In September, Northrop Grumman announced that it had secured a contract from the Air Force to move forward with a new high-speed air-to-ground missile meant to be carried internally by America’s growing fleets of stealth fighters and bombers. This new missile, dubbed the Stand-in Attack Weapon (SiAW), is meant to lead the way in high-end conflicts with modern adversaries like China, rapidly engaging a variety of ground targets deep inside hotly contested airspace from extended ranges.

The new SiAW missile is being built upon the basic structure of the Navy-led Advanced Anti-Radiation Guided Missile-Extended Range (AARGM-ER) program – the long-range radar hunting missile developed to be deployed by carrier-based F-35Cs. In fact, it appears the Air Force’s new SiAW missile may leverage a number of the same internal systems, as well as the same external dimensions.

As noted aviation journalist Tyler Rogoway posited all the way back in 2018, basing the SiAW missile on the AARGM-ER makes good practical sense for a number of reasons. The missile was designed to be carried inside the F-35C’s internal weapons bay and, unlike previous anti-radiation missiles that hone in on electromagnetic radiation alone, boasts an advanced guidance system that allows it to continue closing with enemy radar arrays even after they’ve powered down. As a result, the Air Force’s effort doesn’t need to reinvent any wheels. Instead, the $705 million contract awarded to Northrop Grumman can focus on tailoring the weapon’s capabilities specifically to the Air Force’s broader goals for the SiAW.

Air Force officials are aiming to have this new weapon reach its initial operating capability by 2026, which means the new SiAW missile is clearly on the fast track to service.

AMERICA’S NEED FOR LONGER-REACH IN THE PACIFIC

The Air Force kicked off its Stand-in Attack Weapon development cycle back in January 2020 with a request for information (RFI) to industry partners for a new air-to-ground weapon specifically meant to be carried in the internal weapons bay of the branch’s runway queen (conventional take-off and landing) F-35A. Right from the get-go, one could argue the Air Force had Chinese targets in mind, highlighting the need “to hold at risk surface elements of the A2/AD environment” in the RFI.

That A2/AD acronym, which translates to Anti-Access/Area Denial, could really be attributed to any hotly contested near-peer battlefield, but the term itself is commonly used in reference to China’s approach to fortifying its sovereignty claims over vast swaths of the Pacific Ocean in recent years. This strategy includes the fielding of advanced air defenses, anti-ship weapons, anti-satellite measures, and a rapidly expanding Naval armada made up of the largest standing Navy on the planet, a rapidly growing and militarized coast guard, maritime militia, and even fleets of large-hulled fishing vessels that all fall within the country’s military command structure.

China’s A2/AD methodology pivots largely on a variety of long-range anti-ship missiles designed specifically to keep American aircraft carriers at bay. Weapons like the hypersonic DF-ZF boost-glide missile, which is carried aloft by China’s medium-range DF-17 ballistic missile, have a claimed range of nearly 1,200 miles, and an alleged top speed ranging somewhere between Mach 5 and Mach 10. With the ability to carry large conventional or even nuclear payloads combined with the sheer kinetic force of a hypersonic impact, the DF-ZF may potentially have the power to render even America’s Nimitz and Ford-class supercarriers inoperable with a single strike.

The DF-ZF creates significant challenges for American power projection, as its claimed range of nearly 1,200 miles is nearly twice the combat radius of America’s longest-flying carrier fighter, the F-35C. With about 37% more wing area than the rest of the Joint Strike Fighter family, the F-35C has a combat radius of nearly 690 miles – 510 miles short of China’s hypersonic reach. Put simply, this means sailing one of America’s carriers close enough to China to launch F-35 sorties also means placing that carrier squarely within reach of China’s carrier-killing missiles.

However, the United States Navy has taken a multi-faceted approach to offset this strategic shortcoming, with the highest profile effort arguably being its work on a 6th-generation stealth fighter – currently dubbed F/A-XX – that is intended to offer greater range and larger payloads. Other efforts include fielding carrier-based drone refuelers and operating Marine Corps F-35Bs from more distributed amphibious assault ships.

But American airpower isn’t solely a naval enterprise, and the U.S. Air Force would undoubtedly play a pivotal role in a Pacific conflict. And that’s precisely where the new SiAW missile comes into play.

