The short takeoff and vertical landing capable F-35B, which has handicapped the entire Joint Strike Fighter design since its inception, has another major problem, it can't fit a full load of Small Diameter Bomb IIs in its weapons bay. What's worse is that even though the USMC will declare the F-35B operational this year, it won't be until 2022 that the problem will hopefully be fixed.

The Small Diameter Bomb II (SDB II) is highly anticipated over the SDB I because of its tri-mode seeker capability. Each munition will be able to guide towards its target using laser, imaging infrared or radar homing, or a combination of these modes (embedded GPS/INS, which is how the SDB I navigated to its target, is actually a 4th mode for stationary targets). This will allow SDB IIs to hit moving targets as well as stationary ones in any weather, day or night, at standoff ranges, with incredible reliability and precision.

In its simplest mode, SDB II can just glide its way to a certain set of coordinates and nose dive into a stationary target. This is how SDB 1 accomplished its mission. In laser mode, the aircraft dropping the SDB II can 'lase' the target with its laser designator and the bomb will glide directly into that target just as laser guided bombs have done for decades. In standoff mode, the launch aircraft can release the SDB II at over 40 miles from its target and once it arrives near that target, it can turn on its laser seeker where it can pick up a target being lased by another aircraft or ground troops close by.

The SDB II can also be fired at standoff ranges and its target's location can be updated via Link 16 or UHF data-link. Target updates can come from the launch aircraft or from an external source, such as J-STARS, unmanned aircraft or an electronic intelligence aircraft. Once in the vicinity of the target, SDB II can use its millimeter wave radar to detect that target even through bad weather and smoke, and then use its imaging infrared seeker during the terminal phase of its attack to fully identify and classify the target. It will then strike at the target's most vulnerable point.


By using its own multi-mode guidance for its final attack, SDB II can hit both stationary and rapidly moving vehicles with great precision. It can even be lobbed blindly to an area of known enemy vehicles, surface-to-air missiles sites or even small boat swarms. Once in that area it can then autonomously search for, classify, prioritize and prosecute targets of opportunity on its own accord using target recognition software and onboard AI.

Because of its small size and standoff range, theoretically a single B-2 bomber could one day carry hundreds of the pint-sized munitions on a single, each programmed and networked together to hit a separate targets in a single or multiple target areas. This means a single attack pass on a massive enemy airfield, or even a large enemy armored column, by a lone B-2, or a formation of F-35s, while staying dozens of miles safely away from the target area, could take out every single target on that airfield or in that armored column while keeping the infrastructure around it largely intact.

Quite literally, the SDB II is a super weapon that will be the most versatile air-to-ground munition in the entire Pentagon's air combat inventory. The cost per SDB II is said to be around $250k and the DoD plans on buying as many as 17,000 of them.


When it comes to the F-35B and this game-changing weapon, the problem is fairly simple. The F-35B, even with its truncated weapons bay compared to its A and C model cousins, was supposed to be able to carry eight SDB IIs internally. Because the F-35 has to carry its weapon internally to retain its small radar signature, these pint-sized, 250lb precision attack munitions are key to the aircraft's effectiveness in combat, allowing for up to eight ground targets to be engaged on a single stealthy sortie. This is especially true for the F-35B, with its very tight weight limits, being able to hit eight individual targets at range while in stealthy configuration gives the jet an immense attack per-sortie capability boost compared to packing a pair of 1,000lb or 500lb guided bombs internally. Additionally, considering the F-35B's main focus is to support Marines on the ground, being able to hit eight moving targets via STB II instead of eight stationary targets via STB I is a huge tactical difference.

Because the F-35 is not invisible to advanced radars, no aircraft is, integrating the SDB II with its 40 mile range, onto the jet is key so that it can target enemy SAM and anti-aircraft artillary systems, especially road-mobile pop-up ones, while still remaining out of range of detection. Without this capability, it is unclear exactly what weapon the F-35 will be used to break down an enemy's non-fixed air defenses and how close it will bring the F-35 to those air defenses due to traditional gravity munition's limited range. SDB I will be effective against stationary anti-aircraft and air defense sites, but will lack the enhanced terminal guidance and networking capability.

In other words, a good portion of the concept of operations that makes the F-35 worth the cost of admission, which is close to $150M per F-35B, will have to wait well into the next decade, long after the B model has officially entered 'operational service' later this year. This, along with many other deficiencies, makes the idea that the jet is truly operational when the Marines declare it as such remains more debatable than ever, if not outright laughable.

Originally, the F-35 was going to be one of the first aircraft to receive the SDB II, mainly because the weapon is so well suited to its concept of operations as discussed above and because of its limited internal weapons carriage capability. Now it will be introduced along with more frivolous munitions capabilities (including the 'lock on after launch' AIM-9X as well as the Norwegian Naval Strike Missile based Joint Strike Missile among other weapons and capability upgrades) as part of the Block 4 upgrade somewhere around 2022, hopefully.

At this point, the issue of delayed SDB integration is not so much a software one but a physical one. Crucial hardware within the F-35B's weapons bay interferes with the full contingent of eight SDBs being carried, thus the bay needs to be redesigned to accommodate this very necessary loadout. As a result, the F-35 program has delayed the integration of this key weapon as a whole until 2022, at which time modifications to existing aircraft, which there will be many, will supposedly take place. Thus the Navy and Marines will not have the SDB II capability until then, and apparently neither will the USAF. Instead the Super Hornet and the F-15E will lead SDB II integration in the near term.

Until sometime in 2020s, the F-35 will be shoehorned into attacking moving targets even in the most highly defended areas with 'direct attack' munitions like GPS guided JDAMs and laser guided bombs while maintaining its stealthy lines. This means they will have to nearly overfly these targets to destroy them as opposed to standing off and attacking them outside the detection and/or engagement ranges of enemy air defenses. This would greatly impede the F-35's survivability against near peer-state threats and would basically give the jet the same strike capability against moving targets that was available during the opening of Operation Enduring Freedom some 15 years ago and the same capability against fixed targets that the F-22 has had for many years.

In the end, the lack of SDB IIs in the F-35's quiver till at least 2022 may not be a show-stopper for a jet that has fought one problem after another throughout its development, but it is just another 'wait and see' item on the F-35's growing list of 'wait and see items.' The truth is that, regardless of its price tag, the F-35 will not really exist as promised until the middle of the next decade, assuming development goes as planned and assuming that orders remain intact at current levels. This puts the existence of a fully mission ready F-35 close to 20 years after its first flight, and some 25 years after its technology demonstrator, the X-35, first flew back in 2000.

For some perspective, you were lucky to be carrying an analogue Motorola StarTAC cell phone in 2000, now take a look at your cell phone now. If we can learn anything from the F-35 debacle it is that we need to find another way to design, test and procure high-end weapon systems. A 30+ year cycle just to get the weapon system as originally envisioned is totally unacceptable and in many ways the F-35 is already obsolete both on a sub-system level and on a conceptual level.

If we really want to retain our military supremacy well into this young century than we need to find a new way to evolve our weaponry because our competitors are more than willing to assume more risk in development and testing in order to reach parity sooner.

Source: Inside Defense

Tyler Rogoway is a defense journalist and photographer who maintains the website Foxtrot Alpha for You can reach Tyler with story ideas or direct comments regarding this or any other defense topic via the email address