As The War Zone highlighted just recently, torpedoes, such as the heavyweight Mk 48, are still king among the available weapons across the entire U.S. military when it comes to sinking enemy ships. Now, the U.S. Air Force is exploring ways it might be able to achieve the same kind of anti-ship lethality with air-launched weapons, including modified 2,000-pound class Joint Direct Attack Munition precision-guided bombs. 

The Air Force announced yesterday that three F-15E Strike Eagle combat jets from the 85th Test and Evaluation Squadron, part of the 53rd Wing based at Eglin Air Force Base in Florida, had taken part in an experiment to explore ways to employ modified 2,000-pound class GBU-31/B Joint Direct Attack Munitions (JDAM) against "both moving and static maritime targets." This particular test is part of a larger capabilities demonstration effort, dubbed Quicksink, that the Air Force Research Laboratory (AFRL) is managing.

Four GBU-31/B Joint Direct Attack Munition bombs are seen loaded on an F-15E Strike Eagle from the 85th Test and Evaluation Squadron in this picture released along with its announcement about the Quicksink test in August 2021.

"A Navy submarine has the ability to launch and destroy a ship with a single torpedo at any time, but by launching that weapon it gives away the location of the vessel," an official Air Force news item said. "The QUICKSINK JCTD [Joint Capability Technology Demonstration] aims to develop a low-cost method of achieving torpedo-like seaworthy kills from the air."

The video montage below ends with a clip of a decommissioned Oliver Hazard Perry class frigate having its back broken by a Mk 48 torpedo during a U.S. Navy-led exercise earlier this year, underscoring the anti-ship capabilities that those weapons offer. You can read more about that exercise here.

The August test involving the F-15Es built on lessons learned from another Quicksink experiment conducted last year that saw a B-52H bomber from the 49th Test and Evaluation Squadron drop JDAMs " in order to assess the viability of specific maritime impact conditions," according to the Air Force.

The Air Force did not say how the GBU-31/Bs had been modified to enable them to engage moving targets. Standard JDAMs have a GPS-assisted Interial Navigation System (INS) guidance system that can only be used to point them at specific coordinates. 

There is a dual-mode 500-pound class Laser JDAM that the Air Force, as well as the Navy and Marines, do field, which features the addition of laser guidance that allows it to be used against targets in motion. However, the Air Force has also said that its go-to precision-guided bomb now for anti-ship strikes is the 2,000-pound class GBU-24/B Paveway laser-guided bomb and that this is an increasingly unacceptable option because of the risks imposed by the employment method. A laser-guided weapon would need something to actually lase the target, whether it be the launching aircraft or a separate platform, which would also have to be relatively close to the target (within line-of-sight) throughout the course of the strike.

A Paveway laser-guided bomb seen right as it is about to hit a small boat target during a training exercise.

“Not only is this weapon [the GBU-24/B] less than ideal, it also reduces our survivability based on how it must be employed," Air Force Major Andrew Swanson, an F-15E Weapon Systems Officer from the 85th Test and Evaluation Squadron, explained in a statement. "This munition [the modified GBU-31/B] can change all of that.”

The pictures the Air Force released along with its announcement of the August Quicksink test showed an F-15E carrying four GBU-31/Bs without a fuze or anything else installed on their noses, as one would expect to see. This could suggest that the Air Force has or is in the process of developing a new seeker to go on the front of the bomb to enable it to engage static and moving maritime targets.

A close-up of one of the GBU-31/Bs seen in the pictures the Air Force released along with its announcement about the August Quicksink test, showing no fuze or other seeker system fitted to the nose.

Some sort of multi-mode guidance system with a mix of options, such as millimeter-wave radar and imagining infrared seekers, in addition to the JDAM's standard GPS/INS combination, could provide this capability. The Air Force already has at least one weapon, the GBU-53/B StormBreaker, in service now with this kind of seeker system. Last year, in a separate announcement regarding its Golden Horde networked swarming munitions program, AFRL also indirectly disclosed the existence of a guidance system that is capable, at least in part, of homing in on radio-frequency emissions and that is also small enough to be integrated into the 250-pound class GBU-39/B Small Diameter Bomb (SDB).

