Israeli Military Capabilities and Iranian Nuclear Facilities:
An Assessment of Options

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*A more detailed version of this paper appears in the journal International Security, Spring 2007.  The ideas presented here are the author’s own.     

Introduction

　The use of military force to halt or reverse nuclear proliferation is an option that has been much discussed and occasionally exercised.[1]  Iran’s nuclear ambitions have been the subject of serious debate within the international community for more than four years and the possibility of military action against Iranian nuclear facilities has gained prominence in the public discourse, drawing comments from journalists, former military officers, and defense analysts. [2] 

　Israel has repeatedly stated its unequivocal opposition to a nuclear-armed Iran.  Multiple reports suggest that Israeli leaders are contemplating a preventive military strike to remove the threat of an Iranian nuclear capability.[3]  Such action would not be without precedent: on June 7, 1981, Israel launched one of the most ambitious preventive attacks in modern history.  Israeli Air Force (IAF) F-16 and F-15 fighter jets destroyed the Iraqi reactor at Osirak in one of the earliest displays of what has become known as “precision strike.”  No IAF planes were lost, and despite the political repercussions, the raid was considered a great success.[4]

　As Iran’s nuclear program moves forward, arguments for preventive action may seem increasingly compelling to the government of Israel.  This paper attempts to address the question of whether Israel has the capability to destroy Iranian nuclear facilities.[5]   As an unclassified assessment of military options, this analysis contains a number of assumptions and omissions.  First, it relies on public reports regarding Iran’s nuclear program.  Second, this article does not attempt to address all the military scenarios; we concentrate on a limited military strike against Iranian nuclear sites only.[6]  Finally, this article does not take a position as to whether Israel should attempt to destroy Iran’s nuclear facilities.  The repercussions of such an attack would be significant, in terms of diplomatic condemnation, economic factors, and a variety of potential Iranian military responses.  This article is intended to address the more limited but vitally important question of whether such an attack is even possible.

 

Iranian Nuclear Facilities 

　Iranian officials have claimed that by 2020, the country’s growing population and the expected global demand for oil will require the extensive use of nuclear power to meet Iran’s growing energy needs while still enabling significant petroleum exports.[7]  To support this goal, Iran has been engaged for years in developing a large, predominantly clandestine, nuclear infrastructure.  Having learned from the Israeli strike on Osirak, however, Iran’s nuclear infrastructure is carefully concealed and spread extensively throughout the country, with multiple pathways for nuclear weapon development as well as civilian uses.  Iran is developing both uranium enrichment capabilities to produce weapons-grade uranium and a plutonium production reactor and associated facilities for removing plutonium from spent fuel (a process called reprocessing).[8]  Both developments pose proliferation risks, although at present, Iran’s progress toward enriching uranium appears significantly more advanced than its plutonium production ability.  For this study, given Israel’s limited military means, it is important to distinguish between those activities that constitute a low risk of proliferation and those that pose the most serious threat of nuclear weapon development, or those activities directly involved in the production of fissile material.[9] 

　Iran’s nuclear complex has three critical nodes for the production of fissile material: a uranium conversion facility in Esfahan, a large uranium enrichment facility at Natanz, and a heavy water plant and plutonium production reactors under construction at Arak.[10]  Iran’s uranium conversion facility (UCF) is the primary chemical facility for Iran’s nuclear program.  The facility produces uranium hexafluoride (UF₆), which is the feed gas for uranium centrifuges, the machines used to produce enriched uranium.[11]  The loss of a domestic supply of UF₆ for enrichment activities would greatly reduce Iran’s ability to produce enriched uranium for a nuclear weapon in the future.  Unfortunately, many tons of uranium and fluorine exist at the UCF in various forms.  When fluorine products combine with water in the atmosphere, the likely result is the production of powerful hydrofluoric acid, which can burn skin or lungs if inhaled or contacted.  The Israelis would need to be willing to assume the collateral risks inherent in attacking this facility.

　The Natanz enrichment facility is the next critical link in the production of enriched uranium.  The facility is composed of a pilot fuel enrichment plant and a much larger commercial plant underground, which is awaiting the arrival of tens of thousands of centrifuges.  The site is located approximately 200 miles south of Tehran and about 40 miles from the nearest city.  To maximize delay of the Iranian nuclear program, Israel would have to wait until that the majority of the centrifuges intended for the commercial plant at Natanz are in place.  These thousands of centrifuges represent a massive capital investment that could not easily be replaced.  Thus, the optimal time for launching a military strike would be after the centrifuges have been installed.

