Congress Pushes Navy To Add Hypersonic Missiles To Its Stealthy Destroyers

The move could alter the Navy’s timeline for deploying hypersonic weapons and it could lead to big changes for its Zumwalt class destroyers.

byJoseph Trevithick|
U.S. Homeland photo


Legislators in the U.S. House of Representatives are looking to direct the U.S. Navy to start working on arming its Zumwalt class stealthy destroyers with the new Conventional Prompt Strike hypersonic missile within the next six months or so. As it stands now, the service only plans to integrate this weapon on its future Block V Virginia class submarines and the four Ohio class submarines configured as guided missile submarines, or SSGNs. This push in Congress could lead to a major shift in plans for these missiles and might finally lead to the elimination of the 155mm Advanced Gun Systems on the Zumwalts, also referred as the DDG-1000 class, for which there is no ammunition available at present.

The House Armed Services Committee's Strategic Forces Subcommittee wants to include the provision to add the Conventional Prompt Strike missiles, which you can read about in more detail in this past War Zone piece, to the Zumwalts in the annual defense policy bill, or National Defense Authorization Act, for the 2021 Fiscal Year. On June 21, 2020, this subcommittee publicly released the text of this and other sections that it is hoping to make part of the final NDAA.

"The  Secretary [of the Navy] shall initiate such transfer of [Conventional Prompt Strike] technologies to DDG–1000 class destroyers by not later than January 1, 2021." The Conventional Prompt Strike system is the Navy's version of a hypersonic weapon it is developing jointly with the U.S. Army. Both services will use a common missile and hypersonic boost-glide vehicle warhead design in their respective sea and land-based launch systems.

An infographic the Army has released regarding its Long Range Hypersonic Weapon, which will use the same missile and hypersonic boost-glide vehicle warhead as the Navy's Conventional Prompt Strike., US Army

A hypersonic boost-glide vehicle is an unpowered hypersonic weapon. A rocket booster first gets it to the desired altitude and speed, after which it glides along a relatively flat flight trajectory within the Earth's atmosphere toward its target. During the glide phase, these weapons can make abrupt vertical and horizontal course changes that help make it very hard to defend against. As such, they are very attractive weapons for penetrating dense enemy air defenses to conduct strikes on time-critical or otherwise high-value targets. 

A full-size model of the common hypersonic boost-glide vehicle that the Army's Long Range Hypersonic Weapon and the Navy's Conventional Prompt Strike system will both use., US Army

The newly proposed section in the Fiscal Year 2021 NDAA, described as an "integration" effort, does not appear to be directing the Navy to simply study adding the Conventional Prompt Strike missiles to the Zumwalts. It specifically amends an existing, more ambigious provision in the 2020 Fiscal Year NDAA, which Congress passed and President Donald Trump signed into law in December 2019, that says "The Secretary of the Navy shall ensure that the technologies developed for the conventional prompt global strike weapon system are transferrable to a surface-launched platform."

"Not later than 120 days after the date of the enactment of this Act, the Secretary of the Navy shall submit to the congressional defense committees a report on the programmatic changes required to integrate the conventional prompt global strike weapon system into current or future surface combatant ships," it adds. Based on that timeframe, the House and Senate Armed Services Committee should have received that report on what the available options were, such as adding Conventional Prompt Strike capability to the Zumwalts, by the end of April. 

The Zumwalts, despite the repeated watering down of their capabilities and the continued addition of external systems that negatively impact their reduced radar signature, are arguably the most advanced and survivable surface combatants the Navy has in service today. At present, the service has commissioned two of these ships, the USS Zumwalt and the USS Michael Monsoor, and a third example, the future Lyndon B. Johnson, is in the final stages of construction. The Navy had originally planned to buy 32 Zumwalts, but that total was successively scaled back to just these three hulls.

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The exact expected range of the Conventional Prompt Strike missiles is unknown, but the goal is for it to be in the thousands of miles. As such, the Zumwalts armed with these weapons would be able to use their stealth characteristics to have the best chance of getting close enough to launch the weapons at time-sensitive or critical targets in a contested environment during a major crisis or contingency. Combined with the already extreme speed of the weapons themselves, being able to get closer to the target would further reduce the time an opponent would have to react to the strike, either to try to relocate important assets or otherwise seek cover, increasing the chances of success. 

Adding the Conventional Prompt Strike missiles to Zumwalts could provide a fast path toward making the weapons operational, as well. The Navy's current plan is to reach initial operational capability with these weapons in the 2028 Fiscal Year on the Block V Virginia class submarine. After that, the service would integrate them with the Ohio class SSGNs and it could add them to the arsenal of a future Large Payload Submarine, as well. The Army, by contrast, expects to reach initial operational capability with its land-based version in 2023.

