Deep strike – over-the-horizon targeting and effectors

In the era of great power competition, the ability to conduct deep-strike operations against targets over the horizon and also far behind the front line at distance – on land and at sea – is seen as essential to degrade enemy forces and win a future peer conflict. This article investigates the capabilities being fielded and under development to meet this growing requirement.

The Russo-Ukraine War has given some indication of what a future large-scale conflict might look like between major powers: powerful air defence systems are largely denying the airspace to fighters and bombing aircraft; Russian naval vessels are being pushed back well beyond the horizon into bases across the Black Sea; while defensive lines on land that are long and deep can only be penetrated at significant cost to ground forces. Defensive systems and strategies are making offensive action difficult, so the fight is being continued ever more at arm’s-length using long-range precision (and some not-so-precise) missiles and artillery. These are being used to hit strategic targets such as military logistics sites, depots, training camps, staging posts and command centres as well as important civilian and military infrastructure.

Meanwhile in the Indo-Pacific, China is developing its anti-access/area denial (A2/AD) zones and there is the prospect of a largely maritime conflict taking place over the vastness of the Western Pacific Ocean as well as the crowded littoral areas in the South China Sea. A maritime war could be decided by the ability to target ships and launch large missile salvos to destroy opposing surface ships at long ranges.

Standing off

The extent of A2/AD zones and dangers of integrated air and missile defence systems means that NATO’s military aircraft, which are its preferred platform for delivering ordnance cannot get as close to their targets as they would like. On land, units close to the frontline are at risk of detection and attack at short notice as forward deployed sensors can activate a rapid kill-chain to call in strikes from long-range missiles and artillery. To avoid danger, additional stealth, mobility, deception and camouflage is required or platforms have to be pulled back far out of reach to avoid being targeted. At sea, naval vessels also have to adopt a stand-off position or face heightened levels of danger the closer they get to a coastline and the risk of detection by air, land and seaborne sensors.

With launchers taking an increasingly stand-off position it means the missiles themselves have to do more of the work. Deep-strike missions will require missiles to have increasingly longer ranges and the ability to find and hit targets without recourse to guidance from the launcher or other offboard sensors in case communications are jammed or spoofed.

This creates a challenging environment for long-range missiles to operate in and remain effective. A spokesperson from European missile manufacturer, MBDA, told ESD that the key operational challenges of deep-strike missions are: “to engage targets at long range, penetrate defended airspace, and to accurately engage and defeat the chosen target”.

According to MBDA, recent conflicts have shown the importance of these challenges and it is expected that these will become even more difficult to overcome due to “the increased efficiency of air defences” in the naval or ground environment.

Proving ground

Two missiles that have featured prominently in the Ukraine War have been the Storm Shadow/SCALP from MBDA and the M31 Guided Multiple Launch Rocket System (GMLRS), which are launched from the M270 MLRS or M142 HIMARS launchers from Lockheed Martin.

The GMLRS rounds are 3.96 m in length and 227 mm in diameter, with a range of 84 km, while the GMLRS Extended Range (GMLRS-ER) variant increases this to 150 km. The former have been reported to have made a difference in the Russo-Ukraine War, where the Ukrainian Armed Forces have been able to conduct longer-range strike missions behind Russian front lines.

GMLRS uses the Global Positioning System (GPS) and an inertial navigation system (INS) for navigation. While the INS means they can still be used in GPS-denied environments if GPS is spoofed or jammed, use of INS by itself will result in a reduction to their accuracy compared to using both GPS/INS.

The HIMARS and M270 systems can also launch the MGM-140 Army Tactical Missile Systems (ATACMS) tactical ballistic missile, which have also been delivered to Ukraine in limited numbers. The USD 61 billion US support package to Ukraine, recently signed off in April by the House of Representatives, reportedly contains longer-range 300 km variants of ATACMS. These missiles use multiple INS units linked together by software, which is understood to result in a higher level of accuracy when operating in a GPS-denied environment compared to GMLRS.

