Jeffrey LewisIran Dope Concerns RV Not Warhead

I spent most of the weekend mulling over how best to respond to this collection of half-truths, pablum and recycled news penned by David Sanger and Bill Broad.

In case you missed it, Sanger and Broad recycle old stories about a US briefing from July that alleged some purloined Iranian computer files suggest Tehran is developing a ballistic missile re-entry vehicle with some suspicious properties.

Sanger repeatedly states that the information on the laptop involves a nuclear warhead—something Carla Anne Robbins of the Wall Street Journal has disputed in print.

David Albright, from the Institute for Science and International Security, pens the definitive rebuttal:

Following is ISIS President David Albright’s response to the article “Relying on Computer, US Seeks to Prove Iran’s Nuclear Aims” in the November 13, 2005 issue of the New York Times:

The November 13, 2005 New York Times article “Relying on Computer, US Seeks to Prove Iran’s Nuclear Aims” has a deep and misleading flaw. William J. Broad and David E. Sanger repeatedly characterize the contents of computer files as containing information about a nuclear warhead design when the information actually describes a reentry vehicle for a missile. This distinction is not minor, and Broad should understand the difference between the two objects, particularly when the information does not contain any words such as nuclear or nuclear warhead. The “black box” carried by the re-entry vehicle may appear to be a nuclear warhead, but the documents do not state what the warhead is. In addition, much of what Broad and Sanger report has been reported elsewhere, including the important information about “a sphere of detonators meant to ignite conventional explosives”(see Agence France Press article by Michael Adler on October 9, 2005). These earlier and more accurate articles did not confuse a nuclear warhead with a reentry vehicle.

By replacing warhead with re-entry vehicle throughout the article, the reasons for a healthy skepticism would also become more understandable. For example, a key question becomes much more clear, namely whether this work was initiated by an Iranian missile team on its own, or whether this work was ordered by Iran’s political leadership as part of a concerted nuclear weapons effort? Another important question that is sidestepped by the misleading use of warhead in the article is whether Iran can build the relatively small nuclear warhead able to fit into the triconic re-entry vehicle apparent in photos of a 2004 flight test. Based on publicly available photos of the 2004 test launch, the nuclear warhead would require a diameter of about 600 millimeters. Achieving such a diameter would be challenging for Iran. For example, the diameter of the warhead in the design provided to Libya (and perhaps to Iran) by A.Q. Khan was about 900 millimeters. A legitimate question is whether Iran could successfully build such a small nuclear warhead without outside help.

For an example of the photographic analysis that David Albright used to calculate the diamater of the notional Shahab 3 nuclear weapon at .6 M, see my post confirming Albright’s estimate on the mass of the Chinese design.

For the real wonks out there, has some nice images of the Shahab 3 nosecone—with a little high school geometry, you too can estimate the diameter and mass of the physics package.

Sanger’s language, by the way, is suspiciously careful. Sanger eschews “warhead design” in favor of more convulated formulations using “design” as a verb. Other phrases—such as “warhead plans” or “warhead intelligence”—are employed, misleading the reader about the nature of the information.

Adler, on the other hand, reports that the existence of an implosion warhead was inferred from the spherical shape of the “black box” and the presence of “a set of bridge wires” that would detonate the high explosives that compress the fissile material.

In the end, Sanger’s real contribution was to ascertain that the computer files in question were located on a laptop, rather than a desktop. In subtle recognition of their meager contribution, the Times headlined the story The Laptop.

Next week, Sanger answers the burning question in all of our minds: Tehran Nuclear Program, Mac or PC?


Late Update: A colleague points out that Dafna Linzer, writing in August, quoted Gordon Oehler on the bureaucratic reasons that Iran might develop a nuclear capable missiles that can’t carry an Iranian nuclear weapon:

Last month, U.S. officials shared some data on the missile program with U.N. nuclear inspectors, based on drawings obtained last November. The documents include design modifications for Iran’s Shahab-3 missile to make the room required for a nuclear warhead, U.S. and foreign officials said.

“If someone has a good idea for a missile program, and he has really good connections, he’ll get that program through,” said Gordon Oehler, who ran the CIA’s nonproliferation center and served as deputy director of the presidential commission on weapons of mass destruction. “But that doesn’t mean there is a master plan for a nuclear weapon.”


  1. Bernhard (History)

    Given the small size, could this warhead carry a Uranium based bomb or only a plutonium based one?

    I just want to know as the planed Iranian enrichment efforts don´t make much sense for a plutonium bomb.

    I am definitly no expert here, so pleaase excuse if these questions are dumb.

  2. Jeffrey Lewis (History)

    I don’t know how small a uranium bomb might be made, but the payload is too small to accomodate the Chinese uranium design that the Pakistanis put on the market.

    Most of the mass by volume comes from HE, so the question mass reduction will turn on technical expertise in compressing a ball of uranium with conventional explosives.

  3. John Field (History)

    At the risk of sounding like Gen. Turgetson talking about B52s flying below the radar in Dr. Strangelove, my immediate reaction to this is ‘no problem, you bet they can!’

    Fancy warheads are light because the pit bounces off the tamper. Nominally, this can double the speed of the pit – thus increasing the static compression pressure by as much as a factor of four. Add to that the acceleration in a collapsing spherical geometry, and you can see how the compressional pressures in the center of the pit can rise to a few 10’s of million psi when the explosives are only capable of about 5.

    If you really know what you’re doing, like the US has demonstrated, this can lead to very small, light, and efficient warheads – especially good for kicking off the thermonuclear secondary.

    If you’re Iran – to heck with it – use the Uranium, and lots of it. Lower the ratio of HE to U – so the pit Gurney velocity will be low. Make the reflector and tamper thin and light. The bare critical mass for uranium is about 50 kg; even surrounded by only HE, it will be considerably lower.

    Use an elliptical implosion to fit it into the missile – or even stretch it all the way into a linear implosion fired at both ends. Sure, this causes some issues with oblique shock, but no worse than making the explosive lenses to begin with – a flash radiography system would be nice.

    No matter how you figure it, it will rise past critical way faster than a gun-type design.

    If people are still skeptical, I will elaborate further. Presumably, there are [unconstitutional] government limits on my free speech that I can legally write into a blog though.

  4. jaylay (History)

    Okay but terrorists would not have used an Apple PowerBook. Don’t you watch the movies? Bad guys use Windows.