to reach orbit with two stages. If you assume a fuel combination of LOX-Kerosene, like the Soviet R9/SS8 had, you could in theory get close to 300s sea-level Isp and 350s vacuum Isp. Using these numbers and guesses at other parameters, I find you get roughly orbital speed at an altitude over 200 km with two stages. Moreover, the first stage gives a burnout altitude and splash-down range of about 70 km and 850 km, roughly agreeing with the numbers cited above.

    Since I have not seen any other evidence that the launcher uses cryogenic engines, I’m not sure what to make of this. The other possibility is that the launcher uses storable fuels, but there was a small kick stage on top of the second stage that increased the speed sufficiently to orbit, but was small enough that it was not considered a third stage by Iran. Geoff points out, however, that the second object in orbit appears to be rather large, so that may rule out this possibility.

    David Wright

  40. Major Lemon (History)

    Geoff, fairly significant innovations in rocket technology are definitely happening under our noses, without the spectacular and costly failures of yesteryear. Nowadays you can do all your R&D using computer modeling and simulation.

  41. Geoff Forden (History)

    David, Ive been thinking about cryogenic fuels for some time now. After all, the V2 used LOX and kerosene. This would also explain why the launch of both the August Safir and this Month’s launch took place at night and with a lack of closeup photos of the launcher just before and during liftoff: it hid the visible evidence of cryogenic fuels. Why doesnt someone asking the US Government how many stages were used? Wny arent the reporters following up on this? Im sure they (the US Government) know it from all their assets in the region.

  42. Tal Inbar

    Geoff, I must ask – what fuel do you think is used on the second stage of the Safir?

    (The cryogenic fuels hypothesis is a wild one, which is not supported by any evidences, however circumstanced).

  43. Geoff Forden (History)

    Tal—The whole thrust of this post is that I do not know if it was a three stage or a two stage missile and hence I do not know what type of fuel either the first or second stage used. The PRELIMINARY experimental data seems to favor a two stage hypothesis in which case, the fuel possibilities of both stages would need to be re-evaluated.

  44. Azr@el (History)

    It seems highly unlikely that this rocket had either a cryogenic fuel or a cryogenic oxidizer. The videos of the launch show no condensation vapour indicative of a cryo tank. The 1st stage tankage itself appears a bit too thin to efficiently hold LOX-too much surface area for a given volume. And it seems to be less of a stretch to attribute the performance of the carrier rocket to a more mundane explanation; improved storeable fuel/ox combinations. Nitric acid/UDMH …N2O4/kerosene… and a few others could all give respectable ISPs in excess of 270 at sea level. These are all toxic but not show stoppers. Of course to accept any of these we must conclude that the Safir first stage is not a North Korean design and that may be the most intractable part of the whole exercise.

  45. Geoff Forden (History)

    Let me make this clear: I will not approve messages that use terms that a 4th grader might consider cute for one nationality or another. They are, in reality, stupid and racist and they are not getting approved. If you have a valid point, use language appropriate for a professional discussion. Posts that argue with this rule are not getting in either!

    Oh, yes, I forgot. The rest of your post wasn’t very interesting anyways! (You know who your are.)

  46. Paul (History)
  47. Jochen Schischka (History)


    May i suppose that you mixed up the Scud-B-engine (Isayev 9D21, open-cycle, 13.31 tons SL-thrust, 57.83kg/sec m-dot, 226.4sec Isp-SL-eff, 251.1sec Isp-vac-eff, 69.4at p-c, 124mm d-t; source: “Dienstvorschrift 11/22” of the former east german army) with the standard NoDong-engine (denomination: unknown, open-cycle, ~27t SL-thrust, ~120kg/sec m-dot, ~224sec Isp-SL, ~248sec Isp-vac, ~55bar p-c, ~200mm d-t; source: reconstruction)?

    On the other hand, if we assume that the official figure of 26t for the takeoff-weight of the Safir (maybe identical with the Taep’oDong-B? -> let’s wait and see if there are pictures of the next NK-launch) is correct (could be credible due to reconstruction), then 27t SL-thrust clearly IS insufficient. Analysis of the available video-material now yields a net liftoff-acceleration of the Safir-2 in the order of ~0.3g (consistent with the minimum requirement for a satellite launcher), tempting me to assume a SL-thrust of 33-34t (let’s call this the “NoDong+”-engine-hypothesis) – and that could be consistent with an uprating of the chamber pressure to the level of the 9D21 (i know this is not as simple as it sounds, and i’m still puzzling about how this could have been achieved by simple means…maybe unused reserves of the original engine?).