ATACMS is being replaced by the Precision Strike Missile (PrSM), which can fly out to 499 km. The Increment 1 variant of this missile is provided with GPS/INS guidance, while the Increment 2 variant under development is set to supplement these with a new multi-mode seeker currently in development. The seeker is understood to comprise a passive radio frequency (RF) sensor and an imaging infrared (IIR) sensor, that will provide new levels of precision to hit moving targets. The passive RF sensor will enable the missile to refine its targeting based on detection of enemy radar or communications activity within its target area. These are due to be follower by the Increment 3 variant, which is understood to primarily concern modifications to the missile warhead.

Increment 4 of the PrSM, also known as the Long-Range Maneuverable Fires (LRMF) programme, is expected to develop a variant of the missile that can reach targets at distances of more than 1,000 km. A Lockheed Martin press release indicated the missile will feature an “advanced propulsion solution”, and was accompanied by an artist’s impression of the missile; based on this information, the propulsion system in question is expected to be ramjet-based. Development contracts related to Increment 4 were awarded to Lockheed Martin and a Raytheon Technologies-Northrop Grumman team in 2023.

Meanwhile, deeper and wider technological innovations will have to provide additional solutions to ensure the success of deep-strike missions. This includes low-observability, higher speeds, AI, advanced simulation, and advanced navigation among others. These will be employed along with traditional missile technologies such as guidance and control, system design, mechanical design, integration, requirement management, supply chain management, qualification and testing.

“Investment levels are very significant and the need for a company to be of a sufficient critical mass is becoming more and more a pre-requisite to properly meet the armed forces’ needs for deep strike,” the MBDA spokesperson said.

Seeking solutions

In the meantime, the use of new seeker systems is helping improve accuracy at longer ranges. To successfully conduct over-the-horizon long-range strikes it is essential that once the missile reaches the target it can find it, identify it and complete terminal phase guidance with precision. GPS can no longer be entirely relied upon.

“A decade ago, GPS target data could have been enough for a large variety of scenarios. This is no longer the case, mainly due to jamming,” the MBDA spokesperson said, noting, “A seeker is required to achieve the required precision and limit collateral damages. It could be passive infrared, radio-frequency or both. The choice of the right seeker, but also its development and its integration in the missiles is a significant challenge.”

MBDA’s Storm Shadow/SCALP missile uses a passive IR seeker and the company is also working on the development of the Future Cruise/Anti-Ship Weapon (FC/ASW), which will have RF guidance. Other systems such as MBDA’s Teseo anti-ship missile are being upgraded to have both, with a dual seeker arrangement along with a ECCM capability. The Teseo Mk2/E upgrade programme will provide a new AESA RF seeker jointly developed by Leonardo and MBDA.

The Storm Shadow/SCALP is an air-launched long-range cruise missile that is designed for hitting targets in pre-planned attacks against high value or stationary targets including bunkers and infrastructure. Weighing 1,300 kg and 5.1 m in length, the Storm Shadow/SCALP missile has a range in excess of 250 km (according to some sources, over 550 km). It has been provided to Ukraine by the UK, Italy and France providing the Ukrainian Armed Forces an extended range attack capability allowing the possibility of deep strikes into Russian territory.

The Taurus KEPD 350 is a similar air-launched long-range cruise missile, developed by Taurus Systems GmbH, a collaboration between MBDA Deutschland of Germany and Saab Dynamics of Sweden. As with Storm Shadow/SCALP, the Taurus can be used for attacking well-defended high-value targets. The missile weighs 1,400 kg, measures 5 m in length, has a range in excess of 500 km (according to some sources, over 700 km), and a warhead weight of 480 kg. Ukrainian President Zelensky has requested Taurus as part of future munitions packages, highlighting the importance of deep-strike capabilities to the future of Ukraine’s resistance to the Russian invasion.

The role of both missiles is to defeat hardened, well-defended targets, meaning that they must have the right warhead to neutralise the target. The size of Storm Shadow/SCALP means it can host a dual-charge penetrator warhead that includes a precursor charge and large explosive kinetic energy penetrator with options for airburst, impact and penetrative modes to ensure maximum damage to large defended fixed targets. In the case of Taurus, it features a precursor charge as well as a main charge with a programmable multi-purpose fuze that can detonate at pre-selected floors within a target structure, using layer counting and void-sensing technologies to destroy hard and deeply buried targets (HDBTs).

