Iran plans to shoot down Israel's biggest bombs to defend nuclear sites

Iran completed air defence drills on Tuesday in which it claimed to have shot down a simulated Israeli bunker-busting bomb.

The rehearsal involved defending Natanz, one of Iran’s major nuclear research sites, and represents an unorthodox approach to air defence, where missile systems are typically designed to intercept other missiles, drones or aircraft.

Bombs, by comparison, are said to have a small “radar cross section,” meaning they are difficult to spot and shoot down. A bigger issue in air defence is that aircraft carrying short-range, unpowered bombs – as opposed to missiles – represent a much larger, priority target.

Most modern air defences defend against jet fighters at ranges more than 100 kilometres, threatening them long before they can release their bombs.

Tasnim News reported the exercise, saying Dey-9 air defence missiles hit the simulated bomb at a 17 kilometre range. For comparison, Israel is believed to have an air-launched ballistic missile, Golden Horizon, that can hit Iranian air defences at ranges of 2,000 kilometres.

Iran released images of the drill, highlighted by Russian analyst Yuri Lyamin.

Golden Horizon, also called Blue Sparrow, is believed to have been used in attacks in October that heavily damaged Iran's most powerful radar systems, the Ghadir and the 30N6E, and struck Parchin, a military research site linked to Iran's nuclear programme.

Some experts believe Israel could launch a third air strike on Iran this year, after retaliating for two of the largest ballistic missile attacks in history in April and October, which saw hundreds of the massive projectiles, along with drones and low-flying cruise missiles, strike targets inside Israel, including Nevatim, the country’s most important airbase.

Iran was retaliating for an Israeli strike in April in Syria, which killed two senior generals at their consulate in Damascus, as well as Israel’s assassination of Hamas leader Ismail Haniyeh in Tehran.

Israel has said it is ready to act without US support for the difficult mission of bombing Iran’s nuclear programme. One Israeli expert who worked for the intelligence service focused on Iran told The National that such a strike was likely.

The UN says Iran is close to having the means and technical know-how to create a nuclear bomb, something that has long been a red line for Israel. But Israel lacks aircraft big enough to carry bombs with the capacity to destroy many of Iran’s nuclear sites that are buried within mountains, at weapons sites such as Fordow.

To seriously damage or destroy these sites – rather than destroy tunnel entrances which can be repaired – Israel is thought to need the GBU-57, one of the largest bombs in the world, carried by the US B-2 and B-1 bombers. Israel possesses neither the aircraft, nor the 13,600 kilogram device which burrows deep into the ground before detonating, creating an earthquake-like shock wave to crush bunkers.

One Israeli expert has speculated that Israeli F-15I fighter-bombers could be heavily modified to carry the huge bomb, but there is no evidence of this work being undertaken.

The largest bomb in Israel’s possession is the GBU-28, a 2,260 kilogram device intended to destroy bunkers. Israel is thought to have purchased 100 of the massive, short-range bombs – which fly just 10 kilometres – from the US. Iran’s air defences have stated ranges of hundreds of kilometres.

Carrying the huge weapon more than 1,000 kilometres would greatly complicate a mission over Iran, eating into fuel and leading to long periods of refuelling aircraft mid-flight.

Israel also used dozens of 900kg bombs to “dig” into late Hezbollah leader Hassan Nasrallah’s bunker in Beirut when it assassinated him in September, a tactic experts say might be replicated against some Iranian targets.

Intercepting a bomb

Intercepting a bunker buster could prove tricky for Iran, experts say, and their successful test likely occurred under near “perfect” conditions that wouldn’t be experienced in war.

Experts say the Russian-made TOR air defence system, in Iran’s possession, could theoretically shoot down a large, slow-moving bomb. Iranian Brigadier General Ahmad Sadeqnejad said in March that Iran had modified air defences to hit bunker busters, claiming Israel had used the weapons at “long range” in Syria.

This suggests Israel might have fitted its bombs with gliding wings, a tactic used by Russia in Ukraine to send extremely large bombs like the FAB 3000 out to ranges of 60 kilometres, making them more like unpowered, GPS-guided missiles.

“An exercise such as the Iranians are claiming to have pulled off is only as realistic as it is designed to be, and any kind of attack plan will take account of the capabilities and limitations of the defences,” says Bill Sweetman, an expert at Valkyrie Strategic Solutions, a consultancy, and veteran of the aerospace industry.

“A free-fall bomb, using guidance to stay on a predicted track, is not hard in itself to guide a missile against. Problem one is that the missile warhead to intercept it is almost certainly blast and fragmentation, effective against thin-skinned aircraft – including commercial aircraft – but less so against a hardened-steel bomb casing,” he says.

But Mr Sweetman points out the bigger problem, which is that Israel has an array of countermeasures for air defences. These include HARM missiles, which seek out enemy radar transmissions, in some cases fixing on to the radar position if the radar is switched off as a safety measure.

Israel also has decoy drones, known as the ATALD, which can mimic the radar profile of various jets and weapons, and potentially bunker busters, which could cause Iran to waste ammunition on the decoys, expose their own positions to enemy attack and lose vital seconds working out which aircraft are real, or fake.

Israel also has stealth F-35s, which can get close to enemy radar systems without being detected, and powerful electronic warfare equipment like the Scorpius pod, which can render Iranian radars useless, create misleading radar images or potentially break them.

“Problem two, you have to survive long enough to intercept the bomb, and there will be defence suppression in play. Problem three is electronic warfare, including jamming and decoys,” Mr Sweetman says.

Mr Sweetman says if the Israelis are concerned about Iran shooting down bunker-buster bombs, they could coat the devices with “special materials which could be wrapped around (fuel) drop tanks and bombs,” to make them less visible on radar.

A material called “parabeam,” he says, was used in tests by US defence firm Northrop Grumman. “It was cheap and light and did not have to be as durable as a radar absorber that you'd use on an aeroplane. I somehow doubt the Iranians put something like that on their target, but I would not bet against the Israelis having figured it out.”