This illustration depicts the Defense Advanced Research Products Agency’s (DARPA) Falcon Hypersonic Test Vehicle. (DARPA/DVIDS)

The lure of hypersonic weapons — the ability to strike just about anywhere on the planet in hours or even minutes — is obvious to military leaders. But with the Air Force secretary recently throwing cold water on his own service’s hypersonic plans, now is also the time to take a cold eyed view of where the technology sits, according to the Arms Control Association’s Shannon Bugos. In the op-ed below, Bugos argues that amid the hypersonic gold rush, not enough thought is being put to how to develop and use these systems, and how quickly everything could go wrong.

Hypersonic weapons have been all the rage in recent years. Pentagon officials rarely miss an opportunity to tout the importance of accelerating their development amid the department’s prioritization of enhancing conventional deterrence against Russia and China. Plus, there is strong bipartisan support in Congress for the aggressive pursuit of the weapons.

But a closer look suggests all may not be well in hypersonic paradise.

“I’m not satisfied with the pace,” said Air Force Secretary Frank Kendall at the Air Force Association Air, Space & Cyber conference about the service’s hypersonic weapon development plans.

“The target set that we would want to address, and why hypersonics are the most cost-effective weapons for the US, I think it’s still, to me, somewhat of a question mark,” the secretary said on Sept. 20. “I haven’t seen all the analysis that’s been done to justify the current program.”

We raised similar questions in a new Arms Control Association report published this month, titled “Understanding Hypersonic Weapons: Managing the Allure and the Risks.” It is not clear that the weapons — which are distinguished by their high speed, greater maneuverability, and unique flight altitude relative to existing US non-nuclear missiles — are the military game-changers many proponents make them out to be. And if the missiles do perform as intended, their unique attributes could exacerbate escalation dangers in a conflict, including to the nuclear level.

The US rush to field hypersonic weapons merits more than a simple rubber-stamping and instead much greater scrutiny and oversight than Congress has provided to date.

The upcoming fiscal year will see at least eight prototype hypersonic glide vehicle and cruise missile programs under development. The Trump administration requested $2.6 billion and $3.2 billion in fiscal years 2020 and 2021, respectively, for all hypersonic-related work, while the Biden administration this past May asked for $3.8 billion for fiscal year 2022. The Biden administration appears intent on proceeding all ahead with the development and fielding plans that began under the Trump administration.

Yet, the Defense Department has thus far offered varying and at times conflicting rationales for the US pursuit of hypersonic missiles.

Gen. John Hyten, currently vice chairman of the Joint Chiefs of Staff, has stressed that hypersonic weapons will allow for “responsive, long-range, strike options against distant, defended, and/or time-critical threats when other forces are unavailable, denied access, or not preferred.” (However, recent reports indicate that some of the weapons may not be able to strike mobile targets anytime soon, if at all.)

Meanwhile, other officials have focused less on the military benefits and more on the need to win the competition with China and Russia in the development of the technology.

Russia fielded the Avangard, a hypersonic glide vehicle, in 2019 and is developing an air-launched hypersonic missile (the Kinzhal) and a sea-launched hypersonic cruise missile (the Tsirkon). China displayed a ballistic missile designed specifically to carry a hypersonic glide vehicle (the DF-17) during its 2019 military parade. While the United States is only pursuing conventional hypersonic weapons at this time, Beijing and Moscow appear to be seeking not only conventional but also nuclear or dual-capable hypersonic capabilities.

The US needs to develop hypersonic weapons in order “to allow us to match what our adversaries are doing,” Michael Griffin, a former undersecretary of defense for research and engineering, argued last year.

The different motivations put forward by defense officials raise questions about whether specific military requirements are driving US development decisions — or if the main driver is to weaponize the technology now and figure out specific roles and missions later.

The Pentagon has also not offered a clear concept of operations for the deployment of the weapons or a detailed explanation for why alternative military capabilities are not adequate to meet mission requirements. “We do need to make sure we have an unambiguous, well understood ConOp as we go forward,” Air Combat Command head Gen. Mark Kelley said at the Air Force Association conference.

Other important details about the department’s plans for the weapons are yet to be determined, including the projected costs of the missile systems under development and production quantities.

Furthermore, the Defense Department appears to be paying less attention to the ways in which hypersonic weapons could lead to new conflict instabilities and contribute to a burgeoning arms race. Such risks include those emanating from target and warhead ambiguity, a reduction in response time, the potential ability to improve targeting of mobile missiles, arms racing, and the exacerbation of threats posed by other emerging technologies.

As former Army Secretary Ryan McCarthy noted last year, the use of hypersonic weapons in conflict “can confuse people… And you could end up in an escalatory type of situation.”

There remain numerous questions concerning the rationale for, escalatory and instability risks of, costs of, and potential alternatives to hypersonic weapons that have thus far gone unasked or unanswered. In the new report, we suggest several recommended action items for Congress to enhance its oversight of the Pentagon’s acquisition plans and make better-informed funding decisions.

One suggested step is a rethinking of the Army’s hypersonic program, the Long-Range Hypersonic Weapon (LRHW). The rationale for the program is arguably the weakest among current US hypersonic development programs. The program faces difficult challenges such as where to base the missiles, large projected costs, and is controversial within the Pentagon. Plus, the weapon’s range (at least 2,775 km), speed, and mode of launch (from ground-launchers) poses underexplored stability risks.

Lawmakers should also seek to hold a dialogue with the State Department on possible avenues for future arms control on hypersonic weapons. Already, experts have begun to explore various possible options ranging from confidence-building measures to bans or limits on certain types of hypersonic weapons. And the United States and Russia have previously expressed interest in bringing up hypersonic weapons as a topic in an established dialogue on strategic stability, which is an opportunity that should not go to waste.

It is time — in fact, past time — for Congress to demand answers about the Pentagon’s pursuit of hypersonic weapons capabilities before the military begins fielding the weapons in possibly great numbers and before the ability to mitigate stability risks becomes more difficult.

Shannon Bugos is a research associate at the Arms Control Association, where she focuses on nuclear disarmament, US-Russian arms control, and hypersonic weapons and emerging technologies.