　The final fissile material production facility that Israel could target is the heavy water plant and plutonium production reactors under construction at Arak (heavy water refers to water made with hydrogen that contains an extra neutron, ideal for the production of plutonium when used in certain reactors). The heavy water plant is a large facility located in central Iran approximately 150 miles southwest of Tehran.  The Arak heavy water facility will be able to produce more than 16 tons of heavy water per year – much more than is required by the on-site reactors and more than is needed for virtually all civilian applications.  Iranian officials have declared their intentions to build heavy-water reactors – and, in fact, construction has begun – that will utilize much of the heavy water produced at Arak.[12]  These reactors are scheduled for completion in 2014.  Even though construction of the reactor is only in the initial stages, the Arak facility remains a serious concern, and eliminating the heavy water plant would significantly slow Iran’s future ability to produce plutonium.[13]

　 Iran’s nuclear program contains many more elements, but the three facilities discussed above are critical for nuclear weapons development.  The destruction of these three facilities would have the greatest impact on Tehran’s ability to manufacture nuclear weapons – the UCF by denying Iran the ability to make UF₆ for enrichment, the Natanz facility for enriching uranium for nuclear weapons, and the Arak heavy water plant for use in plutonium production.  Of the three, the Arak heavy water facility is the least important – the plutonium production reactors at the site are not scheduled for completion for years, and thus the heavy water produced by the Arak facility will not be necessary until the reactors are completed – while Natanz is the most important site for nuclear weapon development.[14]  The destruction of this facility, especially if many centrifuges are also destroyed, is critical to impede Iran’s progress toward nuclear weapons. 

 

Weaponeering: How Many and What Kind of Bombs? 

　The IAF has developed substantially better munitions for attacking hardened targets than were used against Osirak in 1981.  These improvements come in two forms: enhanced accuracy and improved penetration.  This makes current bombs both easier to deliver and more likely to destroy the target.

　The acquisition of precision-guided munitions (PGMs) in the 1980s and 1990s changed the dynamics of IAF bombing.  Accurate delivery no longer required approaching at low altitude and then diving directly at the target as at Osirak.[15]  Instead, using both Global Positioning System (GPS) and laser-guided bombs (LGBs) – which utilize a laser light shined from aircraft or ground troops to guide the weapon to its target – the IAF can deliver munitions from high altitude from a longer range, eliminating some of the risk of surface-to-air missiles and anti-aircraft artillery.[16]  In addition, LGBs are incredibly accurate, with half the weapons released at a distance of 15km landing in a circle of 3 meters or less at the target.[17]  Both GPS and LGB munitions can maneuver themselves on target after launch, making the weapons-release criteria much less restrictive.[18]  Similarly, munitions for attacking hardened targets have been significantly improved since the Osirak raid.  These weapons, known as penetrating warheads or “bunker busters,” have seen extensive use by the U.S. Air Force.  Delivered from high altitude and arriving at steep angles, these munitions can penetrate tens of feet of earth, and even several feet of reinforced concrete.[19]

　Israel has recently sought to acquire two heavier penetrating warheads from the United States.[20]  In September 2004, Israel announced that it would purchase approximately 5000 PGMs from the United States, including about 500 equipped with the 2000-lb BLU-109 penetrating warheads.[21]  More recently, Israel has received approval to purchase 100 bunker-busters equipped with the 5000-lb class BLU-113 penetrating warhead.[22]  After the July 2006 conflict with Hezbollah, delivery of these bombs has apparently been expedited and they could be rapidly integrated into the IAF.[23]

　Having presented the general outline of IAF capabilities, we now turn to the application of those capabilities to specific targets. Natanz is both the most difficult and most important target to destroy.  The main enrichment facility apparently has two large (25,000-32,000 square meters) halls located 8 to 23 meters underground and protected by multiple layers of concrete.[24]  The combination of large size, burial, and hardening make this a very challenging target. 