    There are two indications that in my opinion count against your idea of a NTO/UDMH-lower stage engine:

    1.) The ratio of the tank volumes of the lower stage.

    2.) The end diameter and area ratio of the engine of both the iranian Safir lower stage and the pakistani Ghauri (= NoDong-A) are VERY similar (according to photo measurements), use VERY similar-looking jet-vane-casings and have the same open-cycle-exhaust-port in the same location…

    BTW: the closed-cycle main-engine of the R-27/SSN-6/Serb had only a SL-thrust of about 22t (and a different end diameter) – definitely not enough for a 26t-missile.

    And i don’t think that this shot was a failure – due to the fact that the satellite itself (if really the 40cm-cube shown around) has obviously neither an apogee-engine nor any kind of attitude control, such an elliptical orbit is the best that can be expected (compare this to the in this respect quite similar Sputnik).

  48. Jochen Schischka (History)

    David Wright:

    I think Tal Inbar and Azr@el are right on this one:

    Cryogenic propellants would in any case have led to observable icing (have you ever noticed the sheets of ice getting knocked off by the vibrations during ignition and liftoff of such missiles as the Aggregat-4/V-2, Titan-1, Saturn-V or R-7? Or the related characteristical smother? I see no sign of this in any part of the launch of either the Safir-1 or the Safir-2, and there are excellent videos available by now thanks to Paul; BTW, thanks, Paul!). On the other hand, there are also indications for a first-stage propellant combination based on a carbonaceous fuel (the yellow color of the flame) and nitric acid as oxidator (the reddish cloud visible for a short time during ignition – this could also be NTO, but: see my last comment); Second-stage – see icing.

    Oh, and Geoff:

    The Aggregat-4/V-2 (and the “sovietized” post-war-V-2, the R-1/SS-1a/Scunner) did NOT use LOX/kerosene as propellants; Instead it used:
    A-Stoff (LOX) + B-Stoff (75% alcohol/water-mixture) + T-Stoff (80% hydrogen peroxide/water-mixture; gas-generation for the turbo-pump) + Z-Stoff (watery solution of calcium or potassium permanganate; catalyst for T-Stoff).

  49. George William Herbert (History)

    Major Lemon wrote:

    Nowadays you can do all your R&D using computer modeling and simulation.

    That would be news to every government and private company and independent rocket developer in the world, all of whom do a lot of testing to see if their models match reality.

    For example, the existing physics and computer models of how combustion works inside a rocket combustion chamber are known to be grossly simplistic and require significant actual testing to validate.

    Everyone who flies things finds out nasty suprises. Sensible people test and fly enough to get suprised gently rather than all at once and catastrophically…

  50. Azr@el (History)

    I’m wondering if we’re missing the forest for the trees. Iran has just fielded a high ISP lightweight carrier with a slow liftoff phase. It has also recently fielded a relatively large, fast climbing solid state rocket; the Sejil. What if these aren’t separate programs but rather components of a single SLV? This would explain the protrusions around the Sejil.

    If the Safir is the core of a launcher and the Sejils are stage 0 strapons, then of course the Sejils would need a mechanism for safely detaching and maneuvering away from the Safir core stack. Thus the boxes/retro rockets protrusions.

    Now of course this is all speculation…but for the sake of argument if it is accurate then what we are looking at is a flexible family of launchers. Something that might even deploy a light sat to GTO at the high end.

  51. Amir


    Yes I had an observation on Feb 5th, which I had a post about it on the other page. Here is the post:
    I had an visual observation (using binoculars) of the final-stage of Safir-2 (not a very clear sky). I estimate its brightness at its max elevation of 37° to be 3.3+-0.5. I should have a better observation tomorrow as its max elevation is 68° at my location. Fast inspection of photos I captured suggest that I have not took its picture! or it was too dim for the bright sky after sunset. I will try tomorrow as well.

    Calgary, AB, Canada
    Sky was partially cloudy and I saw the final-stage for around 30-40 seconds. I didn’t noticed any change in mag.

