Destruction in depth: This is what the bunker-busting US bomb GBU-57 can do

Should US President Donald Trump decide to intervene militarily in the war between Israel and Iran, the GBU-57 would be his weapon of choice. This bunker-busting bomb is the only strategic weapon capable of destroying Iran's underground nuclear facilities. The 13-ton GBU-57 bomb can embed itself dozens of meters into the ground before exploding. This weapon is missing from Israel's arsenal to achieve its stated war aim: to prevent Tehran from building a nuclear bomb. But what exactly can the bomb do? Key questions and answers.

Why this bomb?

Even though the Israeli army succeeded in decimating the Iranian military command and many surface facilities within five days, "many questions remain regarding the effectiveness of Israeli attacks on the heart of Iran's nuclear program," says Behnam Ben Taleblu. According to the expert from the neoconservative Foundation for the Defense of Democracies, "all eyes are on Fordo."

According to the International Atomic Energy Agency (IAEA), "no damage was detected" at this uranium enrichment facility located south of Tehran. Unlike the Natanz and Isfahan facilities, the Fordow facility is located about 100 meters underground, thus out of range of Israeli bombs.

"Only the United States has the conventional capability" to destroy such a facility, emphasizes Mark Schwartz. The US general served in the Middle East and is now an expert at the Rand Corporation think tank. By "conventional," i.e., non-nuclear capability, he means the GBU-57.

What makes the GBU-57 special?

The US bomb is unique because, according to the US Army, it can penetrate rock and concrete up to 61 meters deep. Unlike many rockets and bombs that detonate their explosives at the moment of impact, bunker-busting bombs first burrow into the ground and only explode once the underground facility is reached.

These weapons have "a very thick hardened steel casing" that allows them to "penetrate the rock layers," says Masao Dahlgren, an armament specialist at the CSIS research center in Washington. This explains their weight: more than 13 tons and a length of 6.6 meters. Their penetration power is also due to their fuze, which "detects the cavities" and "discharges when (the bomb) penetrates the bunker," explains Dahlgren.

Development of this bomb began in the early 2000s. Twenty units were ordered from Boeing in 2009.

How is it dropped?

US B-2 fighter jets are the only ones capable of delivering this bomb. Some of these stealth aircraft were stationed at the US military base Diego Garcia in the Indian Ocean in early May. They were no longer seen there by mid-June, according to an analysis of satellite images by PlanetLabs.

But with their long range, B-2 bombers launched from the US are "capable of flying all the way to the Middle East to drop bombs," Dahlgren explains. Each B-2 aircraft can carry two GBU-57s.

If the decision is made to use them, "they won't just drop a single (bomb) and be done with it, but they will use multiple ones to ensure a 100 percent hit probability," Schwartz says. Israel's air superiority in Iran "reduces the risks" the B-2 bombers could face, the retired general adds.

What consequences would their use have?

Such an intervention would "come at a high political price" for the United States, says Behnam Ben Taleblu. He emphasizes that the GBU-57 would "not be the only solution" to permanently halt Iran's nuclear program—besides a diplomatic solution.

Without this bunker-busting bomb from the US, the Israelis could attack underground facilities like Fordow "by trying to hit the entrances, collapse as much as they can, and cut off the power supply," the expert enumerates. This appears to have been the case with the Natanz nuclear facility.