　One method for defeating hardened targets is to use LGBs targeted on the same aim point but separated slightly in release time to “burrow” into the target.[25]  This takes advantage of the extremely high accuracy of LGBs in combination with a penetrating warhead.  The IAF appears to have purchased penetrating LGBs with this technique in mind.  Gen. Eitan Ben-Elyahu, former commander of the IAF, commented: “Even if one bomb would not suffice to penetrate, we could guide other bombs directly to the hole created by the previous ones and eventually destroy any target.”[26]

　For such a heavily hardened target, the 5000-lb, penetrating BLU-113 would be the most likely weapon to use.  One BLU-113 might be sufficient to penetrate the protective earth and concrete over the Natanz facility, but two properly sequenced almost certainly would.  The probability of two LGBs aimed at the same point hitting essentially one on top of the other is likely to be about 45%.[27]  Sequencing of the BLU-113s would only be necessary for the upper end of the estimated hardness of the Natanz centrifuge halls.  For example, if the facility is protected by 23 meters of concrete and earth, sequencing would only be needed if roughly 2 meters or more of the 23 meter total are concrete.  For the lower estimate of 8 meters of concrete and earth cover, one BLU-113 could easily penetrate. 

　The question then is how many BLU-113s are needed to penetrate and ensure the destruction of the centrifuge halls?  We estimate that the confined blast from three BLU-113s, combined with collapsing ceiling, shrapnel, and incendiary effect, would likely be sufficient to ruin most if not all of the centrifuges present.[28]  According to some analysts’ estimates, even this might be overkill, as centrifuges in operation are vulnerable to violent destruction from disruptions in the power supply.[29]         

　The delivery of six pairs of BLU-113s on each hall, for a total of twelve pairs or twenty-four weapons, would give fairly high confidence of achieving this level of damage.  With each pair having a 45% probability of success, 6 pairs would give a total probability of about 31% of achieving at least 3 successful penetrations in both halls and a 71% probability of at least 2 penetrations in each hall.[30]   In addition to the weapons that actually penetrated the centrifuge halls, all but one or two of the other BLU-113s would be expected to detonate over each hall, possibly collapsing the entire structure.  This gives further confidence in the successful destruction of the facility.  For greater confidence, the BLU-113 impact points could be targeted by additional 2000-lb BLU-109s.  Finally, the above ground pilot plant at Natanz should be destroyed as well; two 2000-lb bombs would likely be sufficient. 

　The next target, the Esfahan UCF, is not buried.  Based on photographs and commercial satellite imagery, the facility appears to be rectangular, roughly 180 meters in length with a varying width of 40 meters up to 80 meters.[31]  The facility does not appear to be hardened so penetrating weapons would probably not be required to destroy it.  However, the IAF could choose to use penetrating weapons to pierce the walls and ensure detonation near critical components.

　In this case, the smaller BLU-109 would be useful.  BLU-109s could easily penetrate, so extremely high accuracy is less important.  The facility appears to be roughly 10,000 square meters; nine BLU-109s would be sufficient to expose the entire facility to sufficient blast to rupture chemical storage tanks.[32]  The accuracy of LGBs is such that there is a much greater than 90% probability of the weapon falling within 10 meters of the aim-point.  Combined with a reliability of 90% for the weapons themselves, targeting the facility with twelve BLU-109s would be more than sufficient to guarantee its destruction.[33]

　The heavy water production plant at Arak is the final target.  This target is not hardened, so it would be relatively simple to destroy.  The central element of the production plant is a set of towers used to manufacture heavy water.  There are three main and nine smaller towers in the complex.  They are located in two clusters of approximately 80 meters length and 30 meters width.  Three nonpenetrating 2000-lb LGBs targeted on each cluster would likely be sufficient to ensure destruction.[34]

　The heavy water reactor construction site consists of an unfinished containment dome and cooling facility.  Assuming this incomplete site is worth targeting, four 2000-lb weapons should be more than sufficient to destroy it.  This brings the total number of weapons needed to have reasonable confidence in destroying all three target sets to twenty four 5000-lb weapons and twenty four 2000-lb weapons. 