  52. Ed LeBouthillier (History)

    Maybe the Iranians are farther ahead than thought (but still behind the state of the art). My figures for a possible model describing their vehicle are here:

    It shows that they are more advanced than a Scud in terms of Structural Coefficient yet still behind in lightening skills. For comparison, here’s a table I’ve made describing other vehicles’ Structural Coefficients:

    Structural Coefficient Table

    It’s not high technology to attain an Isp of 310 for the upper stage and 250 for the first stage. The Structural Coefficients are consistent with modern pressure fed vehicles, so they’re not to the state-of-the-art for pump-fed vehicles, yet.

  53. maddox (History)

    I just wanted to ask if you know for sure that its fule is lox and not solid fule.
    if it was powered by a solid fule as their latest missile I think that makes it much lighter and can help the problem

  54. Amir

    In his speech today, Iran’s president has mentioned that the second stage has few engines and worked for five minutes.

    I thought this may help calculating the Isp.

  55. Tal Inbar

    A new picture of Safir’s first stage engine:

  56. Tal Inbar

    To maddox,

    The Safir launch vehicle is using LIQUID fuel. To my knowledge is UDMH and Nitric Acid.

    To Amir,

    we know – from February 2008 – that the second stage is using 2 liquid rocket engines. At first glance I thought there was a coast phase, but more and more I’m convinced that the 2 rocket engines worked constantly.

  57. Geoff Forden (History)

    Could you explain more why you think it is UDMH? Thanks!

  58. Tal Inbar


    Being hypergolic rocket fuel, there are advantages – for example there is no need for ignition system – less dead weight. Furthermore – if, in the future flight there is going to be a coast phase and re ignition – it will be the more simple way to do it.

    Try to do the calculations of the performance of the second stage – assuming the use of UDMH.

    To sum it up – the Safir launcher would looked very familiar to Valentin Glushko…

  59. Tal Inbar
  60. Jochen Schischka (History)

    George William Herbert:

    Excellent point! The computer-guys and the managers of today seem to think that EVERYTHING can be simulated sufficiently (and thus live in the illusion of being able to do away with all these “unnecessary” expensive prototypes and tests); but, as we should have learned by now (by such “simulation-marvels” as the X-33, the Airbus 380 or the Mercedes A-Class), in the end a computer-model is only as good as the guy programming it (or the data or theory he’s basing his model on); Unfortunately computer-programmers generally tend to have not the best understanding of anything else but programming computers. Hey, even engineers often don’t have full understanding of all this (all too often because of lack of first-hand experience or “intellectual tunnel vision”…), after all it IS rocket science, isn’t it?

    So, in essence, “doing the R&D using computer modeling and simulation” might look good (and faster and easier and above all CHEAPER!) on paper (or a computer screen), but “actual results may differ”…

  61. Jochen Schischka (History)

    To Tal Inbar:

    Have you ever seen how the ignition on the Scud-B-engine with the non-hypergolic propellants AK-27I (IRFNA with 27% NTO-share, Iodine-stabilized) and TM-185 (a Kerosene/Trikresol-mixture) works?

    There are two lightweight burst-diaphragms inserted into the fuel line; the space inbetween is then filled with 30kg of TG-02 (Tonka, a mixture of Xylidine/DETA/TEA; hypergolic with AK-27I) as the missile is readied for launch; At ignition a small pyrotechnical charge spins up the turbopump and lets the diaphragms burst so that AK-27I and TG-02 are injected into the chamber and ignite on contact; After about 2 seconds, the Tonka is used up and supplanted by TM-185 now flowing through the fuel line. By that time, the engine is already running (and hot enough) so that the combustion won’t stop anymore.

    Quite elegant, safe, volume- and weight-efficient for a ground-start vehicle especially since the biggest part of the propellants will not ignite on contact (-> see Nedelin-disaster or the fire in the missile-compartment of the K-219) and thus the missile can be safely handled in fueled condition as long as the Tonka-igniter is not yet poured into the missile or the start-up-charge is not installed.

    On the other hand, i completely agree with you on the big advantages of NTO/UDMH in regard to upper-stage engines.

    But since the lower stage of the Safir evidently IS NoDong-heritage (and there is ample photographic evidence for Scud-like propellants in case of the NoDong – AND an Isayev-heritage of the engine), i’d advise on assuming AK-27I/TM-185/TG-02 as a working hypothesis for the propellants of the first stage.

  62. turbo trabant (History)

    Could it be the launcher is the latent Shahab-4 ? The performance looks quite similar.

    That should mean europe is now in range.