An infographic showing the Block V Virginia class and a cutaway for the new Virginia Payload Module for these boats, which will have four large multi-purpose launch tubes capable of firing the Conventional Prompt Strike missile, as well as other weapons and payloads., USN

However, the modifications required to add the Conventional Prompt Strike missiles to the Zumwalts could be extensive and costly. Each one of the stealth destroyers has 80 Mk 57 Vertical Launch System (VLS) cells able to accommodate a variety of missiles, including quad-packed RIM-162 Evolved Sea Sparrow Missiles (ESSM) and Tomahawk land-attack cruise missiles

An artist's conception of the USS Zumwalt firing missiles from its Mk 57 VLSs., USN

While specific details about the Conventional Prompt Strike missile design, the Navy and the Army have stated that it will use a two-stage rocket booster with a diameter of 34 and a half inches. This is wider than the Mk 57 cell, meaning that Zumwalts will need a new launch system to fire these hypersonic weapons. 

In addition, the Army has said that its ground-based system will use a launcher that uses a modified M870 flatbed trailer and that the missile canister will be roughly as long as that trailer, which is just over 40 feet in length. The longest missile that the Mk 57 can accommodate is just over 20 feet, meaning that any new launcher would extend substantially further down into the ship's hull, which could make it hard, if not impossible to simply swap out some number of the existing VLS arrays. 

As such, the most viable option could be to utilize the space on the ships that their two 155mm Advanced Gun Systems (AGS) occupy. These weapons have effectively been dead weight since the Navy's decision to cancel work on the specialized Long-Range Land-Attack Projectile (LRLAP), each of which was set to cost an exorbitant $800,000, in 2016. There have been discussions about sourcing alternate ammunition types for the AGSs, but no final decision has been made on that front, at least publicly.

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Removing the AGSs and replacing them with some other weapon is something that many, including the War Zone, have proposed in the past. Adding the Conventional Prompt Strike missiles would certainly be in keeping with the Navy's desire to have the Zumwalts focus on stand-off attacks against enemy ships and targets on land.

Interestingly, in a summary of its proposals, the Strategic Forces Subcommittee also calls for the addition of the Conventional Prompt Strike missiles to the Zumwalts in order "to address miscalculation and ambiguity concerns." These missiles have the potential to look just like any other ballistic missile to an opponent's early warning systems at the time of launch. It could be hard, if not impossible, to know that a submarine firing one of the weapons is Virginia class or an Ohio class SSGN, rather than Ohio class ballistic missile submarine, or SSBN, or a future Columbia class ballistic missile boat.

This could raise concerns that a near-peer nuclear-armed adversary, such as Russia or China, might mistake the missile for one carrying a nuclear weapon, or otherwise feel compelled to treat it as such, rather than risk not being able to respond in kind. Critics of the new W76-2 low yield warhead for the Trident D5 submarine-launched ballistic missile, which is now in service on Ohio class SSBNs, have expressed similar fears about how an enemy would interpret the launch of one of those weapons, since there would be no realistic way to verify the warhead type until it detonated. Russia has already publicly said that it will treat it any employment of the W76-2 the same way it would treat the use of any other nuclear weapon.

The USS Tennessee, an Ohio class SSBN., USN

At least right now, there are no nuclear weapons available for Navy surface ships, meaning that there would be no ambiguity about whether a Zumwalt armed with the Conventional Prompt Strike missiles had fired something else. There has been discussion of adding a new nuclear-armed cruise missile to these destroyers, but the launch signature of that weapon would be different. That would, however, undoubtedly raise concerns about whether the ship's launch of a conventionally armed cruise missile, such as the Tomahawk, would then be confused for a nuclear strike. Critics have brought up similar fears with regards to the deployment of a new air-launched nuclear cruise missile, despite U.S. bombers having employed conventional air-launched cruise missiles in combat for decades without any apparent issues, though never against a peer state.

Beyond all of this, there is also a question of how useful a fleet of just three Zumwalts might be for providing this kind of strike capability. Last year the Navy decided to assign the trio of destroyers to a developmental unit, Surface Development Squadron One, where their main job will be testing and evaluating new weapons and systems, as well as tactics, techniques, and procedures for surface ships. Of course, this would not necessarily preclude them from deploying operationally, as needed.

The small size of the class could also exacerbate the already likely high cost burden associated with integrating a whole new VLS and refitting the deck space that goes all the way down to the keel. The Zumwalts have already long been over budget and behind schedule. One would imagine that it would be easier to integrate the Conventional Prompt Strike missiles onto a new class of surface ships, such as the future Large Surface Combatant, which could be designed from the beginning with large modular vertical launch tubes to accommodate various weapons. Unfortunately, those ships are still years away from becoming a reality.

Of course, all of this is dependent on this provision becoming law. The House Armed Services Committee still needs to craft a final draft of the NDAA and make sure it aligns with the version now progressing through the Senate. After that, both chambers would need to pass it and President Donald Trump would have to sign it. 

That being said, the fact that this appears to be a direct follow-on to a provision that did successfully make it into the Fiscal Year 2020 NDAA, based on information and recommendations the Navy provided earlier this year, suggests that there is some bipartisan consensus on this issue already.  If this does become law, the future of the Navy's hypersonic weapons plans and the future of the Zumwalt class destroyers could be set to change significantly in the coming years.

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