 

Israeli and Iranian Forces

　In the 25 years since the Osirak strike, the IAF’s long-range strike capability has improved dramatically.[35]  The IAF’s deep strike capability remains centered on its F-15s and F-16s.  However, Israel now fields twenty-five of the F-15I Ra’am and twenty-five to fifty of the F-16I Soufa, both of which are specially configured for long-range attack.[36]  The F-15I is equipped with conformal fuel tanks (CFTs), which when combined with external drop tanks could give it a combat radius of roughly 1700 kilometers.[37] 

　The F-16I is produced specifically for Israeli deep-strike requirements.  Like the F-15I, it has CFTs to extend its combat range.  The F-16I’s exact combat radius is unknown, but is likely to be on the order of 1700 kilometers with external fuel tanks.[38]  Given the Israeli decision to forgo additional F-15I procurement in favor of increased F-16I procurement, its range is presumably not significantly less than the F-15I. 

　In contrast to the modern systems of the IAF, the Iranian military possesses an odd amalgamation of technologies.  Following the 1979 revolution, much of the Iranian military’s technical competence disappeared as technicians and skilled officers were killed or fled the country.  Spare parts for U.S.-made systems also became difficult to obtain.  Subsequently, Iran has sought to upgrade its military technology with purchases from Russia, China, and elsewhere.[39]  This mixture of various systems is readily apparent in Iran’s air defense capabilities, although its effectiveness cannot be entirely discounted.  The defense is comprised of three elements: aircraft, surface-to-air missiles (SAMs), and antiaircraft artillery (AAA). 

　The quality of inventory and capability of the Islamic Republic of Iran Air Force (IRIAF) is poor; maintenance and training are insufficient to produce an air force capable of competing with a first-class air force such as the IAF.  The IRIAF fields only forty modern MiG-29s; the remainder of its inventory is 1970s or earlier vintage.  Further, most of the air-to-air missiles owned by the IRIAF fleet are old and low quality as well.[40]

　The Iranian SAM inventory is similar in quality to its aircraft inventory, with the further complication that it is divided between the IRIAF, the Iranian Revolutionary Guards Corps, and the Army.  The centerpiece of the inventory is the MIM-23B Improved HAWK, which is of early 1970s vintage.  The combination of age and lack of spare parts probably reduces the utility of the Iranian Improved HAWKs.[41]  Further, Israel also uses the HAWK system and is thus likely to have developed significant capability against it.  Iran’s other SAMs are similarly old and would have limited utility against first class air forces.[42]  Finally, Iran possesses a large quantity of AAA.  In general, AAA is ineffective at higher altitudes, although the sheer volume of fire may be advantageous to Iran.

 

Possible Attack Routes            

　The Israelis have three possible attack routes.  The first is to fly north over the Mediterranean, refuel from airborne tankers and then fly east over Turkey to Iran.  The second is to fly southeast, skirt Jordan and Saudi Arabia, and then fly northeast across Iraq; alternately, the Israelis could fly northeast across Jordan and continue across Iraq.  Finally, the Israelis could fly southeast and then east along the Saudi/Iraqi border to the Persian Gulf and then north.  Most of these routes will require the Israeli pilots to refuel in midair.  Tankers are vulnerable to attack so being able to refuel over the international waters would be a big advantage.  

　The northern route has three main legs.  The first is from Israeli air bases to the Turkish border.  The distance from the most distant Israeli airbase, Hatzerim, north to Turkey is 580 kilometers.[43]  The second leg crosses Turkey from west to east, beginning east of Adana, passing south of Diyarbakir, and ending at the Iranian border west of Orumiyeh.  This is a total distance of about 840 km.  The final leg is southeast across Iran to Arak, Natanz, and Esfahan.  We calculate the end point as the distance to the farthest target, in this case Esfahan.  The distance from the border near Orumiyeh to Esfahan is approximately 800 kilometers, for total route length of roughly 2,220 kilometers. 

　For this route, the Israeli planes could refuel over the Mediterranean, allowing the strike package to maneuver against Iranian air defenses with less concern about fuel.  However, the refueling on the inbound leg of the flight would take place very early (after flying less than 600 kilometers), so only a limited amount of fuel could be offloaded to each aircraft before they would be full again.  The total distance from Adana to Esfahan is about 1640 kilometers, very close to the combat radius predicted for the F-15I.  This would mean the strike aircraft would probably have to refuel a second time, after leaving Turkish airspace on the return trip.  The IAF tankers could wait near the Turkish border to refuel the strike aircraft as they returned to Israel.