  63. Tosk59 (History) says “But there is another reason American military and national security officials are so worried: in at least two earlier ballistic missile launches, the Iranians launched in ways that “appear they were designed to optimize an EMP burst,” according to a Pentagon source with detailed knowledge of the Iranian’s efforts and of space technology”

    Sounds nonsensical, all y’all experts see any validity to this at all??

  64. Jochen Schischka (History)

    Ed LeBouthillier:

    Nice work (i especially appreciate your table on structural coefficients)!

    But have you taken the l/d of the Safir of ~17.5 into account? I also somewhat disagree with your choice of propellant combinations (NTO/Aerozine characteristically is connected to a tank-volume-ratio of about 1:1 -> see Titan-II, while on the Safir upper-stage it’s more like ~1.5:1, if you take a common bulkhead and a turbopump-assembly submerged into the lower tank into account -> see R-27/SSN-6/Serb; This is in my eyes more resembling IRFNA/UDMH, like you assume on the lower stage, where the volume-ratio looks more like the ~2:1 typical for IRFNA/Kerosene to me -> see R-17/SS-1c/Scud-B).

    Back to business: Is it possible that there was Scud-C-like sheet-metal (Steel, 1.5mm thickness) used on the Safir instead of Scud-B-like material (Steel, 2.0mm thickness) as on the NoDong? This could perhaps (in combination with smaller fins from the Scud) explain the necessary decrease in empty weight of about 20%, although the resulting missile would likely be unsuitable for flight at anything but the slightest angle of attack below ~35km, thus a highly optimized “low-strain” angular program with a not too big overall direction change would presumably be necessary below that altitude (especially around q-max at ~40sec and a height of ~8-10km). I’m also not sure if such an increase in fragility would be compatible with a characteristical tank-pressure of ~4bar (possible, but at a maybe inacceptably decreased safety factor according to preliminary analysis).

    Professional/educated opinions on this point strictly welcome!

  65. Jochen Schischka (History)

    To turbo trabant:

    More like the Shahab-5/Taep’oDong-B (?); The performance (2-stage-to-orbit instead of 2-stage + kick-stage) is obviously much better than that of the (never tested in Iran) Shahab-4/Taep’oDong-A;

    And yes, that means europe now IS potentially in range (although i have doubts to what extent this particular missile could be adapted to the surface-to-surface-role)…

  66. Paul (History)

    The Iranian President spoke today at the 30th revolution anniversary celebrations in Tehran.

    According to him the rocket used was a two-stage one. Stage one was operational for three minutes; stage two for five minutes; and satellite deployment was done via a spring and jack mechanism.

  67. turbo trabant (History)

    To Jochen Schischka:

    Please see Paul’s commentary that the Iranian President has mentioned a ‘spring’ mechanism.

    Yes it could be the Shahab-5 rather if deployed this will be doctored down to a Shahab-4 on operational deployment to address those issues mentioned above. I would nominate it an extended Shahab-4.

    The size, diameter, weight all look the same.

    After all, it would make sense to develop the 4 and then to develop the 5th as a ‘heavy space launcher’ which fits with their space program.

  68. Azr@el (History)

    An oxidizer of 50/50 Nitric acid/N2O4 will also have a a brief reddish cloud during the first couple of seconds of chamber activation. Of course it will also have an ISP close to 270 when burned with kerosene; such a combination would better explain the performance of the Safir.

    2 minutes for the first stage is 120 seconds compared to a NoDong burn of 110 seconds. If this is the NoDong wouldn’t it run longer on the stretched tank? Unless they’ve managed to redesign the turbo and the plumbing to increase the flow.

  69. pedram (History)

    Doctor Ahmadinezhad said today that the 1s stage burnt for 3 minutes, 2nd stage for 5 minutes.

    Source: Farsnews agency (Farsi section).

  70. Ed LeBouthillier (History)

    Re: Jochen Schischka

    > Nice work (i especially appreciate your table on structural coefficients)!

    Thanks. The Structural Coefficient is a pretty good measure of the sophistication of the vehicle design. That’s why I like it as metric.

    > But have you taken the l/d of the Safir of ~17.5 into account?

    Yes. Here’s the Cd table I derived:

    This is based on a 1/2 power series nosecone which the Safir nosecone approximates.

