The testimony by Vice Adm. Johnny Wolfe, director for the Navy's strategic systems programs, offers a glimpse into the future scenarios that the U.S. military envisions.
As China fortifies its air defenses, submarine-launched hypersonics offer a better chance than land- or surface-ship- launched variants of penetrating its airspace and taking out key assets, such as command and control facilities. The success of such an opening salvo would be critical for the U.S. to send in follow-on ships and planes into the battle zone, analysts told Nikkei Asia.
The hypersonic missile the U.S. military is building is a non-nuclear weapon that flies five times as fast as the speed of sound on a shallow trajectory. It combines the speed of a ballistic missile and the maneuverability of a cruise missile and is intended to strike a target thousands of kilometers away in roughly 15 to 30 minutes.
In his written statement for a House Strategic Forces Subcommittee hearing held last Tuesday, Wolfe explained that the hypersonic missiles will first be delivered to the Army as the Long Range Hypersonic Weapon, and then to the Navy as a sea-based capability, initially on Zumwalt-class destroyers from the mid-2020s and then on Block V Virginia-class submarines in the early 2030s.
To prepare for the underwater use of the hypersonic launcher, the Navy is building an underwater test facility at the Naval Surface Warfare Center in Crane, Indiana, according to Wolfe.
"This facility will conduct submerged tests to ensure we understand how the missile flies through the water," he said in his statement.
NSWC Crane is the world's third-largest naval installation by geographic area and includes all of the roughly 320-hectare Lake Greenwood.
A hypersonic launch from a submarine would require a "cold launch," in which the missile is ejected from the launch tube by high-pressure gas. The missile's booster only ignites once out of the water and in the air. This is more complicated than the "hot launches" used for the Army's ground-launched missiles, in which the missile ignites and is propelled out of the launcher by its own exhaust.
"There's just a lot of engineering that has to happen," Bryan Clark, a senior fellow at the Hudson Institute and a former submariner, told Nikkei Asia. "That's going to take time."
But Clark said the submarine version is "the most important application to launch hypersonic weapons," owing to the ability to maneuver undetected, including near enemy shores.
He said that from a cost perspective, the hypersonic will be used against high-value targets "like a Chinese aircraft carrier or a Chinese command and control facility, maybe a Chinese sensor system. The target would be something that is small enough that you know a single weapon will make a difference."
China does not have a submarine-launched version of the hypersonic, largely because of its lack of submarine capacity.
Tom Shugart, an adjunct senior fellow at the Center for a New American Security and also a former submariner, said that "it's clear that the U.S. is going to have a challenge operating within long ranges from China" in light of Beijing's improved defenses.
A surface ship, like the Zumwalt destroyer "may not be able to get close enough," he said. A stealthy submarine solves that problem.
Shugart said that taking down enemy communications systems with regular cruise missiles would require much more volume. "Cruise missiles don't go nearly as fast as hypersonics. You can see them come in. We've seen many of them shot down in Ukraine," Shugart said.
"Hypersonics are just really hard to shoot down," he said. "So it may take a much smaller number of weapons to achieve the same effect."
"For example, if you were going to attack one of China's island reef bases in the South China Sea and all you are using are conventional cruise missiles, it may take 100 missiles to get past all the air defenses. If you have much greater confidence that three or four hypersonic weapons are going to make it to the target, you may only need to have half as many weapons," Shugart said.
At a time when the U.S. industrial base is facing limited capacity in producing weapons, this could be beneficial for the military.
But Jennifer Kavanagh, a senior fellow in the American Statecraft Program at the Carnegie Endowment for International Peace, questioned whether the advantages justified the massive cost for the development of hypersonics.
"In terms of capabilities, hypersonics do have some advantages. They can travel faster and at lower altitudes and are better at penetrating air defenses. But their advantages are often overstated and it is not clear just how useful they would be in most military contexts," she said.
"Ballistic missiles cannot travel at low altitudes, but can often reach targets just as fast as hypersonics," Kavanagh said. "Hypersonics are also less stealthy and accurate than some proponents suggest, and they have limited maneuverability."
"It seems like too much to spend on a niche capability," she said.
"A submarine-launched hypersonic would be a capability China doesn't have, but I don't think that alone makes it worth the high cost," Kavanagh said. "There should be a clear strategic purpose and assessment that it provides an essential capability for U.S. forces that cannot be acquired or achieved in any other way."
Meanwhile, China and Russia are expanding their hypersonic capabilities.
At Tuesday's hearing, Jeffrey McCormick, a senior intelligence analyst with the National Air and Space Intelligence Center, said that "China is ahead of Russia in support infrastructure and total inventory. China's missile programs are comparable to top-tier producers internationally, and China leads Russia with its hypersonic arsenal."
Russia, which has performed research on hypersonic weapons technologies since at least the 1980s, currently has three deployed hypersonic systems, McCormick said.
One of them, the air-launched Kinzhal, has been used extensively against Ukraine, "with varying degrees of success and effectiveness," McCormick told lawmakers.