　One disadvantage of this route is that it passes quite close to several Turkish air force bases, including two large ones: Incirlik (near Adana) and Diyarbakir.  Turkey’s reaction to an Israeli incursion is uncertain.  Although it would undoubtedly be angry, the central question is whether it would fire on Israeli aircraft or otherwise disrupt the Israeli mission.[44]  Turkey and Israel have historically enjoyed good military and economic relationships, even if their political rhetoric is sometimes harsh.  On the other hand, the current Turkish government has distanced itself from Israel to some degree.  Furthermore, this route passes near a number of Iranian air bases: Tabriz, Sharohki (near Hamadan), Kermanshah, Khatami (near Esfahan), and Vahdati (near Dezful).[45]  The major bases near Tehran are slightly farther away.  This would put the strike package in range of a number of possible intercept squadrons during both entry and exit from Iran.

　The second, central route is the most direct route, but it carries major political difficulties.  It has one or two main legs, depending on how it is flown.  The first leg of either option would be from Israel to the Gulf of Aqaba.  The length of this leg would be roughly 360 kilometers.  The second leg of the first option is from the northern end of the Gulf of Aqaba to the target zone, a distance of roughly 1800 km.  The total distance traveled, 2160 kilometers, would be scarcely less than that of the northern route.  Refueling would be required at some point.  The second option, directly across Jordan from the Gulf of Aqaba and across Iraq, is much shorter.  From Hatzerim to Natanz would be roughly 1750 kilometers, which is just over the estimated combat radius of the strike aircraft.

　Both options would require cooperation (or at least acquiescence) from the Jordanians and especially from the Americans in Iraq.  The flight path of option two is directly over Jordan and would pass near the capital of Amman and a major air base at Azraq ash Shishan.  Each would traverse all of Iraq, and any refueling would likely occur in Iraqi airspace.  It would be all but impossible to accomplish without the Americans and probably the Jordanians noticing.  While any strike against Iran by Israel would likely be interpreted as having U.S. backing, this option would provide unambiguous evidence of it. 

　The third, or southern, route covers perhaps the least well-defended airspace, at least in its initial legs.  It is also quite long and poses refueling challenges, running west to east across northern Saudi Arabia to the Persian Gulf, then north/northeast into Iran.  The first leg would be the Israel to the Gulf of Aqaba route noted above, a distance of 360 kilometers.  From Aqaba it would cross Saudi Arabia south of the Iraqi border, a distance of roughly 1,350 kilometers.  The second leg would cross the Persian Gulf into Iran and continue north to the target zone.  The farthest target would be Natanz, a distance of about 700 kilometers.  This makes the total route length on the order of 2,410 kilometers.

　The southern route poses the same kind of diplomatic challenges as the northern route, as it crosses Saudi airspace and passes near several Saudi air bases.  Further, Saudi Arabia has invested significantly in air defense.  On paper this appears to be a highly formidable air defense system, but Saudi readiness levels are alleged to be very low.[46]  In addition, much of Saudi Arabia’s northern air defense was intended to protect against Iraq, and presumably readiness levels are much lower now that the threat from Saddam Hussein has been removed.  In addition, the question would still remain whether the Saudis would fire on Israeli aircraft or simply launch a massive diplomatic protest.

　A more serious issue is refueling.  The route would be significantly longer than the estimated combat radius of the strike aircraft.  The IAF would thus have two options: It could attempt to refuel the strike package over Saudi territory, which would be subject to disruption by Saudi forces; or, it could refuel over the Persian Gulf.  It would still require flying the tankers across Saudi Arabia, and would also put the tankers in a position to possibly be engaged by IRIAF interceptors over the Gulf. 

　All of the routes pose significant operational and political risk.  From a technical perspective, none are impossible.  We do not attempt here to judge which route Israel might use, as we do not have insight into the political and security calculations of the Israeli leadership.  Therefore, the remainder of this analysis focuses on Iranian air defenses near the target areas, regardless of the route taken by the IAF.

The Likely Correlation of Forces

　 The analysis below assumes that the IAF will attack Iran’s nuclear facilities using twenty-five F-15Is and twenty-five F-16Is, probably consisting of three smaller packages, one for each of the likely targets.  The interaction of this strike package with Iran’s air defenses is highly contingent: The exact quality and readiness of Iranian equipment is unknown, but with moderate reliability and effectiveness in its air defenses, Iran could credibly respond to an IAF incursion.  In contrast, if reliability and effectiveness are low, then the IAF could brush aside the Iranian forces with relative ease.

