This allow the missiles to hit targets that have stopped emitting radio signals to home in on, or may never have been emitting in the first place, or simply hit a specific location. The missile also has a two-way data link so the launching aircraft, or another source, can feed it new target information in flight. The AARGM-ER will have this exact same guidance package and the Air Force's budget documents make no mention of the SiAW needing a new guidance system.

The AARGM-ER is derived from the AGM-88E Advanced Anti-Radiation Guided Missile (AARGM), the latest variant of the already proven High-Speed Anti-Radiation Missile (HARM), which is already much more than just an air defense-busting radar-homing missile. This missile has multi-mode guidance capability that includes a GPS-assisted inertial navigation system and a millimeter wave radar seeker.

The AARGM-ER is already set to be an extremely capable missile. This is why it seemed like an obvious choice for at least a starting place for the SiAW to us at The War Zone last year.

The Air Force will also need to make sure the flight computer on its jets can “talk” with the missile, something the service has been working on itself since FY19. The USAF's latest budget proposal asks for nearly $163 million in additional funding to continue this developmental work.

The SiAW will feature a different warhead and fuze, of unspecified types, which the Navy began working on in the 2019 Fiscal Year. The Navy already has a requirement for the AARGM-ER to fit inside the weapon bays of its F-35C, so the new variant just needs to retain a similar dimensional profile for the F-35A to carry it internally.

The Navy, which is already the lead on the AARGM-ER program, is in charge of the development of the SiAW variant. The Air Force is handling integrating the missile onto the F-35A, which is its threshold launch platform. Northrop Grumman is developing the weapon having purchased the company that first created the design, Orbital ATK, in 2017.

What appears to be the first public announcement that the AARGM-ER would serve as the basis for what the Air Force officially refers to as the Stand In Attack Weapon, or SiAW, was included in detailed documents about the service’s budget proposal for Fiscal Year 2020, which it released on Mar. 18, 2019 . Mention of the SiAW had first appeared in the Air Force’s budget request for the 2018 fiscal cycle, which came out in February 2017 , but the line items made no mention of using a particular missile as the starting point.

The U.S. Air Force has revealed that it is working to turn the U.S. Navy’ s Advanced Anti-Radiation Guided Missile-Extended Range, or AARGM-ER , into a fast-flying strike weapon that its F-35A Joint Strike Fighters will be able to use against a variety of time-sensitive targets. This is something that The War Zone had thought would be the case based on previous information about this program. The new missile would give those stealthy jets, as well as other aircraft in the future, an important tool for quickly knocking down anti-access and area denial threats, as well as destroying pop-up targets on short notice.

The AARGM-ER shares other features with the AGM-88E, including its warhead and portions of its control section, but it is in many ways an all-new missile with significant improvements in range and speed. We don’t know the exact for the Air Force’s SiAW and those same details regarding the AARGM-ER are classified, but previous reports have suggested the latter missile would have between 20 to 50 percent greater range than the existing AGM-88E.



This means the AARGM-ER, a possibly the SiAW, would have a maximum range of at least somewhere between 96 and 120 miles. The AARGM-ER’s improved rocket motor and streamlined design will also make it faster than the AGM-88E, which reportedly flies at more than twice the speed of sound during a final dash to the target. You can read more about both the game-changing capabilities of the AGM-88E and the up-coming AARGM-ER in detail here.

USMC A slide showing the relationship between the AGM-88E AARGM and the new AARGM-ER.

The SiAW program makes good sense given concerns about increasingly dense integrated air defense environments in the future, especially those that Russia and China are working to establish. Stealthy features and defensive electronic warfare systems may not be enough to guarantee survival against networks of advanced enemy radars and other sensors linked to long-range surface-to-air missiles and increasingly capable jamming systems. There is always the potential for pop-up systems to appear with little notice and for wild card threats to emerge. This is to say nothing of other kinetic and non-kinetic weapons that could challenge American forces on the ground, at sea, or even in space, as the Air Force’s budget documents note. So, there is a clear requirement for a rapid response weapon with significant range and high speed to be able to neutralize these threats quickly, as they appear. The weapon also needs to be able to do so before an opponent can launch their own strikes, relocate elsewhere, or flee to safety. Combining the SiAW with a low-observable platform such as the F-35A only improves the likelihood that it will be able to reach the target in time, even in a high-risk environment. Leveraging the AARGM-ER design is also smart, given that it is already in development, already fits inside the F-35A’s weapon internal bays, and has the range and speed to meet the SiAW’s general requirements. As noted, it also uses a significant amount of technology and components from the older AGM-88E, making it a much more cost-effective option over a completely new design. This will also help simply maintenance and logistics requirements.

Joseph Trevithick A model of the AARGM-ER.

The F-35A will almost certainly only be the first platform to get the SiAW, not the last. The Air Force’s 2018 Fiscal Year budget proposal mentioned a desire to also integrate it onto the upcoming B-21 Raider stealth bomber. A B-21, potentially carrying dozens of SiAWs, would offer a new and impressive means of challenging and defeating enemy anti-access and area-denial threats. A bomber loaded with a mix of AARGM-ERs and SiAWs would be a particularly capable tool for destroying both air defenses and targets of opportunity along a certain route, helping clearing a path for following-on forces both in the air and down below. The truth is that stealthy planes, both manned and unmanned, will need weapons such as SiAW to defend themselves and their companions in ever-increasingly dangerous high-end air defense environments. Stealth technology is not a cloaking device, requiring a blend of additional capabilities to best ensure the survivability of these aircraft in the future. For the B-21, the ability to quickly make changes to its route of best survivability, often referred to as the "blue line," on the fly using real-time intelligence garnered organically from its own sensors and those from third party platforms received via data-link will be key. But also having the ability to blast its way through to its intended target when avoiding a threat isn't possible will be very important. SiAWs would give it this capability. Non-stealth planes could also potentially carry the weapons, improving their ability to neutralize threats in high-risk environments, in turn making older platforms more relevant in future major conflicts. Northrop Grumman is also offering a containerized land-based launcher for the AGM-88E and AARGM-ER, which could allow forces on the ground or ships at sea to employ the weapon, as well.

Joseph Trevithick A model of Northrop Grumman's containerized AARGM/AARGM-ER launcher.

With the impending demise of the Intermediate-Range Nuclear Forces Treaty, or INF, between the United States and Russia, which you can read about in more detail here, the U.S. military will only be presented with more threats from ground-launched cruise missiles and theater ballistic missiles, in the coming years. Ballistic and cruise missile technology, in particular, as well as road-mobile launchers for these weapons, are steadily proliferating, even among non-state actors, as well. With all this in mind, the Air Force’s new “stand-in” missile is one of, if not the most relevant air-launched weapon one could imagine to help the Air Force respond the most significant threats it faces in the near future. Contact the author: jtrevithickpr@gmail.com