    Nose Cone Design

    The Cd is very sensitive to the nosecone shape. Other nosecone shapes produced much larger Cd. I haven’t had the opportunity to simulate the flight path yet to integrate the estimated aerodynamic and gravity losses. But, I left enough extra delta V to handle significant deviations.

    Also, the whole design is VERY sensitive to minor mass differences. It’s in a very non-linear region of the Rocket Equation.

    > I also somewhat disagree with your choice
    > of propellant combinations (NTO/Aerozine
    > characteristically is connected to a
    > tank-volume-ratio of about 1:1 -> see
    > Titan-II, while on the Safir upper-stage
    > it’s more like ~1.5:1, if you take a common
    > bulkhead and a turbopump-assembly submerged
    > into the lower tank into account ->
    > see R-27/SSN-6/Serb; This is in my eyes
    > more resembling IRFNA/UDMH, like you assume
    > on the lower stage, where the volume-ratio
    > looks more like the ~2:1 typical for
    > RFNA/Kerosene to me see R-17/SS-1c/Scud-B).

    Yeah; I’m not certain about the propellants yet. I’ll look into it more. The 2nd stage tank volume ratio I came up with was 1.59:1. But, in retrospect, I didn’t subtract out the submerged pump (which is obvious in some of the pictures). I’m still working out the details.

    But, as a feasibility study, this shows that a 2 stage with only modest technology sophistication is possible.

    Ed LeBouthillier

  71. Jochen Schischka (History)

    To turbo trabant:

    A spring mechanism is NO kick-stage (aka an actively boosting THIRD rocket stage for orbital insertion)!

    And i would strongly advise against BLINDLY believing every single word Mr. Ahmedinejad says (look at his commentaries considering the holocaust…or what he says about gay people in Iran…).

    Considering “size, diameter, weight all look the same”:

    Except that the Taep’oDong-A had a smaller-diametered (~0.88m), but considerably longer second stage, a trellised interstage structure for a completely different staging technique and a shorter first stage with obviously less sea-level thrust (aka is a COMPLETELY different missile!).

    Furthermore i think that Mr. Vick’s/FAS’s mass-estimations shouldn’t be considered the ultima ratio…(e.g. his “Scud-C” is considerably longer than the Scud-B, his initial version of the “Taep’oDong-1”/Taep’oDong-A in 1998 postulated four clustered Scud-engines, although that was clearly NOT the case – and i dissociate myself from his “Taep’oDong-2”/Taep’oDong-B reconstruction as a 2.1m-missile with FOUR clustered NoDong-engines or his “NoDong-B = SSN-6”-theory).

    Neither a “Shahab-4” nor a “Shahab-5” ever existed officially – but there are hints about a cancelled Taep’oDong-A-program in Iran (BTW, look some kilometers northeast of the actual launching site of the Safir on Google Earth – there is an obviously abandoned construction site of something VERY closely resembling the new north korean PongDong-ni-launching site visible from space).

  72. pedram (History)

    Doctor Ahmadinezhad must have talked to experts in the ISA to get some knowledge of public interest and what he said is what he was provided to by ISA people. I personally believe him, he is an honest decent man.

    Anyways, I believe those experts in ISA who managed to do this amazing launch are by far more knowledgable than authors of this blog that collectively failed to be conclusive after some 70 posts.

    Let us not forget Feb. 2008 when you guys spotted “a broken jet vane”, November 2008 where “composite” was thought of as “solid liquid combo”, August 2008 where some “offical” said Safir failed while NORAD declined comments, and FOX News’ claim of Sejjil failing after 9 seconds while 200 miles downrange!!!!

    Bottom line: Dr. Ahmadinezhad’s Iran did it. West failed to stop it.

    As with hollowcaust, I have a story but I am not sure Geoff will let it appear, so I am self-censoring myself. So much for western freedom of speech.

  73. Geoff Forden (History)

    Please believe me when I say there is a lot of hatred out there. Ive already observed that people are very willing to slip incrementally into name calling etc. so when I am censoring this web site it is to prevent that decline into such childishness. Because of this, censorship always seems to cut in too quickly. Im sorry about that but it seems the only way of preventing a few people from escalating. However, you are free to publish what ever you like on somebody else blog or your own website.

    As to your other comments about ideas presented in this web previously, you must remember that in the search for truth some mistakes will be made. I have to say, however, that no one has actually proved that those ideas discussed here were wrong, even if they think they have proved them wrong.

    And that, I think, should close this thread.

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