　In this analysis, we look at the number of aircraft that would have to arrive on target to deliver the ordnance noted in the second section above.  From that, we can determine the attrition levels the Iranian air defense would have to generate to prevent the Israeli strikes from being fully successful.  We can then make some rough guesses about the likelihood of this occurring.

　In the case of Natanz, if each F-15I carried only one BLU-113 (along the centerline) in addition to external fuel tanks and air-to-air missiles, then twenty-four F-15Is would have to arrive at the target complex.  Note that if the F-15Is carried only one BLU-113 centerline, they could potentially carry additional BLU-109s.  Esfahan and Arak, easier targets than Natanz, require fewer aircraft to deliver the requisite ordnance.  In the case of Esfahan, six F-16Is would have to arrive at the target complex if each carried two BLU-109s.  For Arak, only five F-16Is would have to reach the target.

　 Iran’s air defenses would have to impose significant attrition to cause the IAF mission to fail to deliver the ordnance noted above.  The IAF could assign two additional F-16Is loaded with 2000-lb bombs to both Arak and Esfahan and then have ten left for defending the strike package.  The Iranian air defense would have to down three out of seven assigned to Arak and three out of eight assigned to Esfahan, roughly 40 percent attrition.  This would be almost unimaginable given Iranian assets.[47]

　The major vulnerability would be attrition in the F-15I force, assuming each carried only one BLU-113.  Then Iran’s air defenses would only have to impose an attrition rate of 8 percent (downing two out of twenty five) to cause the mission to fail to deliver the designated ordnance.  This is certainly within the realm of possibility.  For example, IAF ground attack aircraft sustained massive attrition in the first days of the 1973 Yom Kippur War, including 8 percent of total fighter strength on the first day.   The average daily attrition rate of IAF aircraft in that conflict was only about 3 percent, however.[48] 

　Of course, reliability is an issue with aircraft as well.  If one F-15I failed to complete the mission due to reliability problems, then the Iranians would only have to down one aircraft.  If two failed to function, then the mission would be unable to deliver the designated ordnance without the Iranians even firing a shot.  Further, the IRIAF does not have to actually down any IAF aircraft.  It must only succeed in engaging the IAF aircraft with sufficient threat to cause them to dump their weapons in order to maneuver. 

　Even if the designated ordnance for total destruction of Natanz were not delivered, the Iranian nuclear program would still be significantly hampered.  Even one large bomb detonating in each centrifuge hall would disrupt operations.  Further, to ensure that total destruction is more likely, the IAF could also supplement the F-15I attack on Natanz by assigning F-16Is armed with BLU-109s after the BLU-113s.  While less certain of penetrating than the massive BLU-113s, the BLU-109 is a very capable weapon in itself.  Assuming that six F-16Is were assigned to supplement the F-15Is, each could deliver two BLU-109s on each of six BLU-113 aimpoints.  This would result in a greater than 0.8 probability of at least one weapon, BLU-109 or BLU-113, penetrating the Natanz facility.[49] 

　Also, as noted earlier, the F-15Is could carry two BLU-109s, adding more firepower.  If each carried one BLU-113 and two BLU-109s, the strike package of twenty five F-15Is would have twenty five BLU-113s and fifty BLU-109s.  Even if the Iranian air defense imposed 40 percent attrition (ten aircraft downed), fifteen BLU-113s and thirty BLU-109s would arrive on target, even without supplemental F-16Is.  This would allow almost four weapons to be targeted for each of the twelve aimpoints (six per hall), even without additional F-16Is. 

 Conclusion

The foregoing assessment is far from definitive in its evaluation of Israel’s military capability to destroy Iran’s nascent nuclear weapons capability.  It does seem to indicate, however, that the IAF now possesses the capability to destroy even well-hardened targets in Iran.  Leaving open the question of whether an attack is worth the resulting diplomatic consequences and Iranian response, it appears that the Israelis have three possible routes for an air strike against three of the critical nodes of the Iranian nuclear program, although each route presents diplomatic and operational difficulties.  However, the operation appears to be no more risky than Israel’s 1981 attack on Osirak and provides at least as much benefit in terms of delaying Iranian development of nuclear weapons.  The question then becomes one of will and individual calculation. 