That latter point is particularly interesting to note because, in the pictures that the Air Force provided in relation to the Quicksink test in August, the GBU-31/Bs have stickers on their noses where a fuze or seeker head would go. These stickers have the logo of the Advanced Concept Demo Programs office within AFRL's Capability Concept Integration Branch. That logo features, in part, artwork showing silhouettes of four munitions networked together that is very similar to other art that the Air Force has released in relation to the Golden Horde program. It also has a silhouette that could represent an air-breathing hypersonic cruise missile, like the ones AFRL is helping to develop as part of the Hypersonic Air-breathing Weapon Concept (HAWC) program, and what may be a reference to the Miniature Self-Defense Munition (MSDM) program, which you can read more about here.

A close-up of the sticker seen on the front of one of the GBU-31/Bs. In the lower third is artwork that is very reminiscent of other art that has been released in relation to the Golden Horde program. At the upper right is a silhouette that could represent an air-breathing hypersonic cruise missile. The silhouette in the upper left could be a representation of the weapon being developed under the Miniature Self-Defense Munition program.

Two-way data-links and other networked munitions capabilities, such as those that the Air Force is developing under Golden Horde, could potentially provide a way to give JDAMs an anti-ship capability without the need for additional guidance options. Off-board assets could be used to track the target and pass constant updates on its position to a GBU-31/B after release. The JDAM's existing GPS-assisted INS guidance package is effectively an autopilot that could be programmed to use that data to extrapolate the likely location of the ship even if these links were broken before impact, as well.

Whatever the case, if the Air Force can succeed in finding a way to give its 2,000-pound class JDAMs the ability to engage moving ships, this would be a major development. It would add new anti-ship options to any aircraft that can carry the GBU-31/B, such as the F-15E and the B-52H. Upgrades to the B-52H, in particular, have already increased the total number of various kinds of JDAMs, as well as other weapons, that the aircraft can carry, both under its wings and inside its bomb bays. 

An Air Force briefing slide that offers an overview of upgrades to the B-52H's internal stories-carrying capabilities in recent years.

If these modified GBU-31/Bs can achieve anywhere near torpedo-like capability when it comes to actually damaging enemy ships, the work being done through the Quicksink program could be even more significant. Add the wing kits that are available for the JDAM series of bombs into the equation, which would give the bombs substantially increased stand-off range, and the final result could be very useful anti-ship capability that can be readily integrated onto existing aircraft leveraging weapons already in widespread service. No matter what, improved stand-off capability of some kind would be critical to improving the survivability of a launch platform using existing laser-guided bombs for maritime strikes.

The costs of converting existing GBU-31/Bs into these maritime strike versions could very be lower than fielding an all-new anti-ship weapon. If a multi-mode seeker is indeed one of the modifications, these bombs could also offer additional flexibility against other targets beyond ships, as well.

Of course, it remains to be seen how close any modified precision-guided bomb can actually get to the anti-ship killing capability of torpedos, which have the added benefit of being able to deliver their destructive force to a ship well below the waterline. This creates completely different kinds of damage control issues for the target's crew compared to what one could expect to see after above-the-water-line strikes. It could be hard for any bomb to reliably hit areas of the ship's hull under the waves, if at all. 

Still, a 2,000-pound class bomb could still do an immense amount of damage to a ship, even in the case of a near-miss. Leveraging the armor-piercing and delayed detonation capabilities found on bunker-buster versions of the GBU-31/B could further increase its effectiveness in the maritime strike role, allowing the bomb to penetrate into a ship before exploding.

Bunker buster versions of the GBU-31/B.

Regardless, it's not at all surprising that the Air Force would be exploring various ways to increase its anti-ship capabilities, especially as the U.S. military's attention, as a whole, has shifted to preparing potential for a potential major conflict against a near-peer adversary, such as Russia or China. China, in particular, has become a major focus area, as has the possibility of a large-scale war in the Pacific region, which would be a heavily maritime-centric fight.

The Air Force has already been expanding its maritime capabilities, particularly on its bombers, in recent years. This includes the integration of the AGM-158C Long Range Anti-Ship Missile (LRASM) cruise missile onto the B-1B bomber and the addition of new air-dropped naval mines to the B-52H's arsenal. Last year, General David Goldfein, then-Chief of Staff the Air Force, alluded to the development of another advanced air-launched anti-ship weapon.

It will certainly be interesting going forward to learn more about these modified maritime strike-focused GBU-31/Bs, as well as other developments, in weapons and in new tactics, techniques, and procedures, which might also emerge from the broader Quicksink program.

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