To achieve its mission, the Storm Shadow/SCALP has an inertial navigation system, GPS and Terrain Reference Navigation system for guidance during the majority of its journey. “Penetration through air defences during the cruise phase requires robust mission planning, fed by good intelligence data,” the MBDA spokesperson said, “The capability to penetrate air defence during the cruise phase can be reinforced through a certain number of characteristics such as low observability, high speed or very low altitude terrain following.”

The missile hugs the terrain to avoid detection and in the terminal phase switches on its IIR seeker and Automatic Target Recognition (ATR) to match the target signature with its stored image database for a precision strike. This final phase is the most difficult as high-value targets are likely to be well-protected by air defence and electronic jamming, which will become more difficult to overcome in the future.

“Currently, medium low-observability, subsonic missile had a very high probability to pass through air defences of some well-defended targets, as demonstrated by SCALP/Storm Shadow engagement in Ukraine,” the MBDA spokesperson said, “Nevertheless, this probability will decrease in the mid/long term in very complex scenarios.”

In the longer term, the FC/ASW weapon will eventually replace the existing inventories of Storm Shadow/SCALP in Italian, UK and French inventories as well as the Exocet and Harpoon anti-ship missiles with their navies. Development started in 2017 and will provide both a low observable cruise missile and a supersonic highly manoeuvrable missile. The project was officially launched in 2024 and the anti-ship missile variant will be in service from 2028, with the land attack system expected in 2030. It is expected that FC/ASW will radically improve deep-strike capabilities on land and at sea by enhancing terminal phase penetration.

MBDA is developing the FC/ASW RJ, which is a supersonic variant powered by a ramjet and the FC/ASW TP, which is subsonic and powered by turbojet propulsion. This means it will have options of low observability to avoid or delay detection by air defence systems as well as high speed and manoeuvrability to avoid being engaged by anti-air missiles.

FC/ASW will also have the capability to conduct a coordinated attack by gathering various missiles in a single raid to destabilise air defence systems. “A co-ordinated approach will be even more efficient when it includes a mix of effectors using both low observability and speed. This is a reason why MBDA is developing both types of missile,” the MBDA spokesperson said.

Maritime strike

Efforts are also being made at sea to ensure that strikes from surface ships and airborne assets can be conducted at longer range. The Naval Strike Missile (NSM) from Norwegian company Kongsberg has become a very popular option for a rapid air and naval deep-strike capability.

It was first delivered to the Norwegian Armed Forces in 2011–15, but since then NSM has been acquired by 13 countries as their anti-ship missile of choice. This includes the US, which chose NSM for its over-the-horizon weapon system (OTHWS) project, and most recently the UK, which achieved IOC for the weapon on its Type 23 frigate to replace its obsolete Harpoon anti-ship missiles.

NSM is 3.96 m in length, weighs 407 kg and can hit surface ships or land-based targets out to ranges in excess of 200 km. The new air-launched version, Joint Strike Missile (JSM), is about the same size (4 m long, weighing 416 kg), with a range of over 275 km.

Hans Jørn Kongelf, Vice President of Business Development at Kongsberg told ESD that NSM and the JSM derivative have similar capabilities, as the defences around land targets are similar to those on a cruiser or destroyer and must be overcome. NSM and JSM are low radar cross-section (RCS) cruise missiles, they are highly manoeuvrable because of high thrust-to-weight ratio and like many other modern cruise missiles, can also use terrain for cover, where appropriate. Both JSM and NSM use GPS/INS guidance, terrain reference navigation, and are fitted with an IIR seeker with automatic target recognition (ATR) software.

“NSM has a very expensive (scanning) IIR seeker, which has a broad view so that it can find moving targets itself, whilst other missiles with standard IR seekers have a narrow field of view and dependent on target updates from other sources,” Kongelf said.