More generally, this assessment illustrates both the utility and limitations of precision-guided weapons for counterproliferation.  Assuming that the intelligence is available to identify targets, precision-guided weapons can fill an important role, leading to smaller strike packages and lower risk to personnel and equipment.  While limitations still exist, especially in the case of hardened targets, precision-guided weapons have become extremely capable, particularly when strike aircraft are confronted by relatively low-quality air defense.  The use of precision strike for counterproliferation should therefore not be discounted lightly.  However, this analysis highlights the critical nature of target knowledge, indicating that in many cases the means of striking or defending WMD targets are less important than the ability to locate or hide them. 

Additionally, the analysis illustrates that the technical ability to conduct an attack may be overshadowed by the “day after” problem.  With Iraq in chaos, a capable proxy in Lebanese Hezbollah and oil prices high, Iran today has much greater ability to strike back against both Israel and the United States than Iraq did after the Osirak strike in 1981.  Although the IAF may be able to destroy known Iran’s nuclear facilities (by extension the U.S. Air Force almost certainly can) and significantly delay Iran’s nuclear program, Iran’s potential responses to this strike may cause policymakers to reject the military option.  Despite its potential utility, military counterproliferation must be complemented by other political and economic efforts if the spread of nuclear weapons is to be checked.   

 

Appendix: Estimating Aircraft Range and Bomb Sequencing 

Aircraft Range Estimates

　The official ferry range (the range the aircraft can fly one way without refueling) for the F-15E using CFTs and three external fuel tanks is given by the U.S. Air Force as 3840 km.  Other sources suggest that the actual ferry range is in excess of 5600 km.  Jane’s All the World’s Aircraft lists it as 4445 km.  In terms of combat radius, the number most often cited for the F-15E is 1270 km, which appears to be with CFTs and a full weapons load.  By replacing two weapons with external fuel tanks, the combat radius could be extended.  A simple estimate can be derived from comparing the fuel load with CFTs only (approximately 23,000 pounds) with the fuel load of CFTs plus two 610 gallon external tanks (approximately 31,000 pounds).  This ratio is about 1.35, which when multiplied by 1270 km yields a combat radius of roughly 1700 km.  This estimate also appears to roughly conform to the official ferry range, as with three drop tanks and CFTs the F-15E can carry about 35,300 pounds of fuel, or a ratio of about 1.53.  This yields a combat radius of about 1900 km, or a ferry range of 3800 km.  Ferry range assumes no combat maneuvering, but the official estimate, as noted is probably highly conservative.  Some sources list the combat radius of the F-15E as in excess of 1800 km, so the 1700 km estimate is probably conservative as well.  Breguet calculations based on unclassified estimates of F-15E performance, a specific fuel consumption of .9, a constant velocity of 700 mph, constant coefficient of lift, lift to drag ratio of 6.193 and a take-off weight of 80,000 lbs with  30,000 lbs of fuel also produce results in this range (approximately 1800 km radius), not accounting for weapons release. 

　The F-16D, which the F-16I is based on, has internal fuel storage of almost 5900 pounds and an estimated combat radius of approximately 540 km.  With the addition of CFTs, one 300 gallon centerline and two 600-gallon external fuel tanks, the F-16I could carry about 19,000 pounds of fuel.  Using the simple estimation method above, this is a ratio of 3.22, which would give the F-16I a combat radius of about 1730 km.  As the CFTs have much lower drag than the external fuel tanks, the actual combat radius will probably be higher.  At least one source, the Jaffee Center, reports a combat radius of 2100 km, so this estimate is probably conservative.  It appears to be roughly in line with other estimates.  Jane’s All the World’s Aircraft lists 1361 km as the combat radius in a hi-lo-lo-hi profile for the F-16C Block 50 with CFTs, a centerline 300 gallon external fuel tank, and two 370 gallon underwing fuel tanks (roughly 17,100 lbs of fuel), while carrying two 2000-lb bombs and two Sidewinder missiles.  This estimate is also in line with the official U.S. Air Force ferry range of in excess of 3200 km.  This ferry range is with two 600 gallon and two 370 gallon fuel tanks for a total of 18,700 pounds of fuel, a ratio of 3.28.  This yields a radius of about 1770 km and a ferry range of at least 3540 km.     

