Pentagon war planners worry that their 30,000-pound “bunker-buster” bomb, the Massive Ordnance Penetrator, might not destroy some of Iran’s deepest facilities, so they want a better bomb:
The Defense Department has spent about $330 million so far to develop about 20 of the bombs, which are built by Boeing Co. The Pentagon is seeking about $82 million more to make the bomb more effective, according to government officials briefed on the plan.
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According to Air Force officials, the 20.5 foot-long MOP carries over 5,300 pounds of explosive material. It is designed to penetrate up to 200 feet underground before exploding. The mountain above the Iranian enrichment site at Fordow is estimated to be at least 200 feet tall.
A small, “tactical” nuclear bomb would likely have a yield measured in kilotons, although we have made artillery shells with yields in the dozens of tons.
A tactical nuclear missile would probably work better than a bomb, because it could avoid almost all air defenses, but we’re deathly afraid of sending nuclear missiles up and scaring other nuclear powers into reacting.
Our other option is to use small conventional weapons on all known entrances and exits to a well-fortified bunker.
What do you think about sending half a dozen bombs in succession all aimed at the same location? Seems like each bomb should make it easier for the ones that come afterward. If we’re talking MOP size weapons, I’m sure the accuracy requirement will not be too difficult.
With modern precision munitions, hitting the same bunker with multiple bombs seems doable, but sending multiple bombers into contested airspace might be an issue.
As I understand it the problem is not one of power, but one of penetration. The bunker buster strikes through 200 ft of material before exploding, so upping the explosive power won’t affect the penetrative ability of the bomb.
In fact, I understand these bombs were originally developed to strike at “nuclear hardened” bunkers.
The keys to a bunker-buster‘s penetration are its high sectional density, its shape, and its hardness. It attains its high velocity from its aerodynamic shape and high sectional density — its terminal velocity can be supersonic — and its hard point directs its high kinetic energy into a small area. Some WWII bunker-busters even used rocket engines to increase their downward velocity before impact.
The bunker-buster’s ability to damage a deep facility depends on literal penetration of the bomb and explosive energy. In WWII, so-called earthquake bombs were designed to liquefy the ground around and underneath hardened bunkers, to bury them in makeshift caverns.
A nuclear bunker-buster relies on its nuclear detonation in the earth to destroy bunkers hardened against near-miss air bursts.
GBU-39 Small Diameter Bomb has a range of over 60 miles by gliding on small wings. I would think wings would help the range of bunker-busters also and thus help keep the launch platforms out of “contested airspace”.
From a defensive perspective, the lesson seems simple: don’t let the bad guy find out where your bunkers are, and have a lot of them.
There was a project a couple of years ago — I believe it was called Prompt Global Strike — to retrofit ballistic missiles with conventional warheads (or just use the kinetic energy of the reentry speed) for destroying deeply buried targets. It seems to have been killed due in part to concerns that any ballistic missile launch might be interpreted as nuclear and bring a nuclear response from the Russians (or some other nuclear power).