The US Navy preferred the NSM for its smaller warships (Littoral Combat Ships, Constellation class frigates) and amphibious warships, stating in its OTHWS budget documents that it will “receive targeting data via tactical communications from combatant platforms or airborne sensors and requires no guidance after launch.” According to the documents: “The NSM is an offensive missile with an imaging infrared seeker and utilizes a semi-armour-piercing warhead optimized for anti-surface warfare.”

NSM is also being fitted to US Marine Corps Joint Light Tactical Vehicles (JLTVs) as part of its Nemesis project to allow Joint Force Commanders “to conduct offensive over-the-horizon and within-the-horizon engagements against maritime targets”, the Navy said.

Opening the skies

In addition to the aforementioned sensors, the JSM is also fitted with a passive RF seeker provided by BAE Systems Australia, enabling it to find emitting targets based on their electronic signature, such as air defence radars.

In this way, JSM/NSM are different to Storm Shadow/SCALP and Taurus, which are intended for use against fixed land targets. According to Kongelf, both JSM and NSM have been designed to destroy air defence systems. By neutralising such defences, it will mean follow-on attacks by less-sophisticated missiles against their targets can be more successful, due to a lower chance of being intercepted.

Kongelf said that the JSM/NSM can operate relatively independently with the expectation that GPS will be jammed or spoofed. He explained that because Norway is a small country with few other surveillance assets, there is little possibility of the missile receiving third party guidance or targeting updates. It means the missiles have to be able to conduct a precision strike alone.

He added that Norway decided to choose a subsonic, stealthy, autonomous missile with ATR for its new missile to ensure that it does not hit the wrong target set. Supersonic missiles were deemed too large for integration onto small ships, helicopters or fighter aircraft, and Kongsberg wanted to ensure JSM/NSM could fit into the bomb bay of the F-35 – it is the only ASCM that can do this. On 3 June 2024, the US Air Force signed a USD 141 million contract with Kongsberg for the supply of JSM for the F-35A from 2026.

Elsewhere in the anti-ship missile domain, Lockheed Martin announced in June 2022 that it had awarded BAE Systems a contract for an advanced RF sensor for the long-range anti-ship missile (LRASM). This will make it more survivable in an electromagnetically-contested environment, as it is able to use a passive RF sensor, along with sensor fusion with the missile’s IIR seeker to provide semi-autonomous guidance for long-range strikes. The missile is also provided with a datalink, allowing it to receive off-board information, though this may not always be possible in electromagnetically-contested environments.

Meanwhile in May 2024, Kongsberg announced that it had reached an agreement with German companies MBDA Deutschland and Diehl Defence to partner in the development of a supersonic cruise missile known as 3SM Tyrfing. This is the next step in a project, first announced in November 2023, for a new stand-off weapon that can deliver an advanced long-range strike capability.

Kongelf said that 3SM will complement JSM/NSM capabilities by hitting different target sets. Kongsberg is acting as the design authority and has responsibility for the nose packages. Norwegian company Nammo is supplying the engine with MBDA Deutschland and Diehl contributing expertise in IIR seekers, warheads and other missile technologies.

Looking ahead, Kongelf said there was a need to stick close to state-of-the-art technologies. “It is easy to make something from 10-year-old technologies, but 3SM will have to be a market leader from 2035–2060 so we need to see what capabilities are necessary for the future to make sure it is good enough,” he said.

“It is in the early stages. The two nations are looking at their portfolio of systems and the ships they will have from 2035 – 3SM will be ship-based at the outset – then truck-based and so on.  It will be different in terms of the platforms it is employed on because it will be bigger than JSM/NSM,” Kongelf said.

Closing thoughts

Although starting from a low base, the need for deep-strike weapons that can launch precise strikes on long-range targets over the horizon is increasing by orders of magnitude. A contested environment means that missiles will not be able to rely on GPS and will face a sophisticated array of defensive systems. To overcome this, these missiles are being fitted with additional seekers, more robust communications and either have to remain subsonic and stealthy, or rely on supersonic or hypersonic speeds to evade defences and reach their targets. Inventories of missiles are being built up, but the industrial capacity to fill up stores and provide replacements for any missiles used in wartime still falls far below requirements.

Tim Fish