Sources:

　John Anderson, Introduction to Flight, 5^th edition, (Boston: McGraw-Hill, 2005); Jane’s All The World’s Aircraft entry for F-15 and F-16; Air Force Fact Sheet F-15, http://www.af.mil/factsheets/factsheet.asp?fsID=102; Global Security, http://www.globalsecurity.org/military/systems/aircraft/f-15-specs.htm; Jaffee Center Middle East Military Balance, http://www.tau.ac.il/jcss/balance/airf.pdf; Air Force Technology, http://www.airforce-technology.com/projects/f15/; and F-15E Strike Eagle,  http://www.f-15estrikeeagle.com/weapons/loadouts/oif/oif.htm; Air Force Fact Sheet F-16, http://www.af.mil/factsheets/factsheet.asp?fsID=103; Jaffee Center Middle East Military Balance, http://www.tau.ac.il/jcss/balance/airf.pdf; Global Security, http://www.globalsecurity.org/military/systems/aircraft/f-16-specs.htm and Air Force Technology, http://www.airforce-technology.com/projects/f16/.
  

Penetrating Bomb Sequencing

　Bomb sequencing is derived from the formula P_k=1-0.5^(LR/CEP), where P_k is the probability of successful landing within the lethal radius of the target.  Additionally, the non-Gaussian distribution of LGBs is represented by the fraction of bombs that exhibit no error (i.e. the directly hit the aimpoint).  The “lethal radius” is crater size, so there is some probability of a near miss still landing in the crater.  In the case of two “near misses,” the lethal radius is reduced by half; in other words if the first bomb lands within half the LR of the aim point, then the second bomb will definitely hit within the LR if it too lands within half the LR of the aimpoint as well.  With these assumptions, there are four probability branches: direct hit-direct hit; direct hit-near miss; near miss-direct hit; near-miss near-miss.  These branches have a probability of (0.65)²=0.42); (0.65*(0.35*0.29)) =0.07; ((0.35*0.29)*0.65=0.07); and (0.4*0.16)²=0.004).  This yields a cumulative probability of 0.56, which is then multiplied by the cumulative reliability (0.9*0.9=0.81) to yield a probability of 0.45.  The assumption of crater width is based on the 0.37 m diameter of a GBU-28 combined with the effect of the explosion occurring in the ground, which will rupture the ground surrounding the explosion as well as being vented to some degree out of the entryway of the warhead.  This is presumed to create sufficient structural damage to allow the second BLU-113 to penetrate easily if it impacts within about 1.8-3.6 m radius (10-20 times the diameter of the bomb) of the entry point of the first bomb.  This calculation is very sensitive to changes in the parameters, so variations are presented below.   

Variation in Parameters of the BLU-113 Sequenced Penetration

Nhit	0.65	0.3	0.5	0.7	0.5	0.15	0.7
Nnm	0.35	0.7	0.5	0.3	0.5	0.85	0.3
CEP	6	3	6	2	3	6	3
LR	3	2	3	3	3	3	2
Rel	0.9	0.85	0.9	0.95	0.9	0.9	0.9
Prob	0.45	0.19	0.33	0.7	0.42	0.09	0.53

N_hit= Percentage of munitions that directly hit aimpoint (i.e. non-Gaussian distribution)

N_nm= Percentage that exhibit Gaussian distribution of a given CEP

CEP= Circular Error Probable; radius in m around aimpoint in which half of Gaussian distributed munitions will fall

LR= Lethal Radius; in this case the radius in m around the impact point of the first BLU-113 that the second must hit within to penetrate the Natanz facility

Rel= Reliability; the probability the BLU-113 will function properly

Prob= the cumulative probability of the two BLU-113s functioning and impacting sufficiently close for the second to penetrate the Natanz facility  

Sources:

C.R. Anderegg, Sierra Hotel: Flying Air Force Fighters in the Decade After Vietnam, (Washington, D.C.: Air Force History and Museums Program, 2001)

Morris Drells, Weaponeering: Conventional Weapons System Effectiveness, (Reston, Va.: American Institute for Aeronautics

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