GIVING THE AIR FORCE A STEALTHY LONG-RANGE PUNCH

The new Stand-in Attack Weapon (SiAW) may be based directly on the Navy’s radar-hunting AARGM-ER, but this new weapon will be going after a much wider variety of targets than enemy surface-to-air missile systems. In fact, there’s a chance these weapons could provide the Air Force with a vital means of eliminating portions of China’s area defense systems in the early stages of conflict, clearing the way for carriers to sail closer to Chinese shores without risking being sunk.

According to the Air Force’s budget request for Fiscal Year 2020: “The Stand In Attack Weapon (SiAW) system will provide strike capability to defeat rapidly relocatable targets that create the Anti-Access/Area Denial (A2/AD) environment. The target environment includes Theater Ballistic Missile Launchers, Land Attack and Anti-Ship Cruise Missile Launchers, GPS Jammers, Anti-Satellite Systems, and Integrated Air Defense Systems.”

In essence, the SiAW is envisioned as a means to engage just about any stationary or moving target on the ground or even at sea, leveraging its multi-mode guidance capabilities to that end. The SiAW will carry a different warhead and fuse than the AARGM-ER, but appears to boast the same GPS-assisted inertial navigation system and millimeter-wave radar seeker. That means these missiles can close with pre-programmed targets, even in GPS-denied environments, or identify targets within a set area to engage. In the AARGM-ER, this capability allows the missile to continue chasing after enemy radar arrays even after they power down – by first identifying the array and then using its inertial and GPS navigation to close with its last broadcast location. The millimeter wave radar seeker can even allow it to close with moving targets within the target area.

If target information changes while the missile is already in flight, a two-data link allows the launching aircraft (or other nearby assets) to update the weapon with new target coordinates on the spot.

Because of its advanced guidance system, the weapon can even be launched toward a set area more or less “blind,” or within a specific intended target in mind. As it flies, it can receive new target information from offboard sensors, identifying a target while in flight and then closing with it on land or sea, even if it’s moving.

When combined with the advanced sensor suite of the F-35A, the SiAW will offer a single weapon that can address a wide variety of surface threats. Its overall range – and that of the AARGM-ER – remain undisclosed, but previous claims have suggested that it will offer an increase in range from 20% to even 50% over the AGM-88E it’s set to replace. This would give the SiAW and its AARGM-ER sibling a range of somewhere between 96 and 120 miles.

The AARGM-ER is approximately 13 feet, four inches long, with an 11.5-inch wingspan and around 1,030 pounds. Despite carrying some slightly different hardware, the SiAW is expected to be about the same, as it too will need to be stowed inside the F-35’s cramped interior.

HOW THE SIAW AND AARGM-ER COULD HAVE A HUGE EFFECT IN THE PACIFIC

F-35As and F-35Cs carrying a combination of ARRGM-ERs and new SiAWs could play a pivotal role in a Pacific conflict, engaging a wide variety of air defense and anti-ship targets from stand-off ranges, well outside the reach of even the most advanced and modern air defense systems.

Russia’s S-400 Triumf surface-to-air missile systems are widely considered to be among the most capable on the planet, despite their recent poor performance in Ukraine. To that end, China first secured a contract to purchase these systems from Russia in 2014, with the second complete system arriving in 2020.

According to a peer-reviewed assessment by Hellenic Air Force Colonel and electronics engineer Konstantinos Zikidis, published by the Journal of Computations & Modelling in 2014, Russia claims the low-frequency arrays leveraged by the S-400’s Nebo-M radar array can detect the F-117 Nighthawk at a range of 350 kilometers (217 miles) in an environment free from electronic warfare (EW), and potentially as far as 72 kilometers (45 miles) under heavy jamming. This serves as the basis for the S-400’s counter-stealth claims.

However, low-frequency arrays are not capable of securing a weapon’s grade lock. In other words, they don’t have the image fidelity to guide a weapon into a target. Instead, the low-frequency array serves as a guide for a higher-frequency targeting array, potentially speeding up the targeting process once a stealth aircraft flies close enough for it to